Surface-modified membranes

Langlotz P and Kroner KH. Surface-modified membranes as a matrix for protein purification. J. Chromatogr. 1992 591 107-113. 

Kim, J.Y., Lim, D.Y., 2010. Surface-modified membrane as a separator for lithium-ion polymer battery. 

Khayet, M., Treatment of radioactive wastewater solutions by direct contact membrane distillation using surface modified membranes, Desalination, 321, 60, 2013. 

Hilal et al. [17] studied the surface structure of a poly(ether sulfone) membrane, the surface of which was modified by depositing a molecularly imprinted polymer layer. They measured the pore size and surface roughness by AFM. It was reported that an increase in the degree of modification, given by the weight of the imprinted polymer layer, led to a systematic decrease in pore size and an increase in surface roughness. As the pore size decreased, the relative water flux (the ratio of the water flux of the surface-modified membrane to that of the unmodified membrane) also decreased. In other words, the flux decreased as the surface roughness increased. 

The rest of this chapter is organized as follows. In Sect. 7.2, we describe the synthesis of surface-modified membranes. We then describe the characterization techniques used and the permeation experiments as well as the methodology of the ab initio quantum simulations using density functional theory (DFT). The characterization and permeation results are then presented and discussed. Finally, we present and discuss the results from DFT calculations. 

Case Study Surface-Modified Membranes Applied for the... 

REMOVAL OF RADIONUCLIDES WITH SURFACE-MODIFIED MEMBRANES LABORATORY EXPERIMENTS UF AND MD... 

For example, during the prolonged exposure of the PAN membrane to 1 A/ NaOH, the surface nitrile groups turned into carboxylic groups (Bryjak et al. 1998). The modified membranes were less prone to fouling with BSA with a reduction in the average pore diameter of about 80% for the untreated membranes and 20% for the surface-modified membranes. 

Atomic force microscopy (AFM) images of the unmodified membrane NFPESIO and all of the surface-modified membranes were taken in an air environment at room tanperature and at different locations across each membrane sample. Figures 5.23 and 5.24 show examples of the three-dimensional AFM images obtained. 

Comparison of Polymer Membranes with the Surface-Modified Membrane... 

Surface modified membrane is a term used for membranes with altered makeup and configuration, though the basic properties of their underlying materials remain intact. 

Figure 53 illustrates the effect of hydrophilic cathode surface modification. The surface-modified membrane (Type B) has a lower cell voltage than the conventional membrane (Type A). The voltage of the surface-modified membrane decreases linearly with decreasing gap size. With these advanced membranes, so-called zero-gap cells have been made possible, and the ohmic loss in electrolytes has been reduced to a minimum. 

Rahbari-Sisakht et al. [54] investigated the effect of novel surface modifying macromolecules (nSMMs) on the morphology and performance of PSf hollow-fiber membrane for CO2 absorption. The performance of surface-modifled membrane in contactor application for CO2 absorption through distilled water as absorbent was studied. The results show that surface-modified membrane had higher performance compared to plain polysulfone membranes. With the membrane prepared from SMM in the spinning dope, a maximum CO2 flux of 5.8 X 10 mol/m s was achieved at 300 ml/min of absorbent flow rate, which was almost 76% more than the other membrane. In a long-term stability study, the initial flux reduction was found to be about 18% after 50 h of operation of the surface-modified membrane. 

The described redox system was used to generate starting radicals for graft polymerization of AA and other hydrophilic monomers on the surface of CA membranes [73]. It was shown that despite the gradual decrease of the flux, the surface-modified membranes had a lower protein sorption and a better and more reversible flux recovery after cleaning [74]. 

A similar approach was used for the in situ preparation of NF PE8 membranes containing hydrophilic functional groups such as 8O3H, COOH, or C(= 0)NH2 [75]. Testing the modified and unmodified membranes over a period of 30 days demonstrated that surface-modified composite membranes have better fouling-resistance characteristics. In the case of the unmodified membranes, the flux decreased from 41.65 to 19.21 1/m h, whereas for the surface-modified membranes under similar conditions, the flux reduced from 46.75 to 31.62 Fm%. However, in the case of NF... 

UF PES membranes with negatively charged sulfonic acid groups on the surface were obtained by the filtration of an aqueous solution of PSS for about 100 min using a dead-end filtration cell [108], It was shown that thin porous membranes are primarily modified only on the top surface because the PSS macromolecules are not able to enter the pores. However, for membranes with wider pores, PSS permeation resulted in the formation of charged groups on both the surface and pore walls of the membrane. The major difference between the modified and unmodified membranes was found in their flux recovery after UF of the PEG and dextrans solutions. Flux recovery ratios of >90% were obtained for the modified manhranes compared with 55% for unmodified membranes. Thus, the surface-modified membranes have better cleanability and antifouling characteristics than the base manbranes. 

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