Optimization of copper removal efficiency by adsorption on amine-modified SBA-15: Experimental design methodology

A 24 factorial design experiments were used to screen the factors affecting the copper removal efficiency using aminopropyl-functionalized SBA-15 silica. The obtained linear model was statistically tested using analysis of variance (ANOVA), Student's t-test, residuals test, and test of curvature. All the tests showed that all the parameters main effects were significant within a 95% confidence level. The test of curvature implied the presence of quadratic effect in the response. Therefore, surface composite design was used to develop a more reliable model. The statistical tests used proved the adequacy of the obtained second order model. Optimization of the factors levels was carried out by minimizing the amount of adsorbent used, minimizing the adsorption temperature, and maximizing the removal efficiency. The recommended optimum conditions are: copper concentration of 20 mg/L, adsorbent/solution ratio of 1.57 g/L, pH of 6.5, and T = 294 K with the % copper removal of 95%.