Upcycling tea waste particles into magnetic adsorbent materials for removal of Cr(VI) from aqueous solutions

In this work, locally available tea wastes were used as precursors for the development of cost-effective bio-sorbent materials for heavy metal removal from wastewater. Chemical and thermal treatments to prepare magnetic/non-magnetic tea waste-based adsorbents were discussed and correlated their properties with corresponding Cr(VI) adsorption capacity. These bio-sorbents were thoroughly characterized by FT-IR, PXRD, N₂ adsorption-desorption surface area techniques and Cr adsorption performance was investigated in batch reactor under different conditions such as adsorbent dosage, initial Cr concentration, solution pH and contact time. Careful bleaching steps, incorporation of magnetic iron nanoparticles and judicious temperature treatments of tea wastes resulted in high performing biosorbents with a complete removal of Cr at a dosage of 0.25 g/mL of the solution. Cr adsorption on these tea waste-based bio-sorbents were found to be fitting to a pseudo 2nd order kinetics.