Surface characterization of a bentonite-vermiculite mixture as a cost-effective adsorbents for oil removal from water

This study assesses the sorption efficiency of mineral-sedimentary rocks—dolomite, bentonite clay, and a vermiculite–bentonite composite—for eliminating petroleum contaminants from wastewater. The adsorption properties and chemical composition of the starting materials were investigated by titrimetry, pH-metry, FTIR, SEM, XRD, and ζ-potential analysis. The results show that adsorption on bentonite clay and on the vermiculite–bentonite composite is governed by the physicochemical characteristics of their surface layers and is accurately described by the PSO kinetic equation, whose parameters display a pronounced linear correlation. An optimal vermiculite-to-bentonite ratio that maximizes sorption capacity was identified. The composite's enhanced efficiency is attributed to surface activation associated with higher contents of silicon and iron oxides, which generate additional active sites. Compared with the pristine natural mineral rocks, the composite exhibits markedly superior removal efficiency and retains its structural integrity after adsorption, highlighting its potential for industrial wastewater-treatment applications.