Utilization of ball clay adsorbents for the removal of crystal violet dye from aqueous solution

In this work, an attempt has been made to find the adsorption characteristics of crystal violet (CV) dye on calcined and uncalcined ball clay using batch adsorption technique. The ball clay adsorbents are characterized using thermo gravimetric analysis (TGA), particle size analysis, X-ray diffraction (XRD), nitrogen adsorption–desorption isotherm, and Fourier transform infrared (FT-IR) spectroscopy. The influence of pH and temperature on the adsorption of CV dye is examined. The experimental results of adsorption isotherms are fitted with Langmuir, Freundlich, and Redlich–Perterson models. Adsorption mechanisms of the CV dye on both the ball clays are investigated using thermodynamic parameters and analytical techniques. The results indicate that the Langmuir and Redlich–Peterson models are found to be the more appropriate model to explain the adsorption of CV dye on ball clays than that of Freundlich model. The maximum adsorption capacity of the calcined and uncalcined ball clay is found to be 1.6 × 10⁻⁴ and 1.9 × 10⁻⁴ mol g⁻¹, respectively. The lower adsorption capacity of the calcined ball clay is due to the reduction in the surface hydroxyl group and surface area. Adsorption capacity and percentage removal of the CV dye on calcined and uncalcined ball clay increase with an increase in the temperature and pH, respectively. The obtained negative ΔG ⁰ values indicate that the adsorption of CV dye on ball clay is feasible and spontaneous in nature at temperatures studied. The energy supplied for calcining the ball clay did not bring any improvement in the adsorption capacity. Rather, a reduction in the adsorption capacity of the CV dye on calcined ball clay suggests that the uncalcined ball clay would be more economic and efficient adsorbent for the removal of CV dye than the calcined ball clay. In conclusion, uncalcined ball clay could be used as a low cost alternate for the expensive activated carbon.