Nanomagnetic Hydrogels Based on Carboxymethylcellulose/Diatomaceous Earth Grafted with Acrylamide for Adsorption of Cationic Crystal Violet Dye

Hypothesis: Removal of toxic dyes from wastewater has attracted considerable attention in recent years. Conventional methods are not usually effective for the removal of dyes. Much effort has been expended on the development of nanocomposite hydrogels with more efficient adsorption properties. In this research, a nanomagnetic hydrogel was synthesized useing carboxymethyl cellulose (CMC), diatomaceous earth (celite), and acrylamide (AAm). The hydrogel was used for adsorption of crystal violet from aqueous solutions.
Initially, the hydrogels were synthesized using CMC, celite, and AAm in the presence of ammonium persulfate (APS) as initiator and methylene bisacrylamide (MBA) as a crosslinker. The nanomagnetic hydrogel was prepared by loading Fe(II) and Fe(III) ions into the hydrogel and subsequent co-precipitation of Fe(II) and Fe(III) ions in an alkaline solution. The hydrogel and nanomagnetic hydrogel were characterized by Fourier transmission infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and a vibrating-sample magnetometer (VSM).
Findings: The results of SEM showed that the magnetic nanoparticles were well dispersed throughout the hydrogel. The TEM images indicated that the size of the magnetic nanoparticles was about 5-15 nm. The effects of various factors such as temperature, contact time, pH, and initial dye concentration on the dye adsorption behavior of the hydrogels were determined. The maximum adsorption at pH 7 in a 10 ppm of dye concentration reached 96% after 60 min at room temperature. The nanomagnetic hydrogel could be used as an effective adsorbent for the removal of cationic crystal violet dye from aqueous solutions and could be easily removed by an external magnetic field and reused. The adsorption behavior was modeled accurately using the Temkin model. The kinetics of adsorption followed a pseudo-second-order kinetic model.