Efficient adsorption-reduction synergistic effects of sulfur, nitrogen and oxygen heteroatom co-doped porous carbon spheres for chromium(VI) removal

The S,N,O-co-doped porous carbon spheres, derived from starch with plentiful oxygen-containing functional groups, acted as an effective adsorbent for the removal of hexavalent chromium (Cr(VI)) from wastewater. The abundant surface functional groups of carbon spheres significantly improved the Cr(VI) adsorption by synergistic effect of multiple functional groups. Meanwhile, these reductive functional groups (such as C-SH, -NH-, C-H and C-OH) could serve as electron donors to efficiently reduce the adsorbed Cr(VI) into Cr(III). Benefiting from the cooperation between adsorption and reduction mechanism of Cr(VI), the S,N,O-co-doped of porous carbon spheres with high specific surface area of 2617 m2/g, exhibited superior efficiency for Cr(VI) removal at 97% and the maximum adsorption capacity could reach 434 mg/g at 298 K.