Development and optimization of a polysilicon-aluminum alkali mineral-enhanced biochar composite for effective heavy metal removal in acidic environments

Abstract

While traditional biochar demonstrates promising performance in diverse settings, its efficacy may be constrained under specific conditions of high acidity and heavy metal concentrations. In this study, researchers developed a new polysilicon-aluminum alkali mineral-enhanced biochar composite material, GBMSs (green biochar-metakaolin-sodium silicate), by pyrolyzing fibers from dragon fruit peels and blending them with metakaolin and sodium silicate. Using a response surface methodology, this environmentally friendly composite material was optimized for removing copper and zinc contaminants across a range of initial pH levels from 2 to 6. Experimental findings indicated that the adsorption capacity of GBMSs for copper and zinc was significantly enhanced, ranging from 1.5 to 4 times greater compared to pure biochar or biochar mixed solely with a silicon-aluminum mineral. Various analytical techniques including scanning electron microscopy, X-ray diffraction (XRD), and Fourier transform infrared (FTIR) spectroscopy were utilized to examine the influence of poly-silica-aluminum alkali minerals (GBMSs) on biochar composites. The findings revealed an upsurge in surface binding locations and oxygen-related functional groups because of integrating GBMSs. This augmentation of electronegative features on the biochar surface was credited to the development of stabilizing silica-aluminum connections, ultimately boosting its adsorption effectiveness in acidic surroundings. By applying Langmuir and Freundlich models, it was deduced that the adsorption of GBMSs adheres to a multilayer uniform adsorption mechanism, with surface ion interchange and complexation restricting the adsorption capability. This research highlights the potential of clay mineral-altered biochar in efficiently dealing with intricate environmental contamination.