Synthesis and Application of Biogenic Iron Phosphate Particles by Shewanella sp. HN-41

Abstract

Phosphorus (P) is a crucial element for biochemical reactions and part of fertilizers. Excessive P and N are flowing into the rivers due to the abuse of fertilizer these days. It can cause increase harmful algal bloom, depletion of oxygen, and death of larger life forms. Heavy metals such as uranium also cause many problems. Uranium is a major contaminant among inorganic contaminants because it is very toxic and stay for a long time in the body of living things. Thus, it is important to remove not only phosphate but also heavy metal ions from wastewater. Here, phosphate removal and uranium adsorbent synthesis by Shewanella sp. HN-41 were conducted simultaneously and eco-friendly. In this study, iron phosphate particles are synthesized in the presence of Fe(Ⅱ) ion and phosphate by Shewanella sp. HN-41. The bacteria transferred electrons obtained from lactate to Fe(III) and reduced it to Fe(II). As a result of observing the biogenic iron phosphate separated from the solution, two types of particle shapes were observed according to the incubation time, the initial concentration of lactate contained in the medium, and the pH of ferric citrate. Depending on certain conditions to extract the precipitate in the culture medium, particles of the desired shape can be obtained selectively. As a result of XRD analysis, the XRD pattern of biogenic iron phosphate was most similar to vivianite. But it did not match the main peaks of vivianite, and its crystallinity was low. Biogenic iron phosphate was also applied as an adsorbent for removing uranium. Although the result was not superior to the chemically synthesized vivianite, it shows 95% efficiency in adsorption of U(Ⅵ). This work shows that iron(Fe) acted an important role in supporting P removal, and iron phosphate, which was formed by bonding with phosphate, showed considerable U(Ⅵ) adsorption capacity. The iron phosphate can be separated from the solution very simply without additional removal conditions or chemical treatment. So, the removal of phosphate by iron phosphate synthesis is eco-friendly and safe as it does not create additional contamination and risk. The biogenic iron phosphate showed the possibility as a solution for eco-friendly removal of uranium from aquatic systems.