Preparation of chitosan beads for the adsorption of reactive blue 4 from aqueous solutions

Abstract

Chitosan is a well-known and effective adsorbent for elimination of anionic or reactive dyes due to its suitable adsorption properties such as high cationicity, high adsorption capacity, macromolecular structure, abundance and low price. However, chitosan suffers from some drawbacks such as low acid stability, low solubility in acidic solutions, low porosity and low surface area. Therefore, modification is an effective solution to produce a product with the desired properties to overcome the limitations of chitosan. Conversion of raw chitosan flakes into beads was one of the physical modification methods reported to be an essential way to improve the adsorption properties of chitosan. However, effect of beading parameters on the dye adsorption was hardly addressed. In the present study, the chitosan beads were prepared at different preparation conditions and then applied for adsorption of Reactive Blue 4 (RB4) in batch adsorption process. Effects of beading parameters such as chitosan concentration, acetic acid concentration and temperature in the removal of RB4 from aqueous solution were investigated. It was found that increasing the concentration of chitosan, acetic acid, and temperature decreased the dye removal. Moreover, results showed that decreasing the pH of the dye solution increased the rate of RB4 removal. The chitosan beads prepared with 2% chitosan and 1 % acetic acid concentration at room temperature (27 ± 2 °C) were more suitable for RB4 removal. Preparation of chitosan beads at appropriate conditions was a suitable method to improve the anionic dyes adsorption from aqueous solutions. The prepared beads were used as an efficient adsorbent for the RB4 removal.