Removal of polyether-polyols by means of ultrafiltration

Abstract

The removal of diethyleneglycol (DEG) and several polyether-polyols of different molecular weights and nature by ultrafiltration was studied. These polyether-polyols are polyethyleneglycols (PEG) of different molecular weights (800 and 6,000) and two ethylene oxide-propylene oxide copolymers: Pluronic PE6100 and Alcupol F4811. Rejection coefficients and permeate fluxes were measured for these compounds and for mixtures of PEG-6000+SDS, glycols + Pluronic and glycols + Alcupol. The main purpose of working with these mixtures is to study how the addition of SDS, Pluronic or Alcupol can enhance rejection coefficients observed for total organic matter present in the target effluent. In a first stage, 0.1% w/w solutions of DEG, PEG-800 and PEG-6000 were ultrafiltered using a CARBOSEP M5 ceramic membrane (MWCO = 10 kDa). No significant retention was obtained for DEG and PEG-800, but for PEG-6000, rejection coefficients higher than 80% were reached. The effects of temperature, transmembrane pressure and feed rate on both permeate flux and rejection coefficient were also studied. Secondly, the same procedure was followed for 0.1% w/w solutions of Alcupol and Pluronic, obtaining rejection coefficients of almost 100%. With respect to the above-mentioned mixtures, total organic carbon (TOC) retention was not enhanced by the addition of either SDS or Pluronic. However, a clear increase was obtained for TOC rejection when Alcupol was added due to the distribution of the PEG-6000 molecules between the aqueous phase and the organic phase formed by the Alcupol emulsion.