Lead stabilization in soil using P-modified biochars derived from kitchen waste

Kitchen waste is increasing rapidly worldwide. Utilization of biochar in pollution remediation is an economical approach to the sustainable management of kitchen waste. To date, information regarding the modification of kitchen waste biochar and their resulting ability to inhibit the bioavailability of toxic metals in soil is limited. Here, a novel type of kitchen waste-derived biochar was constructed through phosphate modification, and the sequestration, speciation, and migration of Pb(II) in the soil–plant system were explored through a combination of batch adsorption and pot experiment. The results indicated that the maximum adsorption capacities of P-modified biochar for Pb(II) reached 257.95 mg g−1, which was approximately 50% higher than pristine biochar; further, P-modified biochar exhibited a greater potential to sequestrate Pb(II), compared to that commonly reported for biochar in previous investigations. In the pot experiments, as compared with the unamended soil, the application of P-modified biochar transformed 42% of acid extractable/exchangeable Pb mainly to easily reducible and residual fractions, significantly decreasing the Pb uptake of ryegrass by 37.9–62.6%. The stable speciation of Pb in soil was attributed primarily to the complexation and precipitation of P-modified biochar with Pb(II). Moreover, the binding of P-modified biochar with Pb(II) was dominated by the surface hydroxyl and phosphate groups, although phosphate modification promoted the formation of mesoporous structures and increased negative charge. The findings could lead to the development of novel methods for the reuse of waste and remediation of toxic metal-polluted soils.