Mixed bacteria passivation for the remediation of arsenic, lead, and cadmium: Medium optimization and mechanisms

Abstract

Lead(Pb), cadmium(Cd), and arsenic(As) are highly bioaccumulative and hazardous to human health. In this study, the effectiveness and mechanism of mixed bacteria applied to Pb, Cd, and As complex contaminated soil were investigated. According to the one factor per time (OFT) method, the optimal medium consisted of 10 g/L corn pulp dry powder, 10 g/L glucose, 3.8 g/L dipotassium hydrogen phosphate, 0.5 g/L sulfate, 1 g/L trisodium citrate at pH 7.2. The gradient test showed that the key fermentation process conditions were the optimal inoculum level of 1% and incubation temperature of 37 ℃. Then the mixed bacteria agent was used to treat the Pb(II), Cd(II), and As(III) contaminated soil. The adsorption amounts of Pb(II), Cd(II), and As(III) by the mixed bacteria were 10.39 μg/g, 1.65 μg/g, and 67.03 μg/g, respectively. The X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), and X-ray photoelectron spectroscopy(XPS) analyses showed that the remediation mechanism of three metals by mixed bacteria involved in extracellular polymer adsorption, biomineralization, and oxidation. This study would provide a potential remediation method for the multi-heavy metal polluted soil.