Adsorption of hazardous dye crystal violet from wastewater by waste materials

The adsorption performance of the materials bottom ash (BA), a power plant waste, and de-oiled soya (DOS), a soya bean industry waste for removal of crystal violet dye, has been investigated through batch and column experiments. Batch studies have been performed to describe the impact of parameters such as pH, amount of adsorbent, dye concentration, temperature, and contact time on the removal of the dye. Experimental data have been modeled by using Langmuir, Freundlich, Tempkin, and Dubinin-Radushkevich (D-R) isotherms. Thermodynamic parameters (ΔG°, ΔH°, and ΔS°) were evaluated for the dye-adsorbent systems, which revealed that the adsorption process is endothermic in nature. Pseudo-first- and second-order kinetic models have been applied to the experimental data and pseudo-second-order kinetics was found to describe the adsorption of the dye (crystal violet) on the adsorbents. In order to achieve bulk removal of the dye, column operations were made. Recovery of the dye was made by eluting HCl solution through the exhausted columns and almost 95% and 78% of the dye was recovered from BA and DOS columns, respectively.