Modeling and Optimization of the Adsorption Process of Pharmaceutical Residues in Aqueous Solution by the Experimental Design Method

The presence of pharmaceutical compounds in hospital and domestic effluents poses a serious environmental problem, hence the need to treat them before discharging into nature. Among the treatment methods, the activated carbon (AC) adsorption process is the method of choice for its simplicity and ease of implementation. However, the high regeneration cost of AC has prompted the scientific community to search for new adsorbents. Our study involves testing a polymer made of cyclodextrins cross-linked with citric acid. The adsorption capacity of this polymer is evaluated against the ibuprofen molecule. To study the effect of certain parameters on the adsorption process, we used the experimental design method, which allows us, with a minimum of experimental trials, to draw a maximum of information on the process under study. The results of the experiments conducted, following a five-level central composite design and respecting the rotatability criterion, are used to find a relationship between the adsorption rate y (%) and the three considered and deemed influential parameters, namely the initial ibuprofen concentration [IB]0, the flow rate of the solution (W), and the mass of the adsorbent (mads). The statistical model that fits our experimental data well is a second-degree model without any interaction between the three factors. A maximum adsorption rate of 78.5% is obtained under the following optimal conditions: [IB]0 = 16.3 mg/L, W = 16.4 rpm, and mads = 147.5 mg. The plotting of iso-response curves allows locating the optimum in the plan of two chosen factors.