Improvement of membrane hydrophobicity by one-step electrospraying for water recovery from textile dye solutions by membrane distillation

Abstract

Membrane distillation is an upcoming technology for water recovery from industrial effluents. However, inherent operational phenomena, such as membrane wetting, compromise its functioning with complex solutions. Membrane modification can be a key to mitigating membrane gaps. Herein, a polypropylene membrane was physically modified via one-step electrospraying using a polymeric blend of polydimethylsiloxane and polyvinylidene fluoride. The main goal was to improve membrane hydrophobicity and enhance DCMD performance with four dye classes (Reactive, Disperse, Direct, and Acid). Polymer reticulation and polymer concentration in dope solution were studied, affecting membrane hydrophobicity. The modification improved the water contact angle by 20% after 90 min under the spray containing 2% PVDF and 6% PDMS-cured. The modified PP membrane reached contact angles of 148.38 ± 2.36° and 151.5 ± 6.18° for direct and acid dyes, respectively. The modified layer increased the membrane thickness by 3 µm without significant porosity alterations, amplifying the pH range where membranes assume negative charges. Stable permeate fluxes on a DCMD operation were reached, varying between 29.7 and 44.85 L m−2 h−1, and the rejection rate increased to 6%. The modification enhanced the membrane performance with textile dye solutions, enabling MD operation to water reclamation from textile effluents.