Anionic channel membrane encircled by SO3H-polyamide 6 particles for removal of anionic dyes

Congo red filtration by polyacrylonitrile-based copolymer membranes

In this study, Congo red removal from wastewater by a filtration method was studied via membranes obtained from polyacrylonitrile-co-poly(2-ethylhexylacrylate) copolymers having various monomer ratios and polyacrylonitrile-co-poly(2-ethylhexylacrylate)/polyaniline blends with various polyaniline contents. It was found that the dye rejection value increased with acrylonitrile content in polyacrylonitrile-co-poly(2-ethylhexylacrylate) membranes. Also, blending copolymers with polyaniline enhanced the dye rejection rate. The performance of membranes showed incremental increase with increase in the polyaniline content. Both pH and concentration effects on the dye rejection rate of membranes were evaluated. The performance of polyacrylonitrile-co-poly(2-ethylhexylacrylate) membranes did not change significantly, whereas polyaniline-containing membranes had higher dye rejection rates at acidic pH levels. PAN(92)-co-P2EHA(8)-PANI(15%) demonstrated the highest dye rejection value of 99.7% at pH 3 when the feed concentration was 50 ppm. It also showed good resistance to increase in feed concentration. It had dye rejection values of 97.2% and 88.5% for 100 and 200 ppm feed concentrations, respectively.

Low pressure modified polyamide 6 membrane for effective fractionation of dyes and NaCl

A co-polymer (SPAA6) of 5-sulfoanthranilic acid (5SAA) and ε-caprolactam was used to prepare membrane through nonsolvent induced phase separation (NIPS) method. The micro-structure of membrane was adjusted by small molecules to improve mechanic strength and performance, involving 7 commercial ionic surfactant and a self-synthesized one, S20. S20 showed the best compatibility with SPAA6, which converted spherical phase into network of strip-like units in micro-structure of membrane. Meanwhile, average pore size of the membrane was narrowed from 4.271 nm to 3.391 nm, tested by BET method. Tensile strength of membrane was improved from 2.5 MPa to 2.9 MPa. Therefore, anionic dyes rejection and membrane stability were both improved. It actually demonstrated that molecular weight distribution of SPAA6 was crucial for micro-structure construction of membrane since S20 was the SPAA6 of low molecular weight. In blend solution filtration test, membrane MS2 (1:2 for S20:SPAA6) displayed 98.22% rejection to Congo Red (CR) acid and 96.18% NaCl permeation under 1 bar. It showed 80.18% rejection to chrome blue K (ABK) and 96.28% NaCl permeation. Both water permeance were higher than 3.5 L·m^-2·h^-1·bar. Membrane MS2 showed the potential of fractionation of dye and NaCl, which was promising in textile waste water treatment.