Carbothermal Reduction Synthesis of Eggshell-Biochar Modified with Nanoscale Zerovalent Iron/Activated Carbon for Remediation of Soil Polluted with Lead and Cadmium

Pollution of soil with lead (Pb) and cadmium (Cd) has been gaining researchers’ attention because of their adverse health effects on the safety of the food chain and environmental health. Hence, their immobilization in the soil is of great interest to environmental scientists globally. In this study, eggshell-biochar modified with nanoscale zerovalent iron/activated carbon (ESB-nZVI/AC) were synthesized via carbothermal reduction synthesis and compared their immobilization efficiency at different temperatures. The results showed that ESBnZVI/ AC is highly efficient in reducing the bioavailability, toxicity leaching, and invitro bioaccessible Pb and Cd in the soil through conversion to their respective carbonate, hydroxide, and iron oxide insoluble forms. The observed results were due to the effects of modification and increment in surface area of the prepared treatments, which further enhance the active functional sites, immobilization effectiveness, and stability of ESB-nZVI/AC. Analysis of ESB-nZVI/AC after reaction using FTIR, XRD, and XPS suggested that: adsorption, coprecipitation/ precipitation, electrostatic interactions, ion exchange, reduction, physical-chemisorption, and surface complexation formation were all involved in the immobilization of Pb and Cd in soil. It can be concluded that co-preparation of ESB-nZVI/AC is another alternative and sustainable adsorbent to remediate soil polluted with toxic metals and simultaneously improve soil nutritional contents.