Pervaporation Separation of Phenol from Water on Polyalkylmethylsiloxane Membranes: the Effect of the Length of the Side Substituent

Phenol and its derivatives pose a significant environmental hazard even at low concentrations, making their efficient removal from industrial wastewater an urgent challenge. Pervaporation using selective membranes represents a promising energy-efficient approach for the concentration and recovery of phenol from aqueous streams. In this work, for the first time, a comprehensive investigation was carried out into the effect of alkyl side-chain length in poly(alkylmethylsiloxanes) on their affinity toward phenol and water, as well as on the transport properties of composite membranes in pervaporation. Hansen solubility parameter calculations revealed that the synthesized polymers are hydrophobic and exhibit a higher affinity for phenol than for water. However, with increasing alkyl chain length, the polymer–phenol interaction parameter decreases due to a reduced contribution of polar interactions. The highest phenol partition coefficients (up to 2.16 g/g) and the smallest polymer–phenol interaction radii were achieved for polymers bearing alkyl substituents with 6–7 carbon atoms. Membranes based on these polymers demonstrated the highest selectivity (~35) and separation factor (~11), performance metrics that are comparable to or exceed those of certain literature-reported analogues in terms of the selectivity–permeability ratio.

wastewater, phenol, composite membranes, pervaporation, polyalkylmethylsiloxanes