Reduction of Cr(VI) by Synergistic Effects of Iron-Rich Biochar and Pseudomonas aeruginosa

Abstract

In view of the poisonous nature of Cr(VI), it is of great significance to explore an effective and environmentally friendly method to remove Cr(VI). The potential synergistic effects of Cr(VI) reduction by iron-rich biochar and Pseudomonas aeruginosa (PA) were systematically explored in this study. Significantly, in association with PA, the biochar produced by pyrolyzing iron-rich sludge at 300 °C (Fe-300) was more efficient at reducing Cr(VI) than that pyrolyzed at 800 °C (Fe-800), and the performance was always better than biochar or PA alone. For instance, upon an incubation for 20 days, the Cr(VI) removal efficiencies in the groups Cr + Fe-300 + PA, Cr + Fe-800 + PA, Cr + Fe-300, Cr + Fe-800 and Cr + PA were 80%, 19%, 51%, 0% and 35%, respectively. Through further analyses of phosphorus (P) and iron species as well as the cell extraction components of PA, the high Cr(VI) efficiency in Fe-300 + PA was mainly attributed to two aspects: (1) more P (mainly in the form of ortho phosphorus) was released from Fe-300 by PA compared to that from Fe-800, and the released P may react with Fe(II), Fe(III), Cr(VI) and Cr(III) ions to form precipitation; (2) cytoplasmic and periplasmic proteins as well as membrane proteins extracted from PA further helped to reduce Cr(VI). A novel approach for reducing Cr(VI) may be proposed by using the potential synergistic effects of iron-rich biochar and PA from this study.