High Selective Composite Polyalkylmethylsiloxane Membranes for Pervaporative Removal of MTBE from Water: Effect of Polymer Side-chain

Abstract

For the first time, the effect of the side-chain in polyalkylmethylsiloxane towards pervaporative removal of methyl tert-butyl ether (MTBE) from water was studied. The noticeable enhancement of separation factor during the pervaporation of 1 wt.% MTBE solution in water through the dense film (40–50 µm) can be achieved by substitution of a methyl group (separation factor 111) for heptyl (161), octyl (169) or decyl (180) one in polyalkylmethylsiloxane. Composite membrane with the selective layer (~8 µm) made of polydecylmethylsiloxane (M10) on top of microfiltration support (MFFK membrane) demonstrated MTBE/water separation factor of 310, which was 72% greater than for the dense film (180). A high separation factor together with an overall flux of 0.82 kg·m−2·h−1 allowed this M10/MFFK composite membrane to outperform the commercial composite membranes. The analysis of the concentration polarization modulus and the boundary layer thickness revealed that the feed flow velocity should be gradually increased from 5 cm·s−1 for an initial solution (1 wt.% of MTBE in water) to 13 cm·s−1 for a depleted solution (0.2 wt.% of MTBE in water) to overcome the concentration polarization phenomena in case of composite membrane M10/MFFK (Texp = 50 °C).

Effect of OH-Group Introduction on Gas and Liquid Separation Properties of Polydecylmethylsiloxane

“…The choice of ethanol in this work was due to two factors: the components under study (C 7 –C 10 aldehydes and C 6 –C 9 olefins) were dissolvable in it, and its sorption interaction with PDecMS was small compared with the liquids under study. The validity of this approach was described in [ 30 ], in which water was taken as a solvent and its zero sorption in polysiloxanes was the main assumption. Each experimental determination of sorption in PDecMS was performed three times.…”

“…Separation was performed using a Phenomenex Zebron ZB-FFAP capillary column, USA (length 50 m, diameter 0.32 mm, phase thickness 0.50 µm) with the phase being a copolymer of 2-nitroterephthalic acid ester and ethylene glycol in the following temperature regime: column—120 °C, detector—150 °C, evaporator—200 °C. The solubility coefficient ( S i , mole solvent/(m 3 polymer·kPa)) was calculated using Formula (2), similar to the calculation scheme described in detail in [ 30 ]: where, p sorb —pressure over solution determined in Aspen plus (NRTL) for a solution with a concentration of w 48 , n s —the amount of sorbate substance in the polymer, and V pol —polymer volume.…”

“…In particular, the hydrophobization of polysiloxanes is of great interest to researchers. Thus, the introduction of alkyl side substituents of lengths 7, 8 and 10 into the polysiloxane chain allowed an increase in the separation factor of 1% wt methyl-tretbutyl ether in water from 111 (for the methyl group) to 161, 169 and 180, respectively [ 30 ]. The introduction of 10% diacetate groups into the polysiloxane chain allowed an increase in the phenol flow from aqueous solution by 15% compared with polydimethylsiloxane, which led to an increase in the phenol/water separation factor to 21.5 [ 31 ].…”

High-Selectivity Polysiloxane Membranes for Gases and Liquids Separation (A Review)

“…For removing methyl tert-butyl ether from wastewater, Borisov et al [124] considered polyalkylsiloxanes with hexyl, octyl, and decyl pendant substituents, and also composite были membranes based on them. The composite membrane based on polydecylmethylsiloxane, prepared in [124], showed the best characteristics (separation factor 310, total flux 0.82 kg m -2 h -1 ) compared to the previous data [125][126][127][128]. Polydecylmethylsiloxane on MFFK-1 microfiltration support showed high selectivity in n-butanol recovery from water (2.8) [129].…”

A Methyl-Modified Silica Layer Supported on Porous Ceramic Membranes for the Enhanced Separation of Methyl Tert-Butyl Ether from Aqueous Solution

“…It is generally believed that some polymers are chemically stable, intrinsically hydrophobic, and relatively low-cost [ 14 , 15 ]. Hydrophobic polymer pervaporation membranes are also suitable for solving the problem of separating MTBE from wastewater [ 16 ]. However, ceramic membranes have their own distinct merits compared to polymer membranes, such as uncomplicated cleaning, excellent non-swelling behavior, high mechanical strength, and anti-fouling property [ 6 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 ].…”