Effect of introducing varying amounts of polydopamine particles into different concentrations of polyethersulfone solution on the performance of resultant mixed-matrix membranes intended for dye separation

In this study, polydopamine (PDA) particles were embedded into polyethersulfone (PES) membrane through wet-phase separation. We considered two concentration of PES solution—17 and 19 wt%. Adding different concentration of PDA (0–0.7 wt%) into the two solutions revealed an opposite effect on the characteristic and performance of the membrane. Incorporating PDA particles in 17 wt% PES solution was resulted in a decreased in pure water flux, and increased in dye rejection; Whereas, incorporating PDA particles in 19 wt% PES solution boosted the pure water flux with keep dye rejection of ~99.0%. At the optimum concentration of 0.5 wt% PDA added to 19 wt% PES solution, the following dye rejections were obtained: RMethylene Blue = 99.90 ± 1.45%; RProcion Blue H-5R = 98.33 ± 0.57%; RDirect Red 23 = 99.90 ± 1.82%; RBrilliant Blue = 99.90 ± 0.94%; RRose Bengal = 99.90 ± 0.0%; RDirect Red 80 = 99.12 ± 0.41%; for the salt rejections: (RNaCl = 10.59 ± 5.23%; RNa2SO4 = 8.87 ± 4.99%; RMgCl2 = 10.45 ± 6.85%; RMgSO4 = 10.02 ± 3.87%). This shows that the selectivity of the fabricated membrane towards different dyes and common inorganic salts is high. PDA is a favorable option for fabricating membranes for dye desalination under appropriate PES concentration.