Incorporation of Graphene-Related Carbon Nanosheets in Membrane Fabrication for Water Treatment: A Review

Abstract

The minimization of the trade-off between the flux and the selectivity of membranes is a key area that researchers are continually working to optimise, particularly in the area of fabrication of novel membranes. Flux versus selectivity issues apply in many industrial applications of membranes, for example the unwanted diffusion of methanol in fuel cells, retention of valuable proteins in downstream processing of biopharmaceuticals, rejection of organic matter and micro-organisms in water treatment, or salt permeation in desalination. The incorporation of nanosheets within membrane structures can potentially lead to enhancements in such properties as the antifouling ability, hydrophilicy and permeability of membranes, with concomitant improvements in the flux/selectivity balance. Graphene nanosheets and derivatives such as graphene oxide and reduced graphene oxide have been investigated for this purpose, for example inclusion of nanosheets within the active layer of Reverse Osmosis or Nanofiltration membranes or the blending of nanosheets as fillers within Ultrafiltration membranes. This review summarizes the incorporation of graphene derivatives into polymeric membranes for water treatment with a focus on a number of industrial applications, including desalination and pharmaceutical removal, where enhancement of productivity and reduction in fouling characteristics have been afforded by appropriate incorporation of graphene derived nanosheets during membrane fabrication.

Short Review on Predicting Fouling in RO Desalination

“…Research that has been undertaken focuses on six key areas: (1) characterization of foulant agents by autopsy studies of membrane elements; (2) understanding of fouling mechanisms; (3) indices for predicting fouling; (4) modeling for full-scale systems; (5) optimization of pre-treatment and chemical cleaning; and (6) optimizing the membrane material and enhanced module design. The first four areas attempt to address directly how fouling occurs and how to predict it, while the others focus more on the mitigation and prevention of fouling, as for example through the use of antifouling membranes [ 11 , 12 , 13 , 14 , 15 ].…”

Biofouling of Polyamide Membranes: Fouling Mechanisms, Current Mitigation and Cleaning Strategies, and Future Prospects

“…Research has been conducted over the last 3 to 5 years with GO thin film composite membranes for higher productivity, resistance to biofouling, and chlorine tolerance [287,288,289,290,291,292]. GO-based membranes are generally classified as polyamide surface coatings or embedded in the polyamide layer as a “nanofiller” [293].…”

“…GO-based membranes are generally classified as polyamide surface coatings or embedded in the polyamide layer as a “nanofiller” [293]. Various preparation methods have been employed to develop GO-based membranes, including embedding GO in the polyamide layer via dissolution in the aqueous, m-phenylenediamine (MPD) solution [292], covalently-bounded surface grafting using azide-functionalized GO (AGO) [290], spin-coating [289,291], and layer by layer coatings on the polysulfone layer prior to forming the polyamide layer [294]. Many of the coating techniques result in a loss of permeability as compared to a commercial polyamide membrane [292,293,295].…”

Laminated, Composite and Sandwich Membranes Based on Graphene-Oxide with Nano-Textiles

“…Pore size and shape subsequently influence the application in Figure 1 [11], which shows the different progression of gas/ion separation for GO and graphene. Membranes based on graphene, GO, rGO are applied in the area of molecular separation, both in selective separation of gases, ions, small and ultra-small particles, desalination and purification of water, including disinfection [4,6,7,[12][13][14][15][16][17]. [9,[20][21][22][23].…”