Coconut shell derived ZnCl₂ activated carbon for malachite green dye removal

The coconut-based agricultural wastes have gained wide attention as an alternative adsorbent for the removal of diverse pollutants from the industrial effluents. This paper presents the zinc chloride activation of adsorbent carbon and the utilization as an adsorbent for the removal of malachite green dye from aqueous solution. The characterisation of activated carbon was performed to get an insight into the adsorption mechanism. The ZnCl₂ activated carbon acquired a higher specific surface area (544.66 m² g^-1) and stability (-32.6 mV). The impact of process parameters including contact time (20-220 min) and initial dye concentration (20-80 mg L^-1) were evaluated on the effectiveness of activated carbon for dye removal. The results concluded that zinc chloride activated carbon showed a significant dye adsorption (39.683 mg g^-1) at an initial concentration of 20 mg L^-1 after 3 hours. Based on the correlation coefficient (R²), the Freundlich isotherm model (0.978-0.998) was best fitted for the experimental data followed by the intraparticle diffusion model (0.88-0.929) as the most appropriate model for malachite green dye removal. Additionally, the energy and thermogravimetric analysis portrayed the suitability of the carbon material to be used as an energy alternative to coal.