Removal of trace organic contaminants by melamine-tuned highly cross-linked polyamide TFC membranes.

In recent years, forward osmosis (FO) has represented numerous potential applications in safe water production. In this study, we improved the performance of FO thin film composite (TFC) membranes for the removal of trace organic compounds (TOrCs) by tuning the chemistry of its top active layer. The TFC membranes were synthesized by interfacial polymerization (IP) reaction between amine-containing monomers, e.g., meta-phenylene diamine (MPD) or para-phenylenediamine (PPD), and an acid chloride monomer, e.g., trimesoyl chloride (TMC). Owing to three free amine functionals over main core, melamine was used in the amine monomers solution to increase cross-linking among polyamide chains. Chemical and morphological characterization of the prepared membranes confirmed that melamine was successfully incorporated into the chemical structure of the top PA layer. Two agricultural toxic materials (atrazine and diazinon) were used to investigate the capability of the newly fabricated membranes in the removal of TOrCs. The obtained results showed that melamine-improved FO membranes provided higher atrazine and diazinon rejections in two different FO membrane configurations, including active layer facing feed solution (ALF) and active layer facing draw solution (ALD). The highest rejections of both diazinon (99.4%) and atrazine (97.3%) were achieved when the melamine modified MPD-based membrane served in ALF mode with 2 M NaCl as a draw solution.

Graphene-based electro-conductive anti-fouling membranes for the treatment of oil sands produced water.

In this study, a thin layer of polyaniline (PANI)-reduced graphene oxide (rGO) was laminated on polyethersulfone (PES) support by pressure-assisted technique. Organic fouling on the resulting robust and electro-conductive membranes reduced significantly by applying an external electric field. The electrical conductivity of pristine PANI film was 0.46 S/m while it was increased up to 84.53 S/m by adding appropriate amount of rGO. Both anodic and cathodic potentials in a wide range were applied to the prepared membranes using synthetic sodium alginate and real oil sands boiler feed water (BFW) waste of Alberta, Canada. Filtration tests showed that fouling resistance of electro-oxidative membranes towards sodium alginate improved, and 31.9% flux decline recovered when 2 V anodic cell potential was applied. By increasing the applied voltage from 3 V to 9 V, the antifouling property of membrane, as well as flux recovery ratio (FRR), improved dramatically and reached to 97.47% in the anodic setting. Such a significant improvement was attributed to electrostatic repulsive force between foulant and membrane surface, massive gas bubble generation, and electro-oxidation reactions. The cathodic electro-reduction configuration was also tested for BFW, where water flux decline and rejection performance were both improved by elevating electric potential.