Methyl Violet Dye Absorption from Aqueous Solutions by Nanomagnetic Hydrogels Based on κ-Carrageenan and Acrylic Acid

Nanomagnetic hydrogels, based on κ-carrageenan and acrylic acid, were prepared for removal of methyl violet from aqueous solutions. κ-Carrageenan/acrylic acid-based hydrogels were prepared in aqueous solution in the presence of methylene bisacrylamide (MBA) and ammonium persulfate (APS), the former as a crosslinking agent and the latter as an initiator. The nanomagnetic hydrogels were obtained by co-precipitation of Fe (II) and Fe (III) ions in presence of ammonia solution. The effects of different variables such as contact time, temperature, amount of adsorbent, and pH were examined in relation to the sorption behavior of the methyl violet. The structure of the nanomagnetic hydrogels were studied by infrared spectroscopy (IR), thermogravimetric analysis (TGA), scanning electron microscopy(SEM) and transmission electron microscopy (TEM). The results of scanning electron microscopy and transmission electron microscopy showed that the magnetic nanoparticles in the hydrogel matrix were dispersed satisfactorily with approximate size of 5-15 nm. The maximum amount of adsorption reached approximately 86% under optimum conditions of 60 min, pH 8 and initial dye concentration of 10 ppm. The adsorption capacity increased with temperature and pH. This study showed that the obtained nanomagnetic hydrogels with high removal efficiency and low reaction time could be used as effective adsorbents of methyl violet dyes from aqueous solution and for simple separation by a magnetic field. The equilibrium process of removing metal ions by nanomagnetic hydrogels could be evaluated efficiently using the Langmuir, Freundlich and Temkin models