Carbonised template silica membranes for desalination

In this work we investigate the performance of inorganic membranes in desalination application using a low pressure pervaporation setup. Inorganic membranes were synthesized via a two-step sol–gel catalysed process employing tetraethylorthosilicate as the silica precursor. In addition, non-ligand surfactants were embedded and carbonized into the silica matrix. Normal silica membranes have typical microporous structural characteristics but were not stable during desalination, as water interacted with the silanol groups and enlarged the silica film pore sizes. On the other hand, the carbon template silica (CTS) membranes were hydrostable and exhibited higher surface area and pore volume as well as improved salt rejection as compared to conventional silica membranes. The longest 16 carbon chain (C16) surfactant derived CTS membrane showed highest NaCl rejection up to 97% with flux in the order of 3 kg mÀ2 hÀ1 at 1 bar pressure difference across the membrane and seawater concentrations. This translated to 1200 ppm of NaCl in the permeate, being close to the standard for drinking water.

Fresh water shortages are a real issue for communities, driving studies to advance desalination of abundant saline resources. We have shown that silica membranes are a suitable candidate for low pressure desalination when carbonized surfactants are included in the membrane synthesis. Rejection correlated with the length of the carbonized surfactant chain for seawater concentrations of NaCl, being highest for highly saline feeds. Decline in flux was recorded with time, but was within experimental error. CTS membranes are therefore suitable candidates for low pressure desalination.