title: Surface modification of PTMSP membranes by plasma treatment: Asymmetry of transport in organic solvent nanofiltration.
abstract: For the first time, the effect of asymmetry of the membrane transport was studied for organic solvents and solutes upon their nanofiltration through the plasma-modified membranes based on poly(1-trimethylsilyl-1-propyne) (PTMSP). Plasma treatment is shown to provide a marked hydrophilization of the hydrophobic PTMSP surface (the contact angle of water decreases from 88 down to 20°) and leads to the development of a negative charge of -5.2 nC/cm(2). The XPS measurements prove the formation of the oxygen-containing groups (Si-O and C-O) due to the surface modification. The AFM images show that the small-scale surface roughness of the plasma-treated PTMSP sample is reduced but the large-scale surface heterogeneities become more pronounced. The modified membranes retain their hydrophilic surface properties even after the nanofiltration tests and 30-day storage under ambient conditions. The results of the filtration tests show that when the membrane is oriented so that its modified layer contacts the feed solution, the membrane permeability for linear alcohols (methanol-propanol) and acetone decreases nearly two times. When the modified membrane surface faces the permeate, the membrane is seen to regain its transport characteristics: the flux becomes equal to that of the unmodified PTMSP. The well-pronounced effect of the transport asymmetry is observed for the solution of the neutral dye Solvent Blue 35 in methanol, ethanol, and acetone. For example, the initial membrane shows the negative retention for the Solvent Blue 35 dye (-16%) upon its filtration from the ethanol solution whereas, for the modified PTMSP membrane, the retention increases up to 17%. Various effects contributing to the asymmetry of the membrane transport characteristics are discussed.
authors.affiliation: Topchiev Institute of Petrochemical Synthesis, Russian Academy of Sciences, Leninsky pr. 29, Moscow 119991, Russia.
authors.forename: A V
authors.initials: AV
authors.lastname: Volkov
authors.affiliation: Topchiev Institute of Petrochemical Synthesis, Russian Academy of Sciences, Leninsky pr. 29, Moscow 119991, Russia.
authors.forename: S E
authors.initials: SE
authors.lastname: Tsarkov
authors.affiliation: Enikolopov Institute of Synthetic Polymer Materials, Russian Academy of Sciences, Profsoyuznaya ul. 70, Moscow 117393, Russia.
authors.forename: A B
authors.initials: AB
authors.lastname: Gilman
authors.affiliation: Topchiev Institute of Petrochemical Synthesis, Russian Academy of Sciences, Leninsky pr. 29, Moscow 119991, Russia.
authors.forename: V S
authors.initials: VS
authors.lastname: Khotimsky
authors.affiliation: Frumkin Institute of Physical Chemistry and Electrochemistry, Russian Academy of Sciences, Leninsky pr. 31, Moscow 119071, Russia.
authors.forename: V I
authors.initials: VI
authors.lastname: Roldughin
authors.affiliation: Topchiev Institute of Petrochemical Synthesis, Russian Academy of Sciences, Leninsky pr. 29, Moscow 119991, Russia; National Research Nuclear University MEPhI, Kashirskoye sh. 31, Moscow 115409, Russia. Electronic address: vvvolkov@ips.ac.ru.
authors.forename: V V
authors.initials: VV
authors.lastname: Volkov
keywords: Organic solvent nanofiltration; PTMSP; Plasma treatment; Transport asymmetry