All-polymer solar cells (all-PSCs) exhibiting superior device stability and mechanical robustness have attracted considerable interests. Emerging polymerized small-molecule acceptors (PSMAs) have promoted the progress of all-PSCs exceeding power conversion efficiency...
The presence of thin aqueous films
and their stability have a profound
effect on the interactions between oil/brine/rock interfaces. In a
previous report, we proposed that hydration forces, originating from
the overlap of hydrated layers of different surfaces in the presence
of sodium chloride, played an important role at short range. In the
present work, divalent ions were introduced to the liquid films and,
the mechanisms in improving oil recovery from low-salinity brine and
the low-salinity effect at the molecular level were revealed. Through
a direct force-measuring technique of chemical force microscopy (CFM),
the functionalized atomic force microscopy (AFM) tips felt a solid
surface to mimic the oil/rock interactions in brine. It was found
that not only did the van der Waals and electrostatic forces have
a great effect on this process due to the interactions between the
charged interfaces of oil/water and water/solid, but also some important
additional interactions appeared at short range under a variety of
salinity concentrations or compositions. Taking into account the important
role of structural forces under a small distance, the force profiles
were fitted well with the theory of extended Derjaguin–Landau–Verwey–Overbeek
(denoted by EDLVO) through a double-exponential or Gaussian model.
Interestingly, low adhesion appeared in the presence of sodium sulfate,
because hydration forces contributed to the resultant force depending
on the intrinsic properties of the solvent or solute molecules, while
in the presence of calcium chloride, high adhesion emerged due to
the dispersion interaction between water and hydrocarbon molecules,
as well as the reorientation or restructuring of water molecules with
tiny breakage of hydrogen bonds. Therefore, on the basis of the EDLVO
theory, additional forces were suggested to play an important part
in short range, proposing a better understanding of the effect of
divalent ions on the thin liquid films in the process of increasing
oil recovery.
The objective of this study was to develop new nanofiltration (NF) membranes capable of providing significantly greater water permeability and higher rejection of water contaminants compared to state-of-the-art NF membranes. The active layer of the new NF membranes is prepared with rigid star amphiphiles (RSAs) synthesized as part of this study. Performance characterization for a first generation of RSA membranes in a bench-scale apparatus reveals that most of the new membranes provide water permeability of 1.3-3.1 times that of two commercial NF membranes with polyamide active layers while providing comparable rejection of the organic contaminant surrogate Rhodamine WT. However, the rejection of arsenious acid (H3AsO3) by most new NF membranes was found to be lower than that by the two commercial NF membranes tested. Future research efforts of this study will focus on exploring if H3AsO3 rejection could be significantly increased, without negatively affecting water permeability and organic contaminant rejection, by addition of various chemical groups to RSA hydrophobic cores and hydrophilic branches, and by RSA cross-linking.
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