Ibuprofen uptake through dimethyl ethylenediamine modified MOF: optimization of the adsorption process by response surface methodology technique

In the present research ibuprofen (IBP) uptake, considered as a pharmaceutical and personal care product (PPCP), using synthesized copper-based metal-organic framework (MOF), HKUST-1, modified by dimethyl ethylenediamine (HKUST-1-mmen) was investigated. The structure of nano-composite and functional groups was characterized using SEM, EDX, FTIR, XRD, and BET analysis. Also, to optimize the experiments of IBP adsorption over HKUST-1-mmen, response surface methodology (RSM) was applied with three variables including pH, adsorbent dosage and contact time using central composite design (CCD). The optimum conditions for pH, adsorbent dosage and contact time were 3, 0.1 g and 83 min, respectively with IBP adsorption efficiency of 86.53%. The equilibrium data were compatible with Langmuir isotherm (q(m)= 1000 mg g(-1)) than other isotherm models, indicating the monolayer adsorption of IBP. According to the characteristics of IBP, HKUST-1, and the results of FTIR analysis, the adsorption of IBP on HKUST-1-mmen was through three possible mechanisms including H-bonding formation, interaction between unsaturated copper sites of HKUST-1 and -COOH from IBP and pi-pi stacking interactions. The kinetic studies also revealed that the Lagergren model was predominant and IBP was not chemisorbed on nano-composite surface. It was concluded from the thermodynamic parameters that the IBP adsorption was spontaneous, endothermic, and physical.