Explaining the adsorption mechanism of the herbicide 2,4-D and the drug ketoprofen onto wheat husks Fagopyrum esculentum treated with H2SO4

In this paper, the adsorption of the herbicide 2,4-D and the drug ketoprofen on wheat husks Fagopyrum esculentum treated with H2SO4 is experimentally and analytically analyzed. The adsorbent is fully characterized through some techniques such as FT-IR, SEM, and XRD. Adsorption tests are carried out to optimize the performances in terms of adsorbent dosage and solution pH. Subsequently, the impact of temperature is determined through the realization of adsorption isotherms. A multilayer model is employed to microscopically interpret the adsorption mechanism of both the investigated compounds. The modelling analysis shows that the number of molecules bound per adsorption site varied from 0.68 to 2.77 and from 2.23 to 3.59 for ketoprofen and herbicide 2,4-D, respectively. These estimated values testify that an aggregation process occurs during adsorption. The global number of formed layers of each adsorbate is also determined, showing a significant reduction from 5.73 to 2.61 for ketoprofen and from 1.79 to 1.5 for herbicide 2,4-D with the temperature. For a complete understanding of the adsorption mechanism, the saturation adsorption capacity and adsorption energy were calculated and interpreted. Overall, it may be inferred that physical interactions govern how these contaminants adsorb on the tested adsorbent.