Dissolved organic matter modified magnetic carbon nanotubes enhance the bioremediation of azo dyes and Cr(vi)

Abstract

Dissolved organic matter and Fe(III) species can serve as electron shuttles in the bioreduction of various pollutants in water treatment, but their residuals are also regarded as contaminants. Herein, immobilization of dissolved organics and Fe on carbon nanotubes still possess electron transfer capacity. Meanwhile, it could also lessen secondary pollution caused by residual DOM and Fe in bioreduction. In this study, anthraquinone-2-sulfonic acid (AQS) or humic acids were immobilized together with Fe₃O₄ on carbon nanotubes. The morphologies, structures and functional groups of the resulting materials were characterized. Nanotubes bearing AQS or humic acids both demonstrated high Cr(VI) and methyl orange reduction effectiveness at pH 8.0. The Cr(VI) and methyl orange were reduced by capturing electrons from microbial metabolism, with the DOM_ox/DOM_red and Fe(III)/Fe(II) cycles promoting the process. The nanotube catalysts showed excellent stability and reusability. This study provided an innovative method for simultaneous bioremediation of Cr(VI) and methyl orange dye in wastewater.