This paper reports the effect of sol size on nanofiltration performances of sol-gel derived microporous zirconia membranes. Microstructure

pure water flux

molecular weight cut-off (MWCO) and salt retention of zirconia membranes derived fromzirconia solswith different sizeswere characterized. Thermal evolution

phase composition

microstructure and chemical stability of unsupported zirconia membranes (powder) were determined by thermogravimetric and differential thermal analysis

X-ray diffraction

nitrogen adsorption-desorption and static solubility measurements. Results show that nanofiltration performance of zirconia membranes is highly dependent on sol size. The solwith an average size of 3.8 nm

which is smaller than the pore size of the γ-Al

2

O

3

support (pore size: 5-6 nm)

forms a discontinuous zirconia separation layer because of excessive penetration of sol into the support. This zirconiamembrane displays a MWCO value towards polyethylene glycol higher than 4000 Da. A smooth and defect-free zirconiamembrane with a MWCO value of 1195 Da (pore size: 1.75nm) and relative high retention rates towards MgCl

2

(76%) and CaCl

2

(64%) was successfully fabricated by dip-coating the sol with an appropri

ate size of 8.6 nm. Zirconia sol with an average size of 12 nm exhibits colloidal nature and forms a zirconia membrane with a MWCO value of 2332 Da (pore size: 2.47 nm). This promising microporous zirconia membrane presents sufficiently high chemical stability in a wide pH range of 1-12.