Selective Intercalation of Graphite Oxide by Methanol in Water/Methanol Mixtures

Abstract

Graphite oxide is selectively intercalated by methanol when exposed to liquid water/methanol mixtures with methanol fraction in the range 20–100%. Insertion of water into the GO structure occurs only when the content of water in the mixture with methanol is increased up to 90%. This conclusion is confirmed by both ambient temperature XRD data and specific temperature variations of the GO structure due to insertion/deinsertion of an additional methanol monolayer observed upon cooling/heating. The composition of GO–methanol solvate phases was determined for both low temperature and ambient temperature phases. Understanding of graphite oxide structural properties in binary water/methanol mixtures is important for understanding the unusual permeation properties of graphene oxide membranes for water and alcohols. It is suggested that graphite oxide prepared by Brodie’s method can be used for purification of water using selective extraction of methanol from water/alcohol mixtures.

The structure of graphene oxide membranes in liquid water, ethanol and water–ethanol mixtures

“…The trend in structural modifications of B-GO membranes is similar to H-GO: addition of ethanol (up to 90%) to water results in progressively smaller inter-layer distance (Figure 7b). Similarly to previously published data for B-GO powder immersed in water/methanol 30 , B-GO powder showed no change in the cell parameter for concentrations of ethanol in the range 10-100%. The membranes did not follow this trend, exhibiting larger layer separation (compared to powders) for concentrations below 60% and smaller separations for ~70-100%.…”

“…The membranes did not follow this trend, exhibiting larger layer separation (compared to powders) for concentrations below 60% and smaller separations for ~70-100%. Therefore, it can be concluded that membranes do not show selective intercalation by ethanol when exposed liquid water/ethanol mixtures which could be expected looking only at powder data 30 . No selective intercalation of GO membranes by methanol from water/methanol mixtures was also found (Figure 8S in SI).…”

“…Humidity-dependent studies of graphene oxide membranes 21 and paper-like materials 20 structure have been reported recently, but no structural data are available for liquid solvents. Hydration and solvation properties of precursor powder graphite oxides have been reported in our earlier studies 11,[28][29][30][31][32][33] but it is an open question to which extent these results can be applied to the GO membranes. The most striking observation is that Hummers graphite oxide powder can be intercalated by three monolayers of water (interlayer distance d(001)=12.4Å at ambient temperature), 12,35 2-3 monolayers of methanol or ethanol (d(001)=15.5Å) at ambient conditions and up to four monolayers at low temperatures (d(001)=20.6Å) 33 .…”

“…According to earlier powder studies, intercalated water and alcohols are responsible for distinctly different structural anomalies in certain temperature intervals [29][30] . However, both H-GO and B-GO revealed absence of such anomalies and almost flat temperature dependence of inter-layer distance for two studied water/ethanol compositions, Figure 8.…”

Graphite oxide swelling in molten sugar alcohols and their aqueous solutions

“…[40,42,45] Moreover, selective intercalation of methanol from water/methanol mixtures was observed for BGO. [46][47] In contrast, HGO shows no selectivity in sorption from binary mixtures, no phase transitions and absence of clearly distinct phases with certain amount of intercalated solvent. The gradual changes in the "inter-layer distance" provided by position of (001) reflection in XRD are likely to be explained by the effects of interstratification [48] and intrastratification.…”