Application of dimocarpus Longan ssp. malesianus leaves in the sequestration of toxic brilliant green dye

Abstract

Recent years have seen the rise in the use of leaf-based adsorbents to remove pollutants. Not only are leaves low-cost and abundant, but they also contain many compounds giving rise to various func-tional groups that could promote the adsorption process. This study focuses on the use of leaves of Dimocarpus longan ssp. malesianus var. malesianus, locally known as “mata kuching” and literally translated as “cat’s eyes”, as an adsorbent for the removal of toxic brilliant green (BG) dye. The mata kuching leaves (MKL) reached equilibrium when in contact with BG dye within 30 min. Its adsorption toward BG was not greatly affected by varying pH solutions or salt concentrations. Of the five models tested, the Sips model was the best fit for the adsorption isotherm data, giving a maximum adsorption capacity of 337.9 mg g–1. Adsorption process followed the pseudo-second-order kinetics and intra-particle diffusion was not the rate-controlling step. Regeneration and reuse of spent MKL were possible especially when treated with a base, maintaining almost 80% dye removal at the 5th consecutive cycle. With its many attractive features such as high adsorption capacity, short contact time, ability to be regenerated, relative stability under varying conditions, availability in abundance throughout the year, MKL, therefore, has potential application as a low-cost adsorbent in wastewater treatment.