Pyrolytic synthesis and performance efficacy comparison of biochar-supported nanoscale zero-valent iron on soil polluted with toxic metals

Toxic and hazardous metals such as cadmium (Cd) and Lead (Pb) can cause cancer in humans; hence, reducing their bioavailability in the soil is crucial for human health and environmental safety. In this study, biochar modified with nanoscale zero-valent iron (nZVI-BC) was synthesized from low-cost adsorbent waste materials and iron (iii) oxide (Fe2O3) via carbothermal reduction process for stabilization of Pb and Cd in the soil. Furthermore, an evaluation of treatment efficiency on exposure health hazards for both carcinogenic and non-carcinogenic risks was done. The results revealed that nZVI-modified eggshell biochar was able to reduce the concentration bioavailable of Pb and Cd in soil by (69-75%) and (62-65%), and reduce the toxicity leaching of Pb and Cd by (53-66%) and (68-75%), respectively. The treatments reduced carcinogenic risk (CR) and hazard index (HI) in children and adults by 35-47% for Pb and 25-36% for Cd, respectively. Hence, this study proposes a new way to reduce and modify environmental wastes to make nZVI-supported biochar that can remediate toxic metals from the soil, improve soil nutrients, reduce human exposure health risks, and enhance the environment's health.