Theoretical assessment of the adsorption mechanism of ibuprofen, ampicillin, orange G and malachite green on a biomass functionalized with plasma

Theoretical assessment and interpretation of the adsorption mechanisms of pharmaceuticals (ibuprofen and ampicillin) and dyes (orange G and malachite green) on a biomass functionalized with a plasma treatment are reported in this paper. This theoretical study was performed via a double-layer adsorption model that was formulated from statistical physics. Modeling results indicated that the adsorption of tested organic adsorbates was affected by the molecular aggregation in the aqueous solution, which depended on the adsorption temperature. These molecules were adsorbed on the functionalized biomass surface via a non-flat orientation (i.e., they interacted with one functional group) at tested operating conditions where thermal agitation and steric hindrance could play a relevant role during the adsorption. Cocoa shell functionalized with plasma showed the highest adsorption for dyes especially orange G at 298 K. Adsorption capacities ranged from 10.32 to 26.14 mg/g, 10.54-15.55 mg/g, 6.31-13.76 mg/g and 4.2-6.54 mg/g for orange G, malachite green, ibuprofen and ampicillin, respectively. Exothermic adsorption energies were calculated for tested adsorbate molecules, which ranged from -10.17 to -18.11 kJ/mol thus indicating that physical forces were involved in the removal of these water pollutants. This study contributes to understand the physicochemical parameters that governed the adsorption of organic molecules on surface functionalized with plasma, which is an alternative for water treatment and purification.