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Researchers have developed a new biochar composite by co-pyrolyzing corn stover and alkali-modified fly ash (FA) that significantly improves the remediation of lead-contaminated soils. This study highlights the physicochemical enhancement of fly ash through NaOH modification, creating biochars that actively stabilize lead through various mechanisms such as precipitation, cation-π interaction, and complexation.

Fly ash, primarily made of silica and alumina, is combined with corn stover to produce alkali-fused FA-CS biochar composites (ABs). These composites are then subjected to co-pyrolysis at different temperatures (300°C, 500°C, and 700°C) and varying corn stover to FA ratios. The optimized ABs, especially those produced at 500°C with a 10:1 ratio, show superior performance by reducing lead bioavailability by 24% compared to other composites.

The effectiveness of these biochar composites in stabilizing lead in soils is linked to their physicochemical properties, which are enriched with oxygen-containing groups and aromatic structures. Additionally, the stabilization performance is influenced by the increase in soil pH and cation-exchange capacity (CEC) due to the application of the biochars.

This research indicates that the lower pyrolytic temperatures and optimal biomass to FA ratios not only enhance the yield and stability of the biochars but also their ability to reduce toxic lead fractions in the soil. The results suggest that these biochar composites facilitate the transformation of bioavailable lead into stable and less harmful residual forms.

This innovative approach of using waste materials such as fly ash and agricultural residues like corn stover to create functionalized biochars opens up new avenues for the effective remediation of heavy metal-contaminated soils, providing a sustainable solution that utilizes agricultural and industrial waste for environmental protection.