Adsorption of brilliant green from aqueous solution by unmodified and chemically modified Tarap (Artocarpus odoratissimus) peel

Tarap peel (TP) and oxalic-acid-modified Tarap peel (TP-OX) were used to remove brilliant green (BG) dye from aqueous solution. Surface modification of TP suggested that functional groups such as carboxyl, hydroxyl and amino were involved in the adsorption of BG onto TP. Parameters such as effects of pH, contact time, ionic strength, initial dye concentration and temperature were included to study the adsorption of BG onto TP and TP-OX. Adsorption isotherm models were used to investigate the adsorption process, while kinetics models were used to provide insight into the adsorption mechanisms. Optimised contact time of 2 h with no pH adjustment was used. Adsorption of BG onto TP was best fitted to the Freundlich model, while experimental data for TP-OX are best described by the Tempkin model. The maximum adsorption capacities were determined as 174 and 275 mg g(-1) for TP and TP-OX, respectively. Thermodynamics study indicated the endothermic nature of adsorptions of BG onto both adsorbents. According to kinetics study, the adsorption mechanisms on both adsorbents followed pseudo-second-order model, and film diffusion might have major role in the adsorption process.