Synthesis of a hydrophilic polyamide constituted by succinyl chloride and 5-carboxy-1,3-phenylenediamine for developing homogeneity with polyvinylidene difluoride matrix, yielding mixed matrix membranes for treating oily wastewater

• A polyamide DACSC was synthesized by amine and acid chloride polymerization. • The DACSC contained hydrophilic -COOH groups on a hydrophobic benzene ring. • The increased homogeneity between DACSC and PVDF yielded defect-free membranes. • 8 %-DACSC/PVDF showed a flux of 114 L m -2 h -1 at 2 bar for crude oil emulsion. • 8 %-DASC/PVDF possessed a separation efficiency of >97 % for crude oil emulsions. This work developed a polymer using a simple, single-step approach, with hydrophilic and hydrophobic components as integral parts of the polymer backbone, to produce mixed-matrix membranes without specific defects. The hydrophilic component was 5-carboxy-1,3-phenylenediamine monomer owing to the carboxylic acid present on the benzene ring, and the hydrophobic fraction was the benzene ring and aliphatic chain of the succinyl chloride (diacid chloride). The condensation polymerization of 5-carboxy-1,3-phenylenediamine and succinyl chloride yielded a polyamide, DACSC, with both hydrophilic and hydrophobic components. The DACSC showed increased homogeneity with the matrix polymer polyvinylidene difluoride (PVDF) owing to their similar polymer natures. The DACSC was decorated in increasing concentrations in the PVDF matrix by dissolving it in the dope solution and underwent phase inversion along with PVDF, giving rise to not only chemical variations, but also physical features, compared to the control PVDF. Hence, the obtained membranes showed increased separation efficiencies for different types of oil/water emulsions (crude oil, motor oil, and diesel oil) and higher permeate flux. The highest separation efficiencies were >99 % for the 2 %-DACSC/PVDF and 4 %-DACSC/PVDF, and slightly reduced to 97 % for the 8 %-DACSC/PVDF across the three types of emulsions. The 8 %-DACSC/PVDF membrane showed the highest flux among the membranes fabricated in the current study, with values of nearly 114, 143, and 126 L m -2 h -1 for crude, diesel, and motor oil emulsions at 2 bar. The fouling and cleaning cycles showed that DACSC-containing membranes have reversible fouling.