Reactive and basic dyes removal by sorption onto chitosan derivatives.

Area of Science:

• Environmental Chemistry
• Materials Science
• Polymer Chemistry

Background:

• Textile industry wastewater often contains persistent reactive and basic dyes.
• Conventional dye removal methods can be inefficient or costly.
• Chitosan, a biopolymer, offers potential for developing novel sorbent materials.

Purpose of the Study:

• To synthesize and characterize cross-linked chitosan derivatives grafted with carboxyl and amide groups.
• To investigate the efficacy of these derivatives as sorbents for reactive (Remazol Yellow Gelb 3RS) and basic (Basic Yellow 37) dyes.
• To evaluate the sorption behavior, kinetics, and reusability of the developed chitosan-based sorbents.

Main Methods:

• Synthesis of cross-linked chitosan derivatives (powder and beads) grafted with carboxyl and amide groups.
• Dye removal experiments using equilibrium, kinetic, and pH-edge studies.
• Sorbent characterization via scanning electron microscopy (SEM), particle size analysis, and Fourier-transform infrared (FTIR) spectroscopy.
• Application of Langmuir, Freundlich, and Langmuir-Freundlich isotherms and pseudo-second order kinetic models.

Main Results:

• Chitosan powder exhibited higher sorption capacity than beads.
• Chitosan grafted with amide groups achieved a maximum sorption capacity of 1211 mg/g for reactive dye at pH 2.
• Chitosan grafted with carboxyl groups demonstrated a maximum sorption capacity of 595 mg/g for basic dye at pH 10.
• Optimal dye removal was achieved within 4 hours using 1 g/L of sorbent.
• Sorbents showed reusability through sequential sorption-desorption cycles.

Conclusions:

• Grafted chitosan derivatives are effective and reusable sorbents for removing reactive and basic dyes from aqueous solutions.
• The specific functional groups (amide or carboxyl) dictate the optimal dye type and pH conditions for sorption.
• Chitosan-based sorbents present a promising sustainable solution for dye wastewater treatment.