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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]

• 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]

• 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]