Application of bimetallic cerium-based biochar adsorbent for efficient removal of Cr(VI): Effective regulation of Fe doping and straw-based biochar incorporation

Cerium-based adsorbent with the merits of variable valence and ample oxygen vacancies was applied for the removal of highly toxic hexavalent chromium (Cr(VI)). However, its cost controllability and recycling stability in practical applications remain to be further explored. Herein, a varieties of bimetallic cerium-based biochar adsorbents (CeFe@BC) were prepared by doping iron (Fe) and loading onto straw-based biochar, and the effects of the introduced Fe and biochar on adsorption performance of cerium-based adsorbent for Cr(VI) were studied. In comparison to pure cerium-based adsorbent (Ce@C), CeFe@BC had a stronger Cr(VI) adsorbability with the maximum adsorption capacity of 57.05 mg/g (25°C). Meanwhile, CeFe@BC had good regeneration stability and environmental friendliness. The adsorption capacity only decreased by 16.11 % after 7 adsorption–desorption cycles, with almost no metal leaching in different pH. Results showed that Fe doping and loading onto straw-based biochar could effectively promote Ce(III) and oxygen vacancy content in Ce@C. Electrochemical and density function theoretical calculations proved that Fe doping and loading onto straw-based biochar could promote the reduction of Ce@C impedance and the increase of current density. In conclusion, Fe doping and loading onto straw-based biochar effectively regulated the intrinsic properties of cerium adsorbent and further accelerated the electron transfer in adsorption. This study shows that bimetallic cerium-based adsorbent is a promising, efficient and stable environmental friendly adsorbent for Cr(VI) removal from wastewater.