Novel Functionalized Poly(Ethylene‐<i>co</i>‐Vinyl Alcohol) as a High‐Performance Adsorbent for Cationic Dyes in Wastewater Treatment

ABSTRACT A novel, reusable, and highly effective adsorbent; functionalized poly(ethylene‐ co ‐vinyl alcohol) was modified by grafting with 5‐sulfonate‐salicylaldehyde sodium (S‐PEVOH) and 2,4‐dihydroxybenzaldehyde (H‐PEVOH). The successful functionalization of PEVOH was confirmed by Fourier‐transform infrared (FTIR) spectroscopy, X‐ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and point zero charge measurements. Subsequently, the adsorption performance of S‐PEVOH and H‐PEVOH towards a variety of dyes, including methylene blue (MB), crystal violet (CV), naphthol blue black (NBB), and acid yellow 23 (AY23), was investigated. Among these dyes, the cationic dye, CV, was chosen as a model adsorbate for further in‐depth adsorption studies. A comprehensive experimental study was conducted to investigate the adsorption behavior of PEVOH, S‐PEVOH, and H‐PEVOH, considering the influence of various factors such as pH, ionic strength, dye concentration, and contact time. The maximum adsorption capacity of H‐PEVOH was 561.36 mg/g, whereas that of S‐PEVOH was 605.28 mg/g compared to the unmodified PEVOH, which was 119.40 mg/g. Moreover, the cationic dye could be selectively adsorbed in a solution containing both anionic and cationic dyes onto functionalized PEVOH. The high performance, selectivity, and reusability of S‐PEVOH make it a potentially desirable adsorbent for industrial‐scale applications.