Optimisation of a back-flush sequence for zeolite microfiltration

Cross-flow microfiltration experiments were performed on a zeolite suspension through a 0.45 μm pore size ceramic membrane. A back-flush device was designed in order to remove fouling deposits periodically from the membrane surface. This device allows a direct measurement of the amount of permeate back-flushed into the system and this feature enables a better understanding of the cake removal. The optimal back-flush conditions minimising the amount of permeate back-flushed and ensuring a complete removal of the cake were 0.2 s back-flushing time at a back pressure of 2 bar. The optimal forward filtration time between flushing depends on the suspension concentration. This technique gave more than a 100% improvement in some cases, and a general model based on a dead-end filtration process was developed and gave very consistent results. The cake deposit on the membrane surface was also studied and compared to a deposit in a dead-end process.