Removal of BB41 dye molecules onto cross-linked chitosan microspheres: synthesis, characterization, and sorption/desorption

This study aimed to synthesize the chitosan-based gel microspheres and use them as a sorbent for Basic Blue 41 dye molecules (BB41) from aqueous solutions. For this aim, polymeric gel microspheres were produced from chitosan by a cross-linking method. The produced gel microspheres were characterized by appropriate instrumental methods such as FTIR and SEM. The effects of deacetylation degree and molecular weight of chitosan, type of cross-linking agent, cross-linking rate and time, etc. on sorption yield and sorption capacity of BB41 dye molecules on chitosan-based microsphere were investigated. It was concluded that epichlorohydrin was used as a cross-linking agent that promoted pore formation and significantly increased the sorption yield of BB41 molecules. It was seen that the concentration of the cross-linker solution and cross-linking time were critical parameters. On the other hand, the sorption yield of BB41 molecules was increased when the degree of deacetylation of chitosan is increased. However, while the molecular weight of chitosan is increased, the sorption efficiency and capacity of the microsphere were decreased. According to the experimental results, the optimum conditions of microsphere production were determined as deacetylation degree: 85%; cross-linker: epichlorohydrin; the concentration of the cross-linker solution: 0.75%; and cross-linking time: 5 min. The sorption yield and capacity of BB41 dye molecules on the microsphere were found to be approximately 99.5% and 10 mg/g under optimum conditions. In addition, the desorption yield of BB41 molecules from the chitosan microsphere was determined to be over 90%. It was discovered that the desorption process had no negative effect on the shape of the chitosan microsphere.