Efficient activation of bentonite clay for cyanide adsorption using sulfuric acid and sodium ion intercalation

Abstract

This study aims to investigate the most effective way to activate bentonite clay using H₂SO₄ and Na⁺ intercalation. The outcomes were assessed using XRD, XRF, and FTIR analyses. The adsorption process was carried out in batches, and the cyanide adsorbate solution was analyzed using UV–VIS spectrophotometry and a ninhydrin reagent. The optimal concentration of H₂SO₄ was established at 1.5 M, whereas the ideal pH for cyanide was identified as 10.2. XRD analysis provided insights into the Miller indices (d_hkl) of mineral components, variations in crystallinity, shifts in 2Ɵ, and a decrease in basal spacing. The FTIR analysis showed vibrations associated with the hydroxyl group, methylenes, carbonate, water-related vibrations, silica-related groups, and metal-oxygen bonds. These findings confirmed the chemical structure and composition of the activated bentonite clay after treatment. XRF analysis revealed a decrease in the concentrations (wt%) of SiO₂, Fe₂O₃, CaO, TiO₂, and other impurities, as well as an increase in K₂O, compared to the pre-intercalation and pure states. During the post-cyanide adsorption phase, the -OH wavenumber shifted to the left, and the intensity of -CN decreased due to competition between CO₃^2- ions in the adsorbate and CN^- ion adsorbate, limited contact time, and suboptimal pH conditions. Under optimal pH conditions, the H-OH wavenumber shifted to the left, the -OH intensity decreased, and the -CN intensity increased for cyanide removal from water.