Highly effective adsorption for both As(III) and As(V) in aqueous medium via magnetic chitosan-based composite microparticles: Low arsenic concentration, high column efficiency and adaptability

To improve the arsenic adsorption efficiency at low concentration and the adaptability of the adsorbents, magnetic composite microparticles based on Fe3O4, TiO2 and chitosan/quaternary ammonium salt chitosan derivatives were prepared. The composites were systematically characterized, and their arsenic removal efficiency was investigated towards several factors. The results showed that MTHCNPs-2 with the highest substitution degree showed the best selectivity and adsorption efficiency towards arsenic even in low concentration, and still had high adsorption efficiency even after 10 cycles, making it an effective and adaptable adsorbent for both As(III) and As(V). Adsorption kinetics showed that MTHCNPs-2 could fast adsorb As(Ⅲ) and As(V), and chemical adsorption played the main role. The maximal adsorption capacities of MTHCNPs-2 for As(Ⅲ) and As(V) were 33.68 mg/g and 34.61 mg/g, respectively. Furthermore, the adsorption mechanism was explored by XPS, and the practical applicability of MTHCNPs-2 was tested towards the removal of both As(III) and As(V) from arsenic-contaminated real effluent using fixed bed column. It is shown that the breakdown volumes for As(Ⅲ) and As(V) reached up to 660 and 600 bed volumes, respectively. 0.1 M NaOH could effectively regenerate the column, and the adsorption capacities for As(Ⅲ) and As(V) only reduced by 0.53% and 0.74% for the second cycle, indicating the excellent regenerative capacity of the column. Furthermore, MTHCNPs-2 still had high removal efficiency towards As(Ⅲ) and As(V) even in the presence of phosphate and iron ions in the column study.