Grafting 3-trimethoxysilylpropyl)diethylenetriamine on microcrystalline cellulose for the adsorption of dyes: Experimental and modeling studies

Textile dyes are one of the most commonly found pollutants in water, and it is necessary to remove them before textile industry effluents are released into the environment. In this study, cellulose-based adsorbents were prepared by grafting N¹-(3-trimethoxysilylpropyl)-diethylenetriamine (TMSPDETA) on microcrystalline cellulose surface for the adsorption of reactive dyes from aqueous solution. Characterization of the produced adsorbents [Cel@TMSPDETA₁₀; composite of cellulose + TMSPDETA (10% weight)] and the experimental and modeling studies were thoroughly investigated. Based on ΔBIC analysis (Bayesian Information Criterion), the fractal-like pseudo-first-order model (FPFO) was the model with the highest degree of adequacy to describe the kinetic behavior for RR-35 (Reactive Red 35) and RG-19 (Reactive Green 19) dye adsorption on Cel@TMSPDETA₁₀. It was observed that the values of t_0.95 (time necessary to attain 95% saturation) of RG-19 dye were 1.81 times slower than those of RR-35. This difference in times to attain 95% saturation of RG-19 with RR-35 could be assigned to the larger size of the RG-19 molecule. Based on the ΔBIC values, the Liu isotherm was better fitted to the experimental data. At 30 °C, the highest Q_max (Liu model) value was 197.0 mg g⁻¹ for RR-35 dye. For RG-19, the highest value of Q_max (Liu model) was 210.5 mg g⁻¹ at 45 °C. Alternatively, a statistical physics model that represents the general case of the Langmuir model was adopted to provide new insights into the adsorption mechanisms of RR-35 and RG-19 dyes on the adsorbents. Interestingly, this new approach showed that RR- 35 was adsorbed via a partial aggregation process, contrary to the RG-19 dyes.