Membrane separation technology offers the advantage of high removal efficiency in treating oily wastewater.However,tiny oil droplets are highly prone to adhering to the membrane surface,leading to severe membrane fouling.Enhancing the surface roughness and hydrophilicity of membranes by loading micro-nano particles is an effective approach to alleviate membrane fouling.Nevertheless,there are few reports on the effect of the size of loaded particles on the anti-fouling performance of modified membranes.In this study,a series of silica(SiO2)microspheres with different particle sizes were prepared by coupling the Stöber method with a multi-step seed growth method.By optimizing the concentrations of tetraethyl orthosilicate(TEOS)and ammonia,as well as the amount of seed added,the SiO2 microspheres achieved uniform and controllable particle sizes in the range of 0.36 μm to 2.10 μm.Four types of SiO2 microspheres with different particle sizes were selected and loaded onto the surface of polyvinylidene fluoride(PVDF)membranes to prepare hydrophilic-oleophobic SiO2/PVDF membranes(abbreviated as SP membranes).Among these modified membranes,the one modified with SiO2 microspheres of 1.08 μm particle size showed the best permeation and anti-fouling performance when treating oil-in-water emulsions.Under operating conditions of 0.7 bar and a backwashing pressure of 0.3 bar,its normalized flux and flux recovery rate reached over 15%and 95%,respectively.This study provides an important basis for the preparation of micro-nano particle-modified membranes for oil-water separation.