Competitive mechanism for capturing heavy metal contamination by iron-based porous composite particles for soil remediation

The heavy metal ions of the Cd and As generally co-exist in soil to threaten crop growth and human health. How to simultaneously reduce the activity of the soil Cd and As is still a big challenge because of their entirely opposite chemical properties. A multi-porous humic acid-ferric oxide (HAs-FeOx) composites composed of the core of FeOx polyhedral nanoparticles and the HAs cover are synthesized by hydrothermal method and coprecipitation for the co-immobilization of the soil Cd and As. A high co-adsorption capacity of 178.5 and 91.0 mg/g is obtained for the heavy metal contamination Cd and As in water and the corresponding available states decrease by 98% and 83% in soil based on the developed HAs-FeOx composite, respectively. First-principles calculations and adsorption kinetics analysis demonstrate that active sites of the HAs-FeOx composites for co-capturing heavy metal contamination presents competitive effect, resulting in the reduction activity of the soil Cd through chemisorption process and the reduction activity of the soil As that involves both chemisorption and physisorption process. This work provides an efficient method based on the interfacial-surface engineering to co-immobilize the heavy metal contaminations for soil remediation.