Spent Chinese Green Tea as an Adsorbent for Simultaneous Removal of Potentially Toxic Metals from Aqueous Solution

Introduction Spent wastes are inexpensive, abundantly available, and environmentally friendly and can be introduced into wastewater to remove toxic metals. This study sought to utilise spent Chinese green tea leaves to simultaneously remove cadmium (Cd), chromium (Cr), mercury (Hg) and lead (Pb) from an aqueous solution. Methodology Batch experiments were performed in binary systems with different initial metal concentrations and dosages using 100 mL of aqueous solution and agitating using an orbital shaker for 60 min . Results The adsorption efficiencies from 98.18 to 99.89% for cadmium, 98.79–99.99% for chromium, 98.18–99.98% for mercury and 86.20–99.99% for lead. The 1 / n values indicate that normal adsorption occurred. The adsorption capacity of Cd, Cr, Hg and Pb ranged from – 2.91 × 10 –6 to 1.58 × 10 –4 mg/g in the study. The correlation coefficient (R 2 ) for Cd, Cr, Hg and Pb in binary components ranged from 0.1434 to 0.9940 for the Langmuir isotherm and 0.0345–0.9993 for the Freundlich isotherm. The pH was between 5.58 and 7.81 which plays a very important role in the adsorption process. Conclusion The Langmuir adsorption isotherm was the best fitting model for the data. The experiment also showed that increasing the adsorbent dosage led to an increase in adsorption efficiency. The spent adsorbent from Chinese green tea was effective in removing cadmium, chromium, mercury and lead in the aqueous solution. Therefore, it can be used as a low-cost and efficient adsorbent for the removal of potentially toxic metals from aqueous environments.