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Abstract
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The main objective of this work is the manipulation of hydrophilic materials in support, intermediate and selective
layer to synthesize a novel nano-tubular ceramic membrane for treatment of oily wastewater. First,
porous mullite-alumina-zeolite composite membranes were prepared by an extrusion method. Changes in
porosity, pore size, shrinkage, and mechanical strength of the support membranes were investigated as function
of percentage composition and sintering temperature in order to obtain the optimal conditions. According to the
results, the most favorable condition set was determined to be a support membrane with a weight percent of 50,
30, and 20 for mullite, alumina, and zeolite, respectively, and a porosity of 38%, a pore size of 0.39 μm, and a
shrinkage of 10.2% sintered at 1250 ◦C and with good mechanical properties at 24.6 MPa. The cross-flow
filtration technique was employed to coat the natural zeolite on the inner surface of the support membrane to
achieve a narrower pore size distribution. Finally, a thick layer of nano-SiO2 was coated on the membrane by
utilizing the dip-coating method to develop a hydrophilic membrane while avoiding defects. Moreover, scanning
electron microscopic (SEM) analysis of the SiO2 membranes showed that the natural zeolite and nano-SiO2 layer
is homogeneous and demonstrates high adhesion to the support membrane. Besides, the result of COD rejection
showed that the SiO2 membranes have an undeniable capability in rejection of oil droplets with a reasonable
permeation flux. Therefore, the obtained membranes are highly promising for practical applications and environmental
remediation in sensitive Persian Gulf zone.
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