Functional Hydrophilic Membrane for Oil–Water Separation Based on Modified Bio-Based Chitosan–Gelatin

In this study, we fabricated a modified biomaterial based on chitosan and gelatin, which is an intrinsic hydrophilic membrane for oil–water separation to clean water contamination by oil. Modification of the membrane with a non-toxic natural crosslinker, genipin, significantly enhanced the stability of the biopolymer membrane in a water-based medium towards an eco-friendly environment. The effects of various compositions of genipin-crosslinked chitosan–gelatin membrane on the rheological properties, thermal stability, and morphological structure of the membrane were investigated using a dynamic rotational rheometer, thermogravimetry analysis, and chemical composition by attenuated total reflectance spectroscopy (ATR). Modified chitosan–gelatin membrane showed completely miscible blends, as determined by field-emission scanning electron microscopy, differential scanning calorimetry, and ATR. Morphological results showed membrane with establish microstructure to further experiment as filtration product. The membranes were successfully tested for their oil–water separation efficiencies. The membrane proved to be selective and effective in separating water from an oil–water mixture. The optimum results achieved a stable microporous structure of the membrane (microfiltration) and a separation efficiency of above 98%. The membrane showed a high permeation flux, generated as high as 698 and 420 L m−2 h−1 for cooking and crude oils, respectively. Owing to its outstanding recyclability and anti-fouling performance, the membrane can be washed away easily, ensuring the reusability of the prepared membrane.

Study of Prepared α-Chymotrypsin as Enzyme Nanoparticles and of Biocatalytic Membrane Reactor

Biocatalytic kinetic effect of α-chymotrypsin enzyme has been investigated in its free and pretreated forms (it was covered by a very thin, porous polymer layer, called enzyme nanoparticle) as well as its immobilized form into pores of polysulfone/polyamide asymmetric, hydrophilic membrane. Trimethoxysilyl and acrylamide-bisacrylamide polymers have been used for synthesis of enzyme nanoparticles. Applying Michaelis-Menten kinetics, the KM and vmax values of enzyme-polyacrylamide nanoparticles are about the same, as that of free enzyme. On the other hand, enzyme nanoparticles retain their activity 20–80 fold longer time period than that of the free enzyme, but their initial activity values are reduced to 13–55% of those of free enzymes, at 37 °C. Enzyme immobilized into asymmetric porous membrane layer remained active about 2.3-fold longer time period than that of native enzyme (at pH = 7.4 and at 23 °C), while its reaction rate was about 8-fold higher than that of free enzyme, measured in mixed tank reactor. The conversion degree of substrate was gradually decreased in presence of increasing convective flux of the inlet fluid phase. Biocatalytic membrane reactor has transformed 2.5 times more amount of substrate than the same amount of enzyme nanoparticles and 19 times more amount of substrate than free enzyme, measured in mixed tank reactor.

Triethylene Glycol Dehydration by Thermopervaporation

A wide range of membranes (hydrophobic and hydrophilic) for the task of triethylene glycol dehydration by thermopervaporation was studied. The transport characteristics of the membranes using individual liquids (water, triethylene glycol) were determined in the thermopervaporation process with varying temperature of the feed flux (40-). The maximum water flux (3.7 kg/m2∙h) in all the studied temperature ranges was demonstrated by the commercial pervaporation hydrophobic PolyAn membrane. For the commercial hydrophilic membrane MDK-I water flux at 80 °С was 2.8 kg/m2∙h. During thermopervaporation of triethylene glycol in the studied temperature range, TEG flux through the membranes was not observed, which shows the advantage of this process for TEG dehydration. For the first time, experiments were provided using PolyAn membranes to removal water from TEG by thermopervaporation with porous condenser. The maximum permeate flux (1.9 kg/m2∙h) was achieved for the PolyAn membrane at a concentration of 70 % wt. TEG in water

Antimicrobial Assay on PVDF Nanofiber Membrane

Many researches concentrated on development of antimicrobial membranes for many applications such as air or water filtration. Disk diffusion was well-known conventional method for antimicrobial assay. However, this method is preferable to hydrophilic materials, where inhibition zone was easily observed. For hydrophobic materials, negative test was always shown, except increase in antimicrobial loading. In this study, glucose fermentation was introduced as a new method for antimicrobial assay. The survived and viable bacteria either at the surface or attached inside the membranes could ferment glucose resulting in acid production and changing color of indicator in the glucose solution from pale orange to pink. FU8M and FA8M nanofiber membrane, loading with AgNO3 and Benzalkonium chloride (0.3-1.0%) were used as hydrophobic and hydrophilic membrane, respectively. The water absorption of these membranes took 2 h and 2 min, respectively, showing that the latter membrane improved its wettability. It is found that FU8M membrane showed no inhibition zone when the antimicrobial loading less than 1%, whereas the FA8M membrane showed inhibition zone from 8.6-14 mm, depending on antimicrobial loading. However, when glucose fermentation method was used, membranes showed the positive test after 9 hours of incubation at the antimicrobial concentration of 0.5%. Hence, this new method can be used as antimicrobial testing for membrane with simple and cost effective.