A new method to prepare organic–inorganic hybrid membranes

In this paper we present a new method to prepare organic–inorganic hybrid PVDF/Si membranes by adding tetraethyl orthosilicate (TEOS) into the polyvinylidene fluoride (PVDF) casting solution. During the membrane coagulation in acid bath (pH = 1), the TEOS was hydrolyzed and polymerized, and silicon–oxygen polymers were formed. The silicon–oxygen polymers may entangle or interpenetrate with PVDF chains, which is beneficial to the mechanical performances of hybrid membranes. Element analysis showed Si existed on the surface and bottom of hybrid membrane when TEOS was added to the casting solution. The effects of TEOS on the performances of hybrid membranes were investigated. The results showed that the pure water flux increased firstly and then decreased and the BSA retention decreased with TEOS content increasing. When TEOS content was about 12 wt.%, the pure water flux of hybrid membrane was similar to that of PVDF membrane without TEOS addition, but the tensile strength and elastic modulus of hybrid membrane was almost twice.

In this paper, PVDF/Si organic–inorganic hybrid membranes were prepared via phaseinversion process. TEOS is directly added into the PVDF casting solution. During the formation of membrane in acid (pH = 1), the TEOS in casting solution could be hydrolyzed and polymerized, and inorganic Si-O polymers were formed, then the organic–inorganic hybrid membranes were prepared. The morphologies and properties of resulting PVDF membranes were greatly affected by the addition of TEOS to polymer casting solution. The main conclusions are as follows: (1) Inorganic component Si could be added into PVDF UF membranes through our method, and a new way to prepare inorganic–organic hybrid membrane was developed. (2) The pure water flux increased firstly and then decreased when the increase of TEOS in casting solutions, while it began to rise again when TEOS content was more than 16 wt.%. The BSA retention of hybrid membranes continuously declined with the increase of TEOS content. The tensile strength and elastic modulus of wet hybrid membranes first rose and then dropped with the increase of TEOS. Each reached their maximum when The authors thank National Natural Science Foundation of China for financial support (20306001). We also thank Prof. Liu Zhongzhou from Research Center for Eco-Environmental Science, the Chinese Academy of Sciences, for valuable discussions.