Bioremoval of toxic dye by using different marine macroalgae

Abstract

The removal of malachite green dye from aqueous solution byUlva lactuca ,Sargassum crassifolium , andGracilaria corticata has been demonstrated in order to examine their potential use as low-cost adsorbents. The optimum pH (8.0), temperature (25 °C),contact time (150 min), and biomass (2.0 g) for removal of dye by algae are reported. The maximum removal percentage of the dyeranged between 95.6% and 98.3% by usingSargassum crassifoliumat the optimal conditions. Minimum removal of dye by algae (69%77.1%) was observed with the high dye concentration of 35 mg L1 at the optimal conditions. Adsorption of the dye by using the biomasswas found to fit well with Langmuir and Freundlich isotherms. The adsorption reaction was spontaneous, exothermic, and highlyfavorable by the tested algae. The FT-IR analyses confirmed that hydroxyl, carboxyl, amino, and carbonyl groups were responsible forthe dye binding process. Scanning electron microscopy showed great porosity on the algal surface, which allows the free passage of dyemolecules. The biomass of brown algae was the most effective in the removal of malachite green, followed by green and red algae. Thehighest affinity of the brown biomass for dye removal may be due to its high binding site affinity, the negative free energy of adsorption,and the great pores on its surface.