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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]

Among homogeneous catalysts, cobalt ions exhibit ultra-high persulfate activation performance. In this work, an electrically supported medium Co(II) activated peroxydisulfate synergistic process was established to eliminate organic contaminants in water. The synergistic catalytic effect was verified by comparing the oxidative degradation performance and reaction rate constant of different coupling systems. The decolorization ability of E-Co(II)-PDS on reactive black 5 (RB5) was explored, and the results showed that the removal rate of RB5 can reach 93.21% under the optimized conditions of current density of 5.71 mA/cm2, initial pH of 4, Co(II) concentration of 0.2 mM and PDS concentration of 5 mM. The effect of water matrix on the removal of RB5 was studied, and it was found that HCO 3 − and humic acid significantly inhibited the degradation of RB5, while Cl− and H 2 PO 4 − could effectively promote it at a certain concentration. Notably, the degradation of RB5 in E-Co(II)-PDS system achieved lower energy consumption, with an energy consumption per unit volume (EE/O) value of 0.4304 kWh·m−3. EPR test, quenching experiments and contribution rate analysis showed that the oxidation active species in E-Co(II)-PDS process were Co(III), sulfate radicals and hydroxyl radicals, and their oxidation contribution rates were 15.72%, 12.69% and 53.25%, respectively. Finally, the decomposition process of RB5 was proposed by the mass spectrometry results. The electric current promotes cobalt ion cycling and PDS activation through electron transfer, and induces Co(II) to promote the activation of PDS, which is the main mechanism of E-Co(II)-PDS system to achieve the robust degradation ability of RB5. • Co(II) greatly improved the activation effect of electroactivated persulfate system. • The current promotes Co(II)/Co(III) cycling and peroxydisulfate activation. • Low energy consumption was achieved by E-Co(II)-PDS system. • Co(III), SO 4.•– and •OH contributed to RB5 removal in E-Co(II)-PDS process. • E-Co(II)-PDS could robustly degrade organic contaminants in water. [ABSTRACT FROM AUTHOR]

In this paper, a novel magnetic sorbent based on silica coated iron oxide (Fe 3 O 4 /SiO 2 , denoted as FS), poly(ethylene imine) (PEI), sodium p-styrenesulfonate (SPS) and sodium alginate (SA) polymer (Fe 3 O 4 /SiO 2 /SA-PEI-SPS, denoted as FSSEP) is successfully prepared by free radical polymerization. Antibiotic (ciprofloxacin, CPX), dye (methylene blue, MB) and heavy metal (copper ion, Cu2+) are used to test the adsorption capacity of the prepared adsorbent. Compared with other adsorbents, FSSEP exhibited good capture efficiency for the pollutants in this study, especially for organic pollutants (CPX and MB). The maximum sorption capacity of FSSEP reached 203.99 mg g−1 for CPX, 423.69 mg g−1 for MB, 41.81 mg g−1 for Cu2+. Hydrogen bonding, electrostatic interaction, π-π interaction and cationic exchange are involved in the sorption mechanism. This study suggests a strategy for the design and synthesis of eco-friendly modified sodium alginate adsorbents through free radical polymerization and explores their potential application in the field of removal of different types of toxic substances. [Display omitted] • A new magnetic composite of FSSEP was synthesized by free radical polymerization. • Dye (MB), antibiotic (CFX) and Cu2+ ion were efficiently captured via FSSEP. • FSSEP microparticles can be regenerated and quickly separated from solution. • Adsorption mechanism of FSSEP was analyzed and discussed in this work. [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]

Diclofenac (DCF), as a typical representative of PPCPs, has potential ecotoxicity to the water environment. In this study, ultrasound (US) enhanced ferrous sulfide (FeS)-activated persulfate (PDS) technology (US/FeS/PDS) was used to degrade DCF. By comparing the degradation effects of US, US/PDS, FeS/PDS and US/FeS/PDS systems on DCF, this study confirmed the synergy and strengthening effects of US. The influences of single-factor experimental conditions on the US/FeS/PDS system were investigated and optimized. The FeS catalysts before and after the reaction were characterized and analyzed by X-ray diffractometer (XRD) and X-ray photoelectron spectroscopy (XPS). The heterogeneous reaction proceeded on the surface of FeS, and a small part of FeS 2 was formed on FeS surface. During the reaction, the proportion of S2− on the catalyst surface decreased from 51% to 44%. Correspondingly, the proportion of S x 2− increased from 21% to 26%. It indicated that S2− was oxidized into S x 2− in the reaction, and the loss electrons of S2− caused the reduction of Fe3+ to Fe2+on the FeS surface, which promoted the cycle between Fe2+ and Fe3+ in turn. Furthermore, SO 4 − and ‧OH were the main active free radicals, of which the contribution rate of ‧OH was about 34.4%, while that of SO 4 − was approximately 52.2%. In US/FeS/PDS, the introduction of US could promote the dissolution of iron on the FeS surface. US contributed to the formation of a redox power motor between S2—S x 2- and Fe2+-Fe3+, which continuously decomposed PDS to generate sufficient active SO 4 − and ‧OH radicals, thereby efficiently and continuously degrading DCF. Finally, the related mechanism of DCF degradation by US/FeS/PDS was summarized. Overall, US/FeS/PDS can not only efficiently degrade and remove DCF, but also has potential application value in organic pollution removal and wastewater purification. [Display omitted] • US/FeS/PDS can efficiently degrade and remove DCF. • US and FeS/PDS showed a good synergistic effect (S = 3.56). • US could accelerate the dissolution of FeS to continuously to release Fe2+. • US helped to form a redox power motor between S2–S n 2- and Fe2+-Fe3+. • The ·OH (34.4%) and SO 4 − (52.2%) make contribution to DCF removal. [ABSTRACT FROM AUTHOR]

The low specific surface area, poor porosity, and weak charge transport caused by the disordered morphology of metal-N-site catalysts are the main factors limiting their environmental applications. Therefore, a hollow-nanotube carbon nitride (Cu-HNCN) catalyst with CuN x sites dispersed in a hollow nanotube-like CN was constructed and used for the degradation of organic pollutants via the photo-Fenton (PF) process. The high specific surface area, rich porosity, and good visible-light trapping capability of the Cu-HNCN nanotubes were identified. The Cu-HNCN/PF system achieved 96.0% degradation efficiency of tetracycline within 50 min and showed efficient degradation of various antibiotic contaminants. Moreover, the short Cu-N bonds contributed to the improved stability and decreased copper leaching in the Cu-HNCN/PF system. Cu-HNCN, with its enhanced photogenerated charge generation, separation, and transport, was the key to the generation of abundant active species and efficient degradation of pollutants. In addition, frontier electron density theory successfully distinguished the roles of different types of active species in the degradation process. This work provides new insights into the development of catalysts with high stability and accelerated electron transfer to enhance the application of the PF process in practical wastewater purification. [Display omitted] • Hollow-nanotube carbon nitride catalyst were designed for antibiotics degradation. • CuN x sites are highly dispersed for effectively avoiding the loss of Cu ions. • Degradation process was contributed by the abundance of active species and nanotube properties. • It provides catalyst with high stability and accelerated electron transfer for photo-Fenton process. [ABSTRACT FROM AUTHOR]

The adsorption performances of adsorbents to dyes are hard to maintain in a wide pH range because most of the reactions are pH-dependent, developing a cost-effective strategy to break the pH-limitation is significant. In this study, an amphoteric self-floating adsorbent (Am-SA) was synthesized by hollow silica microsphere surface modification, which was useful to capture anionic acid orange 7 (AO7) and cationic crystal violet (CV) dyes, but the adsorption performances were also greatly affected by pH. Fortunately, a co-precipitation phenomenon was noticed when the AO7 and CV solutions were mixed with a 1:1 molecule ratio. The precise structures of AO7 and CV molecules were constructed and the AO7-CV-H 2 O mixed system was structured by Materials Studio. Besides, this system was involved in a dynamic simulation to reveal the mechanism of the co-precipitation phenomenon. The simulation results showed H 2 O molecules dispersed out of the system via thermal motions within 30 ps, but the AO7 and CV molecules aggregated to each other via electrostatic attractions. The energy calculations also demonstrated the electrostatic attraction between AO7 and CV is the dominant factor that induced the aggregation. The aggregation phenomena were also observed in various mixed cationic–anionic dyes systems. The removals of dyes significantly improved in a wide pH range in the mixed systems as the captures of the aggregated dye clusters were much easier than that of independent dye molecules, and both co-precipitation and adsorption contributed to it. Proper utilization of the aggregation behaviors between dyes can be regarded as a prospective strategy in cost-effective treatments. [Display omitted] • Precipitation phenomenon is discovered by mixing cation and anionic dye solutions. • The aggregation process between AO7 and CV is simulated at a molecule-scale. • Electrostatic force of AO7 and CV is the dominant inducement for the aggregation. • The pH-limitation of adsorption can be broken via the mixing strategy of dyes. [ABSTRACT FROM AUTHOR]

We developed a one-step hydrothermal strategy to fabricate Co 3 O 4 @NiCo 2 O 4 core–shell arrays on Ni foam. With this method, the ultralong NiCo 2 O 4 nanowires were self-assembled on the Co 3 O 4 nanowire arrays on Ni foam comfortably. Moreover, the eletrochemical properties of the hybird eletrodes were elucidated by cyclic voltammograms, galvanostatic charge/discharge tests and eletrochemical impedance spectroscopy in 2 M KOH electrolyte. The results exhibited a specific capacitance of 672 F g −1 and excellent cycling stability (97.1% retention after 3000 cycles). The excellent electrochemical performance made the hybrid a promising electrode material for electrochemical capacitors. [ABSTRACT FROM AUTHOR]

The selective separation and recovery of valuable metals from complex polluted wastewater is of great significance to the protection of water resources and the realization of resource recycling. Herein, the chitosan-coated magnetic silica core-shell nanoparticles (FO@SD@CS) were fabricated and applied as adsorbents for highly selective removal of precious metals silver ions (Ag(I)) from complex wastewater. In multi-ion compound polluted solutions, FO@SD@CS showed excellent selective adsorption of Ag(I) in a wide pH range, and an enhancement of the highly selective adsorption capacity of Ag(I), which was increased from 85.86 to 126.74 mg g−1 when the concentrations of methyl blue (MB) coexisted in the solution from 0 to 40 mg L−1 at pH 6.0. The results of Ag(I) single system batch adsorption experiments illustrated that the adsorption behavior of FO@SD@CS to Ag(I) shows obvious pH responsiveness, the adsorption capacity of Ag(I) increases with the increasing of pH value. The results of the adsorption isotherm and kinetics demonstrated that Langmuir and pseudo-second-order kinetics can better describe the adsorption behavior of Ag(I) on FO@SD@CS, indicating that the adsorption process was controlled by chemisorption and the maximum monolayer adsorption capacity reached 116.28 mg g−1 at room temperature. Additionally, in the dye-metal binary system, the coexisting MB promoted the adsorption capacity of FO@SD@CS to Ag(I) from 116.28 to 156.25 mg g−1, showing a synergistic adsorption effect. This study shows that the enhanced selective separation and recovery of metal ions from wastewater based on anion-synergistic not only provides new ideas for wastewater treatment, but also has important significance for water resources reuse. [Display omitted] • A magnetic adsorbent with core-shell structure was successfully prepared. • FO@SD@CS exhibited higher acid resistance than uncoated silica adsorbent. • FO@SD@CS showed high selectivity in capturing silver from multi-ion solutions. • Coexisting MB enhanced the selective adsorption of Ag(I) in complex wastewater. • Possible adsorption mechanisms in both single and binary systems were proposed. [ABSTRACT FROM AUTHOR]

A novel chelating flocculant with branched architectures, polyacrylamide grafted maleoyl chitosan-mercaptoacetic acid (PAM-g-M(CS-MA)), was successfully fabricated using maleic anhydride as the "bridge" between chitosan and polyacrylamide. The functional groups and structural characteristic information of copolymers were obtained via characterization analysis. Flocculation performance was systematically investigated via purifying a series of simulated wastewater containing Cu or Cd. The properties of the flocs were studied to give in-depth evidences for the role of chelation groups and branched architectures in flocculation. Results indicated that PAM-g-M(CS-MA) showed excellent flocculation capacity for heavy metals in high concentrations and was superior to other chelating flocculants. The maximum flocculation efficiency of Cu (93.90%) and Cd (92.47%) was achieved by PAM-g-M(CS-MA) at pH 7, dosage of 100 mg L−1 and stirring speed of 90 rpm. The flocculation mechanisms of PAM-g-M(CS-MA) were deeply explored through the analyses of floc properties. The strong synergistic chelation of mercapto, carboxyl, amide and hydroxyl groups predominated for the capturing of heavy metals; and the branched architectures facilitated the formation of large and stable flocs via adsorption and bridging-furl effect. This study provided a solid foundation for the fabrication of flocculants for heavy metal wastewater treatment. [Display omitted] • A flocculant with branch architectures (PAM-g-M(CS-MA)) was synthesized. • PAM-g-M(CS-MA) showed low-dosage and efficient in heavy metals removal. • The maximum removal rates of Cu (93.90%) and Cd (92.47%) can be achieved by PAM-g-M(CS-MA). • Relationship between the branch architectures and flocculation performance was built. • Flocculation mechanism is composed by synergistic chelation, adsorption and bridging-furl effect. [ABSTRACT FROM AUTHOR]

Chlorophenol is a widely used organic compound, and the environmental and health problems caused by it have being worsened in recent years. This study used 2,4,6-trichlorophenol (2,4,6-TCP) as the target pollutant, and employed ultrasound (US) enhanced zero-valent iron (Fe0)/EDTA/air system (FEA), namely US/FEA, to remove 2,4,6-TCP. The influence of single factor experimental conditions such as EDTA concentration, Fe0 dosage, US power, pH and pollutant concentration on the removal efficiency of 2,4,6-TCP was investigated, and the optimal reaction conditions were determined. The mechanism of reactive oxygen species (ROS) produced by US/FEA was explored. The degradation process and removal mechanism of 2,4,6-TCP in the US/FEA were discussed through the determination and analysis of intermediate products. The results showed that US could continuously activate and renew the Fe0 surface, accelerate its oxidation and corrosion process, and then continuously and stably produce sufficient amounts of Fe2+ and Fe3+. Ultrasonic cavitation effect could reduce the difficulty of O 2 activation reaction, and promote the production of sufficient H 2 O 2. The addition of EDTA made the system have a wide range of pH applications, and its performance under neutral and alkaline conditions was also superior. The ROS of US/FEA included ·OH, O 2 ·- and Fe(IV), where Fe(IV) was the main contributor to the removal of 2,4,6-TCP. In addition, the degradation of 2,4,6-TCP had two processes including dechlorination and benzene ring opening. First, 2,4,6-TCP was dechlorinated and degraded into phenol. And then, phenol was degraded into small molecular acids by ring-opening, and finally it was mineralized into CO 2 and H 2 O completely. US/FEA is a promising technology for high-efficiency degradation of organic matter and deep environmental purification. [Display omitted] • US significantly enhances 2,4,6-TCP removal in US/FEA, and expands the pH adaptive range. • US reduces the difficulty of Fe0 dissolved oxygen reaction, promoting the transformation of Fe0 oxidation corrosion into Fe2+ and Fe3+. • EDTA complexed with Fe2+ and Fe3+ to produce FeIIEDTA and FeIIIEDTA to generate multiple ROS for 2,4,6-TCP efficient degradation. • In US/FEA, The ·OH (15.6%)、O 2 ·- (17.8%)、Fe(IV) (21.2%) make contribution to 2,4,6-TCP removal. [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]

Carbamazepine (CBZ) antibiotic organic contamination wastewater poses a huge threat to environmental safety. An advanced oxidation technology (Fe0/PDS/US) of using ultrasound (US) enhanced zero-valent iron/potassium persulfate (Fe0/PDS) can remove CBZ effectively. The optimal reaction conditions were determined by exploring the effect of single-factor experimental conditions such as ultrasonic power, ultrasonic frequency, CBZ concentration, solution pH, PDS dosage, and Fe0 dosage on the removal of CBZ. In addition, we also investigated into the effect of background ions (PO 4 3−, HCO 3 −, Cl− and HA) on Fe0/PDS/US and analyzed the related results. The mechanism of CBZ removal in Fe0/PDS/US were explored by analyzing CBZ removal efficiency and reaction rates, the ion concentration of S 2 O 8 2−, SO 4 2−, Fe2+ and Fe3+, pH and the active radicals. The result indicates that US can improve the efficiency of activated PDS and expand the pH range of Fe0/PDS. It has prominent performance in catalytically degrading CBZ when the pH is 10.0. SO 4 •-, •OH and O 2 •- all coexist in the Fe0/PDS/US and make contribution to CBZ removal, whereas the S O 4 • − plays a key role. US can greatly promotes the degradation of target pollutant CBZ by speeding up the dissolution of the outer portion of iron powder, producing sufficient amount of Fe2+ with a continuous and stable way, and better activating S 2 O 8 2− to generate sufficient S O 4 • − radicals. The degradation of CBZ may embrace three reaction processes, in which organic intermediate products with low molecular weight and biological toxicity is produced, boosting further mineralization and biodegradation of products. The Fe0/PDS/US is of great potential application value in removal of organic pollution and environmental purification. [Display omitted] • Ultrasound (US) significantly enhances CBZ removal in Fe0/PDS/US, and expands the pH adaptive range. • US makes Fe0 to produce sufficient amount of Fe2+ with a continuous and stable way. • The intermediate products of CBZ have low molecular weight and biological toxicity. • The SO 4.•-, •OH and O 2 •- make contribution to CBZ removal, whereas SO 4 •- plays a key role. [ABSTRACT FROM AUTHOR]

The fine molecular structure of a flocculant fundamentally determines the internal flocculation mechanism and the final application property. In this work, three series of chitosan-based polymers (CTS-g-PAMD) with divergent charge densities and graft chain distribution were synthesized by graft copolymerization using acrylamide (AM) and acryloyloxyethyltrimethylammonium chloride (DAC). Meanwhile, flocculant with linear chain structure (CTS-CTA) was prepared by etherification using 3-chloro-2-hydroxypropyltrimethylammonium chloride (CTA). The characterization results confirmed that various monomers had been successfully introduced into chitosan. The reaction basically happened on —NH 2 at C 2 of chitosan, and the ring structure of chitosan was destroyed by free radical reaction. The obtained flocculants were used to flocculate bentonite and humic acid solution. Besides dose, the effects of chain structure, charge density and chain distribution on flocculation performance were systematically studied. Based on the fractal theory and flocculation kinetics, the effects of structural factors on floc characteristics were also investigated. The results showed that, flocculant with abundant graft chains exerts better flocculation performance and floc characteristic due to enhanced adsorption electrical neutralization and adsorption bridging effect. The effects of charge density and chain distribution on the flocculation performance were disparate in the range of insufficient and excessive doses. Furthermore, on the basis of the quadratic polynomial model, quantitative structure-effect relationships were established, which has guiding significance for the development and utilization of flocculants. Image 1 • Four chitosan-based flocculants with distinct molecular structures were prepared. • The cyclic structure of chitosan was destroyed by graft copolymerization. • Flocculants with "comb" branches exhibited better flocculation performance. • Chain distribution contributed differently under overdose and underdose. • The quantitative structure-activity relationships were established through model. [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]

The metal activating sulfite system has attracted widespread attention as a novel advanced oxidation process recently. In this study, a silica-supported highly dispersed cobalt catalyst was prepared using Co ammine complex as precursor, characterized by transmission electron microscope, X-ray diffraction, Brunauer–Emmett–Teller surface area, X-ray photoelectron spectroscopy and so forth, and used to activate sulfite for the removal of organic pollutants. The as-prepared catalyst displayed a durable and remarkable catalytic activation of sulfite for organic degradation in sequential experiments. The mechanistic study corroborated the dual roles of sulfite as a complexing ligand on catalyst surface and a precursor of oxysulfur radicals. The surface-bound and free SO 4 •− were found to be the dominating radicals responsible for organic degradation. The steady-state approximation of SO 4 •− were examined and the apparent reaction rate constant of SO 4 •− generation was 0.60 ± 0.07 M−1 s−1 at 0.25 g L−1 catalyst. The influencing factors and operating parameters, including catalyst dosage, sulfite/contaminant ratio, pH, temperature, anions and natural organic matter were investigated and optimized systematically. As conclusion, the as-prepared catalyst to efficient activation of sulfite can be proposed as a promising advanced oxidation process based on oxysulfur radicals for the treatment of wastewater. Image 1 • The silica-supported cobalt catalyst is synthesized via a complexation process. • CoASi shows an effective performance in sulfite activation for organic degradation. • Sulfite acts as a complexing ligand and a radical precursor in activation process. • Surface-bound and free sulfate radicals are responsible for dye degradation. • The optimal operating conditions are obtained for further application. [ABSTRACT FROM AUTHOR]

Chitosan-based flocculants are efficient and biodegradable, possessing the potential application in water treatment. A chitosan-based flocculant, CTS-g-PAM, was prepared via grafting copolymerization. Two main structures of CTS-g-PAM were detected by X-ray photoelectron spectroscopy (XPS), and they related to the different performances of CTS-g-PAM in the treatment of model azo dyeing wastewater in terms of removal efficiency, floc size and zeta potential. CTS-g-PAM with the optimal ratio of C N to –NH– owned the best performance. C N reinforced the interaction between CTS-g-PAM and azo dyes and charge neutralization while the flocs formed in the case were large and compacted. However, excessive C N accelerated itself hydrolysis and leaded to the decomposition of CTS-g-PAM, deteriorating the performance of the flocculant. Image 1 • Two different structures of CTS-g-PAM were discovered via XPS. • The ratio of two structures was different in various synthesis conditions. • The moderate C N in CTS-g-PAM contributed to its better performance in the treatment. • C N reinforced the interaction between CTS-g-PAM and azo dyes. • Excessive C N accelerated itself hydrolysis and decomposition of CTS-g-PAM. [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]

• CS-g-P(AM-AMPS) possessed the multifarious functional groups. • Two synthesis pathways and two products were discovered in preparation via XPS. • CS-g-P(AM-AMPS) and PAFC played the different roles in hematite wastewater treatment. • Dissolved heavy metals were removed by chelation, adsorption and co-settlement. Hematite wastewater containing dissolved heavy metals is a potential threat to eco-environment and human health. Flocculation as an efficient and cost effective water treatment technology should be applied in its treatment. A sulfonated chitosan-based flocculant (CS-g-P(AM-AMPS)) was prepared via graft copolymerization. Two synthesis pathways and reaction products with different molecular structure were discovered in processes. CS-g-P(AM-AMPS) possessed the multifarious functional groups that contributed to its excellent performance in hematite wastewater treatment. Bridging, adsorption and entrapment in coagulation-flocculation were enhanced due to CS-g-P(AM-AMPS), and the impressive floc size and high removal efficiency were represented in the treatment as well. Dissolved heavy metals in the wastewater were removed by the chelation of sulfonate group in CS-g-P(AM-AMPS), the adsorption of other functional groups and the co-settlement with flocs. CS-g-P(AM-AMPS) will have the potential application in industrial wastewater treatment for its high flocculation performance, thermal stability and solubility. [ABSTRACT FROM AUTHOR]

Carboxylated chitosan (CPCTS) is used as substrates in the design and synthesis of CPCTS-based flocculants through UV-initiated polymerization techniques. The synthesized flocculants are applied to remove Cr and Ni ions from chromic acid lotion and electroplating wastewater through two-stage flocculation. This study investigates the effect of flocculant dosage, pH, reaction time, and stirring speed on the removal efficiency of Cr and Ni ions. Results indicated that the total Cr removal ratios by CPCTS-graft-polyacrylamide-co-sodium xanthate (CAC) and CPCTS-graft-poly [acrylamide-2-Acrylamido-2-methylpropane sulfonic acid] (CPCTS-g-P(AM-AMPS)) are 94.7% and 94.6%, respectively. The total Ni removal efficiencies by CAC and CPCTS-g-P(AM-AMPS) are 99.3% and 99.4%, respectively. The two-stage flocculation with CPCTS-based flocculants could reduce the total concentrations of Cr and Ni to 1.0 mg/L and 0.5 mg/L, respectively. The relationship of removal capacity and structural properties between the flocculants with different functional groups is established through Fourier transform infrared spectroscopy, nuclear magnetic resonance, scanning electron microscopy, and X-ray diffraction. The micro-interfacial behavior between the colloidal particles and the solution during the integrated chelation–flocculation are elucidated. Thus, CPCTS-based flocculants could be a potential material for the removal of high amounts of Cr and Ni ions in industrial wastewater. Image 1 • Chitosan based flocculants with xanthate and sulfonic acid group were designed and synthesized. • Flocculation process was used to treat industrial wastewater containing Cr and total Ni. • Rapid Removal and Separation of Cr and total Ni was obtained by CAC. • The micro-interfacial behavior during the integrated chelation–flocculation was elucidated. • Chitosan based flocculants showed an excellent potential capacity for removing heavy metals. [ABSTRACT FROM AUTHOR]