ZnO@CoO reinforced pectin-acacia hydrogel for efficient removal of toxic dyes from wastewater

In this paper, we explored the synthesis of pectin-acacia based hydrogel (Pec-Aca-cl-polyAA) and zinc oxide‑cobalt oxide heterostruture (ZnO@CoO) incorporated nanocomposite (ZnO@CoO/Pec-Aca-cl-polyAA). Pec-Aca-cl-polyAA hydrogel showed an impressive water absorption capability (1771.25 %) in a neutral environment. The introduction of ZnO@CoO nanoparticles significantly increased the hydrogel's surface area and its capacity to adsorb dyes. The SEM imaging illustrated a transformation from the fragmented, compact structures of pectin and acacia to a highly porous, interconnected 3D network in both the hydrogel and nanocomposite, enhancing their potential for dye adsorption applications. The ZnO@CoO/Pec-Aca-cl-polyAA showed 97.55 % and 99.15 % maximum dye removal efficiency in case of methylene blue (MB) and malachite green (MG), respectively. Further, the maximum adsorption capacity with ZnO@CoO/Pec-Aca-cl-polyAA was found to increase from 209.64 mg/g to 264.27 mg/g in case of MG and from 218.34 mg/g to 312.15 mg/g in case of MB within 10 h. The adsorption isotherm results demonstrated that the adsorption of dyes coordinated with Temkin and Langmuir adsorption isotherm models, indicating monolayer adsorption behaviour. The dye removal process followed a pseudo-second order kinetic model (PSO), showing that the chemical bonding is an important parameter for the adsorption of dyes. The ZnO@CoO/Pec-Aca-cl-polyAA maintained >60 % dye removal efficiency even after six consecutive adsorption-desorption cycles, demonstrating its stability and reusability, and witnessed the potential for wastewater treatment plants, especially for removing toxic textile dyes from the industrially polluted wastewater.