Abstract
Membrane separation is known as an economic and environmental friendly mode of separation and is used in various types of separation processes. The major challenges regarding membrane separation are the internal and external fouling of the membrane which reduces the permeate flux of the membranes by inducing extra resistance to flow. Synthetic membranes are designed and implemented to separate solutes or particles in a feed stream by rejecting them and permitting the liquid to pass through the membrane pores; however, most of the feed streams, such as wastewaters, contain more than one type of solute. This yields a distribution of particle sizes in the feed. Many wastewaters contain supracolloidal particles (1-100μm). Most membrane separations aim to remove these particles from the feed solution. Wastewaters also contain colloidal particles (0.001-1μm). These particles are less concentrated than supracolloidal particles in the feed but they are more problematic since they are able to penetrate into the membrane pores and cause internal fouling which is the main source of irreversible flux decline. Fouling mechanisms are traditionally classified into four types. Among these mechanisms, standard pore blocking (pore constriction) refers to internal fouling while the other types model external fouling. On the effect of pore geometry, as a morphological factor, studies to date have been limited to external membrane fouling. However, it is believed that up to 80% of the permeate flux can be affected by pore constriction which is caused by particle penetration and deposition into membrane pores (internal fouling). The effect of pore geometry, as a factor, in flux decline due pore constriction of membranes was investigated in this work. Pore constriction by particles was approximated by maximum particle deposition onto the interior wall of the pores and simulated using MATLAB image processing toolbox (MIPT). Sixteen different basic geometries were considered for the simulation of pore constriction by particles. These include circular pores, 3 groups of rectangular, triangular and oval geometries at four different aspect ratios (3, 7, 15 and 30) and three combined geometries of star, cross and a rectangle with rounded ends. The
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