Preparation and characterization of new quaternary ammonium salt of guanidine- modified cellulose for effective removal of some anionic dyes

A modified cellulose phase was synthesized by anchoring aminoguanidine onto the surface of cellulose fibers to produce a novel adsorbent (AK1) that is cost-effective, biodegradable, and easily processable. To enhance its affinity for anionic dyes specifically Eriochrome Cyanine R (ECR), Zincon, and Congo Red (CR) the amino groups were cationized through reaction with acetic acid, forming cationic ammonium salts. This reaction yielded the aminoguanidine-functionalized cationic cellulose derivative (AK2).Comprehensive characterization of the modified cellulose materials (AK1 and AK2) was performed using Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Energy-Dispersive X-ray Spectroscopy (EDX), Fourier Transform Infrared Spectroscopy (FTIR), X-ray Photoelectron Spectroscopy (XPS), X-ray Diffraction (XRD), elemental analysis, nitrogen physisorption, and zeta potential measurements. These analyses confirmed the successful incorporation of cationic ammonium salt groups onto the cellulose surface. The maximum adsorption capacities of AK2 for Eriochrome Cyanine R, Zincon, and Congo Red were 252 mg/g, 203.4 mg/g, and 153.2 mg/g, respectively, at pH 3. The adsorption behavior of the modified cellulose toward these anionic dyes was investigated through kinetic and isotherm studies. The results indicated that the dominant adsorption mechanisms were physisorption and monolayer adsorption, with equilibrium data fitting well to the Langmuir isotherm model. Moreover, the adsorption kinetics followed a pseudo-first-order model. The modified cellulose retained more than 92% of its adsorption efficiency after five regeneration cycles, demonstrating excellent reusability.