A novel kaolin coated with ferrihydrite-artificial humic acid for the removal of lead from water and weakly acid barren soil: Preparation, characterization, performance and mechanism

Industrial development has led to frequent heavy metal pollution, adversely impacting the ecological environment and the utilization of productive agricultural resources. Given these concerns, it is imperative to develop a structurally stable lead adsorbent to ensure environmental safety. Consequently, in this study, a highly stable kaolin-coated ferrihydrite-artificial humic acid composite (Fh-AHA-G1.0) was developed for the remediation of Pb2+ in aqueous environments by using a co-precipitation process. The composite was also applied to leadcontaminated weakly acidic barren soils to evaluate its immobilization effect on Pb2+ in the soil environment. The adsorption mechanism of Fh-AHA-G1.0 for Pb2+ in contaminated water was investigated through adsorption experiments, and according to Langmuir fitting, the maximum adsorption capacity of Pb2+ was 123.86 mg/g. The adsorption mechanisms included ion exchange, surface chemical complexation, and lattice substitution. Furthermore, to evaluate the broad applicability of Fh-AHA-G1.0, the material was tested for its ability to immobilize Pb2+ in weakly acidic barren soils, demonstrating a significant ameliorative effect on leadcontaminated weakly acidic barren soils. The incorporation of 2 % Fh-AHA-G1.0 led to a substantial reduction in the effective lead content of the soil, reaching 54.2 %, while concurrently enhancing the soil index. These findings underscore its promise as a potential soil amendment. Hence, Fh-AHA-G1.0, as an environmentally friendly, cost-effective, and efficient adsorbent, not only reduces lead pollution in water bodies but also serves as a soil conditioner to enhance the physicochemical properties of weakly acidic barren lead-contaminated soils while immobilizing soil lead, demonstrating broad application potential in agricultural practices.