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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]

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]

• 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]

Wastewater containing dyes poses a severe threat to human health and to environmental safety. Hence, finding an effective way to treat this wastewater has attracted wide attentions. In this study, quaternary ammonium group-rich magnetic nanoparticles (MNPs), Fe 3 O 4 @SiO 2 -MPS-g-DAC (FSMD), were facilely prepared by grafting polymerization and served as a cationic adsorbent to remove anionic dye Orange G from aqueous solutions. Being compared with Fe 3 O 4 @SiO 2 -MPS MNPs, the adsorption capacity of FSMD MNPs was notably enhanced and it could be maintained in a high level under a wide solution pH range. The dependency on pH and the sensitivity to ionic strength indicated that the main adsorption mechanism was the electrostatic interaction. The adsorption kinetics followed the pseudo-second-order model, and the adsorption isotherms were well described with the Langmuir model. According to the thermodynamic analysis, the adsorption process was spontaneous and endothermic. FSMD MNPs were proved to have advantages of fast adsorption rate, high adsorption capacity, easy separation ability under external magnetic field, and satisfactory reusability, therefore they can be applied in the removal of anionic dyes from wastewater. [ABSTRACT FROM AUTHOR]

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

With the rapidly increased discharges of various complex dyeing wastewaters, adsorbents are required to own more properties such as cost-effectiveness, amphoteric ability, and rapid solid-liquid separation ability, to treat dyeing wastewaters. A multi-functional adsorbent was synthesized by co-grafting m-phenylenediamine and sodium allyl sulfonate on the surface of a low-cost base-material: hollow glass microsphere (HGM). Characterization results indicated the surface roughness and –Si–OH groups of HGM were increased by NaOH corrosion; functional groups such as aromatic-rings, –NH 2 , and –HSO 3 − were grafted on the surface of HGM. The synthesized adsorbent showed amphoteric attraction abilities for anionic acid green 25 and cationic basic fuchsin dyes. Kinetics and isotherms studies suggested the PSO model and Langmuir model were most satisfactory for adsorption processes, the theoretical maximum adsorption capacities for acid green 25 and basic fuchsin reached 454.55 and 588.24 mg g−1, respectively. The mechanism investigations indicated the electrostatic attraction, π-π stacking, and hydrogen bonds were the potential interaction forces between dyes and adsorbents. The synthesized material owns self-floating ability due to the hollow structure of HGM, over 95.7% of adsorbents were collected at water surface via the self-floating process in 12 min, which was beneficial to the solid-liquid separation process and the reuse of adsorbents. The technologies developed by these research efforts can serve as templates for synthesizing multi-functional adsorbents for complex wastewaters decontaminations. [Display omitted] • First demonstration of an amphoteric self-floating adsorbent. • The adsorption capacities of anionic/cationic dyes reached 454.55/588.24 mg g−1. • Electrostatic force, π-π stacking, hydrogen bond were dominant adsorption mechanisms. • Over 95.7% of adsorbents were collected at the water surface within 12 min. • The multi-functional adsorbent is beneficial for cleaner production of dyeing goods. [ABSTRACT FROM AUTHOR]

Environmentally friendly magnetic sodium alginate beads with glutaraldehyde cross-linking catalyzed by acetic acid-hydrochloric acid were successfully designed (FSSi@SA), and the magnetic bio-sorbents after amide reaction (FSSi@SA-sula) were utilized to absorb fluoroquinolone antibiotics in water. After amidation, FSSi@SA-sula exhibited strong pH adaptability (pH = 6.0–12.0). Langmuir and pseudo-first-order models can better describe the isotherm and kinetic process well, respectively. Under the optimization conditions with pH = 7 and temperature of 318.15 K, the maximum adsorption capacities of FSSi@SA-sula on the third-generation FQs ciprofloxacin (CIP) and the fourth-generation FQs moxifloxacin (MOX) respectively reached 365.66 and 149.57 mg g−1. The thermodynamics research indicated that the as-prepared FSSi@SA-sula is spontaneous and feasible. And after five adsorption cycles, the loss of adsorption capacity was less than 20% for both CIP and MOX, demonstrating the fine reusability and stability of the designed magnetic bio-sorbent. This study provides some ideas for facile synthesis of acid-catalyzed sodium alginate-glutaraldehyde cross-linking, which has promising applications in grafting various types of groups onto the retained carboxyl groups of sodium alginate spheres for the various contaminants removal in wastewater. [Display omitted] • FSSi@SA-sula beads were prepared by acid-catalyzed glutaraldehyde cross-linking. • FSSi@SA-sula showed excellent adsorption and reusability for CIP and MOX. • Langmuir and pseudo-first-order models better fitted adsorption process. • The mechanisms include electrostatic interactions, hydrogen bonding and n-π EDA. • Provided new ideas for facile synthesis of functional sodium alginate adsorbents. [ABSTRACT FROM AUTHOR]

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

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]