Highly Adsorptive Organic Xerogels for Efficient Removal of Metformin from Aqueous Solutions: Experimental and Theoretical Approach

Abstract

Metformin, widely prescribed to treat type 2 diabetes for its effectiveness and low cost, has raised concerns about its presence in aqueous effluents and its potential environmental and public health impacts. To address this issue, xerogels were synthesized from resorcinol and formaldehyde, with molar ratios ranging from 0.05 to 0.40. These xerogels were thoroughly characterized using FT-IR, SEM, TGA, and TEM analyses. Batch adsorption experiments were performed with standard metformin solutions at concentrations of 50 and 500 mg/L, varying pH, and temperature to determine the adsorption isotherms of the synthesized xerogels. The adsorption data revealed a maximum adsorption capacity of 325 mg/g at pH 11 and 25 °C. Quantum chemical calculations revealed that electrostatic interactions govern metformin adsorption onto xerogels. The xerogels’ adsorption capacity was evaluated in competitive systems with CaCl2, NaCl, MgCl2, and synthetic urines. Reuse cycles demonstrated that xerogels could be reused for up to three cycles without any loss in adsorptive efficiency. The adsorption mechanisms of metformin in the adsorption process highlight the strong electrostatic interactions and hydrogen bonds between the adsorbate and the adsorbent material. Xerogels synthesized show promise as efficient adsorbents to remove metformin from aqueous solutions, helping to mitigate its environmental impact.