Abstract
Lead (Pb) in soil poses serious environmental and health risks, and its removal requires complex and costly treatment methods to meet strict regulatory standards. To effectively address this challenge, innovative and efficient techniques are essential. Sepiolite-supported MnFe(2)O(4) (MnFe(2)O(4)/SEP) composites were synthesized via a chemical co-precipitation method. The effects of MnFe(2)O(4)/SEP on soil pH, cation exchange capacity (CEC), available Pb content, Pb(2+) uptake, and the activities of antioxidant enzymes in Brassica chinensis (Pak Choi) were examined. MnFe(2)O(4)/SEP showed superior Pb(2+) adsorption compared to SEP alone, fitting Langmuir models, Dubinin-Radushkevich (D-R) models, Temkin models and pseudo-second-order kinetics. The maximum adsorption capacities at 298, 308, and 318 K were 459, 500 and 549 mg·g(-1), respectively. XPS analysis indicated that chemisorption achieved through ion exchange between Pb(2+) and H(+) was the main mechanism. MnFe(2)O(4)/SEP increased the soil pH by 0.2-1.5 units and CEC by 18-47%, while reducing available Pb by 12-83%. After treatment with MnFe(2)O(4)/SEP, acid-extractable and reducible Pb in the soil decreased by 14% and 39%, while oxidizable and residual Pb increased by 26% and 21%, respectively. In Brassica chinensis, MnFe(2)O(4)/SEP reduced Pb(2+) uptake by 76%, increased chlorophyll content by 36%, and decreased malondialdehyde (MDA) levels by 36%. The activities of antioxidant enzymes-superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT)-were decreased by 29%, 38% and 17%, respectively. These findings demonstrate that MnFe(2)O(4)/SEP is an efficient Pb(2+) adsorbent that immobilizes Pb in soil mainly through ion exchange, thereby providing a highly effective strategy for remediating Pb-contaminated soils and improving plant health.