Inorganic nanoparticles fabricated in poly(methyl methacrylate-acrylic acid) hydrogels as efficient catalyst for the reduction of dyes: A RSM study

This study investigates the catalytic reduction of Congo red (CR), a harmful anionic diazo dye, using Ag NPs loaded poly(methyl methacrylate-acrylic acid) microgel [PMMA-AAc@MIc)]. Ag-PMMA-AAc@MIc was prepared via free radical precipitation polymerization followed by the fabrication of Ag NPs using an in-situ reduction method. The synthesized PMMA-AAc@MIc and Ag-PMMA-AAc@MIc were characterized through UV–Visible (UV–Vis) spectroscopy, Fourier Transform Infrared (FTIR) spectroscopy, Dynamic light scattering (DLS), Field Emission Scanning Electron Microscopy (FE-SEM), and Thermo-gravimetric Analysis (TGA). The catalytic efficiency of Ag-PMMA-AAc@MIc particles was evaluated by adopting the reduction of CR dye as benchmark reaction. The reduction process was optimized using Response Surface Methodology (RSM) that considered the effects of varying concentrations of CR, NaBH₄, and hybrid microgel dosage on the values of percentage reduction of CR. The catalytic performance of Ag-PMMA-AAc@MIc for CR reduction was assessed by recording the UV–Vis spectra. Kinetic studies indicate that reduction reaction follows the pseudo first order kinetic model with a rate constant (k_app) found as 0.336 min⁻¹ for reduction of CR. ANOVA analysis further validated the significance of the quadratic model. The optimized reaction conditions favored the rapid degradation of CR while minimizing the use of NaBH₄ and hybrid microgel dose. The catalyst was found efficient for the reduction of CR upon reuse. This research contributes to the development of cost-effective and environmental sustainable catalysts for toxic dye removal from water sources, addressing the urgent need for efficient wastewater treatment.