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• AFA owns self-floating ability to separate from water without external force. • AFA can be conveniently collected from the surface of water. • AFA has ideal adsorption capacities for different cationic dyes. • The adsorption capacities of AFA are little affected by the changes of conditions. In this study, our group grafted 2-acrylamido-2-methylpropane sulfonic acid (AMPS) onto the surface of hollow glass microspheres (HGM) and successfully prepared AMPS grafted floating adsorbent (AFA). The prepared AFA carries a large amount of negative charges, and the adsorptions of cationic dyes are achieved under the action of strong electrostatic interaction. Furthermore, due to the unique shell structure of AFA, it has a stable self-floating ability, which may change the traditional separation method to make the adsorbent easier to enrich and separate from water surface. Characterizations of AFA by scanning electron microscope, energy dispersive spectrometry, X-ray photoelectron spectroscopy. Fourier transform infrared spectra, Brunauer-Emmett-Teller surface areas, thermogravimetric analysis, and X-ray diffractometer shows the successful grafting of AMPS. Adsorption experiments confirmed that the adsorption capacities of AFA for methylene blue, malachite green, basic fuchsin and crystal violet under optimum conditions were 436.8 mg g−1, 637.6 mg g−1, 457.8 mg g−1, and 399.4 mg g−1, respectively. At the same time, AFA has excellent recyclability, and its adsorption capacity can be maintained after 6 cycles of reuse. [ABSTRACT FROM AUTHOR]

The ecological impacts of micro(nano)plastics (MNPs) have attracted attention worldwide because of their global occurrence, persistence, and environmental risks. Increasing evidence shows that MNPs can affect soil nutrient cycling, but the latest advances on this topic have not systematically reviewed. Here, we aim to present the state of knowledge about the effects of MNPs on soil nutrient cycling, particularly of C, N, and P. Using the latest data, the present review mainly focuses on three aspects, including (1) the effects and underlying mechanisms of MNPs on soil nutrient cycling, particularly of C, N and P, (2) the factors influencing the effects of MNPs on soil nutrient cycling, and (3) the knowledge gaps and future directions. We conclude that MNPs can alter soil nutrient cycling via mediating soil nutrient availability, soil enzyme activities, functional microbial communities, and their potential ecological functions. Furthermore, the effects of MNPs vary with MNPs characteristics (i.e., polymeric type, size, dosage, and shape), chemical additives, soil physicochemical conditions, and soil biota. Considering the complexity of MNP-soil interactions, multi-scale experiments using environmental relevant MNPs are required to shed light on the effects of MNPs on soil nutrients. By learning how MNPs influence soil nutrients cycles, this review can guide policy and management decisions to safeguard soil health and ensure sustainable agriculture and land use practices. [Display omitted] • MNPs retard essential nutrient recycling by impeding soil health. • Additives in MNPs affect soil nutrient availability, microbial biomass and activity. • MNPs can directly influence soil nutrient cycling through physicochemical processes. • MNPs in soil contribute to the emissions of greenhouse gases. • Polymer type, shape, dose, and size target the varied soil's responses. [ABSTRACT FROM AUTHOR]

In this study, a novel amphiphilic flocculant TP-ADL was synthesized using acrylamide, methacryloxyethyltrimethyl ammonium chloride and lauryl acrylate as monomers through UV-light-initiating template copolymerization technology. Copolymerization conditions were optimized towards higher intrinsic viscosity and conversion rate. The Fourier transform infrared spectroscopy and 1H nuclear magnetic resonance spectroscopy (NMR) analysis confirms the functional groups composition in TP-ADL, and the thermogravimetric (TGA) analysis indicates its good thermal stability. Furthermore, the detailed 1H NMR and TGA analysis confirms the microblock structure in polymer chain. The amphiphilic rheological characteristics of copolymer were detected according to apparent viscosity. TP-ADL displayed superior flocculation efficiency towards oily wastewater in terms of oil and turbidity removal rate, and zeta potential. The median floc size (d50) and fractal dimension (Df) results indicate a large and compact floc structure. The synergistic effect between cationic microblock structure and inter-molecular hydrophobic association is the main reason for the better treatment efficiency. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Novel cationic polymer modified magnetic adsorbents (MCDs) were fabricated. • MCDs have huge "force field" owing to strong electrostatic attraction. • MCDs have a high adsorption capacity for food dyes Food Yellow 3 and Acid Yellow 23. • The adsorption capacity decreases slightly with pH changing from 2.0 to 10.0. • Multiple adsorption mechanisms are involved in the food dye adsorption. Abstract In this study, modified magnetic chitosan microparticles (MCDs) were fabricated and used as adsorbents for the removal of Food Yellow 3 (FY3) and Acid Yellow 23 (AY23) from aqueous solution. The magnetic microparticles were characterized by scanning electronic microscope, Brunauer-Emmett-Teller specific surface area, elemental analysis, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, thermogravimetry analysis, differential scanning calorimetry, and vibrating-sample magnetometer. Then, the effects of pH value, initial dye concentration, and contact time on the adsorption of FY3 and AY23 by MCDs were investigated. Evidently, MCDs showed excellent adsorption performance for both food dyes, and their adsorption capacities (833.33 mg/g for FY3 and 666.67 mg/g for AY23) were considerably higher than those of unmodified adsorbents, which could be attributed to the electrostatic interaction and ion exchange between the grafted cationic polymer and food dyes. Adsorption isotherm and kinetic data of the magnetic microparticles were well fitted by Langmuir isotherm and pseudo-second-order kinetic model, respectively. The regeneration and reusability of MCDs were also explored. Results showed that more than 80% adsorption capacities of MCDs for FY3 and AY23 remained after five adsorption-desorption cycles. [ABSTRACT FROM AUTHOR]

Due to the complexity of contaminants, the effectiveness of traditional flocculants toward water purification is insufficient. To break the limitation, a novel polymer flocculant [chitosan grafted poly (acrylamide-itaconic acid), CS-g-P(AM-IA)] was synthesized via ultraviolet-initiated graft copolymerization reaction. Characterization results revealed that the graft copolymers were successfully synthesized and with rougher surface structure. The solubility of CS-g-P(AM-IA) and chitosan grafted polyacrylamide (CS-g-PAM) were greatly improved and they can dissolve in the wide pH range of 2.0–12.0. CaCl 2 was used as a source of cation bridge to enhance the flocculation of kaolin particles, and its optimum dosage was 150 mg·L −1 . At dosage of 30 mg·L −1 and pH of 5.0, the turbidity removal efficiency of CS-g-P(AM-IA) reached the maximum of 93.8%, whereas those of CS-g-PAM and CS were 96.7% and 76.9%, respectively. The patchwise adsorption of ionic groups embedded in the molecular chain on Ca 2+ -clay complexes took effect to generate flocs with larger particle size. Besides, the decolorization ability of cationic dyes by CS-g-P(AM-IA) was greatly enhanced due to the role of abundant carboxyl groups. In the crystal violet (CV) adsorption experiment, the maximum CV dye removal efficiency for CS-g-P(AM-IA) reached the maximum of 81.6% at dosage of 0.7 mg·mL −1 and pH of 9.0, while those for CS-g-PAM and CS were 51.7% and 36.5%, respectively. [ABSTRACT FROM AUTHOR]

Graft modified flocculants have recently received increasing attention in the field of water treatment as they have the combinative advantages of synthetic and natural polymeric flocculants. In this work, surface-active monomer benzyl(methacryloyloxyethyl)dimethylammonium chloride (BMDAC) was selected to graft on dextran (DX) with high molecular weight (10.3 × 10 6  g/mol) produced through enzyme-catalyzed process in order to remove dissolved dyes from wastewater. The flocculant (DAB) was fabricated by ultrasound initiated polymerization technique, and the structure characterization of FTIR, 1 H/ 12 C NMR, XRD and XPS spectrum confirmed the successful grafting. Then the Congo red (CR) removal efficiency by DAB was optimized based on the flocculation conditions, including wastewater initial pH, flocculant dosage and initial dye concentration. The effect of suspended solids on the removal of dyes was evaluated in kaolin-CR simulated wastewater. The results indicated that the optimal removal efficiency of CR was 68.1% and 88.2% in single CR and kaolin-CR flocculation system, respectively. The improvement of removal efficiency was attributed to the fact that partial CR molecules were adsorbed onto kaolin particles before flocculation, and were synergistically flocculated accompanied by kaolin particles. Finally, the flocculation mechanism was discussed by a detailed investigation of the zeta potentials, FTIR and XPS spectra of flocs, which can provide important reference for optimizing the flocculation conditions and designing novel high-performance flocculants. [ABSTRACT FROM AUTHOR]

Novel adsorbents, poly([2-(methacryloxy)ethyl]trimethylammonium chloride) modified magnetic chitosan particles (DMCPs), were synthesized via free radical polymerization and applied to adsorb Cr(VI) from aqueous solution. The effects of pH (2–11), Cr(VI) concentration (10–200 mg/L) and contact time (0–420 min) on the adsorption performance were evaluated. The results showed that the adsorption capacity of DMCPs was much larger than that of magnetic chitosan particles (MCPs) in the examined pH range and decreased with Cl − concentration increasing, indicating that electrostatic interaction and ion exchange are the governing mechanisms of Cr(VI) adsorption by DMCPs. The Langmuir isotherm model and pseudo-second-order kinetic model fitted the experimental data well. The maximum adsorption capacity of DMCPs is 153.85 mg/g. Besides, Cr(VI)-loaded DMCPs could be easily separated and efficiently regenerated. Therefore, DMCPs are promising candidates for Cr(VI) adsorption owing to their excellent performance in a wide pH range, easy separation and good reusability. [ABSTRACT FROM AUTHOR]

A novel chitosan-based magnetic adsorbent [poly(2-acrylamido-2-methylpropane sulfonic acid) grafted magnetic chitosan microspheres, PMCMs] was successfully fabricated via free radical polymerization for effectively removing the cationic dye methylene blue (MB). The effects of initial solution pH (1.0–10.0), temperature (30–50 °C), contact time (0–660 min) and initial concentration (50–1600 mg/L) were studied. The results indicated that the adsorption capacity increased with the increasing of initial solution pH and temperature. The adsorption kinetic and adsorption equilibrium data fitted closely to the pseudo-second-order kinetic model and Langmuir isotherm model respectively, confirming monolayer adsorption. The maximum adsorption capacity of PMCMs for MB at initial solution 9.0 were 1000, 1250 and 1428 mg/g at 30, 40 and 50 °C, respectively. Furthermore, the magnetic microspheres could be easily separated using a magnet and effectively regenerated after finishing the treatment process. Therefore, PMCMs are promising candidates for the removal of dye from wastewater. [ABSTRACT FROM AUTHOR]

In this work, a novel chitosan-based magnetic adsorbent [poly(2-(dimethylamino)ethyl methacrylate) grafted magnetic chitosan microspheres, GMCMs] was synthesized by graft polymerization of (2-(dimethylamino)ethyl methacrylate on the surface of magnetic chitosan microspheres (MCMs). The as-prepared GMCMs exhibited significantly enhanced adsorption capacity towards anionic dyes (e.g., Acid Green 25 and Reactive Blue 19) compared with MCMs. It is due to the fact that the abundant tertiary amine groups of the grafted polymer protonated at low pH and the polymer chains stretched as a result of electrostatic repulsions and chain-solvent interactions. The stretched polymer chains provided a variety of adsorption sites, which efficiently adsorbed dyes through electrostatic interactions and hydrogen bonding. While, in alkaline conditions, the tertiary amine groups were deprotonated and the polymer chains collapsed due to hydrophobic interactions, which facilitated the regeneration of the dye-loaded GMCMs at high pH. The regenerated GMCMs showed excellent adsorption performance even after five adsorption–desorption cycles. Besides, the GMCMs could be rapidly separated from aqueous solutions under an external magnetic field. Therefore, the GMCMs materials bear great application potentials in water treatment owing to its high adsorption capacity, pH-responsiveness, facile regeneration and good reusability. [ABSTRACT FROM AUTHOR]

Weak interaction between flocculants and oil is a main bottleneck in the treatment of oil-containing wastewater. To solve this problem, a novel flocculant PAB with cationic micro-block structure and hydrophobic groups of benzene rings was synthesized by ultrasound initiated polymerization technique and applied to remove turbidity and oil from water. To avoid unnecessary addition of reagents in traditional template and micellar copolymerization, surface-active monomer benzyl(methacryloyloxyethyl)dimethylammonium chloride (BMDAC) with self-assembly ability in aqueous solution was employed to synthesize flocculants. The critical association concentration of BMDAC measured by conductivity and surface tension methods was 0.014 mol·L −1 . The results of reactivity ratio, statistical analysis of sequence-length distribution and 1 H NMR provided evidence for the synthesis of copolymer with cationic micro-block. In addition, the apparent viscosity measurement indicated that PAB had an obvious hydrophobic association property. Finally, flocculation tests demonstrated that flocculation performance was greatly improved by adding PAB and the removal rate of oil and turbidity both reached the maximum (87.5% and 92%) at dosage of 40 mg·L −1 and pH of 7.0. Flocculation mechanism investigation demonstrated that the cooperation of charge neutralization, adsorption bridging, and hydrophobic association effect played an important role. The formed flocs by PAB was large, compact, difficult to break, and easy to regrow because of the enhanced interaction between flocculants and oil. In summary, this study can provide important reference in the design of organic flocculants in oily wastewater treatment applications. [ABSTRACT FROM AUTHOR]

In this paper, a procedure for in-situ pre-concentration in graphite furnace by repeated sampling and pyrolysis is proposed for the determination of ultra-trace thallium in drinking water by graphite furnace atomic absorption spectrometry (GF-AAS). Without any other laborious enrichment processes that routinely result in analyte loss and contamination, thallium was directly concentrated in the graphite furnace automatically and subsequently subject to analysis. The effects of several key factors, such as the temperature for pyrolysis and atomization, the chemical modifier, and the repeated sampling times were investigated. Under the optimized conditions, a limit of detection of 0.01 µg L −1 was obtained, which fulfilled thallium determination in drinking water by GB 5749-2006 regulated by China. Successful analysis of thallium in certified water samples and drinking water samples was demonstrated, with analytical results in good agreement with the certified values and those by inductively coupled plasma mass spectrometry (ICP-MS), respectively. Routine spike-recovery tests with randomly selected drinking water samples showed satisfactory results of 80–96%. The proposed method is simple and sensitive for screening of ultra-trace thallium in drinking water samples. [ABSTRACT FROM AUTHOR]

Cationic polyacrylamide (CPAM) has been the focus of research in environmental engineering field, particularly in sludge dewatering. However, poor stability of the existing cationic polyacrylamide has limited its application. In the face of the current complex sewage/sludge environment, CPAM with high efficiency, good stability and economy is remarkably desired in this field. In this study, a CPAM (PAMA) with high acid and alkali resistance was synthesized through copolymerization of acrylamide (AM) and methacrylamido propyl trimethyl ammonium chloride (MAPTAC) under ultraviolet (UV) radiation. The structure, morphology as well as the thermal decomposition property were analyzed through instrumental analysis. Furthermore, influencing factors of the copolymerization reaction were investigated and discussed in detail. The dewatering performance of PAMA was also evaluated by measuring the supernatant residual turbidity (RT), moisture content of the filter cake (FCMC), and specific resistance to filtration of the sludge (SRF). The RT, FCMC, and SRF reached 4.70 NTU, 71%, and 3.94 (10 12 m Kg −1 ), respectively, at 40 mg L −1 of PAMA-25-15.1 and pH of 6.0. Furthermore, these indices did not increase with the pH changes of the original sludge, and which indicated a high acid and alkali resistance of PAMA. [ABSTRACT FROM AUTHOR]

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]

Extracellular organic matter (EOM) is ubiquitous in the algae-polluted water and has a significant impact on the human health and drinking water treatment. We investigate the different characteristics of dissolved extracellular organic matter (dEOM) and bound extracellular organic matter (bEOM) recovered from the various growth period of Microcystis aeruginosa and the interactions of them and polyaluminum chloride (PACl). The roles of the different EOM in the algae-polluted water treatment are also discussed. The functional groups of aromatic, O H, N H, C N and N O in bEOM possessing the stronger interaction with hydroxyl aluminum compared with dEOM is responsible for bEOM and algae removal. Some low molecular weight (MW) organic components and protein-like substances in bEOM are most easily removed. And dEOM weakly reacts with PACl or inhibits coagulation, especially dEOM with the high MW organic components. The main coagulation mechanisms of bEOM are the generation of insoluble Al-bEOM through complexation, the bridge of AlO 4 Al 12 (OH) 24 (H 2 O) 12 7+ (Al 13 ), the adsorption of Al(OH) 3(am) and the entrapment of flocs. The adsorption of Al 13 and Al(OH) 3(am) mainly contribute to dEOM removal. It is also recommended to treat the algae with dEOM and bEOM at the initial stage. [ABSTRACT FROM AUTHOR]

Flocculation as the core technology of sludge pretreatment can improve the dewatering performance of sludge that enables to reduce the cost of sludge transportation and the subsequent disposal costs. Therefore, synthesis of high-efficiency and economic flocculant is remarkably desired in this field. This study presents a cationic polyacrylamide (CPAM) flocculant with microblock structure synthesized through ultraviolet (UV)-initiated template copolymerization by using acrylamide (AM) and methacrylamido propyl trimethyl ammonium chloride (MAPTAC) as monomers, sodium polyacrylate (PAAS) as template, and 2,2'-azobis [2-(2-imidazolin-2-yl) propane] dihydrochloride (VA-044) as photoinitiator. The microblock structure of the CPAM was observed through nuclear magnetic resonance ( 1 H NMR and 13 C NMR) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, and scanning electron microscopy (SEM) analyses. Furthermore, thermogravimetric/differential scanning calorimetry (TG/DSC) analysis was used to evaluate its thermal decomposition property. The copolymerization mechanism was investigated through the determination of the binding constant M K and study on polymerization kinetics. Results showed that the copolymerization was conducted in accordance with the I (ZIP) template polymerization mechanism, and revealed the coexistence of bimolecular termination free-radical reaction and mono-radical termination in the polymerization process. Results of sludge dewatering tests indicated the superior flocculation performance of microblock flocculant than random distributed CPAM. The residual turbidity, filter cake moisture content, and specific resistance to filtration reached 9.37 NTU, 68.01%, and 6.24 (10 12 m kg −1 ), respectively, at 40 mg L −1 of template poly(AM-MAPTAC) and pH 6.0. Furthermore, all flocculant except commercial CPAM showed a wide scope of pH application. [ABSTRACT FROM AUTHOR]

The drawbacks, high energy consumption, rigorous preparation condition and high impurity contents, have been well-recognized in the preparation of widely-used polyaluminum chloride via conventional methods in industrial scale. In order to overcome the drawbacks, the fresh aluminum hydroxide gels were proposed to prepare the polyaluminum chloride (PAC G ) in this study. The optimal preparation condition of PAC G was obtained by optimizing the preparation conditions including temperature, time and acid concentration. The contents of the small/middle polymeric aluminum (Al b ) in an optimized PAC G could reach 80%. During preparation, high temperature significantly reduced the preparation time but led to a poor stability. Lower rate constants of reaction between hydroxyl-Al and Ferron, k b 1 and k b 2 , were almost equal at high basicity value. It implied that the middle polymeric aluminum (Al b 2 ) was dominant in Al b . Besides, the pseudo-first-order kinetics equation was rearranged. Coagulation by PAC G2.0 was found to be the most effective for low-turbidity water treatment but limited to a narrowest optimum range of dosage compared with other PAC G . The residual aluminum concentration of the water after coagulation by the PAC G2.5 with fresh aluminum hydroxide gels was always low even overdosing. Charge neutralization was not the predominant coagulation mechanism in this treatment. [ABSTRACT FROM AUTHOR]

PO43- and SiO32- are often used as modifier to improve stability and aggregating ability of the iron-base coagulants, however, there are few reports about their detailed comparison between the coagulation performance and mechanisms. In this study, three coagulants—polyferric phosphoric sulfate (PFPS), polysilicon ferric sulfate (PFSS), and polyferric sulfate (PFS) were synthesized; their structure and morphology were characterized by Fourier transformed infrared (FT-IR) spectroscopy, X-ray diffraction (XRD) and Scanning electron microscope (SEM). Alkali titration and Ferron species analysis were employed to investigate the hydrolysis performance and species distribution. Jar test was conducted to measure their coagulation behaviors at different dosage, pH, and temperatures in which the flocs properties were measured. The results showed that a number of new compounds were formed due to the presence of PO43- and SiO32-. Moreover, PFPS and PFSS had similar level in Fea as well as Feb. Among them, PFPS produced more multi-core iron atoms polymer and content of Feb, and the formed flocs were larger and denser. It exhibited superior coagulation performance in terms of turbidity reduction, UV254 removal and residual ferric concentration. Jar test and floc breakage/regrowth experiments indicated other than charge neutrality, the dominated mechanism involved in PFSS was the adsorption between polysilicic acid and solution particle, while PFPS was sweeping, entrapment/adsorption resulting from larger polymer colloid of Fe-P chemistry bond. [ABSTRACT FROM AUTHOR]

The effects of the cationic surfactant (cationic cetyl trimethyl ammonium bromide, CTAB) on the improvement of the sludge dewaterability using the cationic flocculant (cationic polyacrylamide, CPAM) were analyzed. Residual turbidity of supernatant, dry solid (DS) content, extracellular polymeric substances (EPS), specific resistance to filtration (SRF), zeta potential, floc size, and settling rate were investigated, respectively. The result showed that the CTAB positively affected the sludge conditioning and dewatering. Compared to not using surfactant, the DS and the settling rate increased by 8%–21.2% and 9.2%–15.1%, respectively, at 40 mg·L−1 CPAM, 10×10−3 mg·L−1 CTAB, and pH 3. The residual turbidities of the supernatant and SRF were reduced by 14.6%–31.1% and 6.9%–7.8% compared with turbidities and SRF without surfactant. Furthermore, the release of sludge EPS, the increases in size of the sludge flocs, and the sludge settling rate were found to be the main reasons for the CTAB improvement of sludge dewatering performance. [ABSTRACT FROM AUTHOR]

In this article, matrix-assisted photochemical vapor generation is proposed for the direct determination of mercury in domestic wastewater by atomic fluorescence spectrometry. With the ultraviolet light irradiation, the matrix (low-molecular-weight organic compounds) in domestic wastewater samples can produce reducing species. These reducing species could reduce mercury from mercury (II) to elemental mercury, subsequently swept by argon to atomic fluorescence spectrometry for detection. The effects of several factors, such as material of the photoreaction coil, ultraviolet light wavelength, ultraviolet light irradiation time, and flow rate of carrier gas, were investigated. Under the optimized condition, a limit of detection of 0.1 µg L−1was obtained. The standard addition method was used for the spiked mercury domestic wastewater sample analysis, with a relative standard deviation (n = 11, at 20 µg L−1) of 4.8%, and recovery test results ranged from 81% to 110%. The proposed method was applied to analyze two certified reference materials and four domestic wastewater samples, with analytical results in good agreement with certified values or those obtained by ICP-MS. Interferences from common transition metals and alkaline metals as well as alkaline earth metals were also investigated. This is a simple, reagent-free, cost-effective, green method for mercury determination in domestic wastewater. [ABSTRACT FROM PUBLISHER]

Twocationic polyacrylamides, PAA and PAD, were synthesized for sludgedewatering. The advanced instruments such as 1H NMR, FTIR,and SEM were used to characterize the two copolymers. Their hydrophobicassociation properties in water were investigated by viscosimetryas well as the dewatering performance studied by the sludge dewateringexperiment. The results showed that the optimum conditions for preparationof PAA were that the initiator concentration, urea concentration,molar ratio of AODBAC to AM, and irradiation time were 0.3‰,1.0%, 10:90, and 60 min, respectively. Also, it was found that PAAhad a stronger hydrophobic interaction with a lower intrinsic viscosityand longer dissolution time as well as a better dewatering performance.Furthermore, the charge neutralization and bridging effects were foundto contribute much to the sludge dewatering by PAA in which the dewateringperformance was able to be enhanced further by the hydrophobic interaction. [ABSTRACT FROM AUTHOR]

Inthis study, a cationic block structure with a strong neutralizingability was formed through template polymerization. Acryloxyethyltrimethylammonium chloride (DAC) and acrylamide (AM) were used as monomers,and the ionic homopolymer sodium polyacrylate (NaPAA) was used asthe template. The product containing NaPAA after template polymerizationis denoted as NTP, whereas the copolymer obtained after removing theNaPAA is denoted as TP. The common polymer (denoted SP) of AM andDAC was copolymerized through solution polymerization. TP and SP werecharacterized and compared by Fourier transform infrared (FT-IR) spectroscopy,scanning electron microscopy (SEM), 1H nuclear magneticresonance (1H NMR) spectroscopy, and thermogravimetricanalysis (TGA). The results of 1H NMR spectroscopy andTGA showed that a cationic block structure was formed in TP. The mechanismof the cationic block polymer used in water treatment was extensivelystudied through a jar test in which turbidity, zeta potential, andaverage floc size were used to evaluate the flocculation performance.The results further supported the cationic block structure of TP.TP, with a different structure than SP, resulting in a stronger neutralizationability, showed a better performance in flocculating kaolin suspensions.The dominant mechanisms for TP flocculation behavior at pH 5, 7, and9 might be patching, charge neutralization, and bridging adsorption.The flocculation performance of NTP was not acceptable, whereas acidicNTP at pH < 2 showed a flocculation effect similar to that of TP. [ABSTRACT FROM AUTHOR]

Highlights: [•] Excellent Flocculant was successfully synthesized through UV-initiation technique. [•] UV and thermal initiation was compared to reveal the role of UV in polymerization. [•] Removal of DOP was realized by flocculation process with synthetic flocculants. [•] The possible flocculation mechanism was analyzed. [ABSTRACT FROM AUTHOR]

PADBwas a highly efficient cationic flocculant, which was synthesizedthrough the copolymerization of acrylamide (AM), acryloyloxyethyltrimethyl ammonium chloride (DAC), and butylacrylate (BA) with ultravioletinitiation by micellar polymerization technology. The PADB was theterpolymer of AM, DAC, and BA. In order to observe this flocculant’sstructural characteristics, nuclear magnetic resonance hydrogen spectroscopy(1H NMR), Fourier transform infrared spectroscopy (FTIR),scanning electron microscopy (SEM), and thermal gravimetric analysis(TGA) were used. The most important study was to analyze its physicochemicalparameters during dewatering of activated sludge. These tested parametersincluded residual turbidity of supernatant, dry solid content (DS),extracellular polymeric substances (EPS), specific resistance to filtration(SRF), ζ-potential, floc size, and settling rate. Results demonstratedthat the PADB have a superiority over both poly(acrylamide-acryloyloxyethyltrimethyl ammonium chloride) (PAD) and commercially available cationicpolyacrylamide (CPAM). However, it was dependent on pH and dosage.A favorable pH was in the neutral range while the appropriate dosage(20 mg·L–1-60 mg·L–1) was crucial to the conditioning process. For the PADB at40 mg·L–1and pH at 7, the residual turbidity of supernatant,DS, SRF, and settling rate could reach 5.5 NTU, 32.2%, 5.51 ×1012m·kg–1, and 3.318 cm·min–1, respectively. During the sludge flocculation process,the charge neutralization mechanism and bridging flocculation playedan important role in floc’s formation and settlement. [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]

Simultaneously removing heavy metal and dye from complex wastewater is of great significance to industrial wastewater treatment. Herein, a novel magnetic adsorbent, DTPA-modified chitosan-coated magnetic silica nanoparticle (FFO@Sil@Chi-DTPA), was successfully prepared and used to enhance the Pb(II) selective adsorption from multi-metal wastewater based on anion-synergism. In the competitive experiment conducted in a multi-ion solution, the type of selective adsorption of metals was changed by the adsorbents before and after amidation, in which FFO@Sil@Chi-DTPA exhibited an excellent selectively for capturing Pb(II), while FFO@Sil@Chi demonstrated highly selective adsorption of silver. More importantly, the selective adsorption of Pb(II)S by FFO@Sil@Chi-DTPA was enhanced from 111.71 to 268.01 mg g−1 when the coexisting MB concentrations ranged from 0 to 100 mg L−1 at pH 6.0. In the Pb(II)-MB binary system, Pb(II) and MB exhibited a synergistic effect, in which the presence of MB strengthened the adsorption effect of Pb(II) due to the sulfonic acid groups in MB molecules that create new specific sites for Pb(II) adsorption, while MB adsorption was also enhanced by the presence of Pb(II). This work provides a new strategy for exploring novel adsorbents that can enhance the selective removal of heavy metal in complex wastewater based on anion-synergism. [Display omitted] • A novel DTPA-modified chitosan-coated magnetic silica nanoparticle was prepared. • FFO@Sil@Chi-DTPA exhibited higher acid resistance than uncoated silica adsorbent. • FFO@Sil@Chi-DTPA showed high selectivity in capturing lead from multi-ion solutions. • Coexisting MB enhanced the selective adsorption of Pb(II) in complex wastewater. • Possible adsorption mechanisms in both single and binary systems were proposed. [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]

[Display omitted] • The magnetic nanoadsorbent with specific core-shell structure was synthesized. • Fe 3 O 4 @Carbon@ZIF-8 showed excellent adsorption capacities for Congo red and Cu(II). • The good adsorption ability was attributed to abundant active sites from ZIF-8. • Fe 3 O 4 @Carbon@ZIF-8 can selectively remove CR and Cu(II) from complex wastewater. • Nanoadsorbent's good stability and reusability indicated its practical application. Efficient and convenient removal of organic dyes and heavy metals from complex wastewater is still a challenge for human health and ecosystem remediation. Novel adsorbent, Fe 3 O 4 @Carbon@ZIF-8 with specific core-shell structure was synthesized by layer-by-layer self-assembly. The hydrophilic carbonaceous shell acts as both a linker and stabilizer between Fe 3 O 4 and ZIF-8. The characteristics of self-made adsorbent were comprehensively identified by numerous characterization methods. The adsorption kinetics, isotherms and the influence of various reacting parameters on its adsorption capacity of Congo red (CR) and Cu(II) were systematically investigated. Compared with other reported adsorbents, the maximum adsorption capacities of Fe 3 O 4 @Carbon@ZIF-8 towards CR (806.45 mg g−1) and Cu(II) (234.74 mg g−1) were much higher. Moreover, the adsorption process followed pseudo-second-order kinetics and Langmuir isotherm models. Selective adsorption of CR was investigated in the presence of cationic and anionic dyes, and the same as Cu(II) in the existence of competitive ions, which revealed that it was appropriate for selective adsorption toward CR and Cu(II) in complex wastewater. On the basis of FT-IR and XPS analyses, electrostatic interaction, hydrogen bonding, π-π bonding and ion exchange were involved in the mechanism of adsorption. Fe 3 O 4 @Carbon@ZIF-8 is suitable for practical application because of its good stability and reusability. [ABSTRACT FROM AUTHOR]

[Display omitted] • Coagulation and degradation of diclofenac sodium were realized simultaneously. • Hydrogen bonding and aromatic stacking play an important role in enrichment process. • The active radicals generated in the removal process were confirmed to be OH and Mn(V) • The coagulant could be reused without rinse process at least ten cycles. In this study, the coagulant was prepared by grafting polydopamine onto chitosan hydrogel which was doped with hollow silica nanoparticles loaded with permanganate and then was coated on the surface of the titanium tablet to realize simultaneous coagulation and degradation of diclofenac sodium (DCFS) combined with UV irradiation. The coagulation kinetics were simulated well with Pseudo-first order and pseudo-second order models compared with Weber-Morris model, inferring the cooperation of chemical and physical processes. The outcomes of isotherm trials were fitted well with Langmuir model except for that at 303.15 K, which was described both well with Langmuir and Tëмкин models, implying monolayer and unsaturated coagulation of DCFS. It was degraded at the copresence of ultraviolet and permanganate released from coagulant in acidic aqueous medium. Hydroxyl and Mn(V) radicals played an important role in DCFS degradation process. Additionally, the coagulant was used directly for DCFS removal for ten times without rinse process, which provided a potential application in environmental remediation. [ABSTRACT FROM AUTHOR]

Abstract: A new composite coagulant polymeric aluminum ferric was synthesized and parameters affecting the coagulant performance such as reaction temperature and time, and OH/Fe, P/Fe and Al/Fe molar ratios in this study, were examined. In addition, to obtain the optimum synthetic conditions resulting in the maximum turbidity removal efficiency, response surface methodology (RSM) was used to assess their interactive effects on coagulation–flocculation performance. The results showed that reaction temperature (60–80°C) and time (30–50min), and OH/Fe (0.1–0.3), P/Fe (0.2–0.3) and Al/Fe (1:9–1:10) molar ratios were favorable to the preparation process. The optimum synthesis conditions were reaction temperature and time, and OH/Fe, P/Fe and Al/Fe molar ratios of 80°C, 40min, 0.1, 0.25 and 1:10, respectively. Evaluation of the coagulation–flocculation process showed that COD (chemical oxygen demand) and turbidity removal efficiency of 82.8% and 98.2%, respectively, were achieved at coagulant dosage of 45mg/L, wastewater initial pH of 8.5, and rapid agitation speed of 250rpm. In addition, charge neutralization and adsorption/bridging coagulation–flocculation mechanisms played an important role in reducing the surface charge of colloids. [Copyright &y& Elsevier]

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]

Abstract: In this paper, results of an experimental study of polymeric phosphate-aluminum chloride (PPAC) as a modified coagulation reagent used to treat wastewater and fractal characteristics of flocs in a sewage treatment process were presented. Operating variables such as P/Al molar ratio, wastewater initial pH, coagulant dosage and agitation speed, which could influence the coagulation behavior of PPAC were experimentally tested. The evaluation of treatment efficiency was determined by measuring both the reduction of chemical oxygen demand (COD) and residual turbidity. It showed that the optimum removal efficiency was achieved when the P/Al molar ratio, wastewater initial pH, coagulant dosage and agitation speed were 1.2, 9.0, 0.36g/L and 100rpm respectively. Under optimum conditions, the removal efficiency was 73.5% and 99.5% for COD and turbidity. In addition, radial basis function (RBF) neural network established in this paper was used to predict the flocculation efficiency. The results revealed a promising operational forecasting capability. Furthermore, an inverted optical microscope was used to investigate the fractal structure of flocs formed during coagulation–flocculation. The results showed that under optimum conditions, with the increase of fractal dimension of the flocs, the COD removal efficiency increased while the flocs became denser with large cutter size. [Copyright &y& Elsevier]

Abstract: Response surface methodology (RSM) based on Box-Behnken design was successfully applied to the optimization of the operating conditions in decolorization of acid green 20 (AG 20) by ultrasonic irradiation in the presence of H2O2. The effects of three operating variables, ultrasonic power density, initial pH value of dye solution and H2O2 concentration on the decolorization efficiency of AG 20 were evaluated. A quadratic model for AG 20 decolorization was proposed. Analysis of variance (ANOVA) indicated that the proposed quadratic model could be used to navigate the design space. The proposed model was approximately in accordance with the experimental case with correlation coefficients R 2 and of 0.9995 and 0.9984, respectively. The optimum operating conditions for AG 20 decolorization were found to be 1.08W/mL of ultrasonic power density, 4.85 of initial pH and 1.94mM of H2O2 concentration, respectively. The predicted decolorization rate under the optimum conditions determined by RSM was 96.8%. Confirmatory tests were carried out under the optimum conditions and the decolorization rate of 96.3% was observed, which closely agreed with the predicted value. The results confirmed that RSM based on Box-Behnken design was an accurate and reliable method to optimize the operating conditions of AG 20 decolorization. [Copyright &y& Elsevier]

Magnetic separation technology is an efficient and feasible way to achieve rapid recovery of adsorbents, thus, the use of magnetic adsorbents has attracted the attention of many researchers. However, currently reported magnetic adsorbents have limited adsorption capacity due to insufficient adsorption sites and reactive groups. In this work, a novel magnetic chitosan-based amphiphilic adsorbent (PFSC) was synthesized by using UV-light irradiation method to combine with acryloyloxyethyl dimethylbenzyl ammonium chloride (AO), a molecule containing benzyl groups. PFSC and its precursors were carefully characterized, and their adsorption performances for the removal of anionic dyes were explored. The characterization results showed that the magnetic copolymers with a type of microsphere structure were successfully synthesized. Moreover, PFSC exhibited superior adsorption efficiency and pH resistance compared to those of an unmodified chitosan-based magnetic adsorbent (FSC). The maximum adsorption capacities of PFSC towards orange II (OG), acid red 88 (AE) and red amaranth (RM) were 955.0, 1075.8 and 567.5 mg/g at pH 3.0, respectively. The adsorption kinetics and isotherms of PFSC were consistent with that of a pseudo-second order kinetic model and the Langmuir isotherm model. In addition, adsorption-desorption experiments showed that PFSC could be rapidly separated and efficiently recycled even after 4 uses. More importantly, the FTIR and XPS results revealed that electrostatic adsorption and π-π stacking interactions were the main adsorption mechanisms for the PFSC-enhanced removal of anionic dyes. [Display omitted] • The chitosan-based amphiphilic magnetic copolymer was successfully synthesized by the UV-light initiated method. • The novel magnetic copolymer can be easily separated from solution by magnetic force. • The enhanced electrostatic adsorption and π-π stacking effect played an important role in the removal of anionic dyes. • The novel magnetic copolymer can be reused by simple acid-alkali adjustment. [ABSTRACT FROM AUTHOR]

Oxidation of acidic dye Eosin Y has been investigated with Fenton process and photo-Fenton process (solar light or artificial light source). With UV–Fenton process and Fenton, 42.5% and 21.3% of dye could be removed from the water, respectively. However, 94.1% of dye was removed in solar-Fenton in 90min. Based on solar-Fenton process, the effect of pH value and the concentration of dye, Fe2+, H2O2 as well as oxalic acid concentration on Eosin Y degradation efficiency were investigated. In 60min, 96% of Eosin Y was degraded when the pH value was 3.5 and the concentration of Fe2+, H2O2 and oxalic acid was 10mol/L, 600mg/L and 300mg/L, respectively. The Eosin Y degradation was dependent on the dye concentration. That is higher Eosin Y concentration resulted in lower degradation efficiency. Under the conditions of pH 3.5, the Eosin Y apparent kinetics equation was −dC/dt =0.000249[Eosin Y]0.78[Fe2+]1.14[H2O2]1.26. Meanwhile, this research also proved that oxalic acid could improve the photocatalytic efficiency in the solar-Fenton process. [Copyright &y& Elsevier]

The solid-liquid separation ability of adsorbents is of great significance for improving the recovery efficiency and reducing the cost. Herein, a novel floating-magnetically responsive silica adsorbent (FMSA) was prepared and applied to the adsorption of cationic dyes from aqueous solution. FMSA with self-floating and magnetic response properties exhibited great solid-liquid separation ability and adsorption performance for cationic dyes. According to the Langmuir model, the theoretical saturated adsorption capacity of FMSA for Basic Blue 7 (BB-7) and Crystal Violet (CV) reached 1632.55 mg g−1 and 1587.23 mg g−1, respectively. Thermodynamic experiments manifested that the adsorption was a spontaneous endothermic process with increasing entropy. After 5 adsorption-desorption processes, FMSA's adsorption capacity for BB-7 and CV remained above 80%, indicating that it has satisfactory stability and reusability. Furthermore, the pH effect, isotherm, kinetics, ion interference experiments and characterization analysis manifested that the adsorption was mainly chemical adsorption with an ion exchange process. This research aims to bring some inspiration for the combined use of floating separation and magnetic separation to achieve more flexible, efficient and energy-saving solid-liquid separation. [Display omitted] • A floating-magnetically responsive silica adsorbent was successfully developed. • Obtained adsorbent has both self-floating ability and magnetic response properties. • FMSA showed great reusability and resistance to ion interference. • BB-7 and CV were efficiently removed in a wide pH range. • Powerful electrostatic interaction and ion exchange ensure efficient adsorption. [ABSTRACT FROM AUTHOR]

• 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]

Developing robust and effective adsorbent for removing ubiquitous pharmaceutical diclofenac (DCF) from the aquatic environment is vitally important for environmental safety. Hence, a novel chitosan-based multilayer adsorbent (FCS-PD) with magnetic separation ability and surface functionality was successfully assembled, which had countless potential for removing contaminants from water. A series of instrumental technologies were performed to demonstrate the physicochemical properties of FCS-PD. Its adsorption performance toward DCF removal was comprehensively evaluated in synthetic water and surface water. The effects of microplastics, inorganic ions and humic acid on the adsorption were investigated. The maximum adsorption capacity of FCS-PD was calculated as 434.78 mg/g under neutral conditions, exhibiting superior adsorption performance than most reported adsorbents. The DCF in surface water was practically removed at low concentration (50 μg/L). FCS-PD presented a multistage kinetics controlled by chemisorption and intraparticle diffusion, which was emphasized by the pseudo-second-order kinetic and intra-particle diffusion analysis. After five cycles of adsorption and regeneration, the adsorption capacity only decreased by 9.9%, indicating the satisfactory regeneration of FCS-PD. The analysis of high-resolution X-ray photoelectron spectroscopic (XPS) and Fourier transform infrared spectroscopy (FTIR) revealed that the quaternary ammonium groups on the outer layer and the amino and hydroxyl groups on the chitosan layer are involved in the capture of DCF under electrostatic force and hydrogen bonding. Unlabelled Image • A novel functionalized multilayer magnetic adsorbent was constructed. • FCS-PD exhibited effective adsorption performance for DCF at pH 6.5. • The effects of microplastics and humic acid on adsorption were investigated. • Coexisting pharmaceuticals experiments showed selective DCF adsorption. • FCS-PD's good stability and magnetic separation facilitated its practical application. [ABSTRACT FROM AUTHOR]

• Enhanced removal of As(III) by MnFe 2 O 4 /sulfite than MnFe 2 O 4 was achieved. • As(III) removal was through a combination of oxidation and adsorption. • Powerful Mn(III) was generated via the MnFe 2 O 4 activation by sulfite. • Resultant As(V) was fixed by forming more monodentate complexes. • The optimal operating conditions were obtained through parameter optimization. As(III) oxidation to As(V) is deemed necessary for better arsenic removal, and separation is still the optimal approach for water remediation from As(III). Herein, sulfite (SIV) was adopted to activate MnFe 2 O 4 for simultaneous oxidation and adsorption of As(III) in neutral water. The As(III) removal was more efficient than a peroxidation of As(III) followed by adsorption. The adsorption capacity of MnFe 2 O 4 /S(IV) for As(III) (26.257 mg g−1) was much higher than those of MnFe 2 O 4 alone for As(III) (9.491 mg g−1) and As(V) (9.142 mg g−1). The mechanistic study corroborated that intermediate Mn(III) was the dominant oxidant responsible for rapid oxidation of As(III), and the dual roles of S(IV) as a complexing ligand and a precursor of oxysulfur radicals accelerated the redox cycle of Mn(II)/Mn(III). Moreover, S(IV) enhanced arsenic adsorption by driving more production of monodentate complexes. As(III) can be effectively removed over a wide range of temperatures (283.15–313.15 K) and pH (3–10) with the optimal pH of 7. The effect of coexisting ions and reusability of MnFe 2 O 4 were also investigated. Especially, the superior performance of MnFe 2 O 4 /S(IV) for As(III) removal in various water matrixes may help develop new removal technologies based on active Mn(III) for the water decontamination from As(III). [ABSTRACT FROM AUTHOR]

In order to deal with the increasingly serious water pollution caused by dye wastewater, a novel sulfonic acid-modified polyacrylamide magnetic composite (Fe 3 O 4 @SiO 2 /P(AM-AMPS)) was facilely prepared by crosslink reaction. The physicochemical properties and adsorption performances of Fe 3 O 4 @SiO 2 /P(AM-AMPS) were systematically studied by different characterization techniques and a series of batch experiments, respectively. It was found that the adsorption capacities of Fe 3 O 4 @SiO 2 /P(AM-AMPS) towards cationic dyes crystal violet (CV) and methylene blue (MB) were largely enhanced than those of silica-coated Fe 3 O 4 (Fe 3 O 4 @SiO 2) and maintained at relatively high levels in a wide pH range, due to the three-dimensional network structure and abundant functional groups of modified polyacrylamide. Besides, owing to the introduction of Fe 3 O 4 @SiO 2 , Fe 3 O 4 @SiO 2 /P(AM-AMPS) presented a unique magnetic property that helped it to be rapidly separated from water in a magnetic field. The maximum adsorption capacities of Fe 3 O 4 @SiO 2 /P(AM-AMPS) were 2106.37 mg g−1 for CV removal and 1462.34 mg g−1 for MB removal at 298.15 K, much higher than those of other reported magnetic composites. Furthermore, Fe 3 O 4 @SiO 2 /P(AM-AMPS) was effectively regenerated with HCl solution and the regeneration rates were higher than 97% and 80% for CV and MB removal after five adsorption-desorption cycles, respectively. With its excellent adsorption capacity, wide pH applicability, high separation speed, and satisfactory regeneration ability, Fe 3 O 4 @SiO 2 /P(AM-AMPS) was expected to become a promising adsorbent in the purification of cationic dye wastewater. Unlabelled Image • Novel PAM-based magnetic composite was facilely prepared by crosslink reaction. • Fe 3 O 4 @SiO 2 /P(AM-AMPS) presented a wide pH applicability for cationic dyes removal. • The maximum adsorption capacities were 2106 mg g−1 for CV and 1462 mg g−1 for MB. • The superior adsorption ability was attributed to multiple adsorption mechanisms. • Unique magnetism and good reusability facilitated its practical application. [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]

• Amphiphilic CPAM was fabricated through ultrasonic initiated template polymerization. • Comparative characterizations confirmed the microblock structure and amphiphilicity. • Template copolymerization met bimolecular termination of free radical polymerization. • The effect of NaPAA followed template polymerization I (ZIP) mechanism. • Cationic microblocks produced stronger flocs to form more permeable filter cakes. Flocculation is an important pretreatment technique for sludge dewatering, the performance of employed flocculants is the key factor determine the flocculation efficiency. Herein, an amphiphilic cationic polyacrylamide (CPAM) with microblock structure was synthesized through template copolymerization initiated by ultrasonic. The chemical components and cationic microblock structure of copolymers were confirmed through comparative characterization by Fourier Transform Infrared (FTIR) and Nuclear Magnetic Resonance (1H NMR) spectrum. The copolymerization mechanism was investigated through kinetics study and association coefficient (K M) determination. The results indicated that the reaction followed free radical copolymerization and terminated mainly through bimolecular termination. The pre-adsorption between acryloyloxyethyltrimethylammonium chloride (DAC) and sodium polyacrylate (NaPAA) before reaction confirmed the template polymerization met the type I (ZIP) mechanism. Cationic microblocks and hydrophobic association together contributed to the optimal dewaterability (FCMC=67.2 %, SRF=3.84×1012 m·kg−1) using TP(AM-DAC-LA). Hydrophobic association enhanced bridging and sweeping effect to promote the floc size growth. Cationic microblocks produced compacter flocs with stronger mechanical strength through enhanced charge neutralization and patching effects, which acted as skeletons to make filter cakes less compressible and more permeable in mechanical dewatering. This work developed a highly effective flocculant for sludge dewatering, the synthesis and working mechanism of which were also given. [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]

Natural polymeric flocculants as sludge conditioners have received great attention due to their non-toxic and biodegradable advantages. However, the application of amphiphilic natural flocculants as sludge conditioners is rarely reported. In this work, the novel chitosan-based flocculants (CS-g-PAO) with amphiphilic structure were synthesized by ultraviolet light initiated method for the enhancement of sludge dewatering performance. The solubility of CS-g-PAO was significantly improved in a wide pH range (2.0–10.0). Various characterization methods were used to investigate the structure, thermal stability and surface morphology of copolymers, suggesting the successful synthesis of CS-g-PAO. In dewatering experiments, CS-g-PAO showed superior dewatering performance, and filter cake moisture content could be decreased to 77.98% from 95.14%. Moreover, the results of extracellular polymeric substances (EPS) components indicated that hydrophobic effect of CS-g-PAO was beneficial to remove the protein in S-EPS and TB-EPS, which had the crucial influence on dewatering performance. Furthermore, the dewatering mechanism was discussed based on the effects of zeta potential, apparent viscosity, surface tension and flocs structure on dewaterability. Results revealed that CS-g-PAO had strong hydrophobic association effect and surface activity. In addition, enhanced charge neutralization and hydrophobic interaction played a synergetic role in improving the dewaterability of CS-g-PAO. Image 1 • A novel chitosan-based flocculant with amphiphilic structure was synthesized. • The water solubility of the amphiphilic flocculant was improved in a wide pH range. • The amphiphilic flocculant showed superior dewatering efficiency under low dosage. • All results confirmed the role of charge neutralization and hydrophobic attraction. [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]

• Self-floating adsorbents can reach surface solid-liquid separation spontaneously. • The two-step synthesis process of SFA is simple and efficient. • Single-layer grafting allows the adsorption to reach equilibrium within 10 min. • Concentrate low concentration dyes to industrially usable levels by desorb method. In the case of a sharp increase in the price of dyes, the dyes concentration of in wastewater is important for environmental protection and industrial costs reduction. In this study, we grafted single-layer amino groups onto the surface of the hollow glass microspheres by a two-step simple synthesis, and the anionic dyes adsorption process reaches equilibrium within 10 min. The as-synthesized adsorbent has self-floating ability to achieve high-efficiency surface solid-liquid separation with water. SEM, EDS, S BET , FT-IR, XPS, TGA characterizations results demonstrated the successful grafting of amino groups and the important role of the pretreatment process in the two-step synthesis. The results of adsorption isotherms and kinetics show the adsorption process belongs to single-layer adsorption with equal adsorption sites, and the adsorption capacities for acid orange 7 and amaranth reach 428.99 mg g−1 and 145.62 mg g−1, respectively. Regeneration of the adsorbent and concentration of the dye solutions can be achieved by dispersing the separated adsorbent in alkaline solution, the maximum concentrated concentration of acid orange 7 and amaranth was 6321.57 mg L−1 and 2431.84 mg L−1, respectively. This study provides new insights for the solid-liquid separation of water treatment agents and the resource regenerating of dyeing wastewater. [ABSTRACT FROM AUTHOR]

• Magnetic biosorbents (PMCCs) were designed and fabricated by radical polymerization. • PMCCs had specific morphological and molecular structure for ciprofloxacin removal. • PMCCs exhibited excellent adsorption capacity of 527.93 mg·g−1 for ciprofloxacin. • The adsorption mechanisms of ciprofloxacin by PMCCs were systematically elucidated. • PMCCs displayed rapid separation and favorable reusability. Magnetic biosorbents with specific morphological and molecular structure (PMCCs) were designed for the removal of ciprofloxacin (CIP) from water. Radical polymerization method was applied to immobilize the designed polymer brushes onto core-shell shaped magnetic microspheres to fabricate PMCCs. PMCCs exhibited a maximum adsorption capacity of 527.93 mg·g−1, which is much higher than reported adsorbents, owing to the complete stretch of polymer brushes and increased active sites as well as enhanced interaction. The investigation on the adsorption behavior of PMCCs for CIP manifested that CIP adsorption well fitted the Langmuir isotherm model and pseudo-second-order kinetic model. The calculated thermodynamic parameters suggested that CIP adsorption onto PMCCs was spontaneous and exothermic. Further recycling experiments showed a loss of less than 20% in the CIP adsorption capacity after five times, demonstrating the reusability of the as-designed biosorbents. [ABSTRACT FROM AUTHOR]

• Self-floating adsorbents can easily achieve surface solid-liquid separation. • The EPDA-SA has multiple adsorption mechanisms. • The EPDA-SA has a rapid adsorption rate under the action of electrostatic force field. • The stable structure of π-π conjugated system enables high-efficient capture of dye. Rapid, high-efficient adsorbents with efficient solid-liquid separation ability has broad application prospects in the treatment of dye wastewater. In this study, polydopamine and methacryloyloxyethyltrimethyl ammonium chloride were grafted onto hollow glass microspheres to prepare the enhanced polydopamine shell structure adsorbent with self-floating ability. Furthermore, the adsorbent achieves high-efficiency surface solid-liquid separation, which overcomes the disadvantages of the traditional separation methods. Characterizations of the as-synthesized microspheres were performed using various techniques such as SEM, EDS, BET, XPS, FT-IR, TGA and XRD. The adsorbent achieved rapid and high-efficient adsorption of alizarin cyanine green F via the interactions of electrostatic attracting and π-π stacking, and under the optimal experimental conditions, the removal efficiency of 0.10 m mol L−1 dye solution reaches 94.51%, and the adsorption process reaches equilibrium within 60 min. Adsorption isotherms and kinetics data of the adsorbent were well fitted by Langmuir isotherm and pseudo-second-order kinetic models, respectively. The as-synthesized adsorbent has excellent recyclability, and its adsorption performance can be maintained after 5 cycles of reuse. The self-floating adsorbent has great potential for the removal of dissolved contaminants and cost-effective separation. [ABSTRACT FROM AUTHOR]

• The β-cyclodextrin grafted flocculants were synthesized by ultrasound-assisted method. • The synthesized conditions of CADs were optimized. • CADs showed excellent flocculation performance in treating HA-kaolin wastewater. • The interaction effect between β-CD and HA could improve flocculation performance. In this work, the novel β-cyclodextrin based polymeric flocculants (CADs) were synthesized and applied on the treatment of humic acid (HA)-kaolin wastewater. Acrylamide (AM) and acryloyloxyethyltrimethyl ammonium chloride (DAC) were grafted onto β-cyclodextrin (β-CD) by ultrasound assisted initiation using ceric ammonium nitrate as initiator. The synthesized conditions were optimized by evaluating the intrinsic viscosity and grafting efficiency of CADs. Furthermore, the characterization methods including Fourier transform infrared spectroscopy (FTIR), 1H nuclear magnetic resonance spectroscopy (1H NMR), thermogravimetric/differential scanning calorimetry (TG/DSC) and scanning electron microscopy (SEM) were used to evaluate and analyze the molecular structure and surface morphology of graft copolymers. In flocculation experiments, the effects of dosage, flocculant types, solution pH and flocs properties on flocculation performance were investigate in detail. CADs exhibited more satisfactory turbidity and HA removal performance than the synthetic cationic flocculants (PAD) and the non-ionic graft polymers (CAM). At the optimum dosage 4 mg/L, the maximum turbidity and HA removal rate of CAD 1# was 97.5% and 68.3%, respectively. Furthermore, CAD 1# exhibited a good flocculation performance and wide flocculation window in the pH range of 2.0–8.0. Lastly, the flocculation mechanism of CAD was detailed discussed by the investigation of zeta potential, surface tension, flocs FTIR and XPS spectra. Results indicated the unique hydrophobic internal structure of β-CD played an important role in improving the removal rate HA of CAD. [ABSTRACT FROM AUTHOR]

• A novel surface-decorated magnetic chitosan biopolymer (VMCP) was fabricated. • VMCP exhibited significantly improved removal performance toward Cr(VI). • Simultaneous adsorption and reduction of VMCP for Cr(VI) was investigated. • The mechanisms of Cr(VI) removal by VMCP were elucidated. Poly(4-vinyl pyridine) decorated magnetic chitosan biopolymer (VMCP), as an absorbent and reductant, was prepared and used to remove hexavalent chromium (Cr(VI)) from aqueous solution. Compared with undecorated magnetic biopolymer, VMCP exhibited significantly improved removal performance under identical experimental conditions. The kinetics, isotherms, and thermodynamics of Cr(VI) adsorption onto VMCP were investigated. Results demonstrated that the maximum monolayer adsorption capacity of VMCP was 344.83 mg/g, which was considerably higher than most reported adsorbents. The mechanism for Cr(VI) removal was explored based on XPS and FTIR analyses. The main mechanisms were concluded to be Cr(VI) adsorption onto the positively charged VMCP surface and the reduction of Cr(VI) to Cr(III), followed by coordination between Cr(III) and N atoms. The easy regeneration, satisfactory reusability, and remarkable performance in column tests revealed the high potential of VMCP in treating Cr(VI)-contaminated water. [ABSTRACT FROM AUTHOR]