Characterisation and application of a novel positively charged nanofiltration membrane for the treatment of textile industry wastewaters

The present study demonstrates the high potential for the application of a novel self assembled positively charged nanofiltration membrane, PA6DT-C, in processes such as the recovery of valuable cationic macromolecules in the bioprocess and pharmaceutical industries or removal of multi-valent cations such as dyes and heavy metals in the paper and pulp, textiles, nuclear, and automotive industries. The nanofiltration membrane, prepared in this laboratory, is further characterised and then tested for the removal and recovery of Methylene Blue from a synthetic dye house wastewater. The characterisation process involved the construction of a rejection profile for NaCl over a wide range of pH and concentration, which illustrates that the optimal process conditions for the removal of small cations using this membrane is in the region pH <8.0 and concentration less than 15 mol m−3. The salt rejection data was used to calculate the magnitude of the effective membrane charge density and this was found to be significantly higher for the PA6DT-C membrane than two commercially available membranes (Desal-DK and Nanomax-50). The membrane flux for this new membrane is also superior to the commercial membranes with an approximate increase of 3–4 fold. The PA6DT-C membrane was successful in removal of Methylene Blue dye from synthetic dye house wastewaters achieving 98% rejection and a membrane flux of ∼17 LMH bar−1. Thus, this new membrane both adds to and complements the existing short supply of positively charged NF membranes.

► A novel positively charged nanofiltration has been created using the self assembly method.
► The membrane exhibits high charge and controlled pore size providing high rejection and high flux.
► The advanced membrane features have been demonstrated with an industrial example.
► Removal of the dye Methylene Blue from a synthetic dye house effluent.
► The membrane is of interest for textiles, pharma, nuclear, automotive and paper industries.