Study on the effect of Shewanella oneidensis MR-1 coupled with the low molecular weight organic acid on the dissimilation reduction of Cd-containing goethite

Microbial dissimilated iron reduction is one of the important driving forces of the biological and geochemical cycles of iron in nature. Plant root exudates dominated by organic acids are important electron donors of the rhizosphere dissimilar iron reduction microorganisms under flooded conditions. In this paper, we investigated the effects of different kinds and concentrations of organic acids on the dissimilation reduction process of goethite by Shewanella oneidensis MR-1, and explored the effect of phase transformation of iron minerals on its adsorption of Cd. The results showed that the low molecular weight organic acid promoted the dissolution of Fe(Ⅲ) in goethite, and ternary carboxylic acids had more obvious effect than binary carboxylic acids. The concentration of the solution of Fe(Ⅱ) increased by 63.95%–342.3%, the Fe(Ⅲ) concentration increased by 2.95%–260.6%. In addition, in the process of dissimilated iron reduction, the concentration of Cd released during the dissolution of iron ore is low due to the complexation of the low molecular organic acid, which will reduce the negative impact of high concentration Cd on Shewanella oneidensis MR-1, and further reduce the inhibitory effect of Cd on dissimilated iron reduction. It is noteworthy that we found that Cd released by soil iron minerals will be adsorbed and fixed again, that is, heavy metals loaded on trivalent iron minerals will be released and redistributed in the process of dissimilated iron reduction, which is one of the migration and transformation ways of heavy metals in the environments.