Efficient adsorption of arsenic in groundwater by hydrated iron oxide and ferromanganese oxide chitosan gel beads

To address the arsenic contamination in groundwater, the hydrated iron oxide gel beads (CS-HFO) and iron manganese oxide gel beads (CS-FMO) adsorbents were prepared. The CS-HFO and CS-FMO adsorbents had porous and adsorption-friendly pore structures inside, with the average pore sizes of 3.45 nm and 7.78 nm, respectively. As compared to the CS-HFO adsorbent, the CS-FMO adsorbent had rich adsorption sites and oxidation capacity and displayed better adsorption performance. According to the Langmuir model, the saturation adsorption of As(V) and As(III) for CS-FMO adsorbent was calculated as 26.65 mg/g and 35.96 mg/g, respectively. After 10 cycles of regeneration, the CS-HFO and CS-FMO adsorbents demonstrated excellent sustainable arsenic removal ability, while the adsorption efficiencies of CS-FMO adsorbent for As(V) and As(III) were maintained over 60 % and 95 %, respectively. In addition, the competing pollutants and fixed-bed column experiments confirmed the high selectivity of the CS-HFO and CS-FMO adsorbents, which showed great promise for the future application of arsenic contamination removal from the actual groundwater environment.