A Sustainable Approach towards the Restoration of Lead-Contaminated Soils through Nutrient-Doped Olive Waste-Derived Biochar Application

The current study was conducted to investigate the efficiency of olive mill waste-derived biochar and its silica-embedded and nutrient-loaded derivatives in immobilizing lead (Pb) and improving nutrients availability in contaminated sandy loam soils. Biochar was produced at 500 °C and latterly modified with silica and enriched with nutrients (P and N). An incubation experiment was conducted for a period of 45 days to observe the dynamics in heavy metals and nutrient release. The produced biochar and its modified versions were characterized for physiochemical and structural properties prior to soil application. The results of incubation trials demonstrated that pseudo second-order kinetic model was fitted best to Pb, P, NO3− and NH4+ release characteristics. Silica embedded and nutrient loaded biochars performed outclass and showed up to 85% decline in Pb release against control treatment. Similarly, 38%, 69% and 59% increase in P, NO3− and NH4+ availability, respectively, was observed with modified biochars, as compared to 22%, 59% and 32% increase with pristine biochar application, respectively. Overall, silica and nutrient doping of biochar resulted in significantly higher immobilization of Pb in contaminated soil and increased the nutrient availability, which could be helpful in restoring heavy metal contaminated soil and improving soil fertility.