Green Tea Leaves as a Natural Adsorbent for the Removal of Cr(VI) from Aqueous Solutions

Chromium(VI) has been found to be one of the toxic metals present in water obtained from industrial effluents. This study deals with the removal of Cr(VI) using used green tea leaves, which is a waste material. The sorption of Cr(VI) was carried out by using a batch method, and its concentration was determined using an ultraviolet visible spectrophotometer at 540 nm. Parameters such as pH, mass of adsorbate, concentration of adsorbent, time of contact, and temperature were optimized. It was observed that, under optimum conditions, the percentage efficiency of removal of Cr(VI) was up to 99%. Adsorption studies were carried out using Langmuir and Freundlich adsorption isotherms. The values of Δ G, Δ H, and Δ S were also calculated, which showed that the process is spontaneous and the extent of adsorption decreases with the increase in temperature. The kinetic studies were carried out, and it was found that the reactions followed pseudo-second-order kinetics. This technique can be used for the removal of Cr(VI) from water obtained from industries, which have chromium as one of the main pollutants in their effluents.