Application of algal biochar to prevent leachate of heavy metals from mine tailings

This paper introduces a biogenic adsorbent derived from microalgae to immobilize copper, iron, and zinc. The adsorbent is made through hydrothermal liquefaction of Cyanidioschyzon merolae to form biochar. We used density functional theory (DFT) and laboratory experiments to elucidate the molecular interactions responsible for metal adsorption onto algal biochar. UV-Vis spectroscopy confirmed metal-ion adsorption independent of solution pH, and thermogravimetric analysis revealed changes in thermal stability, indicating chemical interactions between biochar and metal ions. The dominant mechanisms of adsorption were identified as cation-pi interactions, complexation, and ion exchange. The stability of the adsorption at various pH and temperatures suggest strong binding affinity. Our DFT analysis showed competitive adsorption with the order Cu2+ > Fe2+ > Zn2+, displacing inherent cations such as K+. Algal biochar shows promise as an additive in geopolymer alongside mine tailings to address concerns about heavy-metal leaching, especially in construction elements exposed to water. The study outcomes promote sustainability, resource conservation, and the prevention of environmental pollution.