Dye removal efficiency of fresh and dry alginate beads incorporating zinc oxide

Abstract

Alginate beads incorporating zinc oxide (ZnO) nanoparticles were shown as an alternative to treat water contaminated with sedge dye by combining photocatalytic activity with adsorption. Dry and fresh alginate beads were prepared by changing ZnO contents in the range of 0.5, 1, and 2% (w/w) and then characterized for their morphology as well as dye removal. The dye removal efficiency was increased by increasing the active surface area of the alginate beads and ZnO photocatalytic activity. Under ultraviolet irradiation for 24 h, the dye removal efficiency reached 64% in the case of 2% ZnO loading. The use of alginate beads dried at 80 °C before ZnO loading increased the maximum value to 78%. With more than 20% removal during the first 2 h through the adsorption and diffusion, the dye removal of alginate beads incorporating 1 and 2% ZnO was modeled as a function of time according to the Weber-Morris intra-particle diffusion equation. The dye adsorption per mass of the adsorbent having 0 and 0.5% ZnO loading fitted the Elovich equation better.