Magnetic pectin-Chlorella vulgaris biosorbent for the adsorption of dyes

Treatment of dye-contaminated water systems is a major challenge since a number of dyes are resistant to many conventional water treatments. The aim of this study was to synthesize an efficient biosorbent with easily separation and reusability for adsorption of various dyes from wastewater. A magnetic pectin-Chlorella vulgaris biocomposite (MPC-50) was prepared as a composition of 50% pectin and 50% C. vulgaris determined based on the highest adsorption efficiency of nine different dyes namely methylene blue, methyl red, methyl orange, toluidine blue O, crystal violet, safranin O, bromothymol blue, bromophenol, malachite green and their mixture (Mix). The structures of MPC-50 and its constituents were characterized by FE-SEM, FTIR and XRD. The biosorbent, consisted of amorphous and irregular microparticles, was prepared without chemical reactions. The results showed that pectin incorporated with C. vulgaris not only prevented the adsorbing sites on C. vulgaris from being occupied by Fe3O4 via sacrificing its -COO- groups to magnetize the adsorbent, but also increased the dye adsorption on MPC-50 through the interaction of its hydrophobic backbone with dyes molecules. Moreover, Fe3O4 made the separation of MPC-50 easy, showing a synergistic dye adsorption. The adsorption isotherm parameters were obtained by application of Langmuir and Freundlich models. The microwave-assisted regeneration of biosorbent made it reusable for multiple adsorption cycles corresponding to the removal of 465 mg of Mix by 0.50 g of MPC-50 with the high adsorption capacity (930 mg/g). This study introduced MPC-50 as an efficient, sustainable biosorbent alternative for commercial adsorbents in wastewater treatment.