Performance improvement of triple-doped nanocomposite membrane towards hairwork dyeing effluent reclamation approaching zero liquid discharge

It is highly anticipated that efforts will be made to raise the level of industrial effluent reclamation on the background of continuously minimizing waste stream based on preconcentration tool. For this purpose, a triple-doped nanocomposite (TFN-tri) membrane through partially alternative doping spiro-structured 2,2'-dimethyl-1,1'-biphenyl-4,4'-diamine dihydrochloride and flexible 4,4'-bipiperidyl dihydrochloride and continuous incorporating of molybdenum disulfide quantum dots was successfully fabricated. With the assistance of self-synthesized biodegradable flocculant pretreatment, raw hairwork dyeing effluent (HDE) was stably recycled up to 95.1% on the premise of meeting the requirements of the relevant national standard. As a deep processing unit, TFN-tri membrane displayed accurate salt rejection of nearly 66% as expected. More impressively, it also exhibited permeability basically increased by 2.5 folds, while fouling layer thickness, running time and specific energy consumption decreased by 5 μm, 54.7% and 72.5%, respectively, than its counterpart in long-term reuse testing. These changes may mainly be due to the finely expand sub-nanopores coupled with an enhanced electrostatic exclusion and the improved fouling resistance brought about by other critical skin features in terms of smoothness and hydrophilicity optimization. In brief, this study has taken a vigorous and reliable step towards heavily polluted HDE reclamation approaching zero liquid discharge.