Sandani Buddhima Abewickrama*, Daham Jayawardana, Kalpana Dissanayake, Kuis Gunathilake, P.L.Herath
The main objective of this study is to investigate the sorption behaviour of fluoride in tea waste under various fluoride concentration levels in water in Sri Lanka and to study the chemical kinetics of fluoride adsorption by tea waste with the necessary amendments for fluoride removal from drinking water for effective use of tea waste. The physicochemical characteristics of tea waste were investigated using SEM, AAS, BET, and FTIR analysis. The results obtained by batch experiments showed that the maximum removal efficiency attained was at pH 6, after 20 min of contact time, and with an adsorbent dose of 1.5 g. The adsorption equilibrium isotherms followed by the Langmuir model, and the reaction obeyed the pseudo-second-order model. It was found that phosphate ions have shown maximum influence on the fluoride removal by the soil mixture, and the tea waste-laterite mixture containing 65% tea waste showed the highest removal efficiency with the maximum adsorption capacity of 0.0216 mg/g. Finally, a fluoride removal setup was prepared and the filtering performance of the tea waste-based mixture was studied under selected influent fluoride concentrations of 1.5 ppm, 2.0 ppm, and 2.5 ppm, respectively. The results of this experiment showed that each filtering set-up with different influent concentrations had significant fluoride removal efficiency to the WHO drinking water quality standard limit of 1.5 ppm. The optimum fluoride removal happened at pH6 in both batch experiments and filtering set-up experiments. Therefore, the material can be applied for fluoride removal without changing the normal pH of potable groundwater.
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