Agar/κ-carrageenan composite hydrogel adsorbent for the removal of Methylene Blue from water.

Water pollution caused by dyes is a significant global problem. Adsorption technique is successfully applied for the removal of dyes from water. In this technique, the use of effective adsorbents is very important. Here, agar/κ-carrageenan composite hydrogel adsorbent prepared through free radical cross-linking reaction in the presence of tri (ethylene glycol) divinyl ether as a cross-linker and characterized by using FTIR, SEM and TGA measurements was used to remove Methylene Blue from water. FTIR results exhibited that electrostatic interaction and hydrogen bonding formation were the main interactions in the adsorptive removal of Methylene Blue by agar/κ-carrageenan hydrogel. Pseudo second order and Langmuir models were found to be the most suitable kinetic and isotherm models, respectively. Maximum dye adsorption capacity of 242.3 mg·g was obtained at 35 °C and pH 7. Thermodynamic parameters were calculated to understand the nature of adsorption process. Different solvents were applied for the regeneration of dye adsorbed-agar/κ-carrageenan hydrogel and the most suitable solvent was determined as ethyl alcohol. The results demonstrated that agar/κ-carrageenan hydrogel is a promising adsorbent for the removal of cationic dyes from water.