Environmental Technology

Wang, Wen; Nemati, Mehdi

doi: 10.1080/09593330.2019.1650122pmid: 31378149

Anoxic co-biodegradation of linear and cyclic naphthenic acids (NAs) namely octanoic acid, trans-4-methyl-1-cyclohexane carboxylic acid (trans-4MCHCA), cis- and trans-4-methyl-1-cyclohexane-acetic acids (cis-4MCHAA and trans-4MCHAA) was investigated in denitrifying biofilm reactors. In all evaluated compositions, co-biodegradation of NAs was coupled to denitrification, with octanoic acid showing the fastest biodegradation rate (1180.4 mg L−1 h−1 at loading rate of 1180.4 mg L−1 h−1), followed by trans-4MCHCA (398.1 mg L−1 h−1 at loading rate of 435.8 mg L−1 h−1), trans-4MCHAA (25.7 mg L−1 h−1 at loading rate of 221.7 mg L−1 h−1), and cis-4MCHAA (5.3 mg L−1 h−1 at loading rate of 16.9 mg L−1 h−1). Biodegradation of octanoic acid and trans-4MCHCA were not influenced by the presence of recalcitrant NAs (cis- and trans-4MCHAA). Co-biodegradation of cis- and trans-4MCHAA with octanoic acid, trans-4MCHCA, or their combination enhanced the biodegradability of these recalcitrant NAs, with the positive impact being more pronounced for trans-4MCHCA. Finally anoxic co-biodegradation of NAs under denitrifying conditions proceeded at rates that were faster than the aerobic rates obtained in similar mixtures. Anoxic biodegradation, therefore, is an effective alternative for in situ treatment of oil sands process water in anoxic stabilization ponds amended with nitrate, or as an ex situ treatment approach in denitrifying bioreactors whereby the cost and technical challenges of aeration are eliminated.

Oliveira, H. A.; Azevedo, A.; Rubio, J.

doi: 10.1080/09593330.2019.1650123pmid: 31378156

Engineered nanoparticles of TiO2 (TiO2-NPs) are used in the industry for a great number of applications. After their usage, the particles end up in aquatic environments, contaminating supply waters and watercourses. Bench-scale studies report removal of TiO2-NPs (450 nm, the mean volumetric diameter) by flocculation followed by settling or by dissolved air flotation (4 bar saturation pressure and 30% recycling ratio). Floc formation was conducted after heterocoagulation with iron hydroxide (30–40 mg L−1 Fe3+) and gelatinized corn starch (10–20 mg L−1) as flocculant, at pH 7. Particle size distribution and zeta potential, removal efficiencies as a function of time and microphotography of flocs were analyzed. Mechanisms involve ferric hydroxide precipitation, heterocoagulation with the nanoparticles and flocculation of the loaded carrier precipitates with gelatinized starch. Best results showed removals between 95–100% of TiO2-NPs, either by settling or flotation after 5 min. Clear treated waters with low turbidity < 3 nephelometric turbidity units (NTU) and TiO2-NPs concentrations <1 mg L−1 were obtained. A practical advantage in DAF was the higher solids content (1.9% w/w) of the sludge, when compared to settling (0.7% w/w). This would facilitate the sludge dewatering and disposal, but DAF has the disadvantage of the poor efficiency at high concentration of the nanoparticles of titanium oxide (>100 mg L−1). Conversely, the removal by settling of the flocs increased at high dosages. It is believed that both processes are sustainable in terms of reagents and the removal efficiencies of TiO2 nanoparticles from water.

Milato, Jônatas V.; França, Rodrigo J.; Marques, Mônica R. C.

doi: 10.1080/09593330.2019.1650833pmid: 31378165

Pyrolysis of oil sludge from the petroleum industry in contact with three mesoporous zeolite catalysts (CBV 720, 760 and 780) was carried out at 450°C to obtain oil rich in paraffin. The properties of the catalysts were characterized by XRD, XRF, NH3-TPD, FT-IR, TGA and nitrogen ad/desorption isotherms, while the pyrolysis oil was analysed by GC-MS. The products obtained in the presence of mesoporous zeolites showed selectivity for conversion of light hydrocarbons with decreased content of aromatic compounds. The homogeneous porosity distribution of the CBV 780 was the determining factor in catalytic pyrolysis. The residue could be treated by pyrolysis using mesoporous zeolite. The use of this catalyst produced 56% oil fraction with the highest yield of light hydrocarbons (96%). Compared with the thermal pyrolysis of this waste, the use of mesoporous zeolitic catalysts increased the production of light hydrocarbons and reduced the production of aromatic compounds in the pyrolysis oil from sludge.

Trojanowicz, Karol; Trela, Jozef; Plaza, Elzbieta

doi: 10.1080/09593330.2019.1650834pmid: 31474198

An explanation of possible mechanism of efficient PN/A in hybrid bioreactors was presented. The bottleneck process is nitritation. Surplus nitrite production by ammonium oxidizing bacteria (AOB) is required for assuring the activity of anammox bacteria and eliminating nitrite oxidizing bacteria (NOB). It will be possible if nitrogen removal rate by AOB (r N_AOB) is higher than NOB (r N_NOB). It was shown that in biofilm AnAOB bacteria should out-compete NOB, whereas nitrogen transformation rates by AOB are usually lower than NOB. However, the growth of r-AOB in activated sludge allows out-selecting NOB. Impact of ammonium-, nitrite–nitrogen and suspended biomass concentration in hybrid PN/A systems on nitrogen removal rates in the temperature ranges from 10°C to 25°C was presented and discussed. Because bulk liquid ammonium nitrogen concentration can be higher in SBR bioreactors (after certain period of time after aeration starts) or in the initial zones of plug-flow systems than in fully mixed systems, conditions for running efficient PN/A are more favourable in intermittently aerated ‘IFAS-SBR’ or ‘IFAS-plug flow’ bioreactors.

Vieira, Gabriela Bonfanti; Scaratti, Gidiane; Rodembusch, Fabiano Severo; De Amorim, Suelen Maria; Peterson, Michael; Puma, Gianluca Li; Moreira, Regina De Fátima Peralta Muniz

doi: 10.1080/09593330.2019.1651402pmid: 31407626

The impact of cerium (Ce) and neodymium (Nd) rare-earth metal doping of TiO2 prepared by the hydrothermal method was investigated to tailor effective photocatalytic degradation of coloured wastewater under UV or visible illumination. The hydrothermal treatment of TiO2 decreased the pHpzc from 6.3 to 3.1–3.8 favouring the affinity for cationic water contaminants. Doping with Ce and Nd modified the crystallinity and the morphology of the photocatalysts and significantly increased the BET surface area and the adsorption capacity of cationic dyes. The photocatalytic activity under UV light irradiation decreased due to shielding of the catalyst active area by excessive amount of dye adsorbed. Conversely, the photocatalytic activity of the Ce and Nd doped TiO2 increased under visible light irradiation by 1.2 times as a result of the dye photosensitization effect. It was demonstrated that two-steps dark adsorption and photocatalytic reaction or one-step simultaneous adsorption and reaction can produce significantly different results for the photocatalytic degradation of dyes in coloured waters, the rate being controlled by the competitive adsorption of the reacting organics and the H2O/OH− species. The reaction is driven by the radical oxygen species (ROS) formed on the catalyst surface the nature of which, differs under UV or visible light irradiation. The Ce-doped TiO2 and Nd-doped TiO2 photocatalysts with 0.5% rare-earth content were found to be efficient in the degradation of MB in aqueous solution, removing the colour and reducing the toxicity of wastewaters.

Fang, Yinchun; Liu, Xinhua; Wu, Xiao; Tao, Xuchen; Fei, Wenqing

doi: 10.1080/09593330.2019.1652695pmid: 31401935

Polyurethane (PU) nanofibers possess large specific surface area and excellent mechanical properties which have been used as the matrix for many applications. Phytic acid is the biocompatible and environment-friendly organic acid with excellent chelating ability of heavy metal ions due to it contains 6 phosphate groups. In this study, the PU/phytic acid nanofibrous membrane has been successfully produced by electrospinning which was used for Pb2+ removal. Though phytic acid would improve the hydrophilicity and reduce the mechanical properties to a certain extent, the phytic acid-modified PU nanofibrous membrane still possessed excellent mechanical properties. The PU/phytic acid nanofibrous membrane achieved the highest adsorption capacity (136.52 mg/g) of Pb2+ under the condition of the pH of Pb2+ solution was 6 and the adsorption temperature and time were 20°C and 10 h which was over 6 times higher the unmodified one’s (21.06 mg/g). These results demonstrated that the electrospun PU/phytic acid nanofibrous membrane could obtain high adsorption capacity of Pb2+ and it would achieve the potential application in the fields of the removal of heavy metal ions.

Adesina, Ajayi O.; Elvis, Okoronkwo A.; Mohallem, Nelcy D.S.; Olusegun, Sunday J.

doi: 10.1080/09593330.2019.1652696pmid: 31407630

Alumina–zirconia (Al2O3–ZrO2) composite was prepared by combustion method and used to remove Congo red and Methylene blue from aqueous solutions. It was characterized using SEM–EDS, XRD and gas adsorption techniques. The results obtained from gas adsorption and SEM agree with each other, showing meso- and macro-porosity of inter-agglomerate pores. The removal of the two dyes was pH dependent, acidic pH favoured Congo red removal, while basic pH favoured Methylene blue. The, mechanism of adsorption was not limited to electrostatic attraction between the adsorbent and the dye molecules. Adsorption kinetic of both dyes was consistent with Pseudo-second-order model. The data obtained fitted to Langmuir and Liu isotherm models, with the maximum adsorption capacity of 57. 50 and 53.44 mg g–1 for Congo red and Methylene blue, respectively. The thermodynamic parameters indicated that the adsorption is spontaneous and exothermic. The mechanism of adsorption was elucidated using XRD and FTIR techniques.

Ma, Qiang; Xiang, Jun-chen; Yang, Yi-cong; Xiao, Heng-lin; Wan, Juan

doi: 10.1080/09593330.2019.1652697pmid: 31454300

Mechanical properties of fiber-reinforced soil after soaking in heavy metal ion solution have great influences on safety and stability of the reinforcement, herein the mechanical properties of optimum moisture content of different concentrations of zinc ions contaminated soil were studied through shear test, compression test and triaxial test. The compressive modulus, compression coefficient and porosity ratio of different concentrations of the zinc-ion contaminated soil under different pressure were studied, and the variation characteristics of internal friction angle and cohesion were also investigated, thereafter, the causes of the change of cohesion and internal friction angle were analyzed from the microscopic perspective. The results show that the shear strength of contaminated reinforced soil increases with the increase of confining pressure at the same zinc ions concentration. And at the same confining pressure, with the increase of zinc ions concentration, the shear strength of contaminated reinforced soil first increases and then decreases. With the increase of zinc ions concentration, the internal friction angle and compression coefficient increase, the cohesion and the modulus of compression decrease. With the increase of normal stress, the compression coefficient decreases firstly and then increases, and the compression modulus increases and then decreases. With the concentration of zinc ions increases at lower normal stress, the amount of shrinkage increases and the compression coefficient decreases. While at higher normal stress, the compressive modulus decreases and the compression coefficient increases.

Bi, Wenlong; Dong, Wenbo

doi: 10.1080/09593330.2019.1652698pmid: 31453752

Degradation of OTC under different light with Fe2+/ was investigated, and the reaction mechanism was also discussed. Although Fe(II/III)- complex could weaken the inhibitory effect of Fe(II/III)-OTC complex on the detection of OTC by HPLC, the acidification could make inhibition become minimal. Response surface methodology was used to optimize the Fe2+/ dosage at low concentrations of Fe2+ and H2C2O4. When the OTC concentration was 0.04 mM, the optimal dosage was OTC:Fe2+:H2C2O4 = 1:1.25:2 to attain a removal rate of 80% after 60 min under simulated solar light, and HO• for degradation of OTC with Fe2+/ could be 53%, furthermore, removal rate of OTC just increased 3 percentage points at 60 min when the simulated solar light changed into UV-254 nm, however, OTC could also be degraded for 48.89% removal rate after 3 h illumination of simulated visible light. The influence of Cl−, , , , , or on the degradation of OTC with Fe2+/ under simulated solar light was studied. could inhibit degradation for could react with free radicals, but the reason of inhibition of degradation by , or was its influence on pH, whereas Cl−, and had no influence on degradation. In addition, when the concentration of was higher than 4 mM, could promote the degradation for the direct photolysis of OTC at alkaline (pH > 10). Four products were detected by LC-MS, and the OTC degradation pathway was discussed.

Cusioli, Luís Fernando; Bezerra, Charleston de Oliveira; Quesada, Heloise Beatriz; Alves Baptista, Aline Takaoka; Nishi, Letícia; Vieira, Marcelo Fernandes; Bergamasco, Rosângela

doi: 10.1080/09593330.2019.1653381pmid: 31412750

Atrazine is an herbicide which is widely applied in sugarcane and corn crops. Its frequent use has resulted in environmental impacts, and its traces have been verified in surface and groundwater. Thus, it is necessary to remove this pollutant, and an alternative is the adsorption due to its universal nature, low-cost and ease of operation. Therefore, the objective of the present work was to study the adsorption capacity of atrazine by modified Moringa oleifera Lam. seed husks, a low-cost adsorbent. The biosorbent was subjected to c hemical and thermal treatment and was characterised by structural, morphological and textural analysis, which showed porous and heterogeneous characteristics, with a specific surface area of 5.77 m2 g−1. The kinetic study demonstrated equilibrium at 1200 min, with an adsorption capacity of 1.90 mg g−1 and the best fit was for the pseudo-second-order model. The isotherms were obtained at 298, 308 and 318 K. The Freundlich, Temkin and Langmuir models were applied to the experimental data, the latter being the best. The values of the thermodynamic parameters indicated that the biosorption was spontaneous, endothermic and reversible. The highest adsorption capacity obtained was 10.32 mg g−1, which was higher than several values found in the literature. The biosorbent was regenerated over three cycles, indicating its potential of atrazine removal from surface water.