Membrane filtration with reversible adsorption: Hollow fiber membranes as collectors of colloidal particles

A novel membrane separation process in which outside-in hollow fiber (HF) membranes with axes normal to the flow of the suspension under treatment are used as collectors of the colloidal particles is proposed. This process, called depth membrane filtration, yields two product streams: permeate, the liquid that passed through the semipermeable HF membranes, and filtrate, the liquid that was clarified by collection of the colloidal particles on the HF shells. A mathematical model in which convective transport and reversible adsorption account for the deposition of colloids onto the membrane surface is developed. Analytical expressions for the coefficients of adsorption and peptization are derived. The concentrations of suspended particles in the product water of an HF filter treating a dilute latex suspension in continuous-flow and batch operations were calculated. The calculations based on the values of the latex-solution properties and the HF operating and design parameters available in the literature demonstrated the feasibility of the process.