Graphene oxide grafted poly(acrylic acid) synthesized via surface initiated RAFT as a pH‐responsive additive for mixed matrix membrane

Abstract

Incorporation of nanostructured materials into the membrane matrix is a new strategy to improve mechanical and performance properties. Graphene oxide (GO) is one of the advantageous carbon-based nanomaterials, which recently has been used extensively in this field. However, in the most cases, the surface modification of GO has been considered for the creation of new properties like a response to different stimuli such as temperature, pH, and pressure. In the present study, a well-defined poly(acrylic acid) was grafted on GO using reversible addition-fragmentation chain transfer polymerization technique. This modified GO was incorporated into the mixed matrix membrane as a pH-sensitive additive and its effect on the membrane performance was investigated. The membrane with 5 wt % of modified GO provides better hydrophilicity, flux, antifouling, and rejection properties and so the effect of pH change on the aforementioned characteristic properties was studied for this membrane. It is indicated that modified membrane shows different behaviors in acidic and alkaline conditions. In addition, excellent heavy metal separation was observed among rejection tests, especially for Hg ions.

State of the Art in Alcohol Sensing with 2D Materials

“…As an example, ultrathin 2D nanomaterials, especially single-layer nanosheets, where interlayer interactions are absent or limited, prepare the media suitable for unique electrical properties compared to other nanomaterials [42]. They also possess exceptional properties, due to their finite bandgap, superior flexibility, absence of dangling bonds, and significant resistance to short channel effects, which all could suggest a new generation of smart electronic, optoelectronic, and energy devices [43][44][45][46][47][48][49][50][51][52][53][54][55][56][57][58][59], where the first two promise the modern generation of sensors and biosensors and the last one offers developed, long lasting batteries, and energy devices. In addition, 2D layered nanomaterials are advantageous for gas sensing application specifically due to their large surface area, which facilitates surface reactions [60].…”

Nonporous Cation Exchange Membranes with pH-Responsive Properties as Chemical Valves

“…Acrylic acid has been widely used for the development of chemical valves or stimuli-responsive membranes due to the fact that it contains a carboxylic group that can be deprotonated or ionized below its p K a . However, most research has been directed toward porous ion exchange membranes. − In these types of membranes, acrylic acid chains are tethered to the pores of a porous membrane substrate, which can then adopt either an extended or a compacted conformation dependent on environmental pH, changing the effective pore size and ultimately, the transport properties. We previously stated the importance of investigating stimuli-responsive properties on dense ion exchange membranes, generally used in electrochemical separation processes in which a potential or a concentration gradient acts as the driving force, e.g., fuel cells and electrodialysis .…”

Polydopamine-coated graphene oxide nanosheets embedded in sulfonated poly(ether sulfone) hybrid UF membranes with superior antifouling properties for water treatment

“…To accomplish this, we synthesized PDA coated GO (PDGO) via self-polymerization of Dopa in alkaline tris-buffer solution at room temperature (23 o C). The GO nanosheets were specifically chosen because of their easy synthesis, low cost, hydrophilicity, and the abundant oxygen functional moieties they contain (OH, COOH, and epoxide) [22,26,29,38]. The phase-inverted hybrid UF membranes were prepared by combining sulfonated poly(ether sulfone) (SPES), a negatively charged polymer with hydrophilic PDGO nanosheets, to acquire higher hydrophilicity to the barrier layers due to enriched water-holding functional groups such as SO 3 H, COOH, OH, and NH, while the PDA thin layer promoted a better dispersion and high loading of the PDGO nanosheets into the SPES membrane matrix, resulting in a well dispersed nanosheets, even at PDGO loading up to 10 wt.%.…”