Magnetically modified Sargassum horneri biomass as an adsorbent for organic dye removal

Adsorption of five water-soluble dyes of different chemical structures from aqueous solutions was investigated using magnetically responsive brown algae Sargassum horneri. The simple magnetic modification of Sargassum biomass employing microwave-synthesized iron oxide nano- and microparticles enabled rapid and selective separation by means of external magnetic field. The biosorption was studied in a batch system under different conditions. Time necessary to reach equilibrium was less than 2 h for all tested dyes. The adsorption equilibrium data were analyzed by Langmuir and Freundlich isotherm models. The highest maximum adsorption capacity was observed for acridine orange (193.8 mg/g), the lowest one for malachite green (110.4 mg/g). The sorption kinetics could be described by pseudo-second-order model, and the thermodynamic studies indicated exothermic nature of biosorption process in the temperature range studied. It can be concluded that Sargassum horneri biomass, exhibiting a satisfactory efficacy in dye removal, can be used as an effective, low-cost adsorbent.