Synthesis, morphology and dye removal studies of ternary hydrogels bearing carboxymethyl cellulose, chitosan and glutamic acid

Abstract

Ternary polysaccharide-based hydrogel of carboxymethyl cellulose (CMC) with chitosan (CHT) and L-Glutamic acid (GLU) was synthesized using ZnCl2 as a cross-linker. The feasibility of this ternary engineered hydrogel in removing the acidic dye (Methyl Orange) and basic dye (Amido Black-10B) by the adsorption process from contaminated water was explored. Initially binary blends of CMC and CHT were synthesized bearing different ratios to ascertain the best mixing ratio and subsequently from the best selected ratio (CC-1), another binary blend (CC-Z) was prepared by adding ZnCl2. Lastly, the ternary hydrogel was synthesized using CMC-CHT-GLU with and without chemical cross-linker abbreviated as CCG-Zn and CCG respectively. All four samples were characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), powdered X-ray diffraction (PXRD), thermogravimetric analysis (TGA) and UV-visible spectroscopy. Swelling properties of these hydrogels were studied in demineralised water (DMW), and CCG-Zn gave best results. Adsorption behaviour of CCG-Zn was analyzed in acidic, basic buffer and neutral solution to check its suitability towards different pH environments. Moreover, absorbance of dye-contaminated solutions (treated with CCG-Zn) was measured using UV-visible spectroscopy to determine the removal efficiency (R) and adsorption capacity (q) in mg/g. It was observed that CCG-Zn is suitable for efficient removal of basic dye from aqueous solution and this ternary hydrogel may be effectively used for the large scale removal of cationic impurities.