Oxygenates Removal from Water by Hydrophobic Pervaporation with Polyalkylmethylsiloxane Membranes

Oxygenates removal from wastewater is an actual task for gas- and petrochemical industry. Pervaporation is one of most promising processes for oxygenates recuperation. In this work, pervaporation composite membranes with a polyalkylmethylsiloxane (alkyl substituents: hexyl, heptyl, octyl and decyl) selective layer were developed and studied for the first time during separation of the four-component mixture (1-butanol—1-propanol—ethanol—water). It was shown that an increase in the length of the side substituent of the selective layer leads to an increase in selectivity and a decrease in the permeability of oxygenates and water. The influence of the pore size of the support on the transport and separation properties of the membranes was studied. It was found that an increase in the pore size of the support leads to a decrease in the mass transfer resistance of the composite membrane. For example, for composite membranes based on polyheptylmethylsiloxane, normalized permeability was 33 × 10−3 and 11 × 10−3 molꞏmꞏPa−1ꞏm−2ꞏh−1 for membranes on micro- and ultrafiltration porous supports. The best separation characteristics in comparison with commercial membranes with a selective layer based on silicone rubbers were demonstrated by the polydecylmethylsiloxane and polyheptylmethylsiloxane composite membranes on microfiltration support: selectivities for n-butanol, n-propanol and ethanol were 2.0 and 2.3, 1.8 and 1.8, 1.0 and 0.9, respectively. Normalized permeabilities for n-butanol, n-propanol and ethanol were 33 × 10−3 and 16 × 10−3 molꞏmꞏPa−1ꞏm−2ꞏh−1, 30 × 10−3 and 12 × 10−3 molꞏmꞏPa−1ꞏm−2ꞏh−1, 16 and 6 molꞏmꞏPa−1ꞏm−2ꞏh−1, respectively.