Polymeric homogeneous composite membranes for separations in organic solvents

Abstract

A new generation of organic solvent nanofiltration (NF) composite membranes was prepared combining a support layer with a selective layer made both from the same polymeric material (P84 copolyimide). These membranes, homogeneous in composition, but composite in structure, were defined as polymeric homogeneous composite (PHC) membranes. The composite membranes have the advantage over the asymmetric ones that each layer can be optimized independently. Moreover, the use of the same material for the preparation of both, the selective and the support layer, ensures a high affinity between the two layers and increases the longterm stability of the composite membranes, reducing the possibility of delamination phenomena. In the design of the PHC membranes, a great attention was devoted to the support layer development. The effects of the composition of the casting solutions on the structure of porous P84 copolyimide membranes were investigated allowing to identify the conditions for the preparation of highly permeable, chemically, and mechanically stable P84 sponge like porous membranes. PHC membranes were prepared by coating and controlled solvent evaporation of a P84 solution on the optimized support crosslinked by reaction with a diamine (1,5diamino-2-methylpentane). Pure solvent permeation test and rejection experiments were carried out on the P84 supports and the corresponding PHC membranes in aggressive organic solvents like N-methyl-2-pyrrolidone and N,N-dimethyformamide, in which the original polymer was soluble. The PHC membrane resulted completely stable over long times (>96 h).

Sorption equilibria and diffusion of toluene, methanol, and cyclohexane in/through elastomers

“…). When the predominant flows in the mixtures 1 and 4 are analyzed it is easily foreseen that the transport of the components across the O‐ring forces the composition of the mixture to evolve towards the demixing zone, inherent to this ternary system . In the case of mixture 3, the ternary V E values found are higher than in the binary corresponding methanol + cyclohexane and bearing in mind that the flow of toluene is very high, and that this binary mixture presents a solubility gap in wide range of concentrations, the changes in the composition occurring on the mixture when the molar fraction of toluene decreases lead to volume changes that ultimately are the main responsible factor for the appearance of bubbles in the samples.…”

“…The loss of solvent through desorption is not an exact reversal of sorption, owing to the nonlinear structure of polymeric chains and to possible interactions polymer‐solvent. Permeation of chemicals within an elastomer may affect the mechanical performance of the material when exposed to aggressive organic chemicals, as in the case of O‐rings, a sealing commonly used to avoid or restrict mass leaking. Tests are generally performed by immersing a polymer sample in a pure solvent volume and kept under constant conditions, though real applications of polymeric materials often require contact with solvent mixtures.…”

Selective Separation of Organic Electrolytes by Neutralization Dialysis with Grafted Polyethylene Films

“…A variety of synthesized polymer membranes are involved in membrane-separation processes, such as energy saving, resources recovery [1], and environmental preservation mainly for removal of metal or inorganic ions such as K + , Ca 2+ , Mg 2+ , NO 3 , and SO4 2 [2][3][4] and organic electrolytes [5][6][7][8] and for desalination [9][10][11][12]. Most of these membranes are highly crosslinked in order to increase their mechanical stability and avoid excessive water swelling.…”

Protein mediated textile dye filtration using graphene oxide–polysulfone composite membranes

“…Several studies have been carried out for various applications in order to investigate such above mentioned characteristics of the polymeric membranes by preparation of composites. [1][2][3][4][5][6][7] However, it is still a challenge to produce ideal membranes which possess none of the above mentioned drawbacks.…”