Sorption of Copper and Zinc from Aqueous Solution by Metabasalt Residue and its Mineralogical Behavior

Residues from mining, as metabasalt powder from amethyst exploration, can be used to improve soil properties. Although there is a high-load content of clay minerals in metabasalt, the effects of this residue on cooper (Cu²⁺) and zinc (Zn²⁺) sorption and desorption have not been studied. The aim of this work was to evaluate Cu²⁺ and Zn²⁺ sorption capacity of metabasalt powder and to discuss the mineralogical behavior facing this phenomenon. This residue sorption capacity was compared to reference clay minerals under two Cu²⁺ and Zn²⁺ concentrations (8 and 16 cmol_c/kg) in a competitive system (Cu²⁺ + Zn²⁺). The sorption capacity was estimated by sequential desorption using cation exchange resin. A survey of mineralogical and Cu²⁺ and Zn²⁺ concentrations was performed on metabasalt before and after sorption, and after desorption tests. All materials sorbed higher amounts of Cu²⁺ than Zn²⁺. The sorption magnitude decreased in the following order: metabasalt > montmorillonite > illite > kaolinite. Cu²⁺ and Zn²⁺ desorption from metabasalt is lower than the standard clay minerals, since the metabasalt sorption sites are expandable interlayers of clay minerals. The relevance and application of our findings are critical in providing information for the management of metabasalt residue, suggesting potential use as a remediation agent in contaminated water, especially those with high Cu²⁺ and Zn²⁺ loading. It also suggests that the Cu²⁺ and Zn²⁺ enrichment of this residue could potentially be used for converting the metabasalt into a useful source of slow nutrient supply for agricultural soils.