Enhancement effects of weak electric field on uranium and manganese removal from leachate of uranium tailings impoundment by artificial wetland

Abstract

Artificial wetlands (AWs) planted with Acorus Calamus L. and coupled with weak electric field (WEF) were constructed to investigate the effects of flow direction, hydraulic retention time (HRT), and WEF intensities on the removal of uranium and manganese from leachate of uranium tailings impoundment (LUTI), the distribution characteristics of the uranium and manganese in the AWs, and the growth and physiological responses of the plants in them. The results showed that the optimized removal rates of uranium and manganese from LUTI were observed to be 97.03% and 99.72%, respectively, in the upwelling AW planted with Acorus Calamus L. and coupled with WEF intensity of 0.3 V/cm when the HRT was 72 h. Compared with the group without WEF, the bioaccumulations of uranium and manganese by Acorus Calamus L were increased by 169.23% and 522.91%, respectively, the adsorption capacities of biofilms toward uranium and manganese were increased by 7.38% and 48.90%, respectively, the content of uranium in the substrates was decreased by 10.76%, while the manganese concentration had no significant difference, and the contents of uranium and manganese in the salt scale deposited on the cathode surface reached 51.20 and 653.11 mg/kg, respectively, when the WEF intensity was 0.3 V/cm in the AW. The applied WEF increased the activity of superoxide dismutase (SOD) and the content of glutathione (GSH), and reduced the content of malondialdehyde (MDA) in the leaves of Acorus Calamus L, so as to alleviate the stress of uranium and manganese on wetland plants in the AW. Therefore, the AW has potential application in the removal of uranium and manganese from LUTI.