Remediation of molybdenum(VI) contaminated soil by iron sulfide nanoparticles: mechanism and influencing factors

Although iron sulfide (FeS) has been used to remove heavy metals from the environment, its capability for remediation of molybdenum (Mo) contaminated soil and some important influencing factors are still unclear. The purpose of this study was to investigate whether soil Mo(VI) contamination could be immobilized by using nano-FeS. The effects of FeS dosage, natural organic matter (NOM), and inorganic salts on soil Mo(VI) immobilization properties were compared and analyzed. The results showed that the addition of FeS significantly reduced the leaching of Mo in the soil. The amount of Mo leaching dropped from 87.66 to 2.20 mg/L when the molar ratio of FeS to Mo(VI) increased from 1:1 to 50:1. It was discovered that the major two mechanisms for the immobilization of soil Mo( VI) by FeS were adsorption and reduction. Soil Mo leaching was promoted with the existence of NOM, but the addition of SO42- and H2PO4- prevented soil Mo(VI) leaching. Mo leaching from soil that was polluted with Mo(VI) and included humic acid, salicylic acid, SO42-, or H2PO4- was reduced by 116.41-77.54 mg/L, 116.41-112.72 mg/L, 116.41-72.45 mg/L, and 116.41-84.39 mg/L, respectively, after FeS treatment. Meanwhile, the cabbage mustard growth experiments findings indicated that FeS particles have a significant field application potential for Mo(VI) contaminated soil remediation due to their high Mo(VI) immobilization efficiency.