In consideration of these limitations in conventional treatment
methods and to promulgate ecological consideration, several kinds of
membrane processes including ultrafiltration (UF), nanofiltration (NF)
and reverse osmosis (RO) have been recently employed for oil–water
separation [8,9]. Because of its suitable pore sizes (usually in the range
of 2–50 nm) and the capability of removing emulsified oil dropletswithout
any de-emulsification processes, UF has been demonstrated as an efficient
method or a pre-treatment step before NF and RO in the
treatment of oil–water mixtures [10,11]. However, fouling is a serious
problem inherent in UF membranes that can be caused either by deposition
of an oil layer on the membrane surface or by membrane pore
blocking by oil droplets that ends up in a substantial flux decline [12].
This can be due to a number of factors, such as adsorption inside the
membrane, deposition on the membrane surface forming a cake layer
and blocking of themembrane pores [13]. The membrane pore structure,
the surface characteristics, as well as operating and process conditions
are some of the other factors affecting membrane fouling. Hence, the
proper tailoring of desiredmembranematerial is the convenient method
to reduce fouling and its adverse effects like flux and retention decline.