Enhancing the separation of nano-sized particles in low-salt suspensions by electrically assisted cross-flow filtration

A cross-flow filtration module with a large pore-size membrane and low operation pressure was built, as a first attempt, to test its performance on the separation of synthetic nano-sized alumina and silica particles in the presence of an electric field. For practicality sake, turbidity measurements were used primarily to evaluate the particle removal efficiency and to determine critical currents. The observed critical currents agreed well with theoretically calculated. The critical currents observed were found to be strongly dependent on the conductivity; there was a linear relationship between the critical current and conductivity. Further theoretical analysis of the electrical filtration module reveals that particles of different size or surface charge (e.g., zeta potential) can be separated within a particular size range by controlling the ionic strength or the conductivity of the solution.