A novel hydrazide-modified silica gel as a promising material for adsorption of methyl orange from aqueous solutions: Experiments and theoretical insights

Abstract

In this study, a novel hybrid material was developed by covalently functionalizing silica with hydrazide, resulting in the formation of Si–NCON2H3. Comprehensive characterization of the material was performed using Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), Scanning electron microscopy (SEM) and X-ray diffraction (XRD). The synthesized Si–NCON2H3 was then evaluated for its adsorption capacity to remove methyl orange (MO) from aqueous solutions. Experimental results demonstrated that Si–NCON2H3 exhibited an adsorption capacity of up to 133 mg/g at pH 3, with reaching equilibrium within 60 min. Kinetic and isothermal analysis indicates that adsorption follows a pseudo-first-order kinetic model, with adsorption occurring homogeneously or heterogeneously, depending on solute concentration. Thermodynamic assessments revealed that MO adsorption is spontaneous and endothermic. Regeneration studies showed that the material maintained its adsorption efficiency over five consecutive adsorption-desorption cycles with minimal loss in performance. Molecular dynamics and Monte Carlo simulations revealed that the MO adsorbs strongly and spontaneously onto the surface, favored by its planar orientation and the negative values of its adsorption energies. These results indicate a stable interaction between the MO and the Si–NCON2H3 nanoparticle surface, reinforcing the adsorption process's efficiency. These findings suggest that the newly synthesized material, Si–NCON2H3, has significant potential as an effective adsorbent for the removal of toxic dyes, particularly MO, from wastewater.

Keywords

• Hybrid adsorbent
• Removal of methyl orange
• Water treatment
• Functionalized silica
• Molecular dynamics simulation