Mechanism of peroxymonosulfate activation by nanoparticle Co@N-C: Experimental investigation and theoretical calculation.

The release of organic dyes, such as Rhodamine B (RhB), into industrial wastewater has led to significant issues with color pollution in aquatic environments. Herein, we prepared a cobalt nanoparticles (NPs)-based catalyst with the nitrogen-doped carbon-support (Co@N-C) for effective PMS activation. The Co@N-C/PMS system demonstrated the excellent catalytic activity of Co@N-C for activating PMS, achieving nearly 100% degradation of RhB. Singlet oxygen (1O2) and sulfate radicals (SO4•-) were dominant reactive oxygen species for RhB degradation. Density functional theory (DFT) calculations substantiated that the production of 1O2 commenced with the initial generation of *OH through hydrogen abstraction from PMS, culminating in the direct release of oxygen to form 1O2 (PMS→*OH→O*→1O2). The generation of SO4•- was attributed to electron transfer to PMS from the surface of Co NPs (Co0→Co2+→Co3+) and the C-N shell (Co2+→Co3+). The research findings provided new insights into the development of Co-based heterogeneous catalysis for advanced oxidation of refractory organic pollutants in wastewater treatment.

Management of biofilm by an innovative layer-structured membrane for membrane biofilm reactor (MBfR) to efficient methane oxidation coupled to denitrification (AME-D).

Aerobic methane oxidation coupled with denitrification (AME-D) has garnered significant attention as a promising technology for nitrogen removal from water. Effective biofilm management on the membrane surface is essential to enhance the efficiency of nitrate removal in AME-D systems. In this study, we introduce a novel and scalable layer-structured membrane (LSM) developed using a meticulously designed polyurethane sponge. The application of the LSM in advanced biofilm management for AME-D resulted in a substantial enhancement of denitrification performance. Our experimental results demonstrated remarkable improvements in nitrate-removal flux (92.8 mmol-N m-2 d-1) and methane-oxidation rate (325.6 mmol m-2 d-1) when using an LSM in a membrane biofilm reactor (L-MBfR) compared with a conventional membrane reactor (C-MBfR). The l-MBfR exhibited 12.4-, 6.8- and 3.4-fold increases in nitrate-removal rate, biomass-retention capacity, and methane-oxidation rate, respectively, relative to the control C-MBfR. Notably, the l-MBfR demonstrated a 3.5-fold higher abundance of denitrifying bacteria, including Xanthomonadaceae, Rhodocyclaceae, and Methylophilaceae. In addition, the denitrification-related enzyme activity was twice as high in the l-MBfR than in the C-MBfR. These findings underscore the LSM's ability to create anoxic/anaerobic microenvironments conducive to biofilm formation and denitrification. Furthermore, the LSM exhibited a unique advantage in shaping microbial community structures and facilitating cross-feeding interactions between denitrifying bacteria and aerobic methanotrophs. The results of this study hold great promise for advancing the application of MBfRs in achieving efficient and reliable nitrate removal through the AME-D pathway, facilitated by effective biofilm management.

Selective and Rapid Detection of 4-Nitrophenol in River and Treated Industrial Wastewater by a Luminescent Lanthanide Metal-Organic Framework Sensor.

Phenolic organic compounds are widely used industrial chemicals that exist extensively in the environment and have a significant impact on human health. 4-Nitrophenol (4-NP) is a typical phenolic organic compound found in aqueous environments. Efficient detection of 4-NP in wastewater is highly challenging due to the complexity of testing environmental samples. Herein, a luminescent lanthanide metal-organic framework (MOF) sensor based on the Eu3+ ion {[Eu(HL)(L)(H2O)]·2H2O}n (EuMOF; H2L = 5-(4H-1,2,4-triazol-4-yl)benzene-1,3-dicarboxylic acid) was successfully synthesized for efficient 4-NP detection in wastewater. Fluorescence sensing experiments revealed that 4-NP could greatly quench the EuMOF fluorescence. Subsequently, EuMOF was applied to 4-NP detection in distilled water, tap water, river water, and treated industrial wastewater, exhibiting high sensitivity, a fast response within 30 s, high selectivity, excellent reusability, and a low detection limit. Finally, the fluorescence quenching mechanism was explored and attributed to competitive absorption of irradiated light between 4-NP and the ligand.

Packed OV-SnO2-Sb bead-electrodes for enhanced electrocatalytic oxidation of micropollutants in water.

Electrocatalytic oxidation is an appealing treatment option for emerging micropollutants in wastewater, however, the limited reactive surface area and short service lifetime of planar electrodes hinder their industrial applications. This study introduces an innovative electrochemical wastewater treatment technology that employs packed bead-electrodes (PBE) as a dynamic electrocatalytic filter on a dimensionally stable anode (DSA) acting as a current collector. By using PBE, the electroactive volume is expanded beyond the vicinity of the common planar anode to the thick porous media of PBE with a vast electrocatalytic surface area. This greatly enhances the efficiency of electrochemical degradation of micropollutants. The OV-SnO2-Sb PBE filter achieved a nearly 100 % degradation of moxifloxacin (MOX) in under 2 min of single-pass filtration, with a degradation rate over an order of magnitude higher than the conventional electrochemical oxidation processes. The generation of abundant radical species (•OH) and non-radical species (1O2 and O3), along with the enhanced direct oxidation, led to the outstanding performance of the charged PBE system in MOX degradation. The OV-SnO2-Sb PBE was remarkably stable, and the separation between the electroactive PBE layer and the base Ti anode allows for easy renewal of the bead-electrode materials and scaling up of the system for practical applications. Overall, our study presents a dynamic electroactive PBE that advances the electrocatalytic oxidation technology for effective control of emerging pollutants in the water environment. This technology has the potential to revolutionize electrochemical wastewater treatment and contribute to a more sustainable future environment.

Simultaneous methanogenesis and denitrification in an anaerobic moving bed biofilm reactor for landfill leachate treatment: Ameliorative effect of rhamnolipids.

In this study, an anaerobic moving bed biofilm reactor (AnMBBR) was developed for simultaneous methanogenesis and denitrification (SMD) to treat high-strength landfill leachate for the first time. A novel strategy using biosurfactant to ameliorate the inhibition of landfill leachate on the SMD performance was proposed and the underlying mechanisms were explored comprehensively. With the help of rhamnolipids, the chemical oxygen demand (COD) removal efficiency of landfill leachate was improved from 86.0% ± 2.9% to 97.5% ± 1.6%, while methane yields increased from 50.1 mL/g-COD to 69.6 mL/g-COD, and the removal efficiency of NO3--N was also slightly increased from 92.5% ± 1.9% to 95.6% ± 1.0%. The addition of rhamnolipids increased the number of live cells and enhanced the secretion of extracellular polymeric substances (EPS) and key enzyme activity, indicating that the inhibitory effect was significantly ameliorated. Methanogenic and denitrifying bacteria were enhanced by 1.6 and 1.1 times, respectively. Analysis of the microbial metabolic pathways demonstrated that landfill leachate inhibited the expression of genes involved in methanogenesis and denitrification, and that their relative abundance could be upregulated with the assistance of rhamnolipids addition. Moreover, extended Deraguin - Landau - Verwery - Oxerbeek (XDLVO) theory analysis indicated that rhamnolipids reduced the repulsive interaction between biofilms and pollutants with a 57.0% decrease in the energy barrier, and thus accelerated the adsorption and uptake of pollutants onto biofilm biomass. This finding provides a low-carbon biological treatment protocol for landfill leachate and a reliable and effective strategy for its sustainable application.

Development of a novel three-dimensional biofilm-electrode system (3D-BES) loaded with Fe-modified biochars for enhanced pollutants removal in landfill leachate.

Different mass ratio iron (Fe)-loaded biochars (FeBCs) were prepared from food waste and used in the three-dimensional biofilm-electrode systems (3D-BES) as particular electrodes for landfill leachate treatment. Compared to the unmodified biochar (BC), specific surface area of Fe-loaded biochars (FeBC-3 with a Fe: biochar of 0.2:1) increased from 63.01 m2/g to 184.14 m2/g, and pore capacity increased from 0.038 cm3/g to 0.111 cm3/g. FeBCs provided more oxygen-containing functional groups and exhibited excellent redox properties. Installed with FeBC-3 as particular electrode, both NH4+-N and chemical oxygen demand COD removals in 3D-BESs were well fitted with the pseudo-first-order model, with the maximum removal efficiencies of 98.6 % and 95.5 %, respectively. The batch adsorption kinetics experiments confirmed that the maximum NH4+-N (7.5 mg/g) and COD (21.8 mg/g) adsorption capacities were associated closely with the FeBC-3 biochar. In contrast to the 3D-BES with the unmodified biochar, Fe-loaded biochars significantly increased the abundance of microorganisms being capable of removing organics and ammonia. Meanwhile, the increased content of dehydrogenase (DHA) and electron transport system activity (ETSA) evidenced that FeBCs could enhance microbial internal activities and regulate electron transfer process among functional microorganisms. Consequently, it is concluded that Fe-loaded biochar to 3D-BES is effective in enhancing pollutant removals in landfill leachate and provided a reliable and effective strategy for refractory wastewater treatment.

Enhanced NH4+ Removal and Recovery from Wastewater Using Na-Zeolite-based Flow-Electrode Capacitive Deionization: Insight from Ion Transport Flux.

Flow-electrode capacitive deionization (FCDI) is a promising electromembrane technology for wastewater treatment and materials recovery. In this study, we used low-cost Na-modified zeolite (Na-zeolite) to prepare a composite flow-electrode (FE) suspension with a small amount of highly conductive carbon black (CB) to remove and recover NH4+ from synthetic and actual wastewater (200 mg-N/L). Compared with conventional activated carbon (AC), the Na-zeolite electrode exhibited a 56.2-88.5% decrease in liquid-phase NH4+ concentration in the FE suspension due to its higher NH4+ adsorption capacity (6.0 vs. 0.2 mg-N/g). The resulting enhancement of NH4+ diffusion to the electrode chamber contributed to the improved performance of FCDI under both constant current (CC) and constant voltage (CV) conditions. The addition of CB to the FE suspension increased the conductivity and facilitated Na-zeolite charging for NH4+ electrosorption, especially in CV mode. NH4+-rich zeolite can be easily separated by sedimentation from CB in the FE suspension, producing a soil conditioner with a high N-fertilizer content suitable for soil improvement and agricultural applications. Overall, our study demonstrates that the novel Na-zeolite-based FCDI can be developed as an effective wastewater treatment technology for both NH4+ removal and recovery as a valuable fertilizer resource.

Integrating electrochemical pre-treatment with carrier-based membrane bioreactor for efficient treatment of municipal waste transfer stations leachate.

An integrated process of electrochemical pre-treatment with carrier-based membrane bioreactor (MBR) was constructed for fresh leachate from waste transfer stations with high organic and NH4+-N content. Results showed that within a hydraulic retention time 40 h, the removal efficiencies of chemical oxygen demand (COD), NH4+-N, suspended solids (SS) and total phosphorus (TP) were over 98.5%, 91.2%, 98.3% and 98.4%, respectively, with the organic removal rate of 18.7 kg/m3. The effluent met the Grade A Standard of China (GB/T31962-2015). Pre-treatment contributed about 70 % of the degraded refractory organics and almost all the SS, with the transformation of the humic-like acid to readily biodegradable organics. Biotreatment further removed over 50% of nitrogen pollutants through simultaneous nitrification and denitrification (SND) and consumed about 30% of organics. Meanwhile, the addition of carriers in the oxic MBR enhanced the attached biomass and denitrification enzyme activity, alleviating membrane fouling.

Intracellular electron competition in response to the oxygen pressure of the aerobic denitrification process in an O2-based membrane biofilm reactor (MBfR) for nitrate removal.

This study quantitatively investigated the effect of dissolved oxygen (DO) concentration on aerobic denitrification, and showed the mechanism of aerobic denitrification from the perspective of electron competition by cultivating Pseudomonas stutzeri T13, a typical aerobic denitrifier, in an oxygen-based membrane biofilm reactor (O2-based MBfR). The experiments showed that when the O2 pressure increased from 2 to 10 psig , the average effluent DO concentration during steady-state phases increased from 0.02 to 4.23 mg/L, and the corresponding mean NO3--N removal efficiency slightly decreased from 97.2 % to 90.9 %. Compared to the maximum theoretical flux of O2 in various phases, the actual O2 transfer flux increased from a limited status (2.07 e- eq m-2 d-1 at 2 psig) to an excessive status (5.58 e- eq m-2 d-1 at 10 psig). The increase of DO inhibited the electron availability for aerobic denitrification, which decreased from 23.97 % to 11.46 %, accompanying the increased electron availability for aerobic respiration from 15.87 % to 28.36 %. Unlike the napA and norB genes, the expression of the nirS and nosZ genes was significantly affected by DO, with the highest relative fold-changes of 6.5 and 6.13 at 4 psig O2, respectively. The results contribute to clarifying the mechanism of aerobic denitrification from the quantitative perspective of electron distribution and the qualitative perspective of gene expression, which benefits the control and practical application of aerobic denitrification for wastewater treatment.

Effectiveness and degradation pathways of bisphenol A (BPA) initiated by hydroxyl radicals and sulfate radicals in water: Initial reaction sites based on DFT prediction.

Bisphenol A (BPA), one of the widely known endocrine-disrupting chemicals, can be effectively degraded by advanced oxidation processes in water because of the powerful reactive oxygen species. In this study, Fenton, UV/Fenton, and metal ion/peroxymonosulfate (PMS) processes were compared to investigate BPA degradation efficiency and pathways initiated by hydroxyl radicals and sulfate radicals. In contrast to the Fenton system, which only degraded 60% of BPA within 15 min, the UV/Fenton system could degrade greater than 80% of BPA, because more hydroxyl radicals (•OH) were generated under the reduction of Fe3+ to Fe2+. The optimized parameters of the UV/Fenton system were as follows: 8 µmol/L of Fe2+, 80 µmol/L of H2O2, and a pH value of 3.0. As for the metal ion/PMS system, the BPA degradation efficiency was closely associated with the applied metal ions, and the order was as follows: Co2+/PMS (∼100%) > Fe2+/PMS (∼80%) > Cu2+/PMS (∼79%). The degradation pathways of BPA were theoretically interpreted through density functional theory prediction and degradation products during various processes. Two major initial reaction sites (4C and 6C) for •OH initiated using the UV/Fenton system and one initial reaction site (4C) for sulfate radicals (SO4•-) using the metal ion/PMS system were recognized for BPA degradation processes. The degradation products by •OH showed a larger average molecular weight than those by SO4•-. These studies are instructive for the application of different advanced oxidation systems in the treatment process of BPA in wastewater.

Pilot-scale treatment of municipal garbage mechanical dewatering wastewater by an integrated system involving partial nitrification and denitrification.

The municipal solid waste (MSW) with high water content can be pre-treated by the mechanical dewatering technology to significantly decrease the leachate generation in sequential landfill treatment or to improve the efficiency for solid waste incineration, which has attracted great concerns recently. However, the generated mechanical dewatering wastewater (MDW) containing high organics and nitrogenous content has been one of the big challenges for the sustainable treatment of MSW. In this study, a pilot-scale integrated system composed of physiochemical pretreatment, anaerobic sequencing batch reactor (ASBR), partial nitrification SBR (PN-SBR), denitrification SBR (DN-SBR), and UV/O3 advanced oxidation process, with a capacity of 1.0 m3/d to treat MDW containing over 34000 mg-chemical oxygen demand (COD)/L organics pollutant and 850 mg/L NH4+-N, was successfully developed. By explorations on the start-up of this integrated system and the process conditions optimization, after a long-term system operation, the findings demonstrated that this integrated system could reach the removal efficiency in the COD, NH4+-N and total nitrogen (TN) in the MDW of 99.7%, 98.2% and 96.9%, respectively. Partial nitrification and denitrification were successfully obtained for the TN removal with the nitrite accumulation rate of over 80%. The treatment condition parameters were optimized to be 800 mg/L polyaluminum chloride (PAC) and 2 mg/L polyacrylamide (PAM) under a pH of 9 for pretreatment, 36 h hydraulic retention time (HRT) for ASBR, 24 h for PN-SBR, and 2 h for UV/O3 unit. The organic sources in the MDW were also found to be feasible for the DN-SBR. Consequently, the resulting final effluent was stably in compliance with the discharge standard with high stability and reliability.

Low-temperature-resistance granulation of activated sludge and the microbial responses to the granular structural stabilization.

Completely loss of granular structural stability and reliable start-up of aerobic granular sludge (AGS) system are considered as the biggest challenges for its engineering application under seasonal temperature variation, especially extremely low temperatures. In this study, two identical sequencing batch reactors (SBR) were successfully start-up at 10 °C (R1) and 25 °C (R2), respectively, and then operated under a strategy of stepwise change of temperatures to investigate the stability of the granular sludge by examining its microbial characteristics, bis (3'-5')-cyclic dimeric guanosine monophosphate (c-di-GMP), extracellular polymeric substance (EPS) and sludge physiochemical properties. The results showed that AGS formed under the low temperature preferentially secrete EPS and c-di-GMP for stable granulation and improvement of its resistance to temperature changes. Meanwhile, R1 successfully obtained aerobic granulation with high biomass concentration and superior settleability, as well as high pollutant removal performance. In comparison, R2 took a longer time for granulation and was subjected to serious disintegration of AGS. The matrix structure partially formed by filamentous bacteria during the start-up stage in R1 was one of major reasons for its own superiority beyond R2 in granulation. Slow-growing organisms such as autotrophic nitrifying and Anammox bacteria, phosphorus accumulation organisms, EPS-producing genera, and c-di-GMP pathway-dependent genera, were exclusively enriched in the R1 and resulted in higher pollutants removal efficiencies and stable structure, whereas Sphaerotilus dominated in R2 that related closely with its unstable performance. Therefore, the strategy based on the stepwise change of temperatures from extremely low temperatures may be one feasible way for the sustainable application of AGS system, which is of significance to address the challenging problems of AGS applications.

Micro-polluted water resources treatment by PVDF-TiO2 membrane combined with Fe2+/sodium dithionite (DTN)/O2 pre-oxidation process.

Modifying PVDF membrane by blending hydrophilic nano TiO2 has been highly concerning, but its practical application is not well investigated. In this study, PVDF-TiO2 membrane was employed in two modes to treat micro-polluted raw water for the first time, direct membrane filtration and pre-oxidation assists membrane filtration. At two filtration modes, the PVDF-TiO2 membrane had comparable rejection capability to the unmodified PVDF membrane, as the removal of permanganate index (CODMn) was 0.26-0.72 mg/L, UV254 was 0.0070-0.0618 cm-1, turbidity was 1.60-4.49 NTU, and the total number of colonies was 360-23,780 CFU/mL. As for raw water treatment, using Fe2+/sodium dithionite (DTN)/O2 system as the pre-oxidation process to assist the filtration of the PVDF-TiO2 membrane was feasible. After optimization, the applicable conditions of the Fe2+/DTN/O2 process were DTN dosage at 100 mg/L and a CFe/CDTN of 1:4. As a result, the effluent qualities of the PVDF-TiO2 membrane significantly improved. It was investigated that atrazine (ATZ), CODMn, UV254, and turbidity reduced, which was realized by the synergic effects of the pre-oxidation by free radicals and flocculation by iron. Pre-oxidation of the Fe2+/DTN/O2 process could also enhance the permeability of the PVDF-TiO2 membrane from 53.6 to 58.0 L/(m2·h), nearly two times the PVDF membrane. Besides, the practical fouling of the PVDF-TiO2 membrane was stably alleviated by the reduced Rt, Rre, and Rir, mainly due to constraining the internal pore fouling effectively.

Biofilm stratification in counter-diffused membrane biofilm bioreactors (MBfRs) for aerobic methane oxidation coupled to aerobic/anoxic denitrification: Effect of oxygen pressure.

Aerobic methane oxidation coupled with denitrification (AME-D) executed in membrane biofilm bioreactors (MBfRs) provides a high promise for simultaneously mitigating methane (CH4) emissions and removing nitrate in wastewater. However, systematically experimental investigation on how oxygen partial pressure affects the development and characteristics of counter-diffusional biofilm, as well as its spatial stratification profiles, and the cooperative interaction of the biofilm microbes, is still absent. In this study, we combined Optical Coherence Tomography (OCT) with Confocal Laser Scanning Microscopy (CLSM) to in-situ characterize the development of counter-diffusion biofilm in the MBfR for the first time. It was revealed that oxygen partial pressure onto the MBfR was capable of manipulating biofilm thickness and spatial stratification, and then managing the distribution of functional microbes. With the optimized oxygen partial pressure of 5.5 psig (25% oxygen content), the manipulated counter-diffusional biofilm in the AME-D process obtained the highest denitrification efficiency, due mainly to that this biofilm had the proper dynamic balance between the aerobic-layer and anoxic-layer where suitable O2 gradient and sufficient aerobic methanotrophs were achieved in aerobic-layer to favor methane oxidation, and complete O2 depletion and accessible organic sources were kept to avoid constraining denitrification activity in anoxic-layer. By using metagenome analysis and Fluorescence in situ hybridization (FISH) staining, the spatial distribution of the functional microbes within counter-diffused biofilm was successfully evidenced, and Rhodocyclaceae, one typical aerobic denitrifier, was found to survive and gradually enriched in the aerobic layer and played a key role in denitrification aerobically. This in-situ biofilm visualization and characterization evidenced directly for the first time the cooperative path of denitrification for AME-D in the counter-diffused biofilm, which involved aerobic methanotrophs, heterotrophic aerobic denitrifiers, and heterotrophic anoxic denitrifiers.

Efficient degradation and deiodination of iopamidol by UV/sulfite process: Assessment of typical process parameters and transformation paths.

Iopamidol (IPM) is widely used in medical clinical examination and treatment and has immeasurable harm to the ecological environment. The combination of UV and sulfite (UV/sulfite) process was developed to degrade IPM in this study. In contrast to that almost no removal of IPM was observed under sulfite reduction alone, the UV/sulfite process could efficiently reductively degrade IPM with the observed rate constant (kobs) of 2.08 min-1, which was nearly 4 times that of UV irradiation alone. The major active species in the UV/sulfite process were identified as hydrated electrons (eaq-) by employing active species scavengers. The influence of the initial pH, sulfite dosage, IPM concentration, UV intensity and common water matrix were evaluated. The degradation of IPM reached nearly 100% within only 2.5 min at pH 9, and kobs increased at higher initial sulfite dosages and greater UV intensities. HCO3- had a limited effect on the degradation of IPM, while humic acid (HA) was found to be a strong inhibitor in the UV/sulfite process. With the synergistic action of UV/sulfite, most of the iodine in IPM was found to release in the form of iodide ions (up to approximately 98%), and a few formed iodide-containing organic compounds, reducing significantly the toxicity of degradation products. Under direct UV irradiation and free radical reduction (mainly eaq-), 15 transformation intermediates of IPM were produced by amide hydrolysis, deiodination, hydroxyl radical addition and hydrogen abstraction reactions, in which free radical attack accounted for the main part. Consequently, the UV/sulfite process has a strong potential for IPM degradation in aquatic environments.

A chemosensing approach for the colorimetric and spectroscopic detection of Cr3+, Cu2+, Fe3+, and Gd3+ metal ions.

Metal cations are present in domestic and industrial wastewater and have adverse effects on human and aqueous life. The present study describes the development of the molecular probe 9-anthracen-9-ylmethylene)hydrazineylidene)methyl)-2,3,6,7-tetrahydro-1H,5H-pyrido[3,2,1-ij]quinolin-8-ol (AMHMPQ) to detect Cr3+, Cu2+, Fe3+, and Gd3+ ions by using UV-visible, fluorescence, colorimetric and excitation-emission matrix (EEM) spectroscopy techniques. The interaction of Cr3+, Cu2+, Fe3+, and Gd3+ can be observed by the absorption maxima shift, turn-off, colour changes, and EEM shifts. In addition, fluorescence limits of detection 17.66 × 10-6 M, 6.44 × 10-9 M, 28.87 × 10-8 M, and 12.49 × 10-6 M in wide linear ranges, low limits of quantifications, high values of Stern-Volmer constant, Job's plot and Benesi-Hildebrand plot justify the 1:1 association affinity with association constants of 1.46 × 104 M-1, 1.86 × 107 M-1, 2.69 × 105 M-1, 2.13 × 104 M-1 for AMHMPQ-metal ions (Cr3+, Cu2+, Fe3+, and Gd3+ ions), respectively. Paper- and mask-based kits are developed to explore the utility of the designed chemosensor. Additionally, AMHMPQ acts as a reusable sensor for two, seven, two, and zero cycles for Cr3+, Cu2+, Fe3+, and Gd3+ ions, respectively, when checked with EDTA.

A novel nanofibrous PAN ultrafiltration membrane embedded with ZIF-8 nanoparticles for effective removal of Congo red, Pb(II), and Cu(II) in industrial wastewater treatment.

A novel Polyacrylonitrile (PAN) composite membrane involving ZIF-8 nanoparticles, named as ZIF-8/PAN membrane, was obtained via electrospinning to remove the Congo red (CR), Pb(II) and Cu(II) ions in industrial wastewaters, during which the adsorption mechanisms were examined in this study. The adsorption efficiency of the electrospun ZIF-8/PAN membrane was as high as 89%, 92% and 76% for CR, Pb(II) and Cu(II), respectively. Comparative analysis showed that ZIF-8 nanoparticles embedded in the ZIF-8/PAN membrane accounted for these enhanced adsorption capabilities. The adsorption behaviors of the ZIF-8 nanoparticles were investigated through experiments and theoretical analysis, and the results unraveled that the adsorption for CR by the ZIF-8 was mainly including electrostatic interaction, hydrogen bonding and π-π interaction, while those for Pb(II) and Cu(II) were mainly caused by ion-exchange and chemical adsorption. Parametric studies were conducted to optimize the conditions for removing CR, Pb(II), and Cu(II) by ZIF-8 nanoparticles, during which all of pollutants showed different reactions to the solution pH. This work not only develops a novel ZIF-8/PAN composite membrane for effective removals of pollutants, but also reveals the underlying mechanisms of pollutants adsorption in terms of molecular interactions, providing important understandings on fibrous materials design for efficient heavy metals and dyes removals in industrial wastewater treatment.

Exposure to perfluoroalkyl substances in waste recycling workers: Distributions in paired human serum and urine.

Occupational exposure to per- and polyfluoroalkyl substances (PFASs) is an emerging public health concern, because of their potential adverse health effects. In this study, concentrations of 21 legacy and alternative PFASs in paired serum and urine samples collected from 163 workers (from five waste recycling plants) were analyzed. The results showed that the average concentration of 21 PFASs in urine samples (66.6 ng mL-1) were higher than in serum (31.3 ng mL-1). Concentrations of perfluorocarboxylates (PFCAs) in urine were also considerably higher than perfluorosulfonates (PFSAs), especially for short-chain PFCAs. Demographic factors (such as sex, age, working age, and job assignment) on PFAS exposure were also assessed based on the obtained results. PFAS concentrations in serum samples from males were significantly higher than in females, and working age was positively (p < 0.05) associated with most PFAS serum levels. Higher levels of PFAS were found in sorters than in workers with other job assignments, such as managers, suggesting that sorters may be directly exposed to PFASs. Interestingly, perfluorophosphonates (PFPAs) were first to be detected in human urine with >80% detection frequency. The average level of three PFPAs in the serum (7.58 ng mL-1) and urine (1.45 ng mL-1) samples appeared to be higher in comparison with most PFCAs and PFSAs. Thus, the toxicity of PFPAs in human beings needs to be further studied.

Effects of temperature and relative humidity on soil-air partition coefficients of organophosphate flame retardants and polybrominated diphenyl ethers.

The soil-air partition coefficients (KSA) of polybrominated diphenyl ethers (PBDEs) and organophosphate flame retardants (OPFRs) is important for determining their fate in soil and air media. However, KSA values of OPFRs and PBDEs are not available from the current literature, and the effects of environmental factors such as temperature and relative humidity (RH) on KSA values are not clear. In this study, a solid-phase fugacity meter was used to measure the KSA values of PBDEs and OPFRs at different temperatures (25, 30, 35, 40, and 45 °C) and relative humidity (RH) conditions (<3 and 100% RH), the relationships between KSA and octanol-air partition coefficients (KOA) for OPFRs and PBDEs were analyzed. The results showed that an increase in temperature and RH resulted in a decrease of all KSA values for PBDEs and OPFRs. Furthermore, the effects of RH on the soil-air partitioning behavior of PBDEs were larger than that of OPFRs. In addition, a significant correlation (p < 0.0001) was observed between log KSA and log KOA. The experimental KSA values of OPFRs and PBDEs were quite different from the predicted KSA, when calculated with their KOA values. Overall, this study provides a better understanding for predicting the behavior and fate of OPFRs and PBDEs in soil-air systems.

Facial fabricated biocompatible homogeneous biocarriers involving biochar to enhance denitrification performance in an anoxic moving bed biofilm reactor.

Biochar prepared from pineapple peel was facially combined with polyurethane sponges for the first time to form homogeneous biocompatible biocarriers, which can enhance denitrification performance in an anoxic MBBR. The experiments showed that a higher NO3--N removal efficiency (96.24 ± 1.3%) and kinetic constant (0.26 h-1) were obtained in the MBBR employing these new biocarriers (B-MBBR), compared with a control MBBR with polyurethane sponges (C-MBBR). The attached and suspended biomass of the B-MBBR was increased by 47% and 26%, respectively. Biochar significantly enhanced the abundance of functional bacteria in terms of promoting biofilm (i.e., Leptonema), denitrifying bacteria (i.e., Thauera, Enterobacter and Pseudomonas) and electroactive bacteria (i.e., Geobacter) in the B-MBBR. Meanwhile, based on the content of coenzyme I (NADH) and denitrifying enzymes, biochar would also enhance electron transport activity for denitrification. Consequently, these facial prepared biocarriers are effective to enhance denitrification performance in MBBR with application significance.