Removal of Synthetic Dye by Chlorella vulgaris Microalgae as Natural Adsorbent

Owing to its abundant availability in the nature, microalgae can be served as a potential natural sorbent for water remediation. In this study, Chlorella vulgaris (a species of microalgae) was used to remove two synthetic dyes (i.e. positively charged methylene blue and negatively charged acid orange 7) from water. Results showed that the C. vulgaris able to remove methylene blue by surface adsorption through electrostatic interaction. Nevertheless, poor or even no removal was attained for acid orange 7. Apparently, the adsorption of dye on the C. vulgaris is oriented by the surface charge effect. In the case of methylene blue, the highest removal efficiency was attained at 100 mg/L initial dye concentration, whereby 83.04 ± 2.94% of removal was recorded after 3 days of adsorption. Additionally, the removal mechanism was found to fit better into the Freundlich isotherm which indicates the presence of the multilayer adsorption in this experiment. Biochemical composition of the C. vulgaris was studied after dye removal in order to investigate the effect of dye adsorption on the quality of microalgal biomass and the potential by-products produced from the microalgal biomass. Result showed that the total carbohydrates and total chlorophyll were at the highest amount after 1 week of the adsorption process. Here, the concentration of both total carbohydrates and total chlorophyll was 46.65 ± 2.6 mg/L and 247.31 ± 17.88 mg/L, respectively.