A fractional factorial design applied to organofunctionalized silicas for adsorption optimization

A 24−1 fractional factorial design is employed to study Cu(II) adsorption on organofunctionalized silicas. Two types of immobilized silicas, Sil-et-1 and Sil-et-2, two solvents, water and ethanol, two copper salts, chloride and acetate, as well as 100 and 200 mg quantities of silica are used. For this design, substituting water for ethanol results in an average increase in copper adsorption of 3.57 × 10−4 mol g−1. An increase in silica mass from 100 to 200 mg decreases adsorption by a significant amount. Three important binary effects involving the solvent, salt and silica mass factors are found. All of these effects indicate the existence of antagonistic interactions between these factors. Large values of Cu(II) adsorption, ≈6 × 10−4 mol g−1, are found when 100 mg of silica in ethanol solvent is used in the presence of either Cu salt or silica type.