Novel aminothiazole-supported chlorocellulose composite for the efficient removal of cationic dyes from wastewater

Abstract

This study aimed at synthesizing a fast-responsive chemically modified cellulose (MC) adsorbent for removing organic pollutants, such as cationic dyes, namely, methylene blue (MB), crystal violet (CV), brilliant green (BG), and malachite green (MG), from wastewater. The MC adsorbent was prepared by the chlorination of cellulose using phosphorous oxychloride (POCl₃) to produce chlorodeoxy–cellulose (cellulose–Cl), followed by the nucleophilic attack of 2-(2-aminothiazol-4-yl)acetohydrazide. The prepared material was characterized extensively. The adsorption of dyes onto MC was investigated, individually and in a mixture, in a batch mode under variable experimental conditions, such as pH, contact time, initial dye concentration, temperature, and adsorbent dose, to optimize the adsorption process. From the kinetic investigations, with high R² values and lower error functions ((χ²), (SSE), and (MSE)), the adsorption of MB and CV dyes matched well with the pseudo-second-order kinetic model, while the adsorption of BG and MG dyes matched well with the pseudo-first-order kinetic model. In addition, the Temkin model best fitted the adsorption isotherm data for MB, CV, and BG, while the adsorption data of the MG dye fitted well with the Langmuir isotherm model, with the maximum adsorption capacities of 173.00 mg g⁻¹, 171.80 mg g⁻¹, 188.60 mg g⁻¹, and 82.17 mg g⁻¹ for MB, CV, BG, and MG, respectively, at 308 K. Thermodynamic studies revealed the spontaneous and exothermic nature of the adsorption of these cationic dyes onto MC. The MC adsorbent exhibited good recycling performance. After five regeneration and adsorption cycles, the MC adsorbent still had a removal effect greater than 90% for the studied dyes, which indicated its high structural stability. The prepared MC was successfully applied for the removal of cationic dyes from real water samples and synthetic mixtures, with a recovery (R%) of higher than 97%. The adsorption mechanism of MB, CV, BG, and MG onto the adsorbent was elucidated. Ultimately, this study demonstrated that the fast-responsive MC adsorbent can be effectively utilized to eliminate MB, CV, BG, and MG cationic dyes from a wide range of real water sources. Collectively, the results indicated that the as-prepared MC adsorbent is promising for cationic pollutant adsorption, and our mechanistic results are of guiding significance for environmental cleanup. This work contributes significantly to understanding how experimental conditions influence the mechanism of MB, CV, BG, and MG dye adsorption by the MC adsorbent, offering valuable and new insights for future applications and optimizations in the treatment of effluent-containing cationic species.