Removal of Crystal Violet and Acid Red 1 Dyes from Wastewater by Mechanically Activated Talc

Abstract

Raw talc (RT) and mechanically activated talc (MAT) were prepared and utilized as adsorbents for removing Crystal Violet (CV) and Acid Red 1 (AR1) from aqueous solutions. We investigated the impact of pH, dye concentration, conditioning time, and temperature on the removal efficiency of acid and basic dyes by RT and MAT samples. The results demonstrate that MAT exhibited significantly higher adsorption capacities, with values of 160 mg/g for CV and 130 mg/g for AR1-2-3 times greater than those of RT. Experimental data revealed that the adsorption of both dyes by RT followed the Temkin isotherm, while MAT followed the Freundlich isotherm. Additionally, the adsorption behavior of CV and AR1 on MAT and RT followed a pseudo-second-order process, with intra-particle diffusion being the rate-limiting step for the adsorption kinetics of AR1 onto RT. The enhanced adsorption performance of MAT was attributed to its high pore volume and the presence of multi-charged sites resulting from the rupture of chemical bonds through intensive material grinding. Physical properties of RT and MAT were further investigated using XRD analysis, FTIR, zeta potential, particle size, and Brunauer-Emmet-Teller (BET) analysis. The results revealed that intensive grinding caused significant crystal dislocations in raw talc, leading to a noticeable shift in its isoelectric point (IEP), an increase in surface area, and a decrease in pore size. These findings provide supporting evidence for the observed adsorption results.