Remediation of zinc and cadmium polluted soil using CaCO₃-biochar

Hazardous substances like zinc and cadmium can be released into the soil by ore mining and other industrial operations, which could endanger the environment. Biochar made from biomass pyrolysis is suggested as a sorption treatment for contaminated soils, enhancing microbial activity, soil fertility, and water retention. Utilizing four different biochar the average removal rate of heavy metal from aqueous solution was 48.2-65.7% (Cd), 46.2-59.1% (Pb), 46.7-59.3% (Ni), 45.2-59.4% (Zn), 48.7-62.4% (Cu), and 51.8-63.7% (As) compared to no biochar treatment. The percent decrease of Pb heavy metal adsorption with increase in maximum contaminant level (MCL) from one to five fold was 55.8 (RJB), 54.9 (SBB), 53.6 (PTB), and 51.3 (BMB). Effect of dose study showed that the As adsorption on all the four types of biochar was most favourable and Ni adsorption was the most awful. Results revealed that the wastewater COD_T, TSS, ammonia, TKN and TP values demonstrated an 89.2-91.8%, 85.3-82.7%, 89.4-87.9%, 59.2-70.5% and 89.3-78.8% decrease, respectively. Additionally, the wastewater As, Cd, Cr, Pb, Zn and Cu values resulted an 76.9-84.2%, 50.5-92.4%, 81.5-86.2%, 92.8-75.1%, 88.4-92.5% and 93.3-95.5% decrease, respectively after being passed via biochar bio-filter.