Abstract
Increased water pollution due to the tremendous increase of dye-containing effluent is still a serious problem which, in turn, adversely affects aquatic life and, consequently, the balance of our ecosystem. The aim of this research was to investigate whether Ca-ALG/MgO/Ag nanocomposite beads successfully prepared from calcium alginate hydrogels with MgO (Ca-ALG/MgO) doped with Ag nanoparticles (Ag NPs) caused effective degradation of Direct Red 83 dye. The formation of nanocomposite beads was confirmed by X-ray diffraction (XRD), Transmission Electron Microscope (TEM), Dynamic Light Scattering (DLS), and Energy Dispersive X-ray Analysis (EDX). The results from the EDX analysis proved that both MgO and Ag nanoparticles within the alginate beads network were present. This study also examines the effects of various operating parameters, such as the reducing agent, time of reaction, the concentration of the dye solution, and the catalyst dosage, which were examined and studied carefully to find the optimum degradation conditions. The kinetics and isothermal study revealed that the degradation process using Ca-ALG/MgO/Ag nanocomposite beads as a catalyst in the presence of sodium borohydride (NaBH4) as a reducing agent was the best fit for the pseudo-first-order model and the Temkin isotherm model. The results indicated that the optimum dosage of Ca-ALG/MgO/Ag was 0.3 g for a dye concentration of 50 mg/L, and equilibrium of the degradation process was attained at 340 min. Accordingly, it could be stated that the catalyst, Ca-ALG/MgO/Ag nanocomposite beads, is considered efficient for the degradation of Direct Red 83 dye. The degradation efficiency reached 95% approximately. Furthermore, after four runs of reuse, Ca-ALG/MgO/Ag nanocomposite beads exhibited excellent performance and long-term stability.