A Novel Cellulose-Based Composite Hydrogel Microsphere Material: for Efficient Adsorption of Co(II) and Ni(II) Ions in Water

Heavy metal ions contain highly toxic and non-biodegradable wastewater pollutants seriously contaminating the environment and affecting human health. Removal of heavy metal ions from the environment is a vital step towards the elimination of water pollution on a global scale. Therefore, in this study, cellulose was modified with L-cysteine, sodium alginate and polyethyleneimine to produce cellulose/sodium alginate /polyethyleneimine/L-cysteine composite hydrogel microspheres (WCMs/SA/PEI/L-Cys) in order to efficiently adsorb heavy metal ions. Co(II) and Ni(II) are successfully removed from water. After their production, the sorbents underwent examination using X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy (FT-IR), and Scanning electron microscopy (SEM). In addition, the investigation of the mechanism and adsorption characteristics of cellulose-modified gel microspheres WCMs/SA/PEI/L-Cys has been completed. The majority of the adsorption of contaminants by cellulose-modified gel microspheres WCMs/SA/PEI/L-Cys adhered to the Langmuir isothermal adsorption model and quasi-secondary kinetic model. The intra-particle diffusion model was adopted for improving the fitting of the adsorption process in the materials. It was indicated that the internal and external diffusion acted together to eliminate the contaminants from the materials. When exploring the decontamination mechanism of the materials using XPS, it was shown that the functional groups containing nitrogen, oxygen and sulfur play a key role in removing contaminants. For Co(II) and Ni(II), the highest adsorption capacities of the sorbent were 358 and 373 mg/g, respectively. The material exhibited robust stability and recyclability based on the regeneration experiment results, remaining stable after six adsorption cycles and retaining over 80% of the initial adsorption amount.