Thiosulfate impregnated spent tea leaves for the remarkable uptake of malachite green.

ABSTRACT

Herein we demonstrate an enhanced performance of acid-assisted thiosulfate-impregnated spent/waste tea leaves (TWTL) for the removal of malachite green (MG) from water by batch mode. The material was characterized by pHZPC, FTIR, powder XRD, SEM, and proximate analysis. FTIR suggests the presence of polyphenolic moieties whereas a lignocellulosic peak was observed in powder XRD. SEM image shows a grafted surface texture with intermittent blocks, which upon dye uptake becomes somewhat condensed. Under optimized conditions, the highest removal efficiency of 126.8 mg/g was achieved at pH 7. A fast adsorption process was noticed with >97% removal within the first 10 min. Adsorption follows pseudo-second-order kinetics (R2 = 0.999) and the Langmuir model (R2 = 0.999). The material can be regenerated by dilute hydrochloric acid and can be reused for up to four cycles. Treatment of industrial effluent was successful in up to 47.56%. Our results highlight the potential of thiosulfate-treated spent tea leaves as a choice for the efficient removal of malachite green from water.

Tea, being one of the most popular beverages produces huge waste which requires proper management. With this aim; the thiosulfate-impregnated spent tea leaves have been exercised for effective separation of malachite green from contaminated water. Thiosulfate impregnation under mildly acidic conditions activates the tea leaves and makes the material robust with enhanced water stability than its untreated variety. With a remarkable maximum adsorption capacity of 126.8 mg/g under ambient conditions, the present methodology enjoys the edge over related phytosorbents. The protocol is techno-economic, environment friendly, and could be extended to possible field applications.