Pattern formation on the surface of cellulose membranes prepared by phase inversion technique

Abstract

1335In conclusion, the spinodal curve can be used to set the bounds on vapor pressure in equation of state calculations. If a cubic equation of state is used, the method proposed here yields an initial estimate for P,,, that is close to the final converged value and does not require any iterative procedures. The proposed method should also work for higher order equations although, owing to the necessity of solving the equation of state for the volume V', a simpler strategy, such as that described in the previous paragraph, may be desirable. AcknowledgmentThe author thanks reviewer 2 for his comments.

Control of Membrane Surface Roughness and Pattern Wave Length by Changing the Nonsolvent (Water) Influx Rate

“…The differences in the S/N exchange kinetics are expected to have the following effects on the nanopattern of the membrane surface. In the earlier paper it was argued that, during the S/N exchange in WPIP, the volume expansion of the upper layer of the cast polymer solution results in pattern formation when the expansion of the swollen layer works as compressive force and the latter force is stronger than a critical value [13]. The phenomenon is shown in Figure 2 schematically as the upper surface that is forced to be bent upward.…”

“…In the case of P with intermediate hydrophobicity/-philicity, neither shrinkage nor swelling occurs, resulting in a small amplitude. Regarding the wavelength, it depends on the characteristic length, which in this case is considered to be either the thickness of the skin layer for the hydrophobic membrane or the thickness of the swollen gel layer for the hydrophilic membrane [13]. The skin layer of the hydrophobic membrane is formed fast upon contact of the cast film surface with N and its thickness does not depend very much on N influx rate.…”

“…Although a number of reports are found in the literature on the effect of the surface roughness, either desirable or undesirable, on the membrane performance, the reports on the control of the nanoscale roughness by the choice of membrane material and membrane preparation conditions are scarcely found. As early as 1988, Okada et al studied the pattern formation on the cellulose membrane surface [13]. The patterns were formed in macroscopic micrometer ( m) range and were characterized by the amplitude and wavelength.…”

Developing new CTA/CA-based membrane containing hydrophilic nanoparticles to enhance the forward osmosis desalination

“…Thermodynamics and kinetics are two dominating factors which influence the membrane formation. The former is related to the phase equilibrium between components in the system, and the latter is related to the mutual diffusivities between them [46]. Because of good affinity to water as well as enhancing the instability of solution to non-solvent, boehmite can accelerate phase inversion.…”