Graphene oxide incorporated thin film nanocomposite nanofiltration membrane for multivalent ions removal
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Date
2018
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Universiti Teknologi Malaysia
Abstract
One of the most critical issues encountered by thin film composite (TFC) nanofiltration (NF) membrane for multivalent ions removal is the trade-off between water flux and salt rejection. A novel thin film nanocomposite (TFN) membrane was fabricated and studied in this work by incorporating self-synthesized graphene oxide (GO) into microporous substrate and selective layer of the membrane. A novel interfacial polymerization (IP) technique was also developed to pre-coat the substrate with GO nanosheets followed by vacuum filtration of amine aqueous solution through the substrate before initiating a polyamide cross-linking process in order to avoid nanofillers agglomeration and to minimize the quantity of nanofillers used in membrane fabrication. Compared to the pure water permeability (PWP) of the control TFC membrane, the introduction of 0.3 wt% GO into substrate was reported to improve the PWP of TFN membrane by 50.9%, achieving 2.43 L/m2•h•bar with rejections for Na2SO4, MgSO4, MgCl2 and NaCl recorded at 95.2%, 91.1%, 62.1% and 59.5%, respectively. The enhanced performance is due to the unique properties of GO that play an important role in increasing both membrane hydrophilicity and surface negativity. When novel IP technique was utilized to introduce 0.03 g/m2 GO into the selective layer, the PWP of the resultant TFN membrane was further enhanced to 4.13 L/m2•h•bar, i.e., 71.7% and 129.4% higher than TFC membranes synthesized by conventional and novel IP techniques, respectively. This could be attributed to the existence of hydrophilic GO that was distributed evenly throughout the substrate surface coupled with the formation of porous selective layer and thus reduced water transport resistance. The experimental results also revealed that the optimum GO loading (0.02 g/m2) in the selective layer via novel IP could promise a fabrication of defect-less NF membrane for the removal of multivalent ions that exhibits improved antifouling properties independent of the polyamide chemistry. In conclusion, the GO-incorporated TFN membrane synthesized via the novel IP technique is promising to overcome the technical limitations of conventional IP technique, bringing the new generation TFN membrane one step closer to industrial application
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Thesis (PhD.)
Keywords
Thin films—Materials, Polymerization—Research, Nanofiltration