Physicochemical Modifications in Geomaterials and Their Leachates Extracted from Acidic Attack

Abstract

Exposure of geomaterials to acid leachates may cause chemical species desorption, mineral dissolution, and metal leaching. This study seeks to understand the changes in the physicochemical composition of liquid extracts resulting from the exposure of four different geomaterials (uniform fine sand, basalt residual soil, kaolin, and bentonite) to a blank solution (distilled water) and sulfuric acid solutions at the concentrations of 0.01, and 1.00 mol/L. It was also investigated the relationship between alterations in both chemical and mineralogical constitutions of geomaterials. The elemental composition of the geomaterials was determined by X-ray fluorescence. In the liquid extracts, Na, Mg, Al, K, Ca, Fe, and Mn concentrations were obtained by inductively coupled plasma atomic emission spectrometry, as well as pH and electrical conductivity were evaluated. pH and electrical conductivity data showed that bentonite had buffering capacity until 0.01 mol/L concentration and higher ion dissolution with increasing acid concentration. Acidic attack by the 1.00 mol/L solution resulted in the solubilization of the constituent metals, corresponding to reductions in elemental composition and alterations in geomaterials mineralogy.