Condensation polymerization of 3,5-diaminobenzoic acid and isophthaloyl chloride yielding hydrophilic polyamide and its decoration in polyvinylidene difluoride membranes for the efficient separation of stable oil/water emulsions

Abstract

Enormous quantities of emulsified oily wastewater are released from domestic households and industries and offer a huge challenge for treating such a complex stream. Where this oily emulsified feed is a challenge, it is also an opportunity provided an efficient treatment method is applied. Hence, the current study was designed to fabricate hydrophilic mixed-matrix membranes (MMMs) by incorporating a hydrophilic polyamide, DAIP, as a polymeric filler in the matrix of the polyvinylidene difluoride (PVDF) membrane. The obtained membranes were applied for separating surfactant-stabilized oil/water (O/W) emulsion. First, the DAIP polymer was synthesized via condensation polymerization between 3,5-diaminobenzoic acid (DABA) and isophthaloyl chloride (IPC). Then the obtained DAIP polymer was thoroughly investigated to establish its structure and subsequently decorated in the PVDF matrix in different increasing concentrations (0–3 and 5%). Among the different fabricated membranes, M3 (PVDF-8%, PVP-3%, and DAIP-3% wt/wt of the solution) possessed the desired salient features especially the increased surface features such as surface energy, hydrophilicity, charge, and surface roughness. Hence, the M3 membrane showed excellent separation performance during O/W emulsion separation experiments regarding pure water permeance with a value of 2600 L m⁻² h⁻¹ bar⁻¹ and separation efficiency of >96% for oil-in-water emulsion. In contrast, the control M0 (PVDF-8%, PVP-3%) membrane showed inferior performance with a permeance of 1430 L m⁻² h⁻¹ bar⁻¹ and a separation efficiency of 79% based on total organic carbon (TOC) analysis. Long-term fouling studies revealed that DAIP-decorated membranes exhibited reversible fouling behavior and higher fouling resistance than pristine PVDF membranes. During stability tests, M0 (PVDF-8%, PVP-3%) facilitated the adsorptive removal of total organic carbon (TOC). This study provides valuable insights into designing and developing advanced membranes for efficient O/W separation by exploiting simple and scalable polymerization approaches.