Preparation of hydroxyl group containing bridged organosilica membranes for water desalination

Abstract

Organosilica membranes were prepared by homo-and copolymerization of hydroxymethyl(triethoxy)silane (HMTES) for the first time, and applied to reverse osmosis (RO) to investigate the effects of the hydroxymethyl group. Fourier transform infrared (FT-IR) spectrometry, thermogravimetric analysis (TGA), and water contact angle measurements of the membrane surface indicated that the C-OH group of HMTES underwent a condensation reaction with Si-OH to form an Si-O-C bond during the calcination at 300 °C.Upon RO experiments usinganNaCl aqueous solution, the HMTES membrane exhibited a significant increase of the liquid permeance and a decrease of the NaCl rejection during the measurement, which arose from the hydrolytic cleavage of the Si-O-C bond to form Si-OH and C-OH groups upon contact with water.On the other hand, for a membrane derived from the copolymerization of HMTES and bis(triethoxysilyl)ethane (BTESE) in the weight ratio of 1:1, liquid permeance was increased gradually to reach a steady state of 3.4×10 -13 m 3 /(m 2 •s•Pa), and NaCl rejection was maintained at a

Synthesis of organically bridged trialkoxysilanes bearing acetoxymethyl groups and applications to reverse osmosis membranes

“…Spontaneously, the NaCl rejection decreased, although it is enhanced at the early stage of the experiments to reach maximal values of 96% for the BTES‐Ac‐a membrane. The enhancement is likely due to the adsorption of NaCl to the membrane, which causes electrostatic repulsion, similar to what has been observed for membranes prepared by copolymerization of HMTES and BTES‐E1 . For the BTES‐Ac‐b membrane, however, more rapid decrease of the NaCl rejection was observed from the beginning of the experiment.…”

“…Although the amount of SiOH groups formed by soaking seems small based on the FT‐IR spectra, the formation of these groups would be responsible for the increased water permeance during the RO experiment. Similar formation of SiOH and COH hydroxyl groups by hydrolysis of SiOC bonds during RO experiments to enhance the permeance was observed for the membrane derived from the sol–gel process of mixtures of BTES‐E1 and HMTES (Scheme ) …”

“…Recently, we introduced a new strategy for controlling the hydrophilicity of bridged silica membranes by post‐hydrolysis of the membranes. Polymerization of hydroxymethyltriethoxysilane (HMTES) gave membranes with SiOSi and SiOC linkages, which showed water separation properties . However, the membranes were unstable upon soaking in water and the water permeability gradually increased and the NaCl rejection decreased rapidly during the RO experiments, due to hydrolysis of the SiOC bonds.…”

Preparation of POSS-derived robust RO membranes for water desalination

“…whereas that at 420-600 °C seems to indicate the decomposition of the ethylene units attached to the POSS corners [18]. In accordance to the TGA profile, the signal at approximately 900 cm -1 in the IR spectra, which was ascribed to Si-OH stretching [28], was gradually weakened and finally disappeared when the sol film was treated at approximately 2970 cm -1 and 2880-2930 cm -1 in the IR spectrum of the gel dried at 100 °C, which were ascribed to CH 3 (ν as ) and CH (ν s )/CH 2 (ν s + ν as ), respectively.…”

Preparation of Bridged Polysilsesquioxane Membranes from Bis[3-(triethoxysilyl)propyl]amine for Water Desalination

“…In fact, membranes prepared from bis(triethoxysilyl)-ethane, -ethene, and -ethyne showed improved water permeability as the bridging units became more rigid and polar in the order of ethane < ethene < ethyne. 12,13 We have introduced hydroxyl, 14 acetoxy, 15 triazine, 16 and triazole 17 units to the membranes to increase water permeability by enhancing hydrophilicity.…”