Modeling of fouling mechanisms in the biodiesel purification using ceramic membranes

Since membrane fouling is well acknowledged to be one of the key impediments to more widespread implementation of membrane-filtration processes, this study aimed to assess the fouling mechanisms in the biodiesel separation and purification process using ceramic membranes. The analysis of fouling mechanisms was performed using a model proposed in the literature applied to cross-flow filtration and constant pressure. The experiments were carried out with tubular ceramic membranes with average pore size of 0.2 mu m, 0.1 mu m, 0.05 mu m, and 20 kDa at 1.0, 2.0, and 3.0 bar transmembrane pressures. After transesterification, the reaction mixture was directly processed, eliminating the conventional previous decantation step. It was evaluated the influence of acidified water addition (10, 20 and 30 wt%) on the glycerol retention efficiency and the fouling mechanism. The results obtained demonstrated that the amount of water added influences the formation of the phases and, consequently, the separation performance. The permeate flux profile over time made it possible to determine the predominant fouling mechanism in each evaluated condition. Thus, the predominant fouling mechanisms were complete pore blocking, cake filtration and internal pore blocking when using 10, 20 and 30% water concentration, respectively. It was possible to conclude that the fouling mechanism dominant in each experimental condition is dependent upon the size of aqueous phase droplets and the membrane pore diameter. The results demonstrated that it would be possible to predict the efficiency of glycerol separation by identifying the fouling mechanism, so that the condition of complete pore blocking is the most recommended in this biodiesel purification process, since it indicates a greater retention of glycerol by the membrane, and the stabilization of fluxes at higher rates.