Controllable biosynthesis of nanoscale schwertmannite and the application in heavy metal effective removal

Abstract

Schwertmannite was widely used to control the mobility and bioavailability of heavy metals. However, controllable biosynthesis of schwertmannite through a mild way is challenging. The objective of this research is to systematically investigate the feasibility of controllable biosynthesis of nanoscale schwertmannite through aluminum modification and evaluates the removal efficiency and mechanism of heavy metals. The results showed that Fe(II) oxidizing and biosynthesis ability of Acidithiobacillu ferrooxidans was not inhibited by Al(III) ions. Directional regulation of the morphology, structure, and functional groups of schwertmannite was revealed in the controllable biosynthesis system. Schwertmannite transformed to nanoscale wire in the Fe/Al ratio 15:30 condition, but the phase and crystal structure remain unchanged. Al(III) modification effectively enhanced the content of hydroxyl groups and sulfate in schwertmannite and the adsorption reactivity. The highest adsorption capacity toward Cu(II)/Cr(VI) reached 53.82/87.26 in schwertmannite biosynthesized with Fe/Al ratio 15/30. In addition, biosynthetic schwertmannite possess deep removal capacity toward low concentration metals and selective adsorption capacity to complex metals. Heavy metals adsorbed on schwertmannite through cation exchange, surface complexation and ligand exchange. This research is of great significance for in deep understanding of material biosynthesis and the application of waste water treatment.