Synthesis of Pyrazole Amide-Functionalized Silica for Efficient Methyl Orange Adsorption: A Combined Experimental and Theoretical Study

Abstract

A pyrazole amide grafted onto a silica surface was synthesized to form a new hybrid adsorbent for methyl orange (MO) removal. The synthesized hybrid adsorbent SiNL was characterized by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), X-ray diffraction (XRD), scanning electron microscopy (SEM), and Brunauer–Emmett–Teller (BET), confirming successful functionalization of the silica surface. Adsorption performance was studied using a batch method, evaluating parameters such as pH, time, initial concentration, and temperature. The MO adsorption process was best described by the pseudo-first-order kinetic model and the Redlich–Peterson isotherm model, with a maximum adsorption capacity of 133.12 mg/g achieved in 40 min at 25°C and pH 3. Thermodynamic studies revealed that the adsorption of MO is a spontaneous and exothermic process. The adsorption efficiency of SiNL remained consistently above 95% even after five adsorption–desorption cycles. Molecular dynamics simulations demonstrated the most favorable adsorption configuration of the SiNL substrate in an acidic medium for MO removal and explored the mechanisms underlying their interaction. These results confirm the suitability of SiNL for practical applications. © 2025 John Wiley & Sons Ltd.