Preparation of Rice Hull Cellulose Based Composite Hydrogel and Its Adsorption Properties for Methylene Blue

Dye wastewater pollution constitutes a significant global environmental challenge, critically endangering ecosystems. Within the spectrum of treatment methodologies for dye wastewater, the adsorption is recognized for its simplicity and efficacy, distinguishing itself as a paramount technique. In this study, a high-performance composite hydrogel adsorbent based on rice husk cellulose was prepared by utilizing graft copolymerization. The impacts of different factors, including cellulose content, monomer ratio, initiator dosage and crosslinker content, on the adsorption performance for methylene blue (MB) in water were investigated. Meanwhile, the preparation conditions were optimized by univariate and orthogonal tests and the results indicated that the adsorption performance was optimized when the mass ratio of cellulose, acrylic acid (AA), 2-acrylamido-2-methylpropane sulfonic acid (AMPS), ammonium persulfate (APS), and N, N'-methylenebisacrylamide (MBA) was 60∶350∶75∶10∶40. The adsorption performances of the as-prepared hydrogel were optimized when pH = 6.0 and temperature = 308 K. The adsorption process of the adsorbent could be described by the pseudo-first-order kinetic model and Langmuir isotherm adsorption model. Under optimal adsorption conditions, the Langmuir theoretical maximum adsorption capacity of MB reached 2 170.0 mg·g^-1. Additionally, the as-prepared hydrogel exhibited outstanding adsorption performance after recycling, and the removal rate of MB in water was 82.3% (when the content of the as-prepared hydrogel was 0.5 g·L^-1 and the content of MB in water was 400 mg·L^-1, the adsorption capacity was 658.3 mg·g^-1) after five adsorption-desorption cycles.