Spent green tea leaves for decolourisation of raw textile industry wastewater

True colour measurements of wastewater samples, in terms of American Dye Manufacturers' Institute values, were used to evaluate the effectiveness of decolourisation of textile wastewater using spent green tea leaf powder waste. Raw wastewater samples with a true colour of 868 ADMI were used in the batch adsorption experiments. Results revealed that the true colour removal efficiency of the raw textile wastewater was high in acidic solution and at high temperature, indicating an endothermic nature of the system. The major functional groups of the green tea leaf powder waste involved in adsorption were identified by Fourier Transform-infrared spectroscopy analysis. Adsorption kinetic data were modelled using the modified Freundlich and intraparticle diffusion kinetics equations. Fitting results of the Langmuir adsorption isotherm showed that the adsorption capacity of the green tea leaf powder waste was 775ADMIg(-1), which is higher than that of powder activated carbon (526ADMIg(-1)). The low activation energy values (13.9kJmol(-1)) suggested that adsorption was governed by a diffusion process and the reaction involved a physisorption mechanism. From the perspectives of waste utilisation, remarkable colour adsorption capacity and inexpensive and abundant availability, green tea leaf waste is an attractive alternative for decolourisaton of textile wastewater. Because high temperature favours colour removal, green tea leaf powder can be directly applied in raw textile wastewater treatment.