Feasibility of cleaning As- and U-containing soil of a gold mine by using biologically nano-sized FeS: Implications for soil remediation technology

Abstract

Gold and uranium mining has resulted in elevated concentrations of As and U contaminants in groundwater and soil, which has become a paramount concern for the environment and public health. Nanocleaning technology is one of the few permanent treatment alternatives to remove metal contaminants from soils. In recent years, nano-sized FeS, a washing solution that uses nanocleaning technology, has elicited extensive interest in environmental remediation because it does not produce secondary pollution. In this study, As and U were removed from contaminated soil by employing nano-sized FeS washing solution biologically synthesized by the iron-reducing bacteria Acidiphilium cryputum JF-5 and sulphate-reducing bacteria Desulfovibrio vulgaris miyazaki SRB. After cleaning with a nano-sized FeS suspension solution, culture-medium and pure-water for three cycles, the concentration of As in the nano-sized FeS experiment was higher than that of U, suggesting that the cleaning effect for As was better than that for U. The As and U removal rates of the nano-sized FeS cleaning experiment were 12% and 1.59%, respectively, over the three cycles. By using the sequential extraction method, the nano-sized FeS cleaning experiments mainly removed the As fraction bound to Fe/Al oxides. An ATR-FTIR spectral analysis indicated that the band observed at 461 cm −1 was attributed to the ν 4 symmetric stretching mode of AsO 4 3 − . The obvious vibrations observed at 798 cm −1 and 778 cm −1 , were assigned to the ν 1 vibration of AsO 3 3 − . The band at 834 cm −1 was assigned to the weak vibration of UO 2 while the band at 949 cm −1 was attributed to the Fe–O–D bending vibration. The results of this study provide helpful information and references for designing long-term and efficient bioremediation strategies for As- and U-containing soils. • The cleaning performance of biologically-formed nano-sized FeS for As is better than U. • As in soil was extracted by nano-sized FeS as reductive dissolution and re-adsorption. • The main removal species of As is the bound to Fe/Al oxides state. • The cleaning of biologically FeS can be used for a low-cost in-situ remediation technology.