Enhanced Pervaporation Properties of PVA-Based Membranes Modified with Polyelectrolytes. Application to IPA Dehydration

Abstract

In this work, dense and supported pervaporation polyvinyl alcohol (PVA)-based membranes modified with poly(allylamine hydrochloride) (PAH) and poly(sodium 4-styrenesulfonate)(PSS)/PAH top nanolayers were synthesized. Two main points were investigated: the role of the polyelectrolyte PAH on water selectivity of the selective polymer matrix and the impact of the porous substrate based on polyacrylonitrile (PAN) and aromatic polysulfone amide (UPM-20 ® ), used to get supported high-performance membranes. Various methods of analysis (fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), atomic force microscopy (AFM), small-angle X-ray scattering (SAXS), porosity, contact angles, ultrafiltration) were applied to study the developed membranes. Transport characteristics of the developed membranes were studied in isopropanol dehydration by pervaporation. Obtained results are discussed in the light of the structure and physicochemical characteristics of these PVA/PAH membranes and the types of porous substrate. It was shown that the PAN-supported membrane with the selective layer based on PVA/PAH modified by 10 polyelectrolyte PSS/PAH bilayers possessed~4.5 times higher permeation flux with the same high selectivity level (99.9 wt % water in the permeate) for the dehydration of the isopropanol (20 wt % water) at 60 • C compared to the commercial analog PERVAP TM 1201.Polymers 2020, 12, 14 2 of 22 repellents, etc. Yet, for industrial application, the solvent must usually be anhydrous. In addition, this alcohol forms an azeotropic mixture with water (12 wt % water-88 wt % isopropanol) [8], which considerably hinders its dehydration via simple traditional methods of separation that entail a non-environmentally friendly process (addition of a third harmful organic reagent) and a high energy consumption (high temperature or low pressure, expensive equipment). Pervaporation is a promising and perspective technology for this task. Different types of pervaporation membranes (polymeric, inorganic, and composite) were developed for the dehydration of isopropanol [9][10][11][12]. Polymeric membranes find wider applications and are attractive because of the simplicity of their fabrication and lower price compared to inorganic membranes. The most popular polymer materials for dehydration are green water-soluble polymers, such as polyvinyl alcohol (PVA), chitosan (CS), cellulose, and sodium alginate [1,13,14], because these polymers possess high selectivity to water. However, the use of membranes based on these polymer materials requires additional cross-linking that, as a rule, leads to the decrease of permeation flux [12]. To improve the transport characteristics, additional bulk and surface modification methods can to be successfully applied, as previously shown [15][16][17][18][19][20].In this study, the selected material is polyvinyl alcohol, which is widely used for dehydration purposes due to its high water selectivity, good film-forming properties, and economic accessibility [1,4,21,22]. However, p...

Effect of the Formation of Ultrathin Selective Layers on the Structure and Performance of Thin-Film Composite Chitosan/PAN Membranes for Pervaporation Dehydration

“…One of the wide spread approaches to carry out the surface modification by LbL is via dip-LbL method. In our previous studies [ 15 , 32 , 33 ] it was demonstrated that changing various parameters of LbL assembly such as the selected pair of polycation–polyanion, the order of their deposition, the number of cycles, and additional bulk modification of membranes significantly affected the transport characteristics of the membranes.…”

Novel Membranes Based on Hydroxyethyl Cellulose/Sodium Alginate for Pervaporation Dehydration of Isopropanol

“…PAH, SA, and PSS were used as polyelectrolytes (PEL) in the form of solutions with the concentration of 10 −2 mol/L. The membrane was fixed in the device and alternately immersed in polyelectrolyte solutions for 10 min, and washed in water between them [ 68 ]. First, a membrane is immersed in polyanion solution of the PSS as it is based on the SA, which itself is a polyelectrolyte with positive surface charge, and then it was thoroughly washed with water.…”

“…Various filtration porous commercial or in-house substrates based on aromatic polysulfonamide, polysulfone, polyactrinitrile, etc. (consisting of mechanically rigid materials) are usually selected, depending on the separation task, to develop such supported membranes [ 12 , 68 ].…”

“…The application of layer-by-layer (Lbl) assembly for the deposition of polyelectrolytes (PEL) on supported membrane surface may be the additional approach for modulating properties of developed supported membranes. The improvement of transport characteristics of membranes may be related to the functionalization and changes in the hydrophilic/hydrophobic properties of the membrane surface, charge overcompensation mechanisms, and surface charge [ 68 , 69 , 70 ]. The Lbl technique of PEL deposition is a method of sequential deposition of polycations and polyanions on the membrane surface.…”

“…[ 71 , 72 , 73 ]. In the earliest works of our group, it was shown that a correctly selected PEL pair, the applying of several bilayers, and the order of their deposition by Lbl significantly improved the transport characteristics of the membranes based on polyvinyl alcohol for pervaporation dehydration of isopropanol [ 68 , 69 , 74 ].…”