Swelling Pressures of Graphite Oxide and Graphene Oxide Membranes in Water and Ethanol

Abstract

the methods commonly used for the preparation of GO thin films and freestanding foils/membranes.Most of the applications cited above are enabled by the ability of GO multilayers to swell in polar solvents similarly to their precursor graphite oxides. [18][19][20][21][22] In this respect GO is similar to very common clay minerals, e.g., montmorillonites, [23] vermiculites, [24] and bentonites. [25] Swelling occurs in these materials due to sorption of water (or other solvents) between 2D layers and the expansion of interlayered distance. [26][27][28] The driving force of swelling is hydration of anions in clay minerals and hydration of interlayer functional groups in GO. The crystalline swelling refers to layer-by-layer intercalation of solvent. Osmotic swelling is controlled by the relatively easy flow of solvent in and out of structure regulated by osmotic effects. [29][30][31][32][33] Remarkably, crystalline swelling is found for Brodie GO in all so far studied solvents except water [34][35][36][37][38] while for Hummers GO only osmotic-like swelling was so far reported. [37,39,40] Adding water to clays under conditions of confinement is known to produce pressures in the range of tens or even hundreds of bar. [25,41,42] Swelling pressure is complex phenomena, which depends on many parameters, e.g., degree of compaction, [25] concentration of salts in solution, [43] temperature [44] etc. It is an important factor, e.g., in construction works since the pressure is sufficient to induce damage in buildings or roads. Swelling pressure has been studied in detail for clay minerals but so far not reported for multilayered GO and graphite oxides. At the same time, the swelling pressure is an important factor affecting performance of GO membranes.The swelling of GO membranes is directly related to the size of "permeation channels" which enable a flow of solvents and solutions. Strong variation in the size of the "permeation channels" is observed in GO membranes depending on the solvent used, [45] concentration and chemical nature of dissolved molecules or ions, [17] shelf storage time, [40] and many other parameters related to the preparation of membranes. For example, the swelling in liquid ethanol was reported with significant scatter providing d(001) values in the range ≈11-17.7 Å. [10,16,46,47] Swelling in longer alcohols provides interlayer distances up to ≈50 Å. [10,48] There are also examples showing that the swelling of GO membranes can be significantly different compared to precursor graphite oxides. [16,17] Strong variation of interlayer distance in swollen GO membranes is a problem for nanofiltration applications, which require Swelling of graphene oxide (GO) membranes and bulk graphite oxide under confinement conditions is found to produce pressures up to ≈220 bar. Swelling pressure is important to take into account in many applications of GO membranes, but it has not been previously reported. Swelling pressures are typically measured only for bulk materials. However, it is demonstrated that even µm thick GO ...

Temperature-dependent swelling transitions in MXene Ti3C2Tx

“…The difference in swelling properties could be explained at the qualitative level by taking into account that the 2D sheets of MXenes are thicker and a lot heavier compared with GO sheets. Therefore, a lot of stronger hydration forces and swelling pressures 49 are required to move apart MXene layers. Alcohols are polar solvents due to the presence of the –OH group.…”

Thermal decomposition of hydrated graphite oxide: A computational study

“…Water molecules remain intact up to the disintegration point of the GO backbone, initiated by C-C bond breaking near adsorbed functional groups. At high enough temperatures, liquid water turns into vapor that exerts a significant pressure of GO layers, separating them in a process known as swelling [50][51][52]. Presence of oxygen in functional groups is the microscopic reason for GO -unlike graphene and graphitebeing hydrophilic.…”

Membranes prepared from graphene-based nanomaterials for water purification: a mini-review

“…the filtration process for long due to the swelling effect of the GO laminate in water. 59 To overcome the swelling effect of GO membranes, rGO has become appealing because, after reducing GO to rGO on the microporous support, the rGO nanosheets are held strongly by π-π interaction, resulting in the swelling of the NF membrane being minimized. 60 For instance, Li et al 26 reported the fabrication of rGO on a PES support via vacuum filtration followed by a heat treatment process.…”

“…Despite the high water production rate of GO-based membranes, the rejection rate still cannot sustain the filtration process for long due to the swelling effect of the GO laminate in water. 59…”