Bacteria cell templated porous polyaniline facilitated detoxification and recovery of hexavalent chromium

In this study, bacteria cells served as a novel green pore-forming agent and template to fabricate porous polyaniline (Bac@PANI) by in situ oxidative polymerization. The achieved specific surface area of 51.2 m2 g−1 for Bac@PANI at a bacteria dosage of OD600 = 0.536 was far higher than that of the pristine PANI (27.5 m2 g−1). The Bac@PANI presented an emeraldine form, hydrophilicity and decreased isoelectric point (4.2) after being modified by bacteria. All these properties contributed to an enhanced removal performance of hexavalent chromium (Cr(VI)), with a high removal rate of 0.5 mg (min−1·g−1) and capacity of 835.06 mg g−1 of Bac@PANI. Efficient removal was achieved in both acidic and neutral solutions due to its high H+ storage capacity. More than 90% of Cr(VI) can be reduced to trivalent chromium (Cr(III)) by oxidation of amide groups in both acidic and neutral solutions. These Cr(III) ions can be adsorbed by Bac@PANI simultaneously, resulting from the reversal of negative surface charge after treatment of Cr(VI); then Bac@PANI can be easily recovered in an acidic solution.