Spent Tea Leaves as a Potential Low-cost Adsorbent for the Removal of Azo Dyes from Wastewater

Spent tea leaves (STL), a solid waste that is available in large amounts worldwide, was investigated as a potential low-cost adsorbent for the removal of two azo dyes, Reactive Green 19 (RG19) and Reactive Violet 5 (RV5), from contaminated waters. Preliminary experiments conducted on untreated STL showed that this material exhibited very low removal efficiencies (<10 %). By contrast, thermal activation of STL (200 to 400 °C for up to 2 h) resulted in a significant increase in dye adsorption. After thermal exposure of STL to 300 °C for 1 hour, removal efficiencies of 98.8 % and 72.8 % were observed, respectively, for RG19 and RV5. Characterization of the adsorbent by TG/DTA and FTIR measurements showed that structural and chemical changes occurred in the lignocellulosic material which were probably responsible for the enhancement in adsorption capacity. These results strongly support the use of activated STL as a low-cost alternative to conventional adsorbents.