Environmental Technology

Lu, Wencheng; Lu, Shiyao; Jing, Hua; Sun, Jiaxing; Ji, Lili; Guo, Jian; Wang, Yaning; Cai, Lu; Song, Fuquan; Song, Wendong

doi: 10.1080/09593330.2021.1918261pmid: 33856967

In this work, a new type of micromesoporous substance was prepared with fatty alcohol-polyoxyethylene ether (AEO) surfactant freezing penetration and pyrolysis using shells as raw materials. The obtained material exhibited good adsorbability and could be added to oil-contaminated soil to adsorb the pollutant, which resulted in the regeneration of the initially polluted soil. It was determined that the main component of the developed substance was CaCO3. Importantly, the conducted experiments revealed that the obtained mussel micromesoporous material displayed certain adsorption effects toward petroleum hydrocarbons in a diesel solution. Moreover, it was found that chemical adsorption was more optimal than physical adsorption. The soil remediation effect was the best when the content of the mussel micromesoporous material in the soil was 400 g/kg. Under these conditions, the removal rate of petroleum hydrocarbon was established at 49.38%. This study indicated that micromesoporous material has great potential in the application of oil contaminated soil remediation.

García-Triñanes, Pablo; Chairopoulou, Makrina A.; Campos, Luiza C.

doi: 10.1080/09593330.2021.1918262pmid: 33856974

In response to the escalating world water demand and aiming to promote equal opportunities, reverse osmosis desalination has been widely implemented. Desalination is however constantly subjected to fouling and scaling which increase the cost of desalination by increasing the differential pressure of the membrane and reducing the permeate flux. A bench-scale desalination equipment has been used in this research to investigate the mitigation of fouling and scaling. This study involved the performance of membrane autopsy for fouling characterisation with special attention to flux decline due to sulphate precipitation and biofouling. Visual inspection, scanning electron microscopy (SEM), energy-dispersive x-ray spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR) and microbiology tests (API) were performed. Results obtained showed the presence of diatoms, pseudomonas and polysaccharides as the main foulants causing biofouling. Analysis revealed sulphate deposits as well as aluminium, calcium and silica as the main elements contributing to inorganic scaling. Findings pointed out that the pre-treatment system of the small-scale reverse osmosis water treatment was inefficient and that selection of pre-treatment chemicals should be based on its compatibility with the membrane structure. The importance of characterisation for the verification of fouling mechanisms is emphasised.

Li, Weiying; Li, Yue; Wang, Feng; Chen, Sheng; Chen, Jiping

doi: 10.1080/09593330.2021.1918263pmid: 33856959

Chlorine and chloramine are widely used to maintain the microbial safety after drinking water treatment plants. Particles existing in the treated water may react with these chemical disinfectants, and impact the efficacy of disinfection. However, the protective effects of particles without-disinfectant demand on bacteria in the chlorination/chloramination are not well known. In this study, two laboratory-derived bacteria (Staphylococcus aureus and Escherichia coli) and two no-disinfectant demand particles (Fe2O3 and kaolin) in drinking water were selected to build particle-associated bacteria (PAB) systems, and their resistance to chlorine/chloramine was further assessed. Flow cytometry (FCM) was employed to image PAB systems and assess the removal rate of bacteria. The results were that particles showed protective effects on bacteria in half of chlorine experiments and 90% of chloramination. The protection was related to the combination form of particles and bacteria tied to neither particle species nor size, and there was no positive relationship between the protection effect and water turbidity. S. aureus attached to Fe2O3 had stronger resistance than kaolin, and kaolin protected E. coli better than Fe2O3. The same trend was observed in both chemical disinfectants, and more significant resistance had been shown in chloramination than chlorination. FCM images which gave a qualitative description on the combination states of different PAB systems may be a clue to explain the strength of the resistance. Environmental bacterial strains and particles are recommended in the future to explore practical applications.

Wu, Hongjian; Dorea, Caetano C.

doi: 10.1080/09593330.2021.1920626pmid: 33880970

Chlorine is a widely used water disinfectant in humanitarian emergency water supply. However, its effective application can be limited by the uncertainty in initial dose determination. The target free chlorine residual in water should achieve both health objectives and aesthetic considerations, but the varying field conditions and changing source water quality may affect the performance of chlorination strategies. A chlorine dose predictive tool could assist in initial dose determination. To this end, an accurate chlorine decay kinetic model can serve as a strong foundation for developing such a tool. In this study, a literature search identified 7 basic chlorine decay kinetic models that were subsequently tested with 610 different chlorine decay test data (from a semi-systematic literature search and laboratory-generated results). The models were then ranked based on their goodness of fit (R 2) and root mean square error. An empirical model, power models and parallel models were found able to fit most decay data with more than half of the regressions resulting in R 2 value over 0.97. First order models can achieve R 2 value above 0.95 when the data points in the rapid phase are excluded from the model fitting. The power models and parallel models can form a strong basis for developing a chlorine dose predictive tool if the power term and the ratio term (model parameters) can be controlled. An essential next step is to evaluate the relationships between easily obtainable water parameters in the field and the decay term in the models to allow rapid model calibration.

Guo, Guang; Liu, Chong; Tian, Fang; Ding, Keqiang; Wang, Huiya; Zhang, Can; Yang, Feng; Xu, Jin

doi: 10.1080/09593330.2021.1921042pmid: 33945429

The aim of the study was to verify the effect of bioaugmentation by the bacterial consortium YS with hydroxypropyl-β-cyclodextrin (HPCD) in a soil slurry. The bacterial consortium YS was enriched from a petroleum-polluted soil using pyrene as sole carbon resource. After 3 weeks, the degradation rate of phenanthrene in CK increased from 22.58% to 55.23 and 78.21% in bioaugmentation (B) and HPCD + bioaugmentation (MB) respectively. The degradation rate of pyrene in CK increased from 17.33% to 51.10% and 60.32% in B and MB respectively in the slurry. The augmented YS persisted in the slurry as monitored by 16S rRNA gene high-throughput sequencing and outcompeted some indigenous bacteria. Enhanced polycyclic aromatic hydrocarbon (PAH) degradation was observed in the addition of HPCD due to the enhanced bioavailability of phenanthrene and pyrene. Additionally, the amount of PAH-degrading bacteria and enzymatic activity in bioaugmentation with HPCD were higher than that in the CK group. The results indicated that bioaugmentation with a bacterial consortium and HPCD is an environmentally friendly method for the bioremediation of PAH-polluted soil.

Zhang, Xiuling; Peng, Lichong; Wang, Jiaona; Li, Congju

doi: 10.1080/09593330.2021.1921043pmid: 33881964

The removal of heavy metal ions in wastewater has a great significance to human health and environment protection. Metal organic framework possesses high surface area, rich porosity, tunable pore size and abundant active sites. However, the intrinsic aggregation and fragility of MOF nanoparticles make its poor adsorption and undesirable reusage. Herein, a facile and unique hot-pressing method is adopted to decorate the MOF nanoparticles on nickel foam (ZIF-8/NF), which simultaneously serves as self-supporting substrate of ZIF-8 nanoparticles and electrode of a self-powered multifunctional purification system. In adsorption, the ZIF-8/NF composite presents high Cu2+ removal rate of 49.5% with the concentration of 10 mg/100 ml. More importantly, integrating with electrochemistry, the Cu2+ removal rate of the ZIF-8/NF composite reaches 54.7% in 5 min. The superior performance is attributed to the comprehensive effects of ion exchange, chemical bonding and physical adsorption. Moreover, the low-cost, fast and scalable preparation contributes to commercially fabricate MOF nanoparticles on self-supported substrate to treat wastewater with high efficiency and good recyclability.

Jiang, Guomin; Jin, Linfeng; Pan, Qinglin; Peng, Ning; Meng, Yun; Huang, Lei; Wang, Haiying

doi: 10.1080/09593330.2021.1921044pmid: 33945450

In this paper, the effect of different crystal forms of Al2O3 on fluoride removal was studied. All crystal forms of Al2O3 were based on the same boehmite precursor and were obtained using a hydrothermal and calcination method. γ-Al2O3 had higher fluoride removal performance (52.15 mg/g) compared with θ-Al2O3 and α-Al2O3. Density functional theory (DFT) calculations confirmed that fluoride removal was greatest for γ-Al2O3, followed by θ-Al2O3 and α-Al2O3, and γ-Al2O3 possessed the strongest fluoride binding energy (–3.93 eV). The typical adsorption behaviour was consistent with the Langmuir model and pseudo-second-order model, indicating chemical and monolayer adsorption. Different metal ions were used to modify γ-Al2O3, and lanthanum had the best effect. Lanthanum oxide was shown to play an important role in fluoride removal. The best La/Al doping ratio was 20 At%. The adsorption process of the composite was also consistent with chemical and monolayer adsorption. When the La/Al doping rate was 20%, the adsorption capacity reached 94.64 mg/g. Compared with γ-Al2O3 (1.39 × 10−7 m/s), the adsorption rate of 20La-Al2O3 was 3.93 × 10−7 m/s according to the mass transfer model. Furthermore, DFT was used to provide insight into the adsorption mechanism, which was mainly driven by electrostatic attraction and ion exchange.

Duan, Fu-ang; Wang, Juan; Ismail, Sherif; Sung, Shihwu; Cui, Zhaojie; Ni, Shou-Qing

doi: 10.1080/09593330.2021.1921045pmid: 33944678

Polycyclic aromatic hydrocarbons (PAHs) as polar organic pollutants, their potential harm to the environment has caused widespread concern. This study describes a simple method to prepare modified aerobic granular sludge (AGS) by hydroxypropyl-β-cyclodextrin (HP-β-CD). Using HP-β-CD modified AGS as the adsorbent, the removal of specific PAHs: Fluoranthene (Fla) reached 95% comparing to 80% of the unmodified AGS. The removal of Fla was related to initial concentration, temperature and ion concentration (Na+, Mg2+). The removal efficiency of Fla reached 96.27%, 94.26% and 93.69%, when initial concentration of Fla was 10, 15 and 20 μmol/L. At temperatures of 15°C, 30°C and 45°C, the removal efficiency of Fla (15 μmol/L) gradually improved from 87.20% to 94.84% and 95.73%. The presence of Na+ and Mg2+ ions led to the deterioration of PAHs removal. With the increase of Na+ and Mg2+ concentrations, the removal efficiency of modified AGS on PAHs decreased by 3.9% and 6.5%, respectively. These findings indicate the potential application of cyclodextrins as the active sites of a complex modified polymer network for PAHs wastewater treatment.

Baltrėnas, Pranas; Urbanas, Davyd; Sukackienė, Zita; Stalnionienė, Irena; Tamašauskaitė-Tamašiūnaitė, Loreta; Balčiūnaitė, Aldona; Jasulaitienė, Vitalija

doi: 10.1080/09593330.2021.1921046pmid: 33881966

In this study, Mn-based multicomponent catalysts supported by two different carriers (lightweight expanded clay aggregate and the Ukrainian clinoptiolite) were prepared by electroless metal deposition method and tested for the selective catalytic reduction of NO with ammonia (NH3-SCR de-NO). Prior to the activity test, all the catalysts prepared were characterized by inductively coupled plasma optical emission spectroscopy, field emission scanning electron microscopy (FESEM), energy dispersive X-ray mapping, X-ray photoelectron spectroscopy, H2-TPR and NH3-TPD techniques. The particular interest of the present study was focused on the investigation of the carrier’s role in the NO catalytic reduction and the promoting effect provided by the incorporation of the small amount of Pt (0.1 wt.%) in the Mn-based catalytic layer. The results revealed that the carrier’s role in the NO catalytic conversion can be considered as a factor determining the effectiveness of the conversion process. Ukrainian clinoptiolite was proved to be a more attractive carrier for the preparation of the effective SCR de-NO catalysts due to its intrinsic sorption capacity, surface acidity and the redox potential. The high NO conversion efficiency provided by the Mn-based clinoptiolite-supported catalysts can be explained by the synergistic effect between the carrier and the active species deposited. It was shown that both the Mn97.6Cu2.4/clinoptiolite and the Mn97.5Co2.5/clinoptiolite catalysts can be successfully applied as the low-temperature (100–300°C) catalysts for NH3-SCR de-NO. When the NO removal efficiency varies in the range of 86–91%, the additional incorporation of Pt in the active layer in the amount of 0.1 wt.% can enhance the NO reduction by about 5% on average.

Ding, Chong; Zhang, Youpeng; Di, Xiangyun; Zhang, Na; Zhang, Yihe; Wang, Xinke

doi: 10.1080/09593330.2021.1921047pmid: 33944689

In this study, red mud (RM) was modified with titanate coupling agent (triisostearoyl isopropoxy titanate, KR-TTS), and then the modified RM was melted blending with high-density polyethylene (HDPE) to prepare HDPE-based composite. The action mechanism of KR-TTS on the properties of HDPE composites was analysed combining with the movement mode of polyethylene macromolecular chain segments. The entanglement and mechanical interlocking of long alkyl chains of titanate coupling agent and the polyethylene molecular chains occurs in modified RM/HDPE composite, reflected by fracture morphology within tension process. The stronger interface interaction results in a decrease of polyethylene molecular chain segments motion under external loading, externally expressed as higher tensile strength and tensile modulus as well as storage modulus. Meanwhile, KR-TTS imparts modified RM/HDPE composite with higher elongation at break of uniaxial tension and lower damping ratio. The impact strength presents an improvement from 5.62 kJ/m2 of RM/HDPE composite to 6.56 kJ/m2 of modified RM/HDPE composite due to stronger interface strength. And modified RM/HDPE composite appears higher thermal stability, attributed to better particles dispersion and higher interface adhesion. Differential scanning calorimetric analysis shows that with the addition of coupling agent, the melt enthalpy of modified RM/HDPE composite decreases, indicating a decrement in the crystallinity of polyethylene composites (from 70.2% of RM/HDPE to 63.1% of modified RM/HDPE), resulted from the retarded stacking speed of chain segments into the crystal lattice during crystal growth.