Two-stage hydrothermal oxygenation for efficient removal of Cr(VI) by starch-based polyporous carbon: Wastewater application and removal mechanism

Abstract

Cr(VI) is of concern because of its high mobility and toxicity. In this work, a two-stage hydrothermal strategy was used to activate the O sites of starch, and by inserting K-ion into the pores, starch-based polyporous carbon (S-PC) adsorption sites was synthesized for removal of Cr(VI). Physicochemical characterization revealed that the O content of the S-PC reached 20.66 % after activation, indicating that S-PC has excellent potential for adsorption of Cr(VI). The S-PC removal rate for 100 mg/L Cr(VI) was 96.29 %, and the adsorption capacity was 883.86 mg/g. Moreover, S-PC showed excellent resistance to interference, and an equal concentration of hetero-ions reduced the activity by less than 5 %. After 8 cycles of factory wastewater treatment, the S-PC maintained 81.15 % of its original activity, which indicated the possibility of practical application. Characterization and model analyses showed that the removal of Cr(VI) from wastewater by the S-PC was due to CC, δ-OH, ν-OH, and C-O-C groups, and the synergistic effect of adsorption and reduction was the key to the performance. This study provides a good solution for treatment of Cr(VI) plant wastewater and provides a technical reference for the use of biological macromolecules such as starch in the treatment of heavy metals.

Keywords: Cr(VI); Factory wastewater; Starch.