Removal of Heavy Metals from Freshwater Using Immobilized Microalgae

Abstract

This study focused on the use of Tetradesmus obliquus, a freshwater microalga, immobilized using sodium alginate and polyvinyl alcohol (PVA) for removing heavy metals from water. Experiments conducted during the study demonstrated the adsorption efficacy of microalgae beads with respect to lead, copper, and cadmium, with the adsorption process predominantly facilitated via hydroxyl, carboxyl, and carbonyl groups. Varying the mass of beads between 0.25 and 0.2 g only minimally affected their adsorption capacity for cadmium ions. The highest removal rate was observed for Pb, followed by Cu and Cd. Maximum removal for all tested metals was achieved at an adsorbent dosage of 2 g. Based on optimal data points, the influence of pH on the removal rate was nonlinear. Analyses based on Freundlich and Langmuir models demonstrated the remarkable adsorption capacity of Tetradesmus obliquus with respect to heavy metals, particularly Pb, which increased with temperature.