The use of factorial design for modeling membrane distillation

A two-level factorial experimental design was used to investigate the influence of the main operating parameters on evaporation flux and soluble solid content of apple juice during concentration through osmotic distillation (OD) and membrane distillation (MD) processes. The factorial models have been obtained from experimental design to study all interactions among the considered parameters (osmotic agent concentration (0-65% CaCl(2)), flow rate (10-30 L/h) and temperature difference between feed and osmotic agent (10-30 degrees C)) and validated statistically by analysis of variance (ANOVA). For both responses, the osmotic agent concentration was the most influential factor. The magnitude of the main influence of CaCl(2) concentration was followed by the temperature difference and flow rate, respectively. The analysis of the experimental responses revealed that CaCl(2) concentration and temperature difference had significant interactive effects on evaporation flux. All interactions between the studied parameters were significant in the case of soluble solid content at the 99% confidence level. Although the interaction terms have significant effects, their levels were only a small amount compared to linear effects. The predicted responses were compared with the experimental ones. In general, the predicted values were in reasonable agreement with the experimental data, further confirming the very good prediction ability of the models. (C) 2009 Elsevier B.V. All rights reserved.