*3.1.5 Alumina NPs*

Alumina NPs loaded PVDF membrane fabricated according to the phase inversion method has been demonstrated that the hydrophilicity, permeability, antifouling capacity, and mechanical stability were increased with no considerable change in pore density and size [71]. In another study, fouling resistive, reduced flux decline and less hydrophobic interaction between foulant and membrane surface are some of the outstanding features of the alumina NPs added PES UF membrane [72]. Different types of NPs have been incorporated into variable polymeric matrix to improve separation performances and fouling resistance of the hybrid membranes and their characteristics compared to the pristine ones collected from recently published studies have been listed in **Table 2**.

Nanoparticles used to fabricate a hybrid membrane can also enhance the mechanical stability compared to the pristine membrane by decreasing the impact of the membrane compaction. Compaction is known as the mechanical deformation of the polymeric membrane matrix and observed at the initial stage of the pressure driven membrane operations. Structure densification leads to a flux decline. Blending NPs with polymer matrix allows well distribution of NPs through the thickness of the membrane during phase inversion process. The stability of those NPs in the macrovoid region reduces the loss of membrane structure because compaction is known to occur predominantly in bulk macrovoid region. For instance, Pendergast et al. reported that stability of PSf membranes was improved when silica and zeolite NPs were included in the membrane structure, resulting in less compaction than pure PSf membrane [86].
