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• 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]

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]

[Display omitted] • Self-floating cyclodextrin-modified polymer was prepared. • The adsorption performance of TFCD and FTFCD was compared. • FTFCD simplified the recycling process by wrapping a hollow glass microsphere. • Porous structure and hydrophobic cavity favor the dye adsorption. • Polymers exhibited excellent selectivity toward cationic dyes. The separation and recycling processes of current cyclodextrin (CD)-based adsorbents are complicated. Thus, a novel composite based on a large surface area, porous, and self-floating tetrafluoroterephthalonitrile (TFN)-crosslinked CD polymer (FTFCD), was fabricated, characterized and applied to treat cationic dye pollutants. The characterization showed a porosity, good thermal stability, a stable crystal structure, and abundant functional groups on the prepared FTFCD, which had demonstrated great improvement on its adsorption capacity towards attention grabbing pollutants. The removal efficiency of the adsorbents for malachite green (MG) remained above 95% at pH 1 ∼ 10. In addition, the adsorbents were found to rapidly reach equilibrium governed by the pseudo-second-order kinetic model, and the maximum adsorption capacity of FTFCD was 1390.263 mg/g, as corroborated by the Langmuir isotherm model. While the phenolate groups of FTFCD found to electrostatically interacts with the MG strong cationic quaternary amine group, hydrogen-bonding was responsible for the hydroxyl group of FTFCD and the quaternary amine group binding. Meanwhile, the triangular cone configuration of MG makes it easy to be entrapped and absorbed in the hydrophobic cavity. Besides, after regeneration of exhausted FTFCD for five successive cycles, the MG removal efficiency still reached more than 80%. Thus, FTFCD could be applied as a potential alternative adsorbent for cationic dye removal owing to its excellent adsorption performance, convenient recycling, wide pH application, and environmental friendliness. [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]