Preparation and characterization of biosorbent Sargassum myriocystum for zinc removal

Heavy metal in wastewater is a problem due to its unsafe nature to the surroundings. The adsorption characteristics of brown algae Sargassum myriocystum for Zn2+ ions uptake from metal solutions was investigated. Among various algal pretreatment HCl was found to be the best and was characterized with various methods for example BET, DSC-TGA, proximate and composition analysis, and Point of zero charges. Experiments were performed and adsorption reaches equilibrium at 60 min at pH 5.5 and adsorbate dose decreased when increasing metal concentration 50 g/l and 200 mg/l, respectively. Maximum adsorption efficiencies of Zn2+ ions take place at temperature 30°C and 0.5 g of algae biomass was found to be optimal, with an agitation speed of 150 rpm. Our results suggest that HCl-treated adsorbent could be used as a more effective adsorbent than untreated S. myriocystum for the uptake of Zn2+ from metal solution. Kinetics study was performed for evaluating the sorption kinetics and the obtained data fit best to the pseudo-second-order model for zinc ion when compared with all other given models. It was observed that the Freundlich isotherm showed a good fit to the equilibrium sorption data and shows the highest correlation coefficient values (R2 > 0.90) for zinc, whereas in Van’t Hoff plots a positive value of ΔH°, a negative value of the free energy (ΔG°) and a positive value of ΔSo showed increased randomness at the solid/solution interface as well as the process being feasible and spontaneous by plotting 1/T vs ln Kc.