Enhanced oxidation and adsorption of arsenite by porous Fe-Mn binary chitosan beads and its application in fixed-bed column

Abstract

A novel porous Fe-Mn chitosan bead (PFMB) was fabricated through the freeze-drying technique for the enhanced oxidation and adsorption of arsenite (As(Ⅲ)) from aqueous solution. The porous internal structure of PFMB provided a significantly higher As(Ⅲ) oxidation and adsorption rate than solid Fe-Mn chitosan bead (FMB). The experimental results showed that FMB and PFMB exhibited the theoretical maximum As(Ⅲ) adsorption capacities of 27.42 and 49.80 mg/g, respectively. The real-time oxidation and adsorption progress of As(Ⅲ) onto PFMB was deeply evaluated: PFMB effectively oxidized As(Ⅲ) to As(Ⅴ) and the generated As(Ⅴ) was subsequently adsorbed. The operational parameters (initial pH, adsorbent dosage, ionic strength, and HA concentration) were thoroughly investigated and had no significant influence on As(Ⅲ) removal by PFMB. Finally, the regeneration experiment showed that PFMB can be easily regenerated and the recycled PFMB can successfully remove As(Ⅲ) in the following 5 cycles. Column experiments suggested that the column device could effectively remove the As(Ⅲ) in more than 3830 bed volume with the influent velocity at 0.5 mL/min before effluent concentration reached 0.05 mg/L. These results revealed the enhanced oxidation and adsorption performance of As(Ⅲ) onto PFMB and provided a reference for the future application of PFMB in arsenic-contaminated water treatment.