In-situ remediation of oxytetracycline and Cr(VI) co-contaminated soil and groundwater by using blast furnace slag-supported nanosized Fe0/FeSx

Abstract

The combined pollution of heavy metals and antibiotics in soil and groundwater has caused widespread concern. In this study, a blast furnace slag-supported nanosized Fe0/FeSx composite (Fe0/FeSx@BFS) was synthesized and used for the in-situ remediation of Cr(VI) and oxytetracycline (OTC) co-contaminated soil and groundwater. The effects of pH and initial concentration of contaminants on Cr(VI) and OTC co-adsorption in simulated contaminated groundwater were investigated. Consequently, the adsorption of both Cr(VI) and OTC was highly pH-dependent, while the lower pH value favored the adsorption. Meanwhile, 0.5 g/L of Fe0/FeSx@BFS could efficiently remove approximately 38 mg/g Cr(VI) and 95 mg/g OTC in simulated groundwater at an initial pH of 3.5, initial Cr(VI) concentration of 20 mg/L, and initial OTC concentration of 50 mg/L. During the co-adsorption process, Cr(VI) removal proceeded mainly by reduction and the formation of chromite complex, and OTC removal involved oxidation degradation, adsorption, and complexation. Laboratory incubation experiments were conducted to study the effects of Fe0/FeSx@BFS amendment on Cr immobilization, antibiotic resistance genes (ARGs) distribution, and microbial community in Cr(VI) and OTC co-contaminated soil. Results showed that 3% Fe0/FeSx@BFS treatment could efficiently remove 60% of bio-available Cr and 42.14% of total ARGs copies in the contaminated soil after 49 days incubation. Additionally, Fe0/FeSx@BFS amendment significantly reduced the abundance of ARGs-source bacteria, Firmicutes. The results suggested that Fe0/FeSx@BFS amendment was a feasible method to remediate the Cr(VI) and OTC co-contaminated groundwater and saturated soil.