(90c) Nanometric Graphene Oxide Framework Membrane: Enhancing Heavy Metal Removal Via Nanofiltration

GO framework membranes were developed for effective heave metal removal via nanofiltration. A thin GO framework layer was firstly constructed by the crosslinking with ethylenediamine (EDA) and subsequently assembled on a polycarbonate substrate via a pressure-assisted filtration process. The resultant membrane was further post-treated by hyperbranched polyethyleneimine (HPEI) to alter the charge property on the membrane surface. The EDA crosslinking was found not only to enhance the membrane stability, but also to enlarge the nanochannels between the laminated GO nanosheets for higher water permeability. Different post-treatment agents were compared and HPEI 60K was observed to provide a higher surface charge while lowering the mass transport resistance. In addition, all materials were prepared in aqueous solutions and the as-fabricated GO framework layer was only 70 nm thick, indicating a green and cost effective fabrication process. The newly developed membrane exhibited a high pure water permeability of 5.01 L m^-2 h^-1 bar^-1 and comparably high rejection towards Mg²⁺, Pb²⁺, Ni²⁺, Cd²⁺ and Zn²⁺. These results have demonstrated the great potential of GO framework materials in waste water treatment and may provide insights for the design and fabrication of the next generation 2D-based nanofiltration membrane.