Wang, et al (2024) Enhanced solidification/stabilization (S/S) of fluoride in smelting solid waste-based phosphogypsum cemented paste backfill utilizing biocharBiochar is a carbon-rich material created from biomass decomposition in low-oxygen conditions. It has important applications in environmental remediation, soil improvement, agriculture, carbon sequestration, energy storage, and sustainable materials, promoting efficiency and reducing waste in various contexts while addressing climate change challenges. More: Mechanisms and performance assessment. Journal of Environmental Management. https://doi.org/10.1016/j.jenvman.2024.122088

Phosphogypsum (PG), a byproduct of phosphoric acid production, poses environmental risks due to its acidic nature and potential for fluoride leachingLeaching is the process where nutrients are dissolved and carried away from the soil by water. This can lead to nutrient depletion and environmental pollution. Biochar can help reduce leaching by improving nutrient retention in the soil.   More. Traditionally, PG is treated using cemented paste backfill (CPB) methods, which rely heavily on Ordinary Portland Cement (OPC). However, OPC’s high carbon footprint and cost drive the need for alternative solutions. A recent study published in the Journal of Environmental Management explores an innovative method to address these challenges by utilizing steel slag (SS), ground granulated blast furnace slag (GGBFS), and biochar in PG-based CPB.

The research demonstrates that substituting OPC with SS and GGBFS, and incorporating biochar as a fluoride-fixing agent, significantly improves the mechanical properties and environmental safety of the backfill material. Adding 0.2% biochar by weight enhances strength by 54.3% and reduces fluoride leaching by 39.4%. The biochar facilitates the formation of stable hydration products, including fluorapatite and fluorite, by promoting heterogeneous nucleation and acting as a microfiller.

This novel approach not only reduces carbon emissions and operational costs associated with PG treatment but also effectively stabilizes fluoride, mitigating potential risks to groundwater. The study’s findings offer a promising path forward for sustainable mining practices and the safe reuse of industrial waste materials.