Definitive Screening Design (DSD) Optimization of Methyl Orange Adsorption Onto Moroccan Clay

The dye molecules are scarcely biodegradable. They are stable to light and oxidizing agents, which makes their effluent treatment extremely difficult. In this work, the adsorption of methyl orange dye has been carried out using raw clay samples taken from the Jbel Lehbib region (North of Morocco) in an aqueous medium. The experiments were designed according to the definitive screening design (DSD) method. The DSD of the experiment aimed to evaluate the effect of six factors: initial solution pH, initial concentration of methyl orange dye, clay mass, stirring speed, and the temperature and contact time. Adsorbent material properties were investigated by means of X-ray diffraction and Fourier transform infrared spectroscopy. The adsorption tests were carried out in a batch system, and each experimental parameter was changed within its range. Based on the results obtained, a reduced quadratic model was determined to best fit the experiment data, and the most significant factors were found to be: pH, initial concentration, and quadratic term pH × pH. Detailed analysis of the effect of different factors as well as their interaction on the removal has been carried out as well. Maximum removal of 69% occurred at the following optimum conditions: pH = 3 and initial concentration of the dye 600 mg/L.