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Modified natural polymer flocculants has been the focus of research in environmental engineering field. Natural large molecular compound, chitosan (CTS) with many functional amino and hydroxyl groups can be easily modified to enhance its original functions. This work presents an environmentally friendly chitosan-based cationic polyacrylamide flocculants (CTS-g-PAMA) with enhanced function of sterilization and flocculation. CTS-g-PAMA was synthesized through Ultraviolet (UV)-initiated copolymerization. Structure characterization of FTIR, 1 H NMR, XRD and UV spectrum confirmed the successful grafting of AM and MAPTAC. Scanning electron microscopy (SEM) analysis results showed that CTS-g-PAMA exhibited a porous structure with a prodigious surface area. CTS-g-PAMA was then applied to treat a series of simulated waste water containing kaolin or Escherichia coli . Flocculation tests indicated that CTS-g-PAMA not only showed excellent flocculation effect but also showed high sterilization capability. A series of ONP concentration measurement tests through UV spectra analysis and 3D EEM analysis of suspension before and after flocculation were conducted to study sterilization mechanism, and results revealed the sterilization effect of CTS-g-PAMA was essentially bactericidal, not just antibacterial. [ABSTRACT FROM AUTHOR]

Highlights: [•] A novel cationic flocculant P(AM–DAC–BA) was synthesized and characterized. [•] P(AM–DAC–BA) was synthesized through ultraviolet (UV) initiation. [•] P(AM–DAC–BA) prepared in quartz reactor was porous structure. [•] Comparison between quartz reactor and glass reactor was well studied. [•] P(AM–DAC–BA) was efficient in the dewatering of the textile sewage sludge. [ABSTRACT FROM AUTHOR]

[Display omitted] • A new magnetic composite of FSNCS/SDBS was synthesized at low temperature. • FSNCS/SDBS shows excellent adsorption performance for CIP. • FSNCS/SDBS shows wide pH adaptability. • SDBS enhances CIP's adsorption by improving the surface charge of FSNCS. In this study, a novel magnetic nickel cobalt sulfide/sodium dodecyl benzene sulfonate (FSNCS/SDBS) adsorbent was synthesized successfully by a facile protocol and was developed to remove ciprofloxacin (CIP) for water purification. The FSNCS/SDBS adsorbent is featured with excellent CIP adsorption capacity of 625 mg·g−1 (much higher than reported most adsorbents), wide pH adaptability (little changed CIP adsorption capacity in pH 6–11), and good magnetic property. The effects of pH and ionic strength on CIP adsorption were investigated. The calculative thermodynamic parameters indicated that CIP adsorption by FSNCS/SDBS was spontaneous and exothermic. CIP adsorption followed pseudo-second-order kinetics and an isotherm best fit with the Langmuir adsorption mode. The adsorption mechanism of CIP onto FSNCS/SDBS was proposed and demonstrated, which included the electrostatic interaction, π–π interaction, coordination with metal and hydrogen bonding. [ABSTRACT FROM AUTHOR]

Abstract: Recent advance on the application of the composite coagulant in the coagulation–flocculation process has attracted a widespread interest. Previous research has demonstrated that iron-based composite coagulant could enhance the performance of the coagulation–flocculation. In this research, results of an experimental study using polymeric aluminum ferric sulfate (PAFS) as a modified coagulation reagent for treating wastewater was presented. The structure and morphology of PAFS were investigated using some conventional methods, and response surface method (RSM) was employed to optimized the coagulation–flocculation process while the evaluation of treatment efficiency was determined by measuring both the reduction of turbidity and chemical oxygen demand (COD). In addition, parameters affecting coagulation–flocculation behavior such as coagulant dosage, wastewater initial pH, were also examined. The results showed the structure of PAFS as a non-stoichiometric basic iron sulfate salt taking the shape of a compact network and exhibited better coagulation–flocculation performance when the species distribution of (Fe–Al)a, (Fe–Al)b and (Fe–Al)c in PAFS were 37.4%, 3.79% and 59.08%, respectively. Compared with PFS, PAFS showed a superior flocculation performance with the maximum COD removal efficiency of 83.6% and the lowest residual turbidity of 0.96NTU at the coagulant dosage of 45mg/L. In the coagulation–flocculation process, the adsorption-bridging and charge neutralization mechanisms played an important role in colloidal destabilization and aggregation. [Copyright &y& Elsevier]

• mpg -C 3 N 4 was fabricated by the sol–gel template method. • mpg -C 3 N 4 showed excellent adsorption capacities and high selectivity towards thorium. • The maximum adsorption capacity of mpg -C 3 N 4/r=1.0 was more than three times of g -C 3 N 4. • It displayed good stability and reusability after five-adsorption–desorption cycle. • Adsorbent binds to thorium mainly controlled by the coordination of amine group. Selective separation of thorium resources from aqueous solutions is an ideal strategy for recovering or removing radioactive ions, as well as reducing potential human health and environmental risks. In this study, an effective adsorbent, mesoporous graphite carbon nitride (mpg -C 3 N 4), was synthesized by a simple thermal condensation using a sacrificial LUDOX HS-40 colloidal silica as template and applied to the selective adsorption of thorium ions from the multi-ion solutions. The results of competitive experiments illustrated that mpg -C 3 N 4/r exhibited higher selectivity and efficiency for Th(IV) over other 14 co-existing cations, with the maximum selective adsorption capacities of Th(IV) reaching to 108.18 mg g−1 for mpg -C 3 N 4/r=1.0 which is more than g -C 3 N 4 (36.64 mg g−1) at pH 4.0. The interaction of Th(IV) with mpg -C 3 N 4/r=1.0 and g -C 3 N 4 were performed using batch processing, the adsorption isotherm was well conformed to the Langmuir adsorption model, and the maximum adsorption capacity of thorium at pH 4.0 and 298 K was calculated to be 196.08 mg g−1 which is more than three times of g -C 3 N 4 (60.60 mg g−1). Also, the results of adsorption experiments on monazite leachate showed that mpg -C 3 N 4/r=1.0 can be successfully used as an attractive adsorbent with the high adsorption efficiency (93.53%) of thorium. This work could broaden insights into the tailored design and synthesis of mesoporous adsorbents for the selective adsorption of thorium in multi-ion solutions. [ABSTRACT FROM AUTHOR]

• Multifunctional magnetic composite nanoparticles were facilely prepared. • The as-prepared FS@CS-PAA showed excellent adsorption capacities for cationic dyes. • FS@CS-PAA exhibited satisfactory removal rates for metal ions in a wide pH range. • The good adsorption ability was attributed to abundant active sites from CS-PAA. • FS@CS-PAA's good stability and reusability facilitated its practical application. Wastewater containing highly toxic, non-biodegradable and carcinogenic organic dyes and metal ions has been regarded as a severe threat to ecological environment and human health. Thus, it is of great significance to develop an effective approach to purify this kind of wastewater. Herein, novel magnetic adsorbent FS@CS-PAA was facilely prepared by coating anionic polyacrylamide-modified chitosan (CS-PAA) on the surface of silica-combined Fe 3 O 4 (FS). The morphology, structure, physic-chemical and magnetic properties of as-prepared FS@CS-PAA were fully characterized by various characterization techniques. Its adsorption behaviors towards cationic dyes and metal ions were systematically investigated in single systems, binary systems, and model wastewater. FS@CS-PAA was proved to have superior adsorption capacities of 2330.17 and 1044.06 mg g−1 respectively for crystal violet and methylene blue at 318.15 K, much higher than other reported adsorbents. Besides, FS@CS-PAA exhibited a pH-independent adsorption capability for metal ions, as demonstrated in single systems and in metal ion-dye binary systems, thus it could be used to treat a variety of metal ion wastewaters with different pH values. Moreover, FS@CS-PAA could be effectively and easily regenerated by HCl solution after the treatments of both synthetic wastewater and model wastewater. As revealed in FTIR and XPS analyses, the adsorption mechanism was mainly attributed to the electrostatic interaction, hydrogen bonding, cation exchange and chelating effect. With its excellent adsorption capacity for cationic dyes, pH-independent adsorption capability for metal ions, easy separation ability, satisfactory stability and good reusability, FS@CS-PAA can become an ideal candidate for wastewater treatment. [ABSTRACT FROM AUTHOR]

The novel, highly active, acid resistance and reusable immobilized adsorbent, 2-phosphonobutane-1,2,4-tricarboxylic acid (PBTCA)-decorated chitosan-coated magnetic silica nanoparticle, has been fabricated and applied to the highly selective adsorption of uranium from a multi-ion solution. • Novel PBTCA-decorated chitosan-coated magnetic SiO 2 nanoparticles were fabricated. • A new, highly active, acid resistance, and reusable magnetic sorbent was obtained. • Coexisting ion experiments showed highly selective uranium adsorption. • CoFe 2 O 4 @SiO 2 @CS-PBTCA showed higher acid resistance than uncoated silica adsorbent. • Adsorbent binds to uranium mainly though carboxyl and phosphonic oxygen atoms in PBTCA. The separation and recovery of uranium resources from nuclear waste solutions is important for achieving uranium reuse and environmental protection. In this study, a novel adsorbent, 2-phosphonobutane-1,2,4-tricarboxylic acid (PBTCA)-decorated chitosan-coated magnetic silica nanoparticles, was fabricated and applied to the highly selective adsorption of uranium from aqueous solution. Selective sorption in a multi-ion solution (pH 4.0) containing 14 coexisting cations resulted in CoFe 2 O 4 @SiO 2 @CS-PBTCA showing an excellent uranium adsorption capacity of up to 83.16 mg g−1, which was much higher than that of ungrafted CoFe 2 O 4 @SiO 2 @CS (29.99 mg g−1). The adsorbent also exhibited higher acid resistance than uncoated silica adsorbent under pH 1.0 conditions, with CoFe 2 O 4 @SiO 2 @CS-PBTCA showing barely any iron and cobalt leaching, while CoFe 2 O 4 @CS-PBTCA showed iron and cobalt leaching amounts of 2.97 and 0.93 mg L−1, respectively. The desorption experiment used 0.2 M PBTCA (pH 1.0) as eluent, with the results showing that uranium ions were readily and rapidly desorbed. Furthermore, CoFe 2 O 4 @SiO 2 @CS-PBTCA maintained outstanding stability and adsorption performance after five reuse cycles. The mechanism for U(VI) removal was investigated by X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy, with the results suggesting that the adsorbent binds to uranium mainly though oxygen atoms of carboxyl groups and phosphonic groups in PBTCA. This strategy shows strong potential for developing a variety of novel, highly active, acid resistance, and reusable immobilized functional magnetic materials for effective separation of uranium from a multi-ion solution. [ABSTRACT FROM AUTHOR]

• The relationship between coagulation-flocculation and sterilization was emphasized. • Two flocculants played the different roles in drinking water treatment. • The synergistic effect of two coagulants for sterilization was confirmed by Contour Method. • Sterilization mechanism and kinetics of flocculants were revealed for the first time. • Sterilization was divided into two processes, rapidly adsorbing and slowly killing. In this study, the relationship between coagulation-flocculation and sterilization was studied using two conventional flocculants, polyaluminum chloride (PAC) and poly dimethyl diallyl ammonium chloride (PDMDAAC). Simulated wastewater containing kaolin and Escherichia coli was prepared. The bacterial removal rates of PAC and PDMDAAC under the same dosage are 46.3% and 19.5%, respectively. Which is far less than that of combined flocculants (94% bacterial removal rate). The synergistic effect of two flocculants was proved by contour method. β-Galactosidase activity, extracellular polysaccharides release, bacterial respiration activity and the activity of triphenyl tetrazolium chloride (TTC) dehydrogenase were investigated to clarify the sterilization kinetics and mechanisms. Two flocculants play the different roles in the treatment. PAC plays role of coagulation, charge neutralization, but PDMDAAC with quaternary ammonium groups is responsible for flocculation to form big flocs, which further enhances its contact with E. coli and contributes to sterilization. Sterilization by flocculants is divided into two processes, rapidly adsorbing and slowly killing, since the respiratory activity of E. coli in flocs gradually decreases with increasing contact time. The increase of flocculant dosage overcomes the hindrance of the secretion of extracellular polysaccharide polymers originating from E. coli to coagulation and sterilization. Sterilization of flocculant should be fully considered in drinking water treatment. [ABSTRACT FROM AUTHOR]

Three-dimensional Ti-Sn/γ-Al 2 O 3 particle electrodes were prepared for the efficient degradation of chloramphenicol (CAP) in wastewater. To observe the surface morphology and structural characteristics of the Ti-Sn/γ-Al 2 O 3 particle electrodes, Fourier transform infrared spectroscopy, X-ray fluorescence, scanning electron microscopy, and X-ray diffraction were used for characterization. Parameters affecting the degradation efficiency and energy consumption of the Ti-Sn/γ-Al 2 O 3 particle electrodes, such as conductivity, initial pH of wastewater, current density, air flow, and initial CAP concentration (100 mg·L −1 ), were examined. Results showed that the optimal conditions were 0.1 A current intensity, 1.0 L·min −1 air flow, 6000 μS·cm −1 conductivity, and pH 6. More than 70% of CAP was degraded under the optimal conditions. Based on the reaction intermediate products identified, a possible pathway for the electrochemical oxidation of CAP by the Ti-Sn/γ-Al 2 O 3 particle electrodes was proposed. [ABSTRACT FROM AUTHOR]

[Display omitted] • PVA/PSSNa semi-IPN@Ni foam removes 95.17% CIP and 99.20% Ni(II) from wastewater. • Satisfactory adsorption occurs under neutral to slightly acidic pH (3–7). • In the binary system, Ni(II) greatly affects CIP adsorption, while CIP slightly affects Ni(II). • The interactive term of Ni(II) concentration and pH notably affects the CIP removal. • Removal of CIP and Ni(II) is most affected by their own concentration and pH. The coexistence of antibiotics and heavy metals in wastewater notably influences their adsorption removal behavior. However, the synergistic and antagonistic characteristics and mechanisms of their co-adsorption remain unclear. A novel adsorbent, PVA/PSSNa semi-IPN@Ni foam, was synthesized and applied to study its features and mechanisms in the single and binary systems of ciprofloxacin (CIP) and Ni(II). Exceptional removal efficiencies of 95.17 % for CIP and 99.20 % for Ni(II) were achieved. The interactive effects between CIP and Ni(II) were comprehensively explored through adsorption capacity ratio (Rq) and response surface methodology. Mechanistic insights were obtained through NaCl charge shielding experiments, substructure analog molecule probes experiments, theory calculations, as well as FTIR and XPS characterizations. The outcomes suggest that in the single system of CIP, the adsorption mechanisms include electrostatic attraction, hydrogen bonding, and π-π interactions. In the single system of Ni(II), mechanisms include electrostatic attraction and coordination. In the binary system of CIP + Ni(II), low Ni(II) concentrations facilitate CIP adsorption through coordination and bridging, whereas high Ni(II) concentrations let to competition for adsorption sites. Interestingly, the presence of CIP had minimal impact on Ni(II), exhibiting only a slight synergistic effect. These findings highlight the PVA/PSSNa semi-IPN@Ni foam as a hopeful candidate for removing CIP and Ni(II) from wastewater, and contribute to a deeper comprehension of synergistic and antagonistic mechanisms in the binary system involving CIP and Ni(II). [ABSTRACT FROM AUTHOR]

[Display omitted] • Combining PM and 3D electrode process showed a remarkable synergy for DCF removal. • GAC and organic contaminants promoted the conversion of MnO 2 and PM to Mn(III) aq. • GAC act as a mediator transferring electrons from organic contaminants to PM. • Mn(III) aq and colloidal MnO 2 mainly contributed to ECs removal. • GAC particles exhibited a stable catalytic performance after 10 cycles. Currently, the electro-activated permanganate (PM) process, as one of the reactive manganese species (RMnS)-based advanced oxidation processes, has shown great potential for environmental remediation. However, the activation efficiency of PM in the electro-activated PM (E-PM) process is limited due to the poor mass transfer and electron transfer efficiency in the two-dimensional (2D) process. In this study, to overcome these drawbacks, granular activated carbon (GAC) was introduced as particle electrodes, establishing an efficient three-dimensional (3D) electrode process (E-GAC-PM), which promoted the generation of RMnS. Comparative experiments exhibited the significant synergy between PM and the 3D electrode process, resulting in the highest diclofenac (DCF) removal (90.2 %) with the lowest energy consumption. Electrochemical impedance spectroscopy and Tafel curve showed that the addition of GAC greatly attenuated the electrochemical impedance, facilitating the activation of PM. Further studies revealed that GAC can serve as an electron mediator, transferring electrons from contaminants to PM, thereby generating Mn2+ and promoting Mn(III) aq formation. Meanwhile, in-situ generated Mn2+ can also be oxidized by the anode and particle electrodes into Mn(III) aq. Besides, the in-situ generated MnO 2 facilitates the performance via oxidation and catalysis effects. Under the protection of the electric field, GAC showed a relatively stable performance which could be regenerated and maintain active after 10 cycles. All these results demonstrated that the E-GAC-PM process was an efficient, energy-saving, and sustainable method for refractory organic contaminants removal, which showed potential for practical application. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel enhanced As(III) removal process, MIL-53(Fe)/sulfite, was developed. • As(III) removal was through a combination of oxidation and adsorption. • As(III) oxidation relied on the powerful Fe(IV) and SO 4 •− generated from SO 5 •−. • Oxidation product As(V) was adsorbed by forming monodentate complexes. • Procedure to realize the purification of real arsenic-spiked water was proposed. Iron based metal–organic frameworks (Fe-MOFs) have garnered international interest as a novel and promising category of adsorbent materials for the elimination of arsenic from neutral waters. Nevertheless, their practical implementation is constrained by their inadequate adsorption capacity for aqueous arsenite (As(III)), a prevalent arsenic species found in acidic environments such as acid mine drainage. Herein, a novel oxidation-adsorption process to effectively purify As(III)-contaminated water is constructed by combining the MIL-53(Fe) of high acid resistance with sulfite (S(IV)). Notably, the adsorption capacity of the MIL-53(Fe)/S(IV) process for As(III) at pH 3.5 reached 86.4 mg g−1, surpassing the values achieved by MIL-53(Fe) alone by 21.6 times for As(III) and 1.62 times for As(V) (oxidized As(III)). During the oxidation process, MIL-53(Fe) effectively activated S(IV), leading to the formation of the crucial intermediate SO 5 •−, which then underwent two distinct pathways to respectively generate Fe(IV) and SO 4 •−, accounting for rapid oxidation of As(III). In the adsorption process, the S(IV) activation (i.e., complexation and electron transfer) on the MIL-53(Fe) surface created additional adsorption sites by dredging the pores and altering the electron cloud distribution within the adsorbent. Furthermore, As(V) trended to form monodentate complexes with surface Fe (e.g., Fe O As bond) in the MIL-53(Fe)/S(IV) process. Notably, this oxidative removal process demonstrated reliable performance in complex water matrices and practical arsenic-contaminated waters. Overall, this study presents a promising strategy to enhance the efficacy of Fe-MOFs for the removal of As(III). [ABSTRACT FROM AUTHOR]

[Display omitted] • ACF cathode exhibits excellent performance in PAA activation for SMX elimination. • ACF could maintain persistent catalytic ability under a cathodic electric field. • •OH generated from ACF cathode plays the dominant role in organics degradation. • Degradation intermediates of SMX are harmless to the aquatic ecology. Advanced oxidation processes (AOPs) based on peracetic acid (PAA) could generate various radicals with low by-product generation, making them a vital technology in the remediation of organic pollution. Maintaining the activity and continuous operation of catalytic systems in water treatment processes was a highly challenging research topic. Herein, the electrochemical process with an activated carbon fiber (E-ACF) cathode was devised to boost the activation of PAA (E-ACF-PAA) for persistent elimination of organics. Compared to other commonly used electrodes, the ACF cathode displayed superior PAA activation ability and higher sulfamethoxazole (SMX) removal. The applied cathodic electric field could protect ACF from PAA oxidation, maintaining its long-term catalytic ability over 50 cycles. Based on radical quenching studies, the EPR test, and the estimation of radical contribution, the E-ACF-PAA process was identified as a radical dominant system. Importantly, isolated chamber experiments proved that PAA was mainly decomposed on the cathode to produce hydroxyl radicals (OH) for SMX degradation, while the anode played a negligible role. According to toxicity prediction and algae growth tests, the degradation products were harmless to the aquatic ecology. Remarkably, continuous flow experiments over a 24 h and different water matrix tests have also proven applicability in practical scenarios. This work provided novel insights into the electrochemical activation of PAA and further expanded the potential applications of PAA-based AOPs in the remediation of organic pollution. [ABSTRACT FROM AUTHOR]

• The catalyst possessed excellent separation ability and recyclability. • HSM-N-Cu/S(IV) system could effectively oxidize As(III) at circumneutral pH. • SO 4 − was suggested as the reactive oxidant responsible for As(III) oxidation. • The apparent reaction rate constant of SO 4 − production reached 1.81 ± 0.12 M−1 s−1. • k value of SO 5 −+As(III) → As(IV) + SO 5 2− was first calculated as 2.6 × 106 M−1 s−1. In heterogeneous reactions, efficient solid–liquid separation of catalyst from water after oxidation is a significant approach to reduce possible secondary pollution of aquatic environments. In this work, a hollow-structured self-floating copper-loaded catalyst (HSM-N-Cu) was fabricated using copper ammonia complexes and hollow glass microsphere as the copper source and supporter, respectively. The SEM, TEM, BET, XPS, and XRD characterization results suggested ideal specific surface area and stability of HSM-N-Cu. The prepared HSM-N-Cu in conjunction with sulfite have been successfully applied for As(III) oxidation in near-neutral conditions. In general, HSM-N-Cu effectively activating S(IV) process involved Cu(II)/Cu(I) conversion and chain reactions of oxysulfur radicals, where the S(IV) acted as a complexing ligand to Cu(II) surface and precursor of oxysulfur radicals. SO 4 − was verified as the dominant contributor to As(III) oxidation, the apparent reaction rate constant (k obs ') for SO 4 − generation was 1.81 ± 0.12 M−1 s−1, and the reaction rate constant (k 12) of SO 5 − + As(III) → As(IV) + SO 5 2− was first calculated as 2.6 × 106 M−1 s−1 by kinetic study. The apparent activation energy (E a) was 48.6 ± 0.1 kJ mol−1 at 100 mg L−1 HSM-N-Cu. Additionally, self-floating HSM-N-Cu could be easily separated, and its great stability was proven after six-cycle test. Furthermore, the HSM-N-Cu/S(IV) system can work effectively in broad range of geochemical conditions. In summary, the established process is feasible for remediation of As(III)-contaminated water, the collection of self-floating catalysts by surface separation from water provides a new idea to reduce secondary pollution of water by catalysts. [ABSTRACT FROM AUTHOR]

[Display omitted] • Abundant electron-rich Co centers generated by Mg doping enhanced PMS activation. • MCO@PES membrane/PMS system achieved instant contaminants elimination. • The highly accessible SO 4 −, OH, and 1O 2 were the responsible reactive species. • Catalyst recovery and enhanced mass transfer in membrane provided the application value. The practical application of heterogeneous Fenton-like processes in wastewater treatment is limited by inadequate catalyst recovery and limited mass transfer in traditional batch mode. Consequently, a catalytic membrane composed of inert magnesium (Mg)-doped Co 3 O 4 spinel (MCO) was crafted to activate peroxymonosulfate (PMS) for the elimination of organic contaminants. The incorporation of the less electronegative Mg induced electronic polarization on the MCO surface, resulting in the generation of sufficient electron-rich Co centers, thereby amplifying its electron-donating properties in PMS activation and enhancing the inherent catalytic activity of the spinel. Regarding the catalytic membrane, the stacked porous structure of the MCO layer achieved reactive sites exposure, mass transfer enhancement, and reactive species availability. Remarkably, the MCO@polyethersulfone (PES) membrane/PMS system instantaneously activated PMS, displaying an elimination kinetic constant of 0.039 ms−1 for tetracycline. The MCO@PES membrane exhibited exceptional catalytic performance and stability in long-term operational studies. Mechanistic investigations elucidated that the highly accessible SO 4 −, OH, and 1O 2 within the catalytic membrane facilitated the immediate elimination of contaminants. This study serves as a valuable reference for the application of transition metal spinel-based catalytic membranes in wastewater treatment. [ABSTRACT FROM AUTHOR]

• Captured SO 2 reutilization and water remediation were simultaneously achieved. • An EC/CoSi/sulfite system for efficient sulfate radical production was developed. • Insights for synergy mechanism of EC/CoSi/sulfite system were provided. • Influencing factors were investigated and operating conditions were optimized. The desulfurization by-product (e.g. sulfite) treatment and water pollution are two widespread concerns, while the sulfite activation by transition metals can be adopted to solve both of them simultaneously. In this study, a silica-supported cobalt catalyst (CoSi) was used to activate sulfite for the degradation of organic pollutants in an electrochemical system (the EC/CoSi/sulfite system), which demonstrated remarkable water treatment efficiencies due to sulfate radical oxidation. The synergy mechanisms of the EC/CoSi/sulfite system were revealed. (i) The as-prepared CoSi played the dual roles as an electro-adsorbent and a catalyst for sulfite activation. (ii) The electrolytic oxygenation supported the conversion of cobalt species and the chain reactions of oxysulfur radicals. (iii) The anodic oxidation of sulfite also generated oxysulfur radicals. The influencing factors and operating parameters were investigated and optimized systematically. Moreover, the efficient degradation of highly concentrated X-3B and non-selective oxidation of various organic compounds confirmed the promising application of the EC/CoSi/sulfite system in practical water treatment. Overall, the EC/CoSi/sulfite system created new value of the industrial waste (e.g. sulfite) for further application in the environmental remediation. [ABSTRACT FROM AUTHOR]

[Display omitted] • The synthesized adsorbents captured 94.18 mg g−1 of Co2+ and 62.56 mg g−1 of Ni2+. • <1% of lithium was lost in the cathode leachate during the separation process. • The dominant capture mechanism conversed from physical to chemical adsorption. • The N atoms on the adsorbents were the effective chemical adsorption sites. • Particle movement track in water was predictable via the proposed equation. The effectiveness of lithium recovery determines the future use of the devices powered by lithium-ion batteries (LIBs) under lithium resource shortages. Selective separation of Co2+/Ni2+ from the cathode leachate of LIBs is a key step to reduce the lithium loss in the recovery progress. This study reported a hollow structured self-floating adsorbent synthesized by co-grafting of (3-Aminopropyl)triethoxysilane (APTES) and ethylenediaminetetraacetic acid (EDTA) on hollow glass microsphere (HGM) for selective capture of Co2+/Ni2+ from LIBs cathode leachate. The introduction of the N atom of APTES was crucial for bridging the inorganic HGM and organic EDTA. The organic component of the synthesized adsorbent accounted for 12.82%, which was responsible for the Co2+/Ni2+ adsorptions. Physic- and chemic-adsorptions were the ordinal mechanisms during the three-stages divided adsorption progress. The negative –COO− groups promoted the electrostatic attraction between metal ions and the adsorbents. The N atoms of EDTA were the effective adsorption sites for Co2+ and Ni2+ ions, resulting in chemical chelation of the metal ions with adsorbents followed by ion exchanges of Na+ and Ca2+. The adsorbents captured 94.18 mg g−1 of Co2+ and 62.56 mg g−1 of Ni2+ with a < 1% lithium loss in the LIBs cathode leachate. The self-flotation process of the adsorbent was non-linearly fitted by our original equation for predicting its movement track for further solid–liquid separation. This research proposed a new strategy for the selective adsorption of Co2+/Ni2+ from LIBs cathode leachate with limited lithium loss. [ABSTRACT FROM AUTHOR]

Treatment of a persistent organic pollutant, carbamazepine (CBZ), in aqueous solution by a novel and sustainable method, Electro-activated carbon fiber-peroxydisulfate (E-ACF-PDS), was investigated and compared with ACF adsorption, Peroxydisulfate (PDS), ACF-peroxydisulfate (ACF-PDS), E-Pt (Pt-plating titanium as cathode in electrolysis), E-ACF (ACF as cathode in electrolysis), and Electro-Pt-peroxydisulfate (E-Pt-PDS) processes, respectively. The removal rate of CBZ by E-ACF-PDS was 98.78% in 30 min, which was much higher than that of the others. Besides, several tests were performed to investigate the role of operational conditions (pH, peroxydisulfate concentration, electrode potential, temperature, and water matrix) in E-ACF-PDS process. Moreover, it is worth noting that even after recycling ACF for 100 times, the removal rate of CBZ in 30 min decreased only slightly from 98.78% to 97.35% in E-ACF-PDS process. In addition, the surface functional groups, FTIR spectrum, Raman spectrum, BET surface area, micropore volume, and SEM images of ACF before and after long time service were investigated and the results revealed that the ACF could maintain the original features in E-ACF-PDS process even after 100 cycles, while the ACF alone was seriously damaged in ACF-PDS process after 50 cycles. These results suggested that the E-ACF-PDS process could remarkably enhance the removal of CBZ in aqueous solution due to the simultaneous adsorption of contaminants and the increase in the generation of active radicals on ACF. The electrons on cathode could inhibit the destruction of ACF caused by chemical oxidation such as sulfate radicals, hydroxyl radicals, and peroxydisulfate. Therefore, the E-ACF-PDS process may provide an effective and sustainable approach to water treatment for the elimination of contaminants of emerging concern in water. [ABSTRACT FROM AUTHOR]

[Display omitted] • Promoted removal of arsenic by ZIF-67/sulfite than ZIF-67 is achieved. • Fast As(III) removal is through an integration of oxidation and adsorption. • SO 4 − is responsible for As(III) oxidation in solution and on catalyst surface. • The sulfite activation by ZIF-67 provides extra sites for As(III,V) adsorption. • Operating parameters of ZIF-67/sulfite system for arsenic removal are optimized. Elimination of As(III) from water has gotten more attention in comparison with As(V) due to its higher mobility and toxicity. In this work, we provide an effective method by integrating a cobalt-based metal–organic framework ZIF-67 and sulfite (S(IV)) to purify As(III)-laden water. The coupled oxidation with adsorption process (i.e., As(III) removal by ZIF-67/S(IV)) surpasses a divided preoxidation-adsorption process (i.e., As(V) removal by ZIF-67) for arsenic removal from the multi-component water containing various coexisting anions. Herein, the mechanism investigation corroborated that the S(IV) plays dual roles as a complexing ligand and a precursor of oxysulfur radicals. The enhanced As(III) removal is attributed to the S(IV) activation on the ZIF-67 surface via various reactions (e.g., surface complexation and intramolecular electron transfer), which not only generates SO 4 − radicals for rapid oxidation of As(III) to As(V), but also provides more adsorption sites for the immobilization of the oxidized product (As(V)). Furthermore, the combined process can rapidly treat arsenic in the realistic contaminated water from 242 to 7 μg L−1 within 15 min, directly meeting the provisional maximum contaminant level (<10 μg L−1). Overall, the proposed work may aid the rational design of S(IV) mediated oxidation-adsorption process to remove arsenic from a variety of contaminated waters. [ABSTRACT FROM AUTHOR]

[Display omitted] • La 2 (CO 3) 3 /CoFe 2 O 4 /biochar (LCB) was synthesized by a hydrothermal process. • LCB/PMS system was established to remove P(III) in one step. • LCB/PMS exhibited satisfactory removal rate of P(III) in a wide pH range. • SO 4 •- played a critical role in the oxidation process. • Different types of phosphorus could be rapidly removed by LCB/PMS. Phosphite [P(III)], an emerging eutrophication pollutant, has attracted limited attention in recent years. Owing to the higher solubility and resistance to biotransformation of P(III), oxidation of P(III) to phosphate [P(V)] is considered to be necessary to enhance P(III) removal. Herein, an efficient and regenerable magnetic La 2 (CO 3) 3 /CoFe 2 O 4 /biochar composite (LCB) was constructed through a facile one-pot hydrothermal method to treat phosphite-laden wastewater. LCB coupled with peroxymonosulfate (PMS) exhibited satisfactory P(III) removal performance through a one-step process for simultaneous oxidation and adsorption of P(III). The adsorption capacity of LCB/PMS for P(III) (71.94 mg/g) was much higher than that of LCB. LCB/PMS system showed high P(III) removal efficiency of 96.62 %, wide pH ranging from 4.0 to 9.0, and good reusability. It also worked well in the existence of anions and humic acid. The quenching experiments and electron spin resonance tests (ESR) revealed the critical role of SO 4 •- in the P(III) oxidation process. Characterization results demonstrated that electrostatic attraction and ligand exchange were responsible for P(III)/P(V) adsorption. Moreover, LCB/PMS system presented desirable performance in eliminating a series of typical organic and inorganic phosphorus. The LCB/PMS system provides a promising and sustainable technology for the purification of P(III)-contaminated water. [ABSTRACT FROM AUTHOR]

Removal of nitrobenzene (NB), a carcinogenic and refractory pollutant, in aqueous solution by adsorption, ozonation, electrolysis, and electro-peroxone (E-peroxone) with activated carbon fiber (ACF) was investigated, respectively. Kinetic analyses of NB removal by all the processes followed pseudo-first-order kinetics and the K app of E-peroxone-ACF was 14.90 × 10 −2 min −1 , which was much higher than the others. Besides, the K app of E-peroxone-ACF process reduces slightly to 12.18 × 10 −2 min −1 even after 100 times of ACF recycle, showing a sustainable activity. Moreover, according to the pore texture characteristics, surface functional groups, FTIR, and SEM images, E-peroxone process does not considerably alter the ACF surface, whereas ozone alone can cause substantial damage to it. These results suggested that ACF was induced from an initiator/a promoter into an electrocatalyst in ozonation by free electrons injection. Moreover, comparing with titanium cathode, ACF can remarkably improve the removal of NB in E-peroxone due to the synchronous adsorption of pollutants and ozone as well as the enhancement of H 2 O 2 generation. It indicates that the ACF cathode is a promising material for organic pollutants removal in the E-peroxone process. [ABSTRACT FROM AUTHOR]

[Display omitted] • Peroxymonosulfate could be efficiently activated by piezo-catalysis (PE) with hydraulic mixing. • The energy consumption of hydraulic PE-PMS process was only 2.56% and 22.87% of ultrasonic PE-PMS and traditional E-PMS processes, respectively. • BaTiO 3 as piezoelectric material maintained performance without valence and crystal phase changes after 10 cycles. • There was an optimal hydraulic gradient (7.72 s−1) in hydraulic PE-PMS process. • ·OH played a critical role in the hydraulic PE-PMS process for CBZ degradation. Although peroxymonosulfate (PMS) coupling with ultrasonic piezo-catalysis (PE) or electrolysis (E) exhibited satisfactory efficiency of organics degradation by generating more reactive species, the relatively high energy consumption restricted their application. Hydro-energy, as a clean energy resource, is available in water treatment and transportation processes. Herein, a hydraulic-driven PE-PMS process was proposed, using barium titanate as piezoelectric material for carbamazepine (CBZ) degradation. Results showed that CBZ was efficiently degraded (76.17%, 180 min) in the PE-PMS process with a pseudo-first-order rate constant of 8.15 × 10−3 min−1. Moreover, the degradation ratio of CBZ was still up to 64.19% after 10 cycles without valence and crystal phase changes. Importantly, the energy consumption of the hydraulic PE-PMS process (428.65 kWh m−3 order−1) was only 2.56% and 22.87% of ultrasonic PE-PMS and traditional E-PMS processes, respectively. Finite element method and electrochemical measurement were performed to understand the influence of the hydraulic gradient (G). A positive correlation between G and piezo-potential/current was found in the hydraulic PE-PMS process. However, there was an optimal G value (7.72 s−1) for CBZ degradation. Further studies showed that ·OH played a major role in CBZ degradation during the hydraulic PE-PMS process. Various refractory organics could be effectively degraded in this process, while a satisfactory degradation of CBZ was observed in the actual water matrices. Therefore, the hydraulic-driven PE-PMS system might be an efficient, sustainable, and energy-saving process for water treatment by the potential utilization of residual hydro-energy in water transportation. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel self-floating silica adsorbent was specially designed and synthesized. • -SO 3 H was facilely introduced onto HGM by post-grafting and oxidation techniques. • SO 3 H-HGM exhibited satisfactory reusability with dilute hydrochloric acid eluent. • CIP and Ni2+ were efficiently removed across a wide pH range. • The self-floating capability of SO 3 H-HGM ensured its great separation performance. A novel self-floating silica adsorbent was synthesized by introducing sulfonic acid groups onto the surface of hollow glass microsphere (HGM) through post-grafting technique. The obtained sulfonated HGM (SO 3 H-HGM) not only had satisfactory adsorption performance for ciprofloxacin (CIP) and heavy metal nickel (Ni2+), but also had stable self-floating capability. SO 3 H-HGM exhibited wide pH adaptability. Langmuir and Elovich models well fitted the adsorption isotherm and kinetic data, respectively. Under the optimal experimental conditions, the theoretical saturated adsorption capacities of SO 3 H-HGM for CIP and Ni2+ calculated by the Langmuir model reached 464.78 mg·g−1 and 19.65 mg·g−1, respectively. Thermodynamic calculation verified the spontaneous nature and feasibility of the adsorption processes. The saturated adsorbent could be easily desorbed and regenerated by the eluent, and after five adsorption cycles, there was no serious reduction in adsorption capacity, which proved the good reusability and stability of SO 3 H-HGM. The adsorption mechanism of CIP and Ni2+ by SO 3 H-HGM is mainly electrostatic interaction, followed by hydrogen bond, hydrophobic interaction and coordination. This research demonstrates that HGM is a potential and promising material for the adsorptive purification of water contaminated with CIP and Ni2+, and to realize self-floating solid–liquid separation. [ABSTRACT FROM AUTHOR]

• A photo-enhanced removal of As(III) and Cu(II) was achieved. • As(III) removal was through a combination of photooxidation and coprecipation. • As(III) photooxidation relied on the formation of the Cu(II)–As(III) complex. • As(III) complexed with Cu(II) is photooxidized via direct electron transfer. • Procedures to realize the light-enhanced water's purification were proposed. Arsenic and copper causing water pollution is a worldwide problem, and simultaneously achieving water decontamination from arsenic and copper is immensely attractive. In this study, an economical and eco-friendly light-enhanced removal system was proposed to simultaneously alleviate water contamination from arsenic and copper, where nascent copper hydroxides (CHO) acted as nano-absorbers and electron acceptors for As(III) removal. According to the mechanism studies, the nascent CHO effectively capture As(III) forming surface Cu(II)–As(III) complex (formation constant, log K f1 = 6.0). Then, light induced the ligand-to-metal charge transfer (LMCT) from As(III) to Cu(II) inside the Cu(II)–As(III) complex, thus leading to both As(III) oxidation and Cu(II) reduction under anoxic conditions. The quantum yield of As(III) photooxidation at 365 nm was ascertained as (2.3 ± 0.2) × 10−2. The final photoproducts can be easily recycled as stabilized Cu(II)–As(V) complex and deposit. Real sunlight-driven photooxidation of As(III) in the presence of CHO and As(III) photooxidation to As(V) in solid Cu(II)–As(III) complex were also confirmed, which implying the promising application in practical water treatment. Accordingly, the oxygen-independent and light-enhanced removal of arsenic and copper can help develop recovery strategies for copper and arsenic. [ABSTRACT FROM AUTHOR]

• Carbon-based nanoparticles CoFe 2 O 4 /OSC were fabricated as peroxymonosulfate activator. • Norfloxacin could be effectively degraded by CoFe 2 O 4 /OSC/PMS system. • Redox potentials of Fe(II)/Fe(III) and Co(III)/Co(II) were involved in the system. • CoFe 2 O 4 /OSC nanocomposite provides new insights into the resource utilization of OS. In this study, oily sludge (OS) was pyrolyzed into an environmentally friendly OS carbon (OSC) material, which was used as the carrier of CoFe 2 O 4 nanoparticles to prepare a heterogeneous catalyst CoFe 2 O 4 /OSC, and it was used to catalyze the degradation of norfloxacin (NFC) by peroxymonosulfate (PMS). X-ray diffraction (XRD) and transmission electron microscope (TEM) characterization results show that CoFe 2 O 4 /OSC had a spinel structure under high temperature pyrolysis conditions. The effects of initial pH, PMS dosage, catalyst dosage, and temperature on NFC degradation efficiency were also studied. Under a temperature of 25 °C, an initial pH of 7, a catalyst amount of 0.5 g/L, and a PMS dosage of 0.8 mM, the reaction rate constant reached 0.051 min−1, and the degradation efficiency and total organic carbon of NFC reached 90.8% and 62%, respectively, within 60 min. Trace amounts of Co and Fe ions were leached from the system (both less than 30 μg/L). After ten cycles, the degradation efficiency of NFC decreased to 69.8%. Radical quenching experiments, electron paramagnetic resonance, and X-ray fluorescence spectroscopy characterization proved that free-radical (OH, SO 4 −, and O 2 −) and nonradical (1O 2) active species were present in the system. Moreover, the CoFe 2 O 4 /OSC/PMS system involved the participation of two pairs of redox couples (Fe(II)/Fe(III) and Co(III)/Co(II)). Results from matrix-assisted laser desorption ionization time-of-flight mass spectrometry and ion chromatography proved that the main oxidation pathways of NFC were formed through the fragmentation of heterocycles, defluorination of benzene rings, decarboxylation reactions, and piperazine ring-opening process. At the same time, NFC was eventually oxidized to fluoride. This study provides potential for the resource utilization of OS and the application of sludge-type catalysts in PMS-activated oxidation systems. [ABSTRACT FROM AUTHOR]

• Co 3 O 4 nanoparticles were successfully confined in the internal cavity of CNTs. • Co 3 O 4 @CNT was effective for catalytic activation of PMS to degrade norfloxacin. • Co 3 O 4 nanoparticles filling is a strategy to lower Co leaching. • Non-radical 1O 2 was the major function of norfloxacin degradation. • DFT calculation results confirmed Co 3 O 4 @CNT had high electronic activity. In this work, the tube-filled nanocomposites Co 3 O 4 @CNTs were successfully prepared and applied for the first time in the permonosulfate (PMS) system to degrade norfloxacin (NX). Characterization results showed that Co 3 O 4 nanoparticles served as independent templates and were randomly distributed onto the surface of the internal cavity of CNTs. After five cycles, the removal rate of NX decreased by only 4.5%, indicating its high catalytic activity and stability. This study also proposed a potential mechanism based on Co 3 O 4 @CNT/PMS system catalysis in which 1O 2 was the main cause of NX degradation. DFT calculation results confirmed that the electronic activity of Co 3 O 4 filled CNTs increased, and that the Co 3 O 4 nanoparticles filled in the tube were the main catalytic sites of Co 3 O 4 @CNTs for NX degradation. This work provided the first insight into the effects of metal nanoparticles in the confined structure of CNTs on PMS activation. [ABSTRACT FROM AUTHOR]

• Novel nitrogen-doped carbon fiber aerogel (N-CFA) was obtained by carbonization of cotton and urea in one-step. • 1O 2 instead of radicals was the predominant reactive oxidant species in N-CFA/PMS process. • CBZ degradation pathways mainly by 1O 2 were firstly proposed. • CBZ was removed in different water matrices with a satisfactory efficiency in N-CFA/PMS process. Nitrogen-doped carbon as metal-free catalysts exhibited exceptionally catalytic activities in environmental remediation fields. Herein, a novel nitrogen-doped carbon fiber aerogel (N-CFA), which was conveniently prepared using cotton and urea by a direct high temperature carbonization in one-step, was used to activate peroxymonosulfate (PMS) for the degradation of carbamazepine (CBZ) in water. Characterization results demonstrated that the key active sites (pyridinic N, pyrrolic N, and graphitic N) were formed in the process of nitrogen doping into the carbon fiber aerogel. More importantly, singlet oxygen (1O 2) instead of conventional OH and SO 4 − was suggested as the predominant reactive oxygen species (ROS) during N-CFA/PMS process based on the scavenger inhibition tests, and confirmed by molecular probe and liquid-phase electron paramagnetic resonance (EPR) experiments. It was speculated that nitrogen-containing functional groups played a key role in inducing the non-radical pathway. Moreover, CBZ degradation pathways mainly by 1O 2 were firstly proposed based on intermediates. The N-CFA/PMS system could achieve a CBZ degradation rate of 100% within 50 min, which was significantly higher than the catalytic effect of several carbon materials (ACF, GAC, and GO) and even higher than the catalytic effect of various metal-based catalysts including Co 3 O 4 , CuO, Fe 3 O 4 , and Fe 2 O 3. It was also noted that the CBZ was removed with a satisfactory efficiency in different water matrices with inorganic anions (HCO 3 –, Cl−, H 2 PO 4 −, SO 4 2−, and NO 3 –) and humic acid (HA). Thus, this study proposed a benign and highly efficient oxidation technology, which would exhibit wide potential for environmental restoration. [ABSTRACT FROM AUTHOR]

• Dual-functional flocculant with pH resistant is synthesized and used to remove heavy metals. • Flocculation conditions for reaching high removal efficiencies are optimized. • Optimal operation modulus was identified using 8 Key performance indicators by 3E triangle model. • Multi-objective programming optimization model was also established to evaluate Operation strategies. • Flocculation for heavy metal removal is superior in terms of engineering performance. Carboxymethyl chitosan (CMCTS) with active hydroxyl and amino groups is easily modified for chelating and capturing heavy metal, thus showing great potential for application in heavy metal-contaminated wastewater treatment. In this work, a dual-functional MACA copolymer [CMCTS-graft-P(AM-TGA)] with pH resistant was successfully designed and prepared by grafting acrylamide and thioglycolic acid onto CMCTS through UV-initiated graft polymerization. The spectroscopy characterization of functional groups and apparent morphology confirm the successful preparation of MACA. Flocculation conditions for reaching high removal efficiencies and investigating chelation capacity are optimized. A multiobjective evaluation model and a triangular environmental impact, economic benefit, and energy consumption (3E) evaluation model were established and employed to assess the 3E performance of MACA in heavy metal-contaminated wastewater flocculation. Optimal operation modulus is identified using 8 Key performance indicators by 3E triangle model. This work enriches knowledge about flocculation and provides guidance for flocculation parameter control. [ABSTRACT FROM AUTHOR]