DEVELOPMENT OF A LOW-COST ALTERNATIVE FOR REMOVING AND STABILIZING BORON IN COAL COMBUSTION RESIDUAL (CCR), COAL ASH LEACHATES (CAL) AND FLUE GAS DESULFURIZATION (FGD) WASTEWATER

This study focuses on the effective removal and stabilization of boron from coal ash leachate (CAL), coal ash residuals (CCR), and flue gas desulfurization (FGD) wastewater. The key objective is to develop a cost-effective treatment strategy for addressing boron contamination in CAL, CCR, and FGD wastewater. The proposed methodology combines the sorption efficacy of unaltered and modified biochars with the precipitation of boron minerals and coprecipitation of boron at an optimum concentration of aluminum (Al), calcium (Ca), sulfate, and hydroxide species. Alternative sources of Al, Ca, sulfates, and hydroxides such as steel slag and recycled aluminum cans are utilized. The precipitation and coprecipitation process is optimized within a pH range of 10-12, enabling boron to precipitate as mineral inyoite and coprecipitate with ettringite.

The proposed approach has demonstrated high efficiency of up to 95% removal of boron from CAL and FGD wastewater. Advanced characterization techniques including X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier-transform infrared spectroscopy (FTIR) are employed to analyze the resulting mineral phases. The XRD results confirm the formation of boron mineral inyoite and ettringite as the primary layered double hydroxide (LDH) responsible for boron immobilization. Further the characterization of other minerals by a combination of XRD, SEM, and FTIR is being pursued to identify other minerals and various ions that influence the boron removal process and its long-term stabilization.

The findings from this study provide valuable insights into the successful removal and stabilization of boron in CCR and the impacted soil and water resources. The developed methodology offers a novel and economically feasible solution for boron treatment, thereby benefiting the coal power generation industry.