Polyethylene Terephthalate (PET) is a major commercial plastic polymer with high environmental concerns. Based on sustainable circular pathways, a three-dimensional electrochemical reactor (3DER) was employed to degrade waste PET and recover monomeric TA. Over the 60-h operation, the PET became rougher and exhibited fractures in its morphology as degradation advanced. Chemically, the molecular weight of PET decreased significantly, accompanied by a marked increase in the carbonyl index. Research on the PET degradation mechanism in 3DER reveals that indirect oxidation processes mediated by hydroxyl and superoxide radicals are crucial for degrading the PET film. These radicals primarily promote ester bond cleavage, facilitating the breakdown of PET’s primary structure. In addition, precise control of the reactor was conducted under Box-Behnken design to optimize the 3DER. Under the 8-batch experiment with optimized operating parameters, this reactor achieved 92.8% degradation of PET and 18.1% recovery of monomeric terephthalic acid (TA) within 5.3 hours at a low current density of 0.2 mA/cm². The results of this study indicate that 3DER with low-cost, reusable natural tourmaline particle electrodes is a promising approach for PET degradation and TA recovery.

The impacts of microplastics (MPs) prevalent in soil on the transport of pollutants were urged to be addressed, which has important implications for ecological risk assessment. Therefore, we investigated the influence of virgin/photo-aged biodegradable polylactic acid (PLA) and non-biodegradable black polyethylene (BPE) mulching films MPs on arsenic (As) transport behaviors in agricultural soil. Results showed that both virgin PLA (VPLA) and aged PLA (APLA) enhanced the adsorption of As(Ⅲ) (9.5%, 13.3%) and As(Ⅴ) (22.0%, 6.8%) due to the formation of abundant H-bonds. Conversely, virgin BPE (VBPE) reduced the adsorption of As(Ⅲ) (11.0%) and As(Ⅴ) (7.4%) in soil owing to the “dilution effect”, while aged BPE (ABPE) improved arsenic adsorption amount to the level of pure soil due to newly generated O-containing functional groups being feasible to form H-bonds with arsenic. Site energy distribution analysis indicated that the dominant adsorption mechanism of arsenic, chemisorption, was not impacted by MPs. The occurrence of biodegradable VPLA/APLA MPs rather than non-biodegradable VBPE/ABPE MPs resulted in an increased risk of soil accumulating As(Ⅲ) (moderate) and As(Ⅴ) (considerable). This work uncovers the role of biodegradable/non-biodegradable mulching film MPs in arsenic migration and potential risks in the soil ecosystem, depending on the types and aging of MPs.

Photoelectrocatalysis (PEC) technology requires catalysts with narrow bandgap for high visible-light activity and efficient charge separation. In this study, self-interspersed porous nanoplates assembled WO3 (s-i-WO3) are synthesized via a dissolution-calcination method in the absence of templates. The results show that the s-i-WO3 catalyst exhibits excellent PEC activity and high stability. The bisphenol A (BPA) degradation efficiency of PEC system (93.7%) is significantly higher than those of photocatalysis (22.0%) and electrocatalysis (43.8%) systems. The two-dimensional porous structure and small-size mesopores of s-i-WO3 improve PEC reactions by enlarging specific surface area and providing more catalytic sites. Furthermore, the self-interspersed structure promotes the separation and transfer of photogenerated electron/hole pairs under light irradiation. Moreover, hydroxyl radicals are demonstrated to be the most prevalent reactive oxygen species in the developed PEC system. Our work sheds light on designing photoelectrocatalysts with high visible-light activity, abundant catalytic sites, and efficient charge separation.

Here, a low-cost acid-base and temperature tolerant algal bloom derived activated carbon (ABAC) was successfully prepared to remove rhodamine B (RhB) from water. The ABAC exhibited maximum adsorption capacity of RhB (1101 +/- 11 mg/g), higher than that of laboratory-prepared rape straw activated carbon (176 +/- 5 mg/g) and commercial activated carbon (489 +/- 5 mg/g). It is attributed to larger surface area and mesoporous structure of the ABAC. Furthermore, the effective adsorption of RhB by using ABAC was achieved at a wide range of solution pH (3.2-10.8) and temperature (25-50 degrees C). The mass transfer resistance of RhB adsorption process well depicted by Langmuir model was controlled by external mass transfer. The adsorption process involved both secondly chemisorption (H-bonds and pi-pi interaction) and dominated physisorption. Four dyes in river water were efficiently removed. This work provides a promising approach for developing high-absorption biomass materials for actual dye wastewater treatment.

The completely biological degradation of Tetrabromobisphenol A (TBBPA) contaminant is challenging. Bioelectrochemical systems are efficient to promote electrons transfer between microbes and pollutants to improve the degradation of refractory contaminants. In particular, three-dimensional biofilm electrode reactors (3DBERs), integrating the biofilm with particle electrodes, represent a novel bio-electrochemical technology with superior treatment performances. In this study, the electroactive biofilm is cultured and acclimated on two types of particle electrodes, granular activated carbon (GAC) and granular zeolite (GZ), to degrade the target pollutant TBBPA in 3DBERs. Compared to GZ, GAC materials are more favorable for biofilm formation in terms of high specific surface area and good conductivity. The genus of Thauera is efficiently enriched on both GAC and GZ particles, whose growth is promoted by the electricity. By applying 5 V voltage, TBBPA can be removed by over 95% in 120 min whether packing GAC or GZ particle electrodes in 3DBERs. The synergy of electricity and biofilm in TBBPA degradation was more significant in GAC packed 3DBER, because the improved microbial activity by electrical stimulation accelerates debromination rate and hence the decomposition of TBBPA. Applying electricity also promotes TBBPA degradation in GZ packed 3DBER mainly due to the enhanced electrochemical effects. Roles of particle electrode materials in TBBPA removal are distinguished in this work, bringing new insights into refractory wastewater treatment by 3DBERs.

Coking wastewater is highly concentrated and extremely toxic, greatly challenging the treatment technologies. Conventional biological technology such as anaerobic-anoxic-oxic (A2O) system is inefficient, since various biological reactions are inhibited by toxicants in coking wastewater. In this work, a pilot-scale three-dimensional electrochemical reactor (3DER) is integrated into the A2O system as a pretreatment unit to improve the treatment efficiency of coking wastewater. The results indicate that 3DER pretreatment increased the biodegradability of coking wastewater, promoting the degradation of coking wastewater in A2O system. The integrated 3DER-A2O system can remove 94.4% of COD and 76.2% of TN from coking wastewater, and the energy consumption was only 0.22 kWh/kg COD and 4.69 kWh/kg TN. The components of coking wastewater were significantly simplified and the acute toxicity was reduced from 99% to 12% after the treatment. The integrated 3DER-A2O system provides a new solution for coking wastewater treatment, showing a promising application potential.

Coking wastewater is highly toxic and refractory industrial wastewater, and is thus extremely challenging to treat. Currently, most treatment technologies focus on degrading carbonaceous pollutants, while insufficient attention is placed on ammonium nitrogen (NH4+-N), the most important nitrogenous contaminant in coking wastewater and with a high biological toxicity. In the current study, we developed an integrated electrochemical system comprising two three-dimensional electrochemical reactors (3DERs), two three-dimensional biofilm electrode reactors (3DBERs) and one three-dimensional biofilm electrode reactor for denitrification (3DBER-De) to treat coking wastewater rich in NH4+-N. Our integrated system is able to remove 70.7% of total nitrogen (TN) at the low energy consumption of 1.29 kWh m(-3), and can reduce COD by 55.8%. The 3DERs primarily degrade NH4+-N, nitrate nitrogen (NO3--N), and COD by electrochemical redox reactions, while the 3DBERs convert residual NH4+-N to NO3--N by fusing biofilm and electricity. Moreover, the 3DBER-De further eliminates NO3--N by bio-electrochemical denitrification. The coking wastewater is purified as it flows through the integrated treatment system, with only a few hydrocarbon residuals detected that are able to be readily biodegraded by conventional biological treatments. The proposed 3DERs/3DBERs/3DBER-De system provides a new solution for coking wastewater with high concentrations of NIH4+-N. (C) 2019 Elsevier Ltd. All rights reserved.

In this study, zeolitic imidazolate framework-67 (ZIF-67) derived Co3O4/NiCo2O4 double-shelled nanocages (DSNCs) were fabricated and utilized as catalysts to activate peroxydisulfate (PDS) for bisphenol A (BPA) de-gradation. The results showed that Co3O4/NiCo2O4 DSNCs exhibited superior BPA degradation performance over Co3O4 NCs and NiCo2O4 NCs. PDS combined with the interfaces of both the Co3O4 inner shell and NiCo2O4 outer shell to form complex, inducing the nonradical oxidation of BPA by electron abstraction. The double shelled hollow structure helped to increase the instantaneous concentration of reactants in the void space of Co3O4/NiCo2O4 DSNCs, thus promoting the decomposition of BPA. The Co3O4/NiCo2O4 DSNCs had high selectivity for BPA degradation and were resistant to halogens and background organic matter in wastewater. Our work indicated that metal-organic framework (MOF)-derived nanomaterials with a hollow structure have a promising application prospect for persulfate-based advanced oxidation technology.

The wide application of bisphenol A (BPA) leads to the emergence of BPA residuals in natural water environments. Dissolved organic matter (DOM) existed in water can bind with BPA, hence influencing the migration and transformation of BPA in aquatic environments. pH is a crucial factor governing the binding interactions between DOM and BPA. However, the mechanisms driven the binding process under different pH conditions are still unclear. In this study, the interactions between BPA and humic acids (HA), a primary component of DOM, are investigated over a wide pH range of 3–12 by integrating fluorescence quenching, dynamic light scattering and microcalorimetry. pH dependence of the binding interactions between HA and BPA are interpreted from a thermodynamic perspective. The results indicate that HA can spontaneously interact with BPA to form a stable HA-BPA complex. With the increasing pH, the binding interactions change from entropy driven to entropy-enthalpy co-driven. Hydrophobic force dominate the binding interactions under acidic condition. The synergy of hydrophobic force and hydrogen bond promotes the binding process under neutral condition. Under alkaline conditions, electrostatic repulsion participates the binding process in addition to hydrophobic force and hydrogen bond, weakening the binding strength. Therefore, neutral pH is favorable for HA to bind with BPA, consequently enhancing the dissolution of BPA in natural water bodies. The results are beneficial to better understand the pH dependent distribution of BPA in aquatic environments.

Three-dimensional biofilm electrode reactors (3D-BERs) represent a novel technology for wastewater denitrification. Formation of mature electroactive biofilm on particle electrodes is crucial to realize successful denitrification in 3D-BERs. However, long start-up time and low electroactivity of the biofilm formed on particle electrodes limit the further application of 3D-BERs in wastewater treatment. In this work, self-assembled hybrid biofilms (SAHB) was cultivated on granular activate carbon particle electrodes of the 3D-BER by assembling nano ɑ-Fe2O3 into the biofilm. ɑ-Fe2O3 was selected due to its high affinity to bacterial outer-membrane cytochromes, an important mediator for microbial electron transfer. SAHB formed on particle electrodes were characterized and the denitrification performance of 3D-BERs was also investigated. Results indicate that nano ɑ-Fe2O3 plays positive roles in the start-up of 3D-BER, which captures more microbes into SAHB and constructs thick biofilm on particle electrodes. Special microorganisms with denitrification function related with genera of Hydrogenophaga and Opitutus are distinctively enriched in SAHB. Nano ɑ-Fe2O3 induced SAHB exhibit superior denitrification performance compared to natural biofilm. The average denitrification rate increases from 0.62 mg total nitrogen/L/h for natural biofilm to 1.73 mg total nitrogen/L/h for SAHB, mainly ascribed to accelerated nitrites reduction. Our work provides new technical solution to enhance nitrates removal in 3D-BERs and brings deep insights into application of bio-electrochemical system in wastewater treatment.

Three-dimensional electrochemical reactor (3DER) is a highly efficient technology for refractory wastewater treatment. Particle electrodes filled between anode and cathode are the core units of 3DER, determining the treatment efficiency of wastewater. However, particle electrodes deactivation due to catalytic sites coverage seriously impedes the continuous operation of 3DER. In this work, granular sludge carbon (GSC) particle electrodes being resistant to deactivation are fabricated by pyrolyzing the mixture of waste sludge, polymethyl methacrylate (PMMA), and copper tailings, whose performances are evaluated by degrading rhodamine B (RhB) wastewater in a continuous-flow 3DER. Results indicate that hierarchical-pore structure comprising macro-, meso-, and micropores is developed in GSC-10-CTs by doping 10 g PMMA and 5 g copper tailings into 100 g waste sludge. PMMA contributes to construct macropores, which is essential for the mass transfer of RhB into GSC particle electrodes of centimeter-size. Copper tailings promote the formation of meso- and micro-pores in GSCs, as well as improving the electrochemical properties. Consequently, GSC-10-CTs packed 3DER exhibits the highest removal efficiency and lowest energy consumption for RhB treatment. In addition, the compressive strength of GSC-10-CTs is enhanced by copper tails, that is crucial to fill into 3DER as particle electrodes. The high-efficient and cost-effective GSC-10-CTs fabricated by waste materials have the potential of substituting commercial granular activated carbon catalysts in the future, consequently promoting the application of 3DER in wastewater treatment.

Bisphenol A (BPA) in wastewater has high risks of causing biological feminization. During the wastewater treatment process, large amounts of BPA are accumulated in activated sludge. However, the mechanisms of BPA interacted with activated sludge are still unclear. Especially, the roles of extracellular polymeric substances (EPS), which are major components of activated sludge, in the removal of BPA have never been concerned. In this study, the binding interactions between sludge EPS and BPA are explored combining fluorescence spectroscopy and dynamic light scattering. The thermodynamic mechanisms driving the binding behavior of BPA to EPS are illustrated by isothermal titration calorimetry. The results indicate that the binding interaction between BPA and EPS is spontaneous. BPA mainly binds with the proteins of EPS by hydrophobic association. The random-coiled structure of EPS transforms into relatively condensed cores after binding with BPA. A neutral pH, high ionic strength, and high temperature promote the binding process, facilitating to stabilize BPA in sludge EPS. This study provides new insights into the roles of sludge EPS in the migration and removal of BPA in activated sludge system.

Treatment of coking wastewater is a great challenge due to their instinct characteristics of high concentration, complex composition and biological toxicity. In this work, a novel integrated system comprising three-dimensional electrochemical reactors (3DERs) and three-dimensional biofilm electrode reactors (3DBERs) in series is developed for coking wastewater treatment. Results indicate that 79.63% of COD as well as 76.30% of total nitrogen could be removed at the low energy consumption of 15.6 kWh/m(3). 3DERs mainly contribute to COD and nitrogen removal through electrochemical oxidation/reduction, while 3DBERs are responsible for nitrification process by enriched functional microbes. After treating by the integrated system, only long-chain alkanes are left in the wastewater and the toxicity of effluent is significantly reduced. This integrated 3DERs-3DBERs system exhibits capability of simultaneously eliminating carbonaceous and nitrogenous contaminants in coking wastewater, and greatly saves the energy with synergy of electricity and biofilm.

Three-dimensional biofilm electrode reactors (3D-BERs) represent an environmentally acceptable and cost effective technology for refractory wastewater treatment. Previous studies on 3D-BERs primarily focused on treatment performance, and little information is available about the microscopic mechanisms of contaminant degradation. The reactions occurred on particle electrodes, the core units of the 3D-BERs served as both electrodes and biofilm carriers, are still unclear. This study comprehensively elucidated the synergistic effects of electricity and biofilm on Rhodamine B (RhB) removal in 3D-BERs from both macroscopic and microcosmic aspects. Continuous-flow 3D-BERs were operated to evaluate overall treatment performance. Batch experiments were conducted to explore the kinetics of RhB degradation as well as the contributions of various physical, chemical, and biological processes to RhB removal. The biofilm formed on the particle electrodes was characterized by imaging and microbial analyses. The results indicated that applying voltage promoted degradation of RhB. Three processes, including electro-adsorption, electrochemical oxidation and electro-biodegradation, were identified to contribute to RhB degradation. Microorganisms in the Rhodanobacter and Thiomonas genera were distinctively enriched under acclimation voltage, which was attributed to the accumulation of intermediates generated by electrochemical oxidation. This study demonstrated that the synergistic effects of electricity and biofilm were dependent on applying voltage, that would be beneficial to comprehensively understand the contaminants removal process in 3D-BERs.

An efficient cascade reaction of propargyl amines with AgSCF3 and KBr is developed, affording allenyl thiocyanates at room temperature in high yields. This transformation proceeds via the in situ formation of isothiocyanate intermediates, followed by a [3,3]-sigmatropic rearrangement. The resulting allenyl thiocyanates bearing 3-(electro-donating phenyl) substitutions without isolation can then be reacted with di- tert-butyl peroxide and AgSCF3 under reflux to generate novel allenyl trifluoromethylthioether compounds in moderate to good yields via a "one-pot" three-step process.

Antibiotics residuals in the environments receive wide concerns due to the high risk of generating antibiotic resistance. Natural organic matters (NOM) existed in the environments are considered to have the capacity of binding with organic contaminants, consequently influencing their speciation and transformation in the natural environments. To assess the migration of antibiotics in the environments, it is crucial to understand the binding mechanisms between NOM and antibiotics, which is still unclear due to the limit of available research methods. In this study, the interaction between fulvic acids (FA), one of the main components of NOM, and sulfamethazine (SMZ) was characterized by nuclear magnetic resonance (NMR) combined with surface plasmon resonance (SPR) and isothermal titration calorimetry (ITC) technology. The parameters related to kinetics and thermodynamics of the interaction were determined, and the possible mechanisms driving the interaction were also proposed. In addition, density functional theory (DFT) was used to predict the binding mode between FA and SMZ to reveal the interaction mechanism. Results indicate that FA can effectively bound with SMZ to form a stable complex with a binding constant at the level of 10(3) L/mol. The kinetic parameters including association and dissociation constants were 29.4 L/mol/s and 6.64 x 10(-3) 1/s, respectively. Hydrophobic interaction might play significant roles in the binding interaction with ancillary contribution of pi-pi conjunction arising from the aromatic rings stacking of FA and SMZ. (C) 2018 Elsevier Ltd. All rights reserved.

Chemically enhanced primary sedimentation (CEPS) technology has been widely applied in Hong Kong, exhibiting excellent performance in contaminants removal from sewage. The generated CEPS sludge contains abundance of organics which could be recovered as volatile fatty acids (VFAs) by fermentation for further utilization. In this work, the effect of calcium peroxide (CaO2) on the fermentation of FeCl3 based CEPS sludge was investigated. The feasibility of utilizing the fermentation liquor as substrate for polyhydroxyalkanoates (PHAs) biosynthesis was also evaluated. Results demonstrated that CaO2 addition facilitated the disintegration of CEPS sludge and enhanced VFAs production. The maximum VFAs yield of 455.8 mg COD/g VSS was obtained with the dosage of 0.1 g CaO2/g SS, improving by 44.7% compared with the control sludge. Acetic and propionic acid were the predominant components of the VFAs. Microbial analysis indicated that CaO2 induced microbial reduction of Fe(III), accelerating the initial disintegration of FeCl3 based CEPS sludge. Microbial communities with hydrolysis and acidogenesis functions were enriched effectively. CaO2 treatment had no significant influence on the release of ammonia nitrogen (NH4+-N), while reduced the concentration of orthophosphate (PO43--P) and ferrous (Fe2+) in fermentation liquor, that was beneficial to the further utilization as substrate for PHAs biosynthesis. The VFA-rich fermentation liquor was proved to be a suitable substrate for PHAs biosynthesis. After cultivation, the PHAs content in activated sludge reached 22.3%, which was comparable to those obtained using waste materials as carbon source. This integrated technology could be a superior alternative of realizing sludge disposal and bioplastic production simultaneously.

Triclosan (TCS) contaminant has aroused wide concerns due to the high risk of converting into toxic dioxin in aquatic environments. During the wastewater treatment process, considerable amounts of TCS are accumulated in activated sludge but the mechanisms are still unclear. Especially, roles of extracellular polymeric substances (EPS), the main components of activated sludge, in TCS removal have never been addressed. In this work, the binding properties of loosely-bound EPS (LB-EPS) and tightly-bound EPS (TB-EPS) of activated sludge to TCS are investigated by fluorescence quenching approach. The influences of aquatic conditions including solution pH, ionic strength and temperature on the interactions between EPS and TCS are explored. Possible interaction mechanisms are discussed as well as the corresponding environmental implication. Results indicate that binding processes of EPS to TCS are exothermic mainly driven by the enthalpy changes. The proteins components in EPS dominate the interactions between EPS and TCS by hydrogen bond and hydrophobic interaction. The binding strength could be improved under the condition of weak alkaline and relative high ionic strength. Generally, LB-EPS exhibit stronger binding ability to TCS than TB-EPS under neutral environment, playing more crucial roles in the binding process. This work highlights the important contributions of EPS to TCS removal, that is beneficial to comprehensively understand the migration of TCS in activated sludge system.

Recycling sewage sludge from wastewater treatment plants is one of the most challenging environmental problems. In this work, we develop a one-step facile synthesis method of converting iron-rich sewage sludge into granular sludge carbon (GSC), further applying as particle electrodes in three-dimensional electrochemical reactor (3DER) for wastewater treatment. Iron in sludge and zinc in activator are insitu loaded on particle electrodes as catalytic ingredients. The prepared GSC under different pyrolysis temperature are characterized to investigate the physical, chemical and electrochemical properties. The treatment performances of GSC as particle electrodes are evaluated by degrading bisphenol A (BPA) and Rhodamine B (RhB) in a continuous-flow 3DER. The stability of the GSC are evaluated and possible reaction mechanism are explored. Results indicate that GSC fabricated are typical macroporous material, exhibiting good electrocatalytic activity. The 500 degrees C/GSC packed 3DER shows the best performances in contaminants removal, that was attributed to larger specific surface and superior electrochemical properties with cooperation of iron oxide and zinc oxide components. The 500 degrees C/GSC prepared are proved to be suitable for utilizing as particle electrodes in 3DER. Our work offers a new strategy for sewage sludge reuse and provides a promising future for 3DER applications. (C) 2018 Elsevier Ltd. All rights reserved.

The removal of high-concentration rhodamine B (RhB) wastewater was investigated in a three-dimensional electrochemical reactor (3DER) packed with granular activated carbon (GAC) particle electrodes. Response surface methodology (RSM) coupled with grey relational analysis (GRA) was used to evaluate the effects of voltage, initial pH, aeration rate and NaCl dosage on RhB removal and energy consumption of the 3DER. The optimal conditions were determined as voltage 7.25 V, pH 5.99, aeration rate 151.13 mL/min, and NaCl concentration 0.11 mol/L. After 30 min electrolysis, COD removal rate could arrive at 60.13% with an extremely low energy consumption of 6.22 kWh/kg COD. The voltage and NaCl were demonstrated to be the most significant factors affecting the COD removal and energy consumption of 3DER. The intermediates generated during the treatment process were identified and the possible degradation pathway of RhB was proposed. It is worth noting that 3DER also showed an excellent performance in total nitrogen (TN) removal under the optimal condition. The activated chlorine generated from chloride had great contributions to eliminate carbon and nitrogen of RhB wastewater. The treatment effluent had a good biodegradability, which was suitable for subsequent biological treatment.