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Separation of acid blue 25 from aqueous solution using water lettuce and agro-wastes by batch adsorption studies

Separation of acid blue 25 from aqueous solution using water lettuce and agro-wastes by batch... Three plant-based materials, namely water lettuce (WL), tarap peel (TP) and cempedak peel (CP), were used to investigate their potentials as adsorbents using acid blue 25 (AB25) dye as a model for acidic dye. The adsorbents were characterised using Fourier transform infrared spectroscopy, X-ray fluorescence and scanning electron microscope. Batch experiments involving parameters such as pH, temperature, contact time, and initial dye concentration were done to investigate the optimal conditions for the adsorption of AB25 onto the adsorbents. Thermodynamics study showed that the uptake of AB25 by the three adsorbents was feasible and endothermic in nature. Both the Langmuir and Freundlich isotherm models can be used to describe the adsorption process of AB25 onto WL and CP while pseudo-second-order fitted the kinetics data, suggesting that chemisorptions were majorly involved. The use of 0.1 M of NaOH showed the best results in regenerating of the WL, TP and CP’s adsorption ability after AB25 treatment. Keywords Acid blue 25 · Adsorption · Artocarpus odoratissimus · Artocarpus integer · Pistia stratiotes · Water remediation Introduction industrial discharge to the water bodies is a major concern to both human and other living things as it directly affects One of the basic necessities of every living organism is water their health and food sources. and on Earth, the water sources come from seawater (96.5%) Synthetic dye is one of the industrial discharges which and freshwater (2.5%) such as river, glacier and lakes. Of is non-biodegradable, potentially carcinogenic and muta- these two sources, only freshwater is suitable for human use genic. This coloured compound, even in low concentration, as seawater has high salinity. Unfortunately, the usable water is highly visible if it is present in the water bodies causing source is not inn fi ite and the usage of this water grows as the unaesthetic view. Therefore, it is imperative that dye waste- human population grows which brings problems as industri- water is remediated before discharging into the environment. alisation increases to provide for the population need. The Various methods of treating the dye wastewater have been researched and they are discussed in the literature (Robinson et al. 2001). * Muhammad Raziq Rahimi Kooh One of the wastewater treatment methods discussed is [email protected] adsorption; a simple method that utilises a variety of mate- Muhammad Khairud Dahri rials such as leaf (Kooh et al. 2017a, b), bacteria (Pearce [email protected] et al. 2003), fungi biomass (Fu and Viraraghavan 2001) and Linda B. L. Lim agriculture wastes (Crini 2006) as adsorbents. This method [email protected] adopts the concept of adhering the pollutant onto the adsor- Lee Hoon Lim bent which is not only simple but also does not produce [email protected] any harmful by-products from chemical reactions. Another Chin Mei Chan attractive feature of adsorption is its simple procedural [email protected] design and the overall cost is relatively low. Faculty of Science, Universiti Brunei Darussalam, This study aims to investigate the performance of water Jalan Tungku Link, Pengkalan Gadong, lettuce (WL), tarap (Artocarpus odoratissimus) peel (TP) Bandar Seri Begawan BE 1410, Brunei Darussalam Vol.:(0123456789) 1 3 61 Page 2 of 10 Applied Water Science (2018) 8:61 and cempedak (Artocarpus integer) peel (CP) in removing electron microscope (SEM) (Tescan Vega XMU) for the the anionic dye acid blue 25 (AB25) from aqueous solu- surface morphology analyses. The point of zero charge tion. AB25 is chosen as it has wide applications in cosmetic, (pH ) of the adsorbents was determined by the salt addi- pzc −1 fabric and aluminium finishing and can serve as a model tion method using 0.1 mol L KNO solutions following anionic dye compound. The objectives of this study include procedures from the literature (Zehra et al. 2015). the various characterisations of the adsorbents, investigation of the effects of initial dye concentration, pH, contact time, Batch adsorption procedures and also thermodynamics and regeneration experiments. WL is scientifically known as Pistia stratiotes and it is The adsorption experiment was performed by agitating mainly found in tropical and subtropical regions around the 0.04 g adsorbent with 20 mL dye solution in 100-mL conical world. It is usually found to choke drain and water channel, flasks at the speed of 250 rpm using a Stuart orbital shaker. and thrive in water with minimal nutrients. The prolifera- The filtrate was analysed using a UV–visible spectropho- tive growth leads to formation of dense mat on the surface tometer (Shimadzu UV-1601PC) at wavelength of 597 nm. of water, reducing sunlight penetration into the water, and To evaluate the performance of the adsorbent in the is associated with decreased dissolved oxygen content. The −1 removal of dye, adsorption capacity q (mg g ) and the high-proliferative growth behaviour with minimal input and percentage removal were calculated, and the equations are attention makes WL an attractive adsorbent. Tarap and cem- as follows: pedak belong to the same genus Artocarpus, and they are vastly available in Southeast Asia (Tang et al. 2013). The (C − C )V i e q = , (1) sweet edible pulp is consumed, while large portion of the thick rind is usually discarded and hence it is utilised as an adsorbent. Previous study on the use of water lettuce to (C − C )× 100% i e % removal = , (2) remove a triphenylmethane dye (methyl violet) from aque- ous solution has been reported (Lim et al. 2016) and the −1 where C is the initial adsorbate concentration (mg L ), C Artocarpus spp. were used in adsorption studies to remove i e is the concentration of adsorbate left in the solution after methylene blue, cadmium and copper (Kooh et al. 2016a, b; −1 equilibrium (mg L ), V is the volume of adsorbate solution Lim et al. 2012, 2015, 2017; Priyantha et al. 2013), show- (L) and m is the mass of adsorbent (g). ing their potentials as adsorbent to remove basic dyes and The parameters included in this study are the effects of heavy metals. contact time (5–240 min), pH (2–10) and initial AB25 con- −1 centrations (20–500 mg L ), with the change of one param- eter at a time while keeping the rest constant. Materials and methods There are many models that have been used for character- ising the adsorption process. Data from the effect of initial Preparation of adsorbents and adsorbate dye concentration were fitted into three adsorption isotherm models (Langmuir, Freundlich and Dubinin–Radushkevich Water lettuce (WL) was collected from a choked drain in the models) while the data from effect of contact time were fit- Rimba Horticulture Centre, Brunei-Muara district, Brunei ted into three kinetics models (pseudo-first-order, pseudo- Darussalam, while tarap and cempedak fruits, sold in local second-order and intraparticle diffusion models). The best markets, were randomly selected and purchased. The peels models that described the adsorption data were determined were separated from the fruit. After washing all the three by looking at the values of the R and two error functions samples with distilled water, they were then dried in an oven which are the sum of absolute error (EABS) and Chi-square at 70 °C. The dried adsorbents were then blended, sieved and test (χ ) as shown in Eqs. (3) and (4), respectively: kept in desiccators. −1 AB25 (C H N NaOS, M 416.38 g mol , 45% dye 20 13 2 5 r purity, Sigma-Aldrich) was used as received. EABS: q − q , (3) e,exp e,cal i=1 Characterisation of adsorbents (q − q ) e,exp e,cal The adsorbents were characterised using an X-ray fluores- ∶ , (4) max cence (XRF) spectrophotometer (PANalytical Ax ios ) for q e,exp i=1 the elemental analyses, a Fourier transform infrared (FTIR) spectrophotometer (Shimadzu Model IRPrestige-21 spec- where q is the experimental data while q is the calcu- e,exp e,cal lated data from the isotherm or kinetics model. trophotometer) for functional group analyses and a scanning 1 3 Applied Water Science (2018) 8:61 Page 3 of 10 61 Table 1 XRF elemental Thermodynamics experiments Normalised percentage (%) analyses of WL, TP and CP Element WL TP CP The Van’t Hoff equation was used for determining the ther - modynamics nature of the adsorption process and the equa- Mn 0.41 0.57 0.82 tions are as follows: Al 0.55 0.18 0.19 Si 1.21 1.46 2.05 ◦ ◦ ◦ ΔG =ΔH − TΔS , (5) Mg 1.45 1.75 2.13 Na 1.55 ND ND ΔG =−RTln k, (6) S 1.59 1.89 1.89 P 1.79 1.88 0.75 k = , (7) Cl 18.30 3.07 0.13 Ca 19.70 3.49 9.60 ◦ ◦ O 22.80 26.60 28.50 ΔS ΔH ln k = − , (8) K 28.70 38.00 28.70 R RT −1 where ∆G° (kJ  mol ) is the Gibbs free energy, ∆H° ND not undetected −1 −1 −1 (kJ mol ) is the change in enthalpy, ∆S° (J mol  K ) is the change in entropy, T (K) is the temperature, k is the dis- present in an adsorbent. Figure 1 shows the FTIR spectra −1 tribution coefficient for adsorption, C (mg L ) is the con- for WL, TP and CP before AB25 treatment. In general, centration of AB25 adsorbed on the adsorbent at equilibrium hydroxyl and/or amino group can be found at the stretching −1 −1 and R is the gas constant (8.314 J mol  K ). −1 −1 band of around 3300–3400 cm . Band at around 2900 cm The adsorption experiment was carried out at five differ - indicates the C–H bond stretching while N–H bending ent temperatures (25, 40, 50, 60 and 70 °C) using 20 mL of −1 −1 −1 (1630 cm ), phenyl (1413 cm ) and C–O–C (1022 cm ) −1 50 mg L AB25 at solution pH of 2.0. The thermodynam- −1 can be found at around 1610, 1400 and 1060 cm , respec- ics parameter ∆G° was calculated using Eq. (6), while ∆H° tively. After AB25 treatment as shown in Fig. 1b, it can be −1 and ∆S° were calculated from the linear plot of ln k vs T observed that there is a significant shift in stretching band of Eq. (8). for OH and NH groups as well as NH bending band. Hence, these functional groups could be involved in AB25 adsorp- Regeneration experiments tion onto the adsorbents’ surfaces. The surface morphology analyses of the WL, TP and CP The detailed procedures of the regeneration experiment are shown in Fig. 2, which provide visual insights into the surface of adsorbent particles. Both WL and CP have rough were described in our previous work (Dahri et al. 2014). In short, the spent adsorbents were prepared using 20 mL and uneven surface while TP has smoother looking surface. −1 All the adsorbents did not have any orderly pattern. of 50 mg L AB25 and regenerated using distilled water, −1 −1 0.1 mol L HNO and 0.1 mol L NaOH. The regeneration Study of pH medium experiments were carried out for five cycles. The electrostatic interactions between the adsorbent’s sur- face and the dye are directly affected by pH, thus making Results and discussion it important to investigate the effect of pH. The pH is a pzc point where the net charge on the surface of the adsorbent is Characterisations of adsorbents zero. When solution pH > pH , the adsorbent’s surface is pzc predominant negatively charged, while pH < pH resulted pzc Characterisations of the adsorbents are important as they in predominantly positively charged surface. The pH of pzc provide much useful information regarding the adsorbents. WL and CP was determined to be 6.40 and 4.01, respec- The elemental analyses of adsorbents are summarised in tively, while for TP was determined as 4.40 in previous work Table 1, which provide the information regarding the micro- (Lim et al. 2015). Figure  3 indicates that as the solution mineral and macro-mineral contents. pH decreased, the dye removal gradually increased for the Molecules such as hydroxyl and carbonyl groups con- all three adsorbents (WL, CP and TP). The optimum pH tain dipole moment which can absorb infrared radiation at was observed to be at pH 2.0 for all three adsorbents. This specific frequencies and is characteristic for each functional behaviour is explained with the concept of pH , where at pzc group (Pavia et al. 1996). This makes FTIR analysis to be pH 2, the anionic AB25 dye molecules are attracted to the very useful in the characterisation of functional groups predominant positively charged surface and this observation 1 3 61 Page 4 of 10 Applied Water Science (2018) 8:61 Fig. 1 FTIR spectra of a WL, b TP, c CP, d WL-AB25, e TP-AB25 and f CP-AB25 suggests that the adsorption of AB25 onto these adsorbents place. The dye adsorption slowed down to a plateau which depends mainly on ionic interaction. was due to saturation of adsorption sites and reaching the equilibrium of the adsorption process. Time duration of Eec ff t of contact time and kinetics modelling 120 min was sufficient for WL-AB25 system to attain equi- librium, while 180 min was sufficient for both CP-AB25 and The effect of contact time is important in adsorption study TP-AB25 systems. as vital information such as the time required for adsorption Three most commonly used kinetics models (pseudo- process to attain complete equilibrium can be obtained. The first-order (Lagergren 1898), pseudo-second-order (Ho and data of the effect of contact time are summarised in Fig.  4. McKay 1999) and intraparticle diffusion (Weber and Morris The observed trend for all the three adsorption systems 1963) models) were used for characterising the kinetics data was the rapid increase in adsorption during the start of the and their equations are as follows: adsorption process which was attributed to the presence of many vacant sites being available for adsorption to take Pseudo-first-order: log(q − q )= logq − k , (9) e t e 1 2.303 1 3 Applied Water Science (2018) 8:61 Page 5 of 10 61 Fig. 2 SEM images displaying the surface morphologies of a WL, b TP and c CP at ×500 magnification −1 pseudo-first-order rate constant (min ), k is pseudo-sec- −1 −1 ond-order rate constant (g mg min ), k is the intraparti- −1 −1/2 cle diffusion rate constant (mg g   min ) and C is the intercept. The parameters of the pseudo-first-order, pseudo- second-order and intraparticle diffusion models were obtained from the linear plots of ln(q − q ) vs t, vs t and q e t t vs t , respectively. The kinetics parameters for all adsorbents are sum- marised in Table  2. The values of R were highest for pseudo-second-order model for all three adsorbents 2468 10 TP CP WL pH when compared to pseudo-first-order which indicates that the pseudo-second-order model was the most suit- Fig. 3 The effect of pH on the removal of AB25 using WL, CP and able to describe the kinetics data. This was reinforced TP by the lower values of the error functions χ and EABS for pseudo-second-order model and also the agreement between the values of q and q . e,exp e,cal t 1 t According to Liu (2008), a pseudo-second-order kinet- Pseudo-second-order: = + , (10) q q k q ics implies that the adsorption rate follows a second-order t 2 e rate law with respect to the adsorbent’s surface adsorption 1∕2 sites instead of the adsorbate in bulk solution. The poor Intraparticle diffusion: q = k t + C, (11) t 3 fitting of pseudo-first-order model is due to it not being a where q is the amount of adsorbate adsorbed per gram of true order equation but rather an approximate solution to −1 adsorbent (mg  g ) at time t (min), k is the 1 3 Percentage removal (%) 61 Page 6 of 10 Applied Water Science (2018) 8:61 20 categorised into three phases, which are the initial fast exter- (A) nal diffusion, surface adsorption (intraparticle diffusion) and lastly the equilibrium phase. By fitting the kinetics data into the intraparticle diffusion model, the rate-limiting phase of the adsorption process can be determined. According to the intraparticle diffusion model, if the linear plot of q vs t crossed the origins, then the intraparticle diffusion is the rate-limiting step. As seen in Table 2, all the values of the intercepts are not zero, this indicates that the rate-limiting step was not intraparticle diffusion and other mechanism may have been involved. This observation is very common and has been reported in the removal of hazardous dyes 050100 150200 250 (malachite green and rhodamine B) using water fern (Kooh t (min) 20 mg L⁻¹ 50 mg L⁻¹ 100 mg L⁻¹ et al. 2016d, e), and also in the adsorption of methyl violet 2B using soya waste (Kooh et al. 2016c). (B) Eec ff t of initial dye concentration and isotherm study The effect of varying the initial dye concentration on the removal of AB25 onto the adsorbents is shown in Fig. 5. Both WL and CP showed increase in dye uptake as the con- centration increased while TP only showed an increase up to −1 200 mg L before the dye uptake decreased. The increase in dye concentration provided enough force for the mass 050100 150200 250 20 mg L⁻¹ 50 mg L⁻¹ 100 mg L⁻¹ t (min) transfer to occur from the bulk solution and, therefore, an increase in the dye uptake was observed. TP, however, dis- played different trend from the other adsorbents whereby (C) −1 the dye uptake decreased after 200 mg L . This might be due to the low affinity of TP towards AB25 and although both TP and CP are both of the same genus, their affinities 5 toward AB25 may differ as the peels are made up of different chemical compositions. The adsorption data were characterised using three iso- therm models: Langmuir (Langmuir 1916), Freundlich (Fre- undlich 1906) and Dubinin–Radushkevich (D–R) (Dubinin 050100 150200 250 and Radushkevich 1947) as follow: 20 mg L⁻¹ 50 mg L⁻¹ 100 mg L⁻¹ t (min) C C e e Langmuir: = + , (12) q k q q e L m m Fig. 4 The adsorption of AB25 as function of time by a WL, b TP and c CP Freundlich: ln q = ln C + ln k , e e F (13) the first-order rate mechanism. The reason being the num- 2 2 D−R: lnq = ln q − k  , (14) e m DR ber of sites available does not equate to q of the pseudo- first-order model, and also the parameter of log q often = RT ln 1 + , differs from the intercept of the plot of (log q  − q ) vs t (15) e t (Eq. 9) (Aharoni and Sparks 1991). The diffusion mechanism of the adsorption process where q is the maximum adsorption capacity of the adsor- −1 is characterised using the intraparticle diffusion model bent (mg  g ), k is the Langmuir adsorption constant −1 1−1/n 1/n −1 because the pseudo-first and pseudo-second-order models (L mg ), k (mg L g ) is the adsorption capacity of are not applicable. The diffusion process can generally be the adsorbent, n is the Freundlich constant where adsorption 1 3 -1 q ( mg g ) q (mg g⁻¹) q ( mg g⁻¹) e e Applied Water Science (2018) 8:61 Page 7 of 10 61 Table 2 Summary of the kinetic Absorbent WL TP CP parameters −1 C (mg L ) 20 50 100 20 50 100 20 50 100 Pseudo-first order −1  q (mg g ) 3.5 5.1 5.6 2.3 0.9 5.1 3.7 2.6 5.6 e,cal −1  q (mg g ) 9.1 14.2 17.5 3.3 3.5 5.6 4.9 6.5 7.4 e,exp  k 0.019 0.017 0.009 0.011 0.010 0.010 0.013 0.009 0.012  R 0.911 0.868 0.781 0.948 0.501 0.863 0.991 0.560 0.931  χ 46 75 108 7 24 3 7 36 10  EABS 63 96 127 13 27 7 15 45 21 Pseudo-second order −1  q (mg g ) 9.4 14.6 17.1 3.5 3.5 11.3 5.3 6.4 8.1 e,cal −1  q (mg g ) 9.1 14.2 17.5 3.3 3.5 5.6 4.9 6.5 7.4 e,exp  k 0.013 0.009 0.008 0.010 0.051 0.0003 0.006 0.014 0.003  R 0.999 0.999 0.996 0.980 0.998 0.267 0.984 0.991 0.991  χ 4 8 7 3 2 4 5 4 4  EABS 14 23 24 7 5 8 11 10 14 Intraparticle diffusion  k 0.810 0.905 0.993 0.176 0.183 0.386 0.323 0.582 0.526  C 2.5 5.8 7.7 0.7 1.7 − 0.5 0.7 1.2 0.5  R 0.980 0.954 0.627 0.925 0.943 0.856 0.950 0.891 0.946 R = , (16) (1 + k C ) L o −1 where C (mg L ) is the highest initial dye concentration. The value of R indicates if the isotherm is unfavour- able (R > 1), favourable (0 < R < 1), linear (R = 1), or L L L irreversible (R = 0). The Freundlich model is another commonly used iso- therm model, and if applicable, would assume formation of multilayer of adsorbates on adsorbent’s surface, and the D–R isotherm also assumes heterogeneous surface of the adsorbent and is temperature dependent. D–R isotherm 0100 200300 400500 600 is also used to determine the thermodynamic nature of -1 WL TP CP C (mg L ) the adsorption by estimating the mean free energy of the −1 sorption per molecule of adsorbate, E (kJ mol ), which Fig. 5 The effect of AB25 concentration on the adsorption process of is expressed as WL, TP and CP E = . (17) process is considered favourable if 1 < n < 10, k is a D–R F DR 2k DR 2 −2 constant (mol  kJ ), ε is the D–R isotherm constant which is also known as the Polanyi potential, R is the gas constant The linear plots of C /q vs C , ln q vs ln C , and ln q vs e e e e e e −3 −1 −1 (8.314 × 10  kJ mol  K ) and T is temperature (K). ε were used for calculating the parameters for the Langmuir, The Langmuir model assumes a maximum adsorption Freundlich and D–R isotherm models, respectively. resulting in a monolayer film whereby once an adsorption Table  3 summarises the isotherm models’ parameters site is occupied it will not be available for another adsorbate. for the adsorption of AB25 by WL, TP and CP. The Lang- The favourability of the adsorption process can be assessed muir, Freundlich and D–R isotherm models are compared by a dimensionless constant, separation factor (R ), which is with each other to determine which model is suitable to expressed as describe the adsorption process of AB25 onto the adsor- bents. Between the three models, the Langmuir possessed the highest R values for TP and WL while the Freundlich 1 3 -1 q (mg g ) e 61 Page 8 of 10 Applied Water Science (2018) 8:61 Table 3 Parameters of the Langmuir, Freundlich and D–R isotherm (A) models T (°C) WL TP CP Langmuir isotherm −1  q (mg g ) 24.5 10.5 21.2  k 0.070 0.015 0.013  R 0.027 0.104 0.121  R 0.992 0.685 0.963  χ 4.4 5.4 2.7  EABS 19.2 16.1 13.1 H₂O HNO₃ NaOH Number of Cycle Freundlich isotherm 1−1/n 1/n −1  K (mg L g ) 7.6 1.6 2.5 (B)  n 5.0 3.5 3.1 2 30  R 0.906 0.654 0.972  χ 1.6 5.0 1.2  EABS 14.0 15.1 8.6 Dubinin–Radushkevich isotherm −1  q (mg g ) 19.7 7.2 12.1 2 −2  k (mol  kJ ) 1.8 25.4 14.7 DR −1  E (kJ mol ) 0.521 0.140 0.184  R 0.691 0.386 0.448 H₂O HNO₃ NaOH Number of cycle  χ 21.4 7.2 10.2  EABS 41.0 18.5 30.1 (C) model has the highest R value for CP. In terms of error analyses, however, the Freundlich model showed the lowest value amongst the isotherm models. Hence, the adsorption process fitted to both the Langmuir and Freundlich models which can be used for describing the adsorption process. Compared to CP and WL, TP has lower R values (< 0.700) for all of isotherm models which showed the incompatibility of these models in describing the adsorp- H₂O HNO₃ NaOH Number of cycle tion of AB25 onto TP probably due to their low affinity for each other. Fig. 6 Regeneration experiment of a WL, b TP and c CP −1 The q of the WL, TP and CP are 24.5, 10.5, 21.2 mg g , respectively, which are of similar levels with other adsor- bents that were reported in the literature: diatomite (21.4) adsorption systems were endothermic in nature where heat −1 (Badii et al. 2010) and wood dust (24.4 mg g ) (Hanafiah was gained from the surrounding. ∆S° for WL, CP and TP −1 −1 −1 et al. 2012), but lower than soya bean waste (38.5 mg g ) was determined to be − 75, 42 and 32 J mol  K . −1 (Dahri et al. 2016) and water fern (50.5 mg g ) (Dahri et al. 2016). Regeneration experiment Thermodynamics studies Spent adsorbents contain hazardous dye substances which should be disposed properly by incineration. Dumping to The thermodynamics parameters were investigated for tem- landfill is not a proper way of disposing hazardous waste peratures ranging from 25 to 70 °C. All the three adsorbents as leaching of the dye may occur. However, incineration (WL, CP, TP) displayed ∆G° that became more negative as also has many disadvantages, as it may cost more due to the temperature increased, and this indicates the spontaneity fuel needed for burning, and hazardous gas being released of the adsorbent–adsorbate systems. The ∆H° for WL, CP to the environment. Regeneration experiment in this study −1 and TP were determined to be 20.3, 15.2 and 12.4 kJ mol , investigated an alternative route to direct disposal of the respectively, where these positive values indicate these spent adsorbent. It is perceived that regeneration of spent 1 3 Percentage removal (%) Percentage removal (%) Percentage removal (%) Applied Water Science (2018) 8:61 Page 9 of 10 61 Dahri MK, Kooh MRR, Lim LBL (2014) Water remediation using adsorbent may further reduce the total cost of treatment by low cost adsorbent walnut shell for removal of malachite green: adsorption. The regeneration experiments’ data are summa- equilibrium, kinetics, thermodynamic and regeneration studies. J rised in Fig. 6. For WL, it can be observed that all the three Environ Chem Eng 2:1434–1444 solvents’ washing successfully maintained the dye adsorp- Dahri MK, Kooh MRR, Lim LBL (2016) Adsorption of toxic methyl violet 2B dye from aqueous solution using Artocarpus hetero- tion close to the original level. For CP and TP, there were phyllus (Jackfruit) seed as an adsorbent. Am Chem Sci J 15:1–12 slight reductions in dye adsorption for every successive Dubinin MM, Radushkevich LV (1947) Equation of the characteristic cycle for water and acid wash; however, improvement was curve of activated charcoal. Proc Acad Sci 55:327 observed for basic wash. This behaviour may be due to the Freundlich HMF (1906) Over the adsorption in solution. J Phys Chem 57:385–471 removal of low molecular fats, lignin and other plant materi- Fu Y, Viraraghavan T (2001) Fungal decolorization of dye wastewaters: als with uncovered functional groups that may have inter- a review. Biores Technol 79:251–262 acted with the adsorbates. Investigations on the improvement Hanafiah MAKM, Ngah WSW, Zolkafly SH, Teong LC, Majid ZAA in dye adsorption by basic wash have been reported in few of (2012) Acid blue 25 adsorption on base treated Shorea dasyphylla sawdust: kinetic, isotherm, thermodynamic and spectroscopic our previous works (Dahri et al. 2014; Kooh et al. 2016d). analysis. J Environ Sci 24:261–268 Ho YS, McKay G (1999) Pseudo-second order model for sorption pro- cesses. Process Biochem 34:451–465 Kooh MRR, Dahri MK, Lim LBL (2016a) Jackfruit seed as a sustain- Conclusions able adsorbent for the removal of Rhodamine B dye. J Environ Biotechnol Res 4:7–16 The optimal conditions of the adsorption of AB25 by WL, Kooh MRR, Dahri MK, Lim LBL (2016b) The removal of rhodamine TP and CP were 2 h of contact time at pH 2. FTIR analysis B dye from aqueous solution using Casuarina equisetifolia nee- dles as adsorbent. Cogent Environ Sci 2:1140553 indicated both the OH and NH groups might be involved Kooh MRR, Dahri MK, Lim LBL, Lim LH, Malik OA (2016c) Batch in the adsorption of the dye on the adsorbents’ surfaces. adsorption studies of the removal of methyl violet 2B by soya bean CP and WL’s experimental data can be described using the waste: isotherm, kinetics and artificial neural network modelling. Langmuir, Freundlich and pseudo-second-order models. TP Environ Earth Sci 75:783 Kooh MRR, Lim LBL, Lim LH, Bandara JMRS (2016d) Batch has the lowest affinity towards AB25 resulting in incompat- adsorption studies on the removal of malachite green from water ibility with the isotherm models. The spent adsorbents can by chemically  modified Azolla pinnata. Desalin Water Treat be regenerated using 0.1 M NaOH. 57:14632–14646 Kooh MRR, Lim LBL, Lim LH, Dahri MK (2016e) Separation of toxic Acknowledgements The authors are grateful to the Government of rhodamine B from aqueous solution using an efficient low-cost Brunei Darussalam and the Universiti Brunei Darussalam for their sup- material, Azolla pinnata, by adsorption method. Environ Monit port. The authors expressed their gratitude to the Centre for Advanced Assess 188:1–15 Material and Energy Sciences (CAMES) of Universiti Brunei Darus- Kooh MRR, Dahri MK, Lim LBL (2017a) Removal of methyl violet salam for their generosity in the usage of XRF machine. 2B dye from aqueous solution using Nepenthes rafflesiana pitcher and leaves. Appl Water Sci 7:3859–3868 Kooh MRR, Dahri MK, Lim LBL (2017b) Removal of the methyl Compliance with ethical standards violet 2B dye from aqueous solution using sustainable adsorbent Artocarpus odoratissimus stem axis. Appl Water Sci 7:3573–3581 Conflict of interest All authors declare no conflict of interest. Lagergren S (1898) Zur Theorie der Sogenannten Adsorption gel Ster Stoffe. K Sven Vetenskapsakad Handl 24:1–39 Open Access This article is distributed under the terms of the Crea- Langmuir I (1916) The constitution and fundamental properties of sol- tive Commons Attribution 4.0 International License (http://creat iveco ids and liquids. J Am Chem Soc 38:2221–2295 mmons.or g/licenses/b y/4.0/), which permits unrestricted use, distribu- Lim LBL, Priyantha N, Tennakoon DTB, Dahri MK (2012) Biosorp- tion, and reproduction in any medium, provided you give appropriate tion of cadmium(II) and copper(II) ions from aqueous solution credit to the original author(s) and the source, provide a link to the by core of Artocarpus odoratissimus. Environ Sci Pollut Res Int Creative Commons license, and indicate if changes were made. 19:3250–3256 Lim LBL, Priyantha N, Hei Ing C, Khairud Dahri M, Tennakoon DTB, Zehra T, Suklueng M (2015) Artocarpus odoratissimus skin as a potential low-cost biosorbent for the removal of methylene blue and methyl violet 2B. Desalin Water Treat 53:964–975 References Lim LBL, Priyantha N, Chan CM, Matassan D, Chieng HI, Kooh MRR (2016) Investigation of the sorption characteristics of water lettuce Aharoni C, Sparks DL (1991) Kinetics of soil chemical reactions—a (WL) as a potential low-cost biosorbent for the removal of methyl theoretical treatment. In: Sparks DL, Suarez DL (eds) Rates of soil violet 2B. Desalin Water Treat 57:8319–8329 chemical processes. Soil Science Society of America, Madison, Lim LBL, Priyantha N, Tennakoon DTB, Chieng HI, Dahri MK, pp 1–18 Suklueng M (2017) Breadnut peel as a highly effective low-cost Badii K, Ardejani FD, Saberi MA, Limaee NY, Shafaei S (2010) biosorbent for methylene blue: equilibrium, thermodynamic and Adsorption of acid blue 25 dye on diatomite in aqueous solutions. kinetic studies. Arab J Chem 10(Suppl 2):S3216–S3228 Indian J Chem Technol 17:7–16 Liu Y (2008) New insights into pseudo-second-order kinetic equa- Crini G (2006) Non-conventional low-cost adsorbents for dye removal: tion for adsorption. Colloids Surf A Physicochem Eng Asp a review. Biores Technol 97:1061–1085 320:275–278 1 3 61 Page 10 of 10 Applied Water Science (2018) 8:61 Pavia DL, Lampman GM, Kriz GS (1996) Introduction to spectros- Weber W, Morris J (1963) Kinetics of adsorption on carbon from solu- copy, 2nd edn. Saunders College Publishing, San Luis Obispo tion. J Sanit Eng Div 89:31–60 Pearce C, Lloyd J, Guthrie J (2003) The removal of colour from textile Zehra T, Priyantha N, Lim LBL, Iqbal E (2015) Sorption characteris- wastewater using whole bacterial cells: a review. Dyes Pigments tics of peat of Brunei Darussalam V: removal of Congo red dye 58:179–196 from aqueous solution by peat. Desalin Water Treat 54:2592–2600 Priyantha N, Lim LBL, Tennakoon DTB, Mansor NHM, Dahri MK, Chieng HI (2013) Breadfruit (Artocarpus altilis) waste for biore- Publisher’s Note Springer Nature remains neutral with regard to mediation of Cu (II) and Cd(II) ions from aqueous medium. Cey- jurisdictional claims in published maps and institutional affiliations. lon J Sci (Phys Sci) 17:19–29 Robinson T, McMullan G, Marchant R, Nigam P (2001) Remedia- tion of dyes in textile effluent: a critical review on current treat- ment technologies with a proposed alternative. Bioresour Technol 77:247–255 Tang YP, Linda BLL, Franz LW (2013) Proximate analysis of Arto- carpus odoratissimus (Tarap) in Brunei Darussalam. Int Food Res J 20:409–415 1 3 http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Applied Water Science Springer Journals

Separation of acid blue 25 from aqueous solution using water lettuce and agro-wastes by batch adsorption studies

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Springer Journals
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Copyright © 2018 by The Author(s)
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Earth Sciences; Hydrogeology; Water Industry/Water Technologies; Industrial and Production Engineering; Waste Water Technology / Water Pollution Control / Water Management / Aquatic Pollution; Nanotechnology; Private International Law, International & Foreign Law, Comparative Law
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Abstract

Three plant-based materials, namely water lettuce (WL), tarap peel (TP) and cempedak peel (CP), were used to investigate their potentials as adsorbents using acid blue 25 (AB25) dye as a model for acidic dye. The adsorbents were characterised using Fourier transform infrared spectroscopy, X-ray fluorescence and scanning electron microscope. Batch experiments involving parameters such as pH, temperature, contact time, and initial dye concentration were done to investigate the optimal conditions for the adsorption of AB25 onto the adsorbents. Thermodynamics study showed that the uptake of AB25 by the three adsorbents was feasible and endothermic in nature. Both the Langmuir and Freundlich isotherm models can be used to describe the adsorption process of AB25 onto WL and CP while pseudo-second-order fitted the kinetics data, suggesting that chemisorptions were majorly involved. The use of 0.1 M of NaOH showed the best results in regenerating of the WL, TP and CP’s adsorption ability after AB25 treatment. Keywords Acid blue 25 · Adsorption · Artocarpus odoratissimus · Artocarpus integer · Pistia stratiotes · Water remediation Introduction industrial discharge to the water bodies is a major concern to both human and other living things as it directly affects One of the basic necessities of every living organism is water their health and food sources. and on Earth, the water sources come from seawater (96.5%) Synthetic dye is one of the industrial discharges which and freshwater (2.5%) such as river, glacier and lakes. Of is non-biodegradable, potentially carcinogenic and muta- these two sources, only freshwater is suitable for human use genic. This coloured compound, even in low concentration, as seawater has high salinity. Unfortunately, the usable water is highly visible if it is present in the water bodies causing source is not inn fi ite and the usage of this water grows as the unaesthetic view. Therefore, it is imperative that dye waste- human population grows which brings problems as industri- water is remediated before discharging into the environment. alisation increases to provide for the population need. The Various methods of treating the dye wastewater have been researched and they are discussed in the literature (Robinson et al. 2001). * Muhammad Raziq Rahimi Kooh One of the wastewater treatment methods discussed is [email protected] adsorption; a simple method that utilises a variety of mate- Muhammad Khairud Dahri rials such as leaf (Kooh et al. 2017a, b), bacteria (Pearce [email protected] et al. 2003), fungi biomass (Fu and Viraraghavan 2001) and Linda B. L. Lim agriculture wastes (Crini 2006) as adsorbents. This method [email protected] adopts the concept of adhering the pollutant onto the adsor- Lee Hoon Lim bent which is not only simple but also does not produce [email protected] any harmful by-products from chemical reactions. Another Chin Mei Chan attractive feature of adsorption is its simple procedural [email protected] design and the overall cost is relatively low. Faculty of Science, Universiti Brunei Darussalam, This study aims to investigate the performance of water Jalan Tungku Link, Pengkalan Gadong, lettuce (WL), tarap (Artocarpus odoratissimus) peel (TP) Bandar Seri Begawan BE 1410, Brunei Darussalam Vol.:(0123456789) 1 3 61 Page 2 of 10 Applied Water Science (2018) 8:61 and cempedak (Artocarpus integer) peel (CP) in removing electron microscope (SEM) (Tescan Vega XMU) for the the anionic dye acid blue 25 (AB25) from aqueous solu- surface morphology analyses. The point of zero charge tion. AB25 is chosen as it has wide applications in cosmetic, (pH ) of the adsorbents was determined by the salt addi- pzc −1 fabric and aluminium finishing and can serve as a model tion method using 0.1 mol L KNO solutions following anionic dye compound. The objectives of this study include procedures from the literature (Zehra et al. 2015). the various characterisations of the adsorbents, investigation of the effects of initial dye concentration, pH, contact time, Batch adsorption procedures and also thermodynamics and regeneration experiments. WL is scientifically known as Pistia stratiotes and it is The adsorption experiment was performed by agitating mainly found in tropical and subtropical regions around the 0.04 g adsorbent with 20 mL dye solution in 100-mL conical world. It is usually found to choke drain and water channel, flasks at the speed of 250 rpm using a Stuart orbital shaker. and thrive in water with minimal nutrients. The prolifera- The filtrate was analysed using a UV–visible spectropho- tive growth leads to formation of dense mat on the surface tometer (Shimadzu UV-1601PC) at wavelength of 597 nm. of water, reducing sunlight penetration into the water, and To evaluate the performance of the adsorbent in the is associated with decreased dissolved oxygen content. The −1 removal of dye, adsorption capacity q (mg g ) and the high-proliferative growth behaviour with minimal input and percentage removal were calculated, and the equations are attention makes WL an attractive adsorbent. Tarap and cem- as follows: pedak belong to the same genus Artocarpus, and they are vastly available in Southeast Asia (Tang et al. 2013). The (C − C )V i e q = , (1) sweet edible pulp is consumed, while large portion of the thick rind is usually discarded and hence it is utilised as an adsorbent. Previous study on the use of water lettuce to (C − C )× 100% i e % removal = , (2) remove a triphenylmethane dye (methyl violet) from aque- ous solution has been reported (Lim et al. 2016) and the −1 where C is the initial adsorbate concentration (mg L ), C Artocarpus spp. were used in adsorption studies to remove i e is the concentration of adsorbate left in the solution after methylene blue, cadmium and copper (Kooh et al. 2016a, b; −1 equilibrium (mg L ), V is the volume of adsorbate solution Lim et al. 2012, 2015, 2017; Priyantha et al. 2013), show- (L) and m is the mass of adsorbent (g). ing their potentials as adsorbent to remove basic dyes and The parameters included in this study are the effects of heavy metals. contact time (5–240 min), pH (2–10) and initial AB25 con- −1 centrations (20–500 mg L ), with the change of one param- eter at a time while keeping the rest constant. Materials and methods There are many models that have been used for character- ising the adsorption process. Data from the effect of initial Preparation of adsorbents and adsorbate dye concentration were fitted into three adsorption isotherm models (Langmuir, Freundlich and Dubinin–Radushkevich Water lettuce (WL) was collected from a choked drain in the models) while the data from effect of contact time were fit- Rimba Horticulture Centre, Brunei-Muara district, Brunei ted into three kinetics models (pseudo-first-order, pseudo- Darussalam, while tarap and cempedak fruits, sold in local second-order and intraparticle diffusion models). The best markets, were randomly selected and purchased. The peels models that described the adsorption data were determined were separated from the fruit. After washing all the three by looking at the values of the R and two error functions samples with distilled water, they were then dried in an oven which are the sum of absolute error (EABS) and Chi-square at 70 °C. The dried adsorbents were then blended, sieved and test (χ ) as shown in Eqs. (3) and (4), respectively: kept in desiccators. −1 AB25 (C H N NaOS, M 416.38 g mol , 45% dye 20 13 2 5 r purity, Sigma-Aldrich) was used as received. EABS: q − q , (3) e,exp e,cal i=1 Characterisation of adsorbents (q − q ) e,exp e,cal The adsorbents were characterised using an X-ray fluores- ∶ , (4) max cence (XRF) spectrophotometer (PANalytical Ax ios ) for q e,exp i=1 the elemental analyses, a Fourier transform infrared (FTIR) spectrophotometer (Shimadzu Model IRPrestige-21 spec- where q is the experimental data while q is the calcu- e,exp e,cal lated data from the isotherm or kinetics model. trophotometer) for functional group analyses and a scanning 1 3 Applied Water Science (2018) 8:61 Page 3 of 10 61 Table 1 XRF elemental Thermodynamics experiments Normalised percentage (%) analyses of WL, TP and CP Element WL TP CP The Van’t Hoff equation was used for determining the ther - modynamics nature of the adsorption process and the equa- Mn 0.41 0.57 0.82 tions are as follows: Al 0.55 0.18 0.19 Si 1.21 1.46 2.05 ◦ ◦ ◦ ΔG =ΔH − TΔS , (5) Mg 1.45 1.75 2.13 Na 1.55 ND ND ΔG =−RTln k, (6) S 1.59 1.89 1.89 P 1.79 1.88 0.75 k = , (7) Cl 18.30 3.07 0.13 Ca 19.70 3.49 9.60 ◦ ◦ O 22.80 26.60 28.50 ΔS ΔH ln k = − , (8) K 28.70 38.00 28.70 R RT −1 where ∆G° (kJ  mol ) is the Gibbs free energy, ∆H° ND not undetected −1 −1 −1 (kJ mol ) is the change in enthalpy, ∆S° (J mol  K ) is the change in entropy, T (K) is the temperature, k is the dis- present in an adsorbent. Figure 1 shows the FTIR spectra −1 tribution coefficient for adsorption, C (mg L ) is the con- for WL, TP and CP before AB25 treatment. In general, centration of AB25 adsorbed on the adsorbent at equilibrium hydroxyl and/or amino group can be found at the stretching −1 −1 and R is the gas constant (8.314 J mol  K ). −1 −1 band of around 3300–3400 cm . Band at around 2900 cm The adsorption experiment was carried out at five differ - indicates the C–H bond stretching while N–H bending ent temperatures (25, 40, 50, 60 and 70 °C) using 20 mL of −1 −1 −1 (1630 cm ), phenyl (1413 cm ) and C–O–C (1022 cm ) −1 50 mg L AB25 at solution pH of 2.0. The thermodynam- −1 can be found at around 1610, 1400 and 1060 cm , respec- ics parameter ∆G° was calculated using Eq. (6), while ∆H° tively. After AB25 treatment as shown in Fig. 1b, it can be −1 and ∆S° were calculated from the linear plot of ln k vs T observed that there is a significant shift in stretching band of Eq. (8). for OH and NH groups as well as NH bending band. Hence, these functional groups could be involved in AB25 adsorp- Regeneration experiments tion onto the adsorbents’ surfaces. The surface morphology analyses of the WL, TP and CP The detailed procedures of the regeneration experiment are shown in Fig. 2, which provide visual insights into the surface of adsorbent particles. Both WL and CP have rough were described in our previous work (Dahri et al. 2014). In short, the spent adsorbents were prepared using 20 mL and uneven surface while TP has smoother looking surface. −1 All the adsorbents did not have any orderly pattern. of 50 mg L AB25 and regenerated using distilled water, −1 −1 0.1 mol L HNO and 0.1 mol L NaOH. The regeneration Study of pH medium experiments were carried out for five cycles. The electrostatic interactions between the adsorbent’s sur- face and the dye are directly affected by pH, thus making Results and discussion it important to investigate the effect of pH. The pH is a pzc point where the net charge on the surface of the adsorbent is Characterisations of adsorbents zero. When solution pH > pH , the adsorbent’s surface is pzc predominant negatively charged, while pH < pH resulted pzc Characterisations of the adsorbents are important as they in predominantly positively charged surface. The pH of pzc provide much useful information regarding the adsorbents. WL and CP was determined to be 6.40 and 4.01, respec- The elemental analyses of adsorbents are summarised in tively, while for TP was determined as 4.40 in previous work Table 1, which provide the information regarding the micro- (Lim et al. 2015). Figure  3 indicates that as the solution mineral and macro-mineral contents. pH decreased, the dye removal gradually increased for the Molecules such as hydroxyl and carbonyl groups con- all three adsorbents (WL, CP and TP). The optimum pH tain dipole moment which can absorb infrared radiation at was observed to be at pH 2.0 for all three adsorbents. This specific frequencies and is characteristic for each functional behaviour is explained with the concept of pH , where at pzc group (Pavia et al. 1996). This makes FTIR analysis to be pH 2, the anionic AB25 dye molecules are attracted to the very useful in the characterisation of functional groups predominant positively charged surface and this observation 1 3 61 Page 4 of 10 Applied Water Science (2018) 8:61 Fig. 1 FTIR spectra of a WL, b TP, c CP, d WL-AB25, e TP-AB25 and f CP-AB25 suggests that the adsorption of AB25 onto these adsorbents place. The dye adsorption slowed down to a plateau which depends mainly on ionic interaction. was due to saturation of adsorption sites and reaching the equilibrium of the adsorption process. Time duration of Eec ff t of contact time and kinetics modelling 120 min was sufficient for WL-AB25 system to attain equi- librium, while 180 min was sufficient for both CP-AB25 and The effect of contact time is important in adsorption study TP-AB25 systems. as vital information such as the time required for adsorption Three most commonly used kinetics models (pseudo- process to attain complete equilibrium can be obtained. The first-order (Lagergren 1898), pseudo-second-order (Ho and data of the effect of contact time are summarised in Fig.  4. McKay 1999) and intraparticle diffusion (Weber and Morris The observed trend for all the three adsorption systems 1963) models) were used for characterising the kinetics data was the rapid increase in adsorption during the start of the and their equations are as follows: adsorption process which was attributed to the presence of many vacant sites being available for adsorption to take Pseudo-first-order: log(q − q )= logq − k , (9) e t e 1 2.303 1 3 Applied Water Science (2018) 8:61 Page 5 of 10 61 Fig. 2 SEM images displaying the surface morphologies of a WL, b TP and c CP at ×500 magnification −1 pseudo-first-order rate constant (min ), k is pseudo-sec- −1 −1 ond-order rate constant (g mg min ), k is the intraparti- −1 −1/2 cle diffusion rate constant (mg g   min ) and C is the intercept. The parameters of the pseudo-first-order, pseudo- second-order and intraparticle diffusion models were obtained from the linear plots of ln(q − q ) vs t, vs t and q e t t vs t , respectively. The kinetics parameters for all adsorbents are sum- marised in Table  2. The values of R were highest for pseudo-second-order model for all three adsorbents 2468 10 TP CP WL pH when compared to pseudo-first-order which indicates that the pseudo-second-order model was the most suit- Fig. 3 The effect of pH on the removal of AB25 using WL, CP and able to describe the kinetics data. This was reinforced TP by the lower values of the error functions χ and EABS for pseudo-second-order model and also the agreement between the values of q and q . e,exp e,cal t 1 t According to Liu (2008), a pseudo-second-order kinet- Pseudo-second-order: = + , (10) q q k q ics implies that the adsorption rate follows a second-order t 2 e rate law with respect to the adsorbent’s surface adsorption 1∕2 sites instead of the adsorbate in bulk solution. The poor Intraparticle diffusion: q = k t + C, (11) t 3 fitting of pseudo-first-order model is due to it not being a where q is the amount of adsorbate adsorbed per gram of true order equation but rather an approximate solution to −1 adsorbent (mg  g ) at time t (min), k is the 1 3 Percentage removal (%) 61 Page 6 of 10 Applied Water Science (2018) 8:61 20 categorised into three phases, which are the initial fast exter- (A) nal diffusion, surface adsorption (intraparticle diffusion) and lastly the equilibrium phase. By fitting the kinetics data into the intraparticle diffusion model, the rate-limiting phase of the adsorption process can be determined. According to the intraparticle diffusion model, if the linear plot of q vs t crossed the origins, then the intraparticle diffusion is the rate-limiting step. As seen in Table 2, all the values of the intercepts are not zero, this indicates that the rate-limiting step was not intraparticle diffusion and other mechanism may have been involved. This observation is very common and has been reported in the removal of hazardous dyes 050100 150200 250 (malachite green and rhodamine B) using water fern (Kooh t (min) 20 mg L⁻¹ 50 mg L⁻¹ 100 mg L⁻¹ et al. 2016d, e), and also in the adsorption of methyl violet 2B using soya waste (Kooh et al. 2016c). (B) Eec ff t of initial dye concentration and isotherm study The effect of varying the initial dye concentration on the removal of AB25 onto the adsorbents is shown in Fig. 5. Both WL and CP showed increase in dye uptake as the con- centration increased while TP only showed an increase up to −1 200 mg L before the dye uptake decreased. The increase in dye concentration provided enough force for the mass 050100 150200 250 20 mg L⁻¹ 50 mg L⁻¹ 100 mg L⁻¹ t (min) transfer to occur from the bulk solution and, therefore, an increase in the dye uptake was observed. TP, however, dis- played different trend from the other adsorbents whereby (C) −1 the dye uptake decreased after 200 mg L . This might be due to the low affinity of TP towards AB25 and although both TP and CP are both of the same genus, their affinities 5 toward AB25 may differ as the peels are made up of different chemical compositions. The adsorption data were characterised using three iso- therm models: Langmuir (Langmuir 1916), Freundlich (Fre- undlich 1906) and Dubinin–Radushkevich (D–R) (Dubinin 050100 150200 250 and Radushkevich 1947) as follow: 20 mg L⁻¹ 50 mg L⁻¹ 100 mg L⁻¹ t (min) C C e e Langmuir: = + , (12) q k q q e L m m Fig. 4 The adsorption of AB25 as function of time by a WL, b TP and c CP Freundlich: ln q = ln C + ln k , e e F (13) the first-order rate mechanism. The reason being the num- 2 2 D−R: lnq = ln q − k  , (14) e m DR ber of sites available does not equate to q of the pseudo- first-order model, and also the parameter of log q often = RT ln 1 + , differs from the intercept of the plot of (log q  − q ) vs t (15) e t (Eq. 9) (Aharoni and Sparks 1991). The diffusion mechanism of the adsorption process where q is the maximum adsorption capacity of the adsor- −1 is characterised using the intraparticle diffusion model bent (mg  g ), k is the Langmuir adsorption constant −1 1−1/n 1/n −1 because the pseudo-first and pseudo-second-order models (L mg ), k (mg L g ) is the adsorption capacity of are not applicable. The diffusion process can generally be the adsorbent, n is the Freundlich constant where adsorption 1 3 -1 q ( mg g ) q (mg g⁻¹) q ( mg g⁻¹) e e Applied Water Science (2018) 8:61 Page 7 of 10 61 Table 2 Summary of the kinetic Absorbent WL TP CP parameters −1 C (mg L ) 20 50 100 20 50 100 20 50 100 Pseudo-first order −1  q (mg g ) 3.5 5.1 5.6 2.3 0.9 5.1 3.7 2.6 5.6 e,cal −1  q (mg g ) 9.1 14.2 17.5 3.3 3.5 5.6 4.9 6.5 7.4 e,exp  k 0.019 0.017 0.009 0.011 0.010 0.010 0.013 0.009 0.012  R 0.911 0.868 0.781 0.948 0.501 0.863 0.991 0.560 0.931  χ 46 75 108 7 24 3 7 36 10  EABS 63 96 127 13 27 7 15 45 21 Pseudo-second order −1  q (mg g ) 9.4 14.6 17.1 3.5 3.5 11.3 5.3 6.4 8.1 e,cal −1  q (mg g ) 9.1 14.2 17.5 3.3 3.5 5.6 4.9 6.5 7.4 e,exp  k 0.013 0.009 0.008 0.010 0.051 0.0003 0.006 0.014 0.003  R 0.999 0.999 0.996 0.980 0.998 0.267 0.984 0.991 0.991  χ 4 8 7 3 2 4 5 4 4  EABS 14 23 24 7 5 8 11 10 14 Intraparticle diffusion  k 0.810 0.905 0.993 0.176 0.183 0.386 0.323 0.582 0.526  C 2.5 5.8 7.7 0.7 1.7 − 0.5 0.7 1.2 0.5  R 0.980 0.954 0.627 0.925 0.943 0.856 0.950 0.891 0.946 R = , (16) (1 + k C ) L o −1 where C (mg L ) is the highest initial dye concentration. The value of R indicates if the isotherm is unfavour- able (R > 1), favourable (0 < R < 1), linear (R = 1), or L L L irreversible (R = 0). The Freundlich model is another commonly used iso- therm model, and if applicable, would assume formation of multilayer of adsorbates on adsorbent’s surface, and the D–R isotherm also assumes heterogeneous surface of the adsorbent and is temperature dependent. D–R isotherm 0100 200300 400500 600 is also used to determine the thermodynamic nature of -1 WL TP CP C (mg L ) the adsorption by estimating the mean free energy of the −1 sorption per molecule of adsorbate, E (kJ mol ), which Fig. 5 The effect of AB25 concentration on the adsorption process of is expressed as WL, TP and CP E = . (17) process is considered favourable if 1 < n < 10, k is a D–R F DR 2k DR 2 −2 constant (mol  kJ ), ε is the D–R isotherm constant which is also known as the Polanyi potential, R is the gas constant The linear plots of C /q vs C , ln q vs ln C , and ln q vs e e e e e e −3 −1 −1 (8.314 × 10  kJ mol  K ) and T is temperature (K). ε were used for calculating the parameters for the Langmuir, The Langmuir model assumes a maximum adsorption Freundlich and D–R isotherm models, respectively. resulting in a monolayer film whereby once an adsorption Table  3 summarises the isotherm models’ parameters site is occupied it will not be available for another adsorbate. for the adsorption of AB25 by WL, TP and CP. The Lang- The favourability of the adsorption process can be assessed muir, Freundlich and D–R isotherm models are compared by a dimensionless constant, separation factor (R ), which is with each other to determine which model is suitable to expressed as describe the adsorption process of AB25 onto the adsor- bents. Between the three models, the Langmuir possessed the highest R values for TP and WL while the Freundlich 1 3 -1 q (mg g ) e 61 Page 8 of 10 Applied Water Science (2018) 8:61 Table 3 Parameters of the Langmuir, Freundlich and D–R isotherm (A) models T (°C) WL TP CP Langmuir isotherm −1  q (mg g ) 24.5 10.5 21.2  k 0.070 0.015 0.013  R 0.027 0.104 0.121  R 0.992 0.685 0.963  χ 4.4 5.4 2.7  EABS 19.2 16.1 13.1 H₂O HNO₃ NaOH Number of Cycle Freundlich isotherm 1−1/n 1/n −1  K (mg L g ) 7.6 1.6 2.5 (B)  n 5.0 3.5 3.1 2 30  R 0.906 0.654 0.972  χ 1.6 5.0 1.2  EABS 14.0 15.1 8.6 Dubinin–Radushkevich isotherm −1  q (mg g ) 19.7 7.2 12.1 2 −2  k (mol  kJ ) 1.8 25.4 14.7 DR −1  E (kJ mol ) 0.521 0.140 0.184  R 0.691 0.386 0.448 H₂O HNO₃ NaOH Number of cycle  χ 21.4 7.2 10.2  EABS 41.0 18.5 30.1 (C) model has the highest R value for CP. In terms of error analyses, however, the Freundlich model showed the lowest value amongst the isotherm models. Hence, the adsorption process fitted to both the Langmuir and Freundlich models which can be used for describing the adsorption process. Compared to CP and WL, TP has lower R values (< 0.700) for all of isotherm models which showed the incompatibility of these models in describing the adsorp- H₂O HNO₃ NaOH Number of cycle tion of AB25 onto TP probably due to their low affinity for each other. Fig. 6 Regeneration experiment of a WL, b TP and c CP −1 The q of the WL, TP and CP are 24.5, 10.5, 21.2 mg g , respectively, which are of similar levels with other adsor- bents that were reported in the literature: diatomite (21.4) adsorption systems were endothermic in nature where heat −1 (Badii et al. 2010) and wood dust (24.4 mg g ) (Hanafiah was gained from the surrounding. ∆S° for WL, CP and TP −1 −1 −1 et al. 2012), but lower than soya bean waste (38.5 mg g ) was determined to be − 75, 42 and 32 J mol  K . −1 (Dahri et al. 2016) and water fern (50.5 mg g ) (Dahri et al. 2016). Regeneration experiment Thermodynamics studies Spent adsorbents contain hazardous dye substances which should be disposed properly by incineration. Dumping to The thermodynamics parameters were investigated for tem- landfill is not a proper way of disposing hazardous waste peratures ranging from 25 to 70 °C. All the three adsorbents as leaching of the dye may occur. However, incineration (WL, CP, TP) displayed ∆G° that became more negative as also has many disadvantages, as it may cost more due to the temperature increased, and this indicates the spontaneity fuel needed for burning, and hazardous gas being released of the adsorbent–adsorbate systems. The ∆H° for WL, CP to the environment. Regeneration experiment in this study −1 and TP were determined to be 20.3, 15.2 and 12.4 kJ mol , investigated an alternative route to direct disposal of the respectively, where these positive values indicate these spent adsorbent. It is perceived that regeneration of spent 1 3 Percentage removal (%) Percentage removal (%) Percentage removal (%) Applied Water Science (2018) 8:61 Page 9 of 10 61 Dahri MK, Kooh MRR, Lim LBL (2014) Water remediation using adsorbent may further reduce the total cost of treatment by low cost adsorbent walnut shell for removal of malachite green: adsorption. The regeneration experiments’ data are summa- equilibrium, kinetics, thermodynamic and regeneration studies. J rised in Fig. 6. For WL, it can be observed that all the three Environ Chem Eng 2:1434–1444 solvents’ washing successfully maintained the dye adsorp- Dahri MK, Kooh MRR, Lim LBL (2016) Adsorption of toxic methyl violet 2B dye from aqueous solution using Artocarpus hetero- tion close to the original level. For CP and TP, there were phyllus (Jackfruit) seed as an adsorbent. Am Chem Sci J 15:1–12 slight reductions in dye adsorption for every successive Dubinin MM, Radushkevich LV (1947) Equation of the characteristic cycle for water and acid wash; however, improvement was curve of activated charcoal. Proc Acad Sci 55:327 observed for basic wash. This behaviour may be due to the Freundlich HMF (1906) Over the adsorption in solution. J Phys Chem 57:385–471 removal of low molecular fats, lignin and other plant materi- Fu Y, Viraraghavan T (2001) Fungal decolorization of dye wastewaters: als with uncovered functional groups that may have inter- a review. Biores Technol 79:251–262 acted with the adsorbates. Investigations on the improvement Hanafiah MAKM, Ngah WSW, Zolkafly SH, Teong LC, Majid ZAA in dye adsorption by basic wash have been reported in few of (2012) Acid blue 25 adsorption on base treated Shorea dasyphylla sawdust: kinetic, isotherm, thermodynamic and spectroscopic our previous works (Dahri et al. 2014; Kooh et al. 2016d). analysis. J Environ Sci 24:261–268 Ho YS, McKay G (1999) Pseudo-second order model for sorption pro- cesses. Process Biochem 34:451–465 Kooh MRR, Dahri MK, Lim LBL (2016a) Jackfruit seed as a sustain- Conclusions able adsorbent for the removal of Rhodamine B dye. J Environ Biotechnol Res 4:7–16 The optimal conditions of the adsorption of AB25 by WL, Kooh MRR, Dahri MK, Lim LBL (2016b) The removal of rhodamine TP and CP were 2 h of contact time at pH 2. FTIR analysis B dye from aqueous solution using Casuarina equisetifolia nee- dles as adsorbent. Cogent Environ Sci 2:1140553 indicated both the OH and NH groups might be involved Kooh MRR, Dahri MK, Lim LBL, Lim LH, Malik OA (2016c) Batch in the adsorption of the dye on the adsorbents’ surfaces. adsorption studies of the removal of methyl violet 2B by soya bean CP and WL’s experimental data can be described using the waste: isotherm, kinetics and artificial neural network modelling. Langmuir, Freundlich and pseudo-second-order models. TP Environ Earth Sci 75:783 Kooh MRR, Lim LBL, Lim LH, Bandara JMRS (2016d) Batch has the lowest affinity towards AB25 resulting in incompat- adsorption studies on the removal of malachite green from water ibility with the isotherm models. The spent adsorbents can by chemically  modified Azolla pinnata. Desalin Water Treat be regenerated using 0.1 M NaOH. 57:14632–14646 Kooh MRR, Lim LBL, Lim LH, Dahri MK (2016e) Separation of toxic Acknowledgements The authors are grateful to the Government of rhodamine B from aqueous solution using an efficient low-cost Brunei Darussalam and the Universiti Brunei Darussalam for their sup- material, Azolla pinnata, by adsorption method. Environ Monit port. The authors expressed their gratitude to the Centre for Advanced Assess 188:1–15 Material and Energy Sciences (CAMES) of Universiti Brunei Darus- Kooh MRR, Dahri MK, Lim LBL (2017a) Removal of methyl violet salam for their generosity in the usage of XRF machine. 2B dye from aqueous solution using Nepenthes rafflesiana pitcher and leaves. Appl Water Sci 7:3859–3868 Kooh MRR, Dahri MK, Lim LBL (2017b) Removal of the methyl Compliance with ethical standards violet 2B dye from aqueous solution using sustainable adsorbent Artocarpus odoratissimus stem axis. Appl Water Sci 7:3573–3581 Conflict of interest All authors declare no conflict of interest. Lagergren S (1898) Zur Theorie der Sogenannten Adsorption gel Ster Stoffe. K Sven Vetenskapsakad Handl 24:1–39 Open Access This article is distributed under the terms of the Crea- Langmuir I (1916) The constitution and fundamental properties of sol- tive Commons Attribution 4.0 International License (http://creat iveco ids and liquids. J Am Chem Soc 38:2221–2295 mmons.or g/licenses/b y/4.0/), which permits unrestricted use, distribu- Lim LBL, Priyantha N, Tennakoon DTB, Dahri MK (2012) Biosorp- tion, and reproduction in any medium, provided you give appropriate tion of cadmium(II) and copper(II) ions from aqueous solution credit to the original author(s) and the source, provide a link to the by core of Artocarpus odoratissimus. Environ Sci Pollut Res Int Creative Commons license, and indicate if changes were made. 19:3250–3256 Lim LBL, Priyantha N, Hei Ing C, Khairud Dahri M, Tennakoon DTB, Zehra T, Suklueng M (2015) Artocarpus odoratissimus skin as a potential low-cost biosorbent for the removal of methylene blue and methyl violet 2B. 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Desalin Water Treat 54:2592–2600 Priyantha N, Lim LBL, Tennakoon DTB, Mansor NHM, Dahri MK, Chieng HI (2013) Breadfruit (Artocarpus altilis) waste for biore- Publisher’s Note Springer Nature remains neutral with regard to mediation of Cu (II) and Cd(II) ions from aqueous medium. Cey- jurisdictional claims in published maps and institutional affiliations. lon J Sci (Phys Sci) 17:19–29 Robinson T, McMullan G, Marchant R, Nigam P (2001) Remedia- tion of dyes in textile effluent: a critical review on current treat- ment technologies with a proposed alternative. Bioresour Technol 77:247–255 Tang YP, Linda BLL, Franz LW (2013) Proximate analysis of Arto- carpus odoratissimus (Tarap) in Brunei Darussalam. Int Food Res J 20:409–415 1 3

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