Scalable sulfonate-coated cotton fibers as facile recyclable adsorbents for the highly efficient removal of cationic dyes

Adsorbents that exhibit a high adsorption capacity and facile recyclability are considered promising materials for dye wastewater remediation. In this work, a novel sulfonate-decorated cotton fiber was fabricated as a recyclable adsorbent for the highly efficient removal of cationic dyes. Herein, poly(sodium p-styrene sulfonate-co–N-methylol acrylamide) (P(SSNa-co-NMAM)) with SSNa units as adsorption sites and NMAM units as thermal-crosslinking points was synthesized for the modification of cotton fibers. As expected, the as-obtained P(SSNa-co-NMAM)-coated cotton fibers (PCFs) presented outstanding adsorption capacities toward cationic dyes, even in the simulated effluents. The processes of cationic dye absorbing onto the PCFs were well fitted by the Langmuir isotherm model and pseudo-second-order kinetics. The thermodynamic study revealed that the adsorption reaction of the cationic dyes onto PCF was spontaneous, and the efficiency of adsorption was more desirable at higher temperatures. The maximum adsorption capacities of PCF toward methylene blue (MEB), rhodamine B (RhB), and malachite green (MG) were 3976.10, 2879.80, and 3071.55 mg/g, respectively. The dye removal mechanism was ascribed predominantly to electrostatic interactions. Moreover, the adsorption capacity of the PCFs toward cationic dyes was slightly influenced by the pH of the solutions because of the sulfonate moieties, which exhibit stability under acidic and alkaline conditions. Furthermore, the recyclability and reusability of the as-prepared PCFs were satisfactory and good mechanical properties and thermal stability were observed compared to those of pristine cotton fibers. Given the aforementioned results, the as-obtained PCFs are highly promising as ideal adsorbents for the remediation of dye-contaminated wastewater. Graphical abstract: [Figure not available: see fulltext.].