The adsorption of Tenofovir in aqueous solution on activated carbon produced from maize cobs: Insights from experimental, molecular dynamics simulation, and DFT calculations

Abstract

The aim of this work is to evaluate the adsorption of Tenofovir using activated carbon (ACc) produced from local maize cobs by the thermochemical activation method with phosphoric acid (H3PO4). The ACc proprieties were evaluated using a variety of methods, including Fourier Transform Infrared Spectrometry (FTIR), Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDS), X-Ray Diffractometry (XRD), and Thermogravimetric Analysis (TG/DTG). The prepared ACc was also subjected to physicochemical tests such as humidity level, ash content, volatile matter, iodine value, and point of zero charge (pHpzc). The kinetic studies showed that the adsorption data followed a second-order reaction. Meanwhile, the experimental isotherms analysis demonstrated that the Langmuir isotherm fits well the adsorption data with a maximum adsorption capacity (Qmax) of 145.194 mg g−1. The thermodynamic parameters demonstrate an exothermic and spontaneous behavior. An experimental combination of Response Surface Methodology (RSM) with Box-Behnken Design (BBD) was used to optimize the three adsorption principal parameters (pH, dose of ACc, and initial Tenofovir concentration). The results showed that maximum adsorption of 95.13% was achieved at a pH of 4.33, an initial Tenofovir concentration of 0.1 mM, and a mass of ACc of 1 g L-1, however, the desorption was favored in a basic pH (pH ≥ 12). Density functional theory was used to study the global and local quantum descriptors and the interaction energy between the Tenofovir and the ACc surface. Monte Carlo simulation was used to calculate the adsorption energy of the adsorption process between Tenofovir and the ACc. Theoretical results revealed that Tenofovir has strongly interacted with the ACc, which supports the experimental results.

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