Enhanced Stabilization of Lead in Soil Using Novel Biochar Composites Under Simulated Accelerated Aging Conditions

Straw biochar (BC) and four innovative biochar environmental materials (AFFA/BC) were synthesized via oxygen-limited pyrolysis at different ratios and applied for the remediation of lead (Pb)-contaminated soils. Accelerated aging, which mimics the effects of natural aging on heavy metal fixation properties, was induced through alternating dry and wet conditions. Two models, which are based on conditional probability-induced failures, were developed to characterize the aging process more effectively. The results indicated that the novel biochar material presented elevated Si, Al, and Na contents, increased specific surface area, pore volume, and yield, and the formation of chemical bonds such as T-O-T and T-O (T = Si or Al). Simultaneously, synchronous and asynchronous spectral analysis methods were used to demonstrate that fly ash leads to the formation of new chemical bonds and protects the functional groups of biochar from the destructive effects of high temperatures. Compared with the original biochar, the application of the new biochar material to Pb-contaminated soil increased the soil pH, cation exchange capacity (CEC), and soil organic matter (SOM) content while reducing toxic Pb leaching, resulting in conversion to a more stable residual state. Throughout wet–and–dry cycles, the Pb leaching concentration from the soil gradually increased, with AFFA/BC-2 resulting in a lower aging rate. This study provides a method for preparing low-cost and green soil amendments, which have great potential for repairing HM-contaminated soil and achieving value-added utilization of coal-based solid waste and agricultural waste.