Arsenic(V) removal behavior of schwertmannite synthesized by KMnO4 rapid oxidation with high adsorption capacity and Fe utilization

Adsorption is a simple and efficient way for arsenic contamination purification in water, with a pressing challenge to find a cheap and efficient adsorbent. As a poorly crystalline Fe(III)-oxyhydroxy sulfate mineral, schwertmannite can be As(V) adsorbent because of its tunnel structure and low cost. However, the schwertmannite synthesized commonly by H2O2 rapid oxidation suffers from the low Fe utilization and limited As(V) adsorption capacity. In this research, the schwertmannite is synthesized by KMnO4. The results show that the Fe utilization can be improved from 40% to 56%, with the As(V) adsorption capacities double times better than those synthesized by H2O2 at pH 7 and 2. The As(V) adsorption mechanisms at different pHs and the reason for the improvement of As(V) adsorption capacity are thoroughly investigated. The FTIR and EDS images confirm that As(V) adsorption exchange with SO42− is the dominant mechanism at pH 7 and 2. At pH 11, the As(V) is mainly removed by surface complexation because the surface SO42− is exchanged by OH−. The intraparticle diffusion model fitting and XPS results further reveal that the tunnel structure built by Fe–SO4 in the KMnO4 oxidized schwertmannite is more stable, possibly resulting in the better As(V) adsorption performance.