Experimental investigation on the separation of bentonite using ceramic membranes: Effect of turbulence promoters

The static turbulence promoters presented in this work are designed to enhance filtration within tubular ceramic membranes of 0.5 micron pore size. Permeate flux enhancement still remains a topical problem during tangential crossflow filtration. The decline in flux with time is due to the usual phenomena of concentration polarization and membrane fouling, operating parameters including the system pressures, feed composition, membrane type and configuration, and the hydrodynamics within the membrane module. Solute accumulates on the membrane surface and forms a high concentration gel layer, thus increasing the effective membrane thickness and reduces its hydraulic permeability. Turbulence promoters of varying pitch lengths have been incorporated into the work to ultimately reduce the deposition of bentonite particles on the membrane surface during microfiltration. Yeast suspensions have previously been used as feed suspensions in order to compare the effectiveness of the turbulence promoters with an organic foulant. The objective of this work was to investigate the influence of static promoter geometry on flux sustainability enhancement during bentonite suspension filtration. All experiments have been conducted on a tubular ceramic membrane and the experimental membrane rig as shown in this paper. The effects of feed concentration, feed temperature, system pressures, and crossflow rates on the membrane flux sustainability were investigated. It was found that the promoters greatly improved flux sustainability and membrane efficiency over time and in some cases, a loss of 3% in membrane efficiency was realized with turbulence promoters at higher feed temperatures. The use of the turbulence promoter caused a large scouring of the membrane surface and membrane cleaning was significantly improved compared to the experiments without the promoters.