Green surface modification of polyvinyl alcohol fibers and its application for dye removal using Doehlert experimental design

The use of eco-friendly techniques and green reagents to modify the properties of synthetic biopolymers is attracting an increasing attention. In this work, L-cysteine (CYS) modified polyvinyl alcohol electrospun fibers (PVA-CYS) were prepared using an easy, fast, and green technique. The incorporation of CYS as a source of nitrogen and sulfur shows an important enhancement in dye removal efficiency compared to polyvinyl alcohol fibers (PVA). The successful grafting of CYS on PVA was proved by FTIR, elemental analysis, SEM, AFM and TGA analysis. Doehlert experimental design was used to optimize the adsorption process of crystal violet (CV) on PVA and PVA-CYS. The two models show good correlations between experimental and predicted responses, with coefficients of determination equal to 0.946 and 0.976, for PVA and PVA-CYS, respectively. The most influencing parameter was the pH for CV removal by adsorption on PVA. However, this parameter affects less the dye removal using PVA-CYS. The modified fibers exhibit excellent adsorption ability toward CV, and the maximum adsorption capacity reaches 197 mg g−1 at neutral pH. An application of this process on a doped real wastewater demonstrates its efficacity and selectivity with a percentage of removal up to 85%.