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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]

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]

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]

• 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]