Adaptation of bovine milk towards mares’ milk composition by means of membrane technology for koumiss manufacture

This study was carried out to determine the physical, chemical, microbiological and organoleptic properties of koumiss made from bovine milk. The bovine milk was modified according to the composition of mares’ milk using ultrafiltration, microfiltration and nanofiltration. Koumiss made from modified bovine milk and mares’ milk were compared. In order to assess options for a consistent fermentation, a starter culture, instead of the prevailing spontaneous flora in traditional manufacture of koumiss, was used. Key compositional factors modified were the contents of dry matter, mineral, protein and lactose and the casein-to-whey protein ratio. Koumiss made from modified bovine milk and by starter cultures was found to be very similar to koumiss from mares’ milk in terms of pH, titratable acidity, alcohol, proteolytic activity, apparent viscosity, and microbiological composition, when assessed both in the freshly made product and that after 15 days storage at 4°C.     

Color and COD retention by nanofiltration membranes

In the present study the application of the nanofiltration process was investigated mainly in the retention ofcolor and chemical oxygen demand (COD) present in textile industry wastewater. Nanofiltration experiments were carried out in a pilot unit, operating in crossflow. Three different types of spiral wound membranes, DK 1073, NF 45 and MPS 31 were used simultaneously in the same unit. The results of the tests showed that for color retention, the values were around 99% for the DK 1073 and NF 45 membranes and the 87% for COD retention for the DK 1073. The permeate flux for the different wastewaters varied from 30.5 to 70 L/h.m². Fouling was observed in all membranes due to the accumulation of molecular species close to the filtering surface. The process was efficient and promising for the reuse of wastewater from this type of industry.     

Reactive dye removal in dye/salt mixtures by nanofiltration membranes containing vinylsulphone dyes: effects of feed concentration and cross flow velocity

In this study, DS5 DK type nanofiltration membranes were tested to recycle the reactive dye bath effluents. Reactive black 5 (RB5), reactive orange 16 (RO16), reactive blue 19 (RB19) and NaCl were used in the experiments to prepare the synthetic dye and salt mixtures. Effects of feed concentration, pressure and cross flow velocity on the permeate flux and color removal were investigated. Permeate flux increased with increasing pressure for all NaCl solutions. Dye concentration had a significant effect on flux values. Under the fixed NaCl concentrations the flux decreased with increasing dye concentrations. Dye rejections greater than 99% were achieved. Permeate was almost colorless. A gel layer formed by the rejected dye on membrane surface operates as a resistance to the permeation of dyes due to complete rejection of high molecule weight dyes, especially for the low salt concentrations. The presence of salt concentration has an interesting effect on color removal. Color removal decreased with increasing salt concentration. Cross flow velocities had also a significant effect on flux values. The dye formed agglomerates at high NaCl concentrations. High cross flow velocities decreased this effect.     

Modelling of membrane nanofiltration—pore size distribution effects

The effects of log-normal pore size distributions on the rejection of uncharged solutes and NaCl at hypothetical nanofiltration membranes have been assessed theoretically. The importance of pore radius-dependent properties such as solvent viscosity and dielectric constant is increased by the introduction of a pore size distribution in calculations. However, the effect of porewise variation in viscosity is less apparent when considered at a defined applied pressure rather than at a defined flux, showing a further advantage of basing theoretical analysis of nanofiltration in terms of applied pressure.Truncated pore size distributions gave better agreement than full distributions with experimental rejection data for a Desal-DK nanofiltration membrane. Such truncation is in agreement with the findings of atomic force microscopy (AFM). Analysis of uncharged solute rejection data alone could not give useful information about membrane pore size distribution. Neither could such a distribution be obtained quantitatively directly from AFM images. However, use of the shape of the distribution obtained by AFM in conjunction with experimental rejection data for an uncharged solute allows calculation of corrected distributions. Importantly, incorporation of such a corrected pore size distribution in calculations of NaCl rejection gave better agreement with experimental data, compared to calculations assuming uniform pores, at high pressure, the region of industrial interest.     

Effect of operating conditions in removal of arsenic from water by nanofiltration membrane

The removal of arsenic from synthetic waters and surface water by nanofiltration (NF) membrane was investigated. In synthetic solutions, arsenic rejection experiments included variation of arsenic retentate concentration, transmembrane pressure, crossflow velocity and temperature. Arsenic rejection increased with arsenic retentate concentration. Arsenic was removed 93-99% from synthetic feed waters containing between 100 and 382 μg/L as V, resulting in permeate arsenic concentrations of about 5 μg/L. Under studied conditions, arsenic rejection was independent of transmembrane pressure, crossflow velocity and temperature. In surface water, the mean rejection of As V was 95% while the rejection of sulfate was 97%. The co-occurrence of dissolved inorganics does not significantly influence arsenic rejection. The mean concentration of As in collected permeated was 8 μg/L. The mean rejection of TDS, total hardness and conductivity were 75, 88 and 75% respectively.     

Counter-current Electrophoresis

Abstract

Historical development, principal operation, different ways of experimental realization, and typical examples of application of countercurrent electrophoresis are reviewed. The separation process is principally capable of being applied to all types of ions, as far as any difference is shown in their ionic behavior. Different types of columns can be adapted to varying amounts of substance from approximately 10^?6 mole up to several moles (in the laboratory scale). The production of high purity components and the use of the column as an absolute ion filter are further possible applications.     

纳滤膜的污染成因及防止技术研究

结合科学实验研究成果分析了纳滤膜无机污染、有机污染和微生物污染三种主要污染的机理。首次提出了动态有机污染模型理论,并就纳滤膜污染的防止提供了一些有效可行的技术处理方案,为纳滤膜的推广应用提供参考。     

Preparation of yttria-stabilized ZrO2 nanofiltration membrane by reverse micelles-mediated sol-gel process and its application in pesticide wastewater treatment

8 mol% yttria-stabilized ZrO₂ (8YSZ) nanofiltration (NF) membranes were prepared from size-controlled spherical ZrO₂ nanoparticles with an average diameter of ˜10 nm and a particle roundness value greater than 0.90, and the nanoparticles were efficiently fabricated by a reverse micelles (RMs)-mediated sol-gel process. It was found that yttria doping not only suppressed the tetragonal to monoclinic (t-m) phase transition, ensuring the membranes integrity, but also decreased the tetragonal grain size, increased the specific surface area, narrowed the pore size distribution and thus optimized the NF performance. The as-prepared 8YSZ NF membranes with a thickness of ˜260 nm exhibited high NF performances, while the pure water permeability and molecular weight cut-off (MWCO) were 3.9-4.2 L m⁻² h^-1 bar^-1 and 800 ± 50 Da respectively. In the treatment of pesticide wastewater, the removal rate of carbofuran by 8YSZ NF membranes was more than 82%, while the maximum removal rate could reach 89%. Furthermore, the contaminated membranes could be restored as ever after alkali wash and low-temperature calcination, implementing multiple reuses.     

Recent advances in nanofiltration,reverse osmosis membranes and their applications in biomedical separation field

In the face of human society’s great requirements for health industry, and the much stricter safety and quality standards in the biomedical industry, the demand for advanced membrane separation technologies continues to rapidly grow in the world. Nanofiltration(NF) and reverse osmosis(RO) as the highefficient, low energy consumption, and environmental friendly membrane separation techniques, show great promise in the application of biomedical separation field. The chemical compositions, microstr...     

Rejection of As(III) and As(V) from arsenic contaminated water via electro-cross-flow negatively charged nanofiltration membrane system

A specially designed electro-cross-flow nanofiltration (NF) membrane system was used for this investigation. To enhance the rejection of arsenic ionic species like H₂AsO₄⁻, a NF membrane having a negative surface charge was fabricated via the interfacial polymerization process. The membrane was characterized by SEM, AFM, surface charge density, molecular weight cut-off (MWCO), total and skin thickness and pure water flux. The parameters that affected the rejections of As(III) and As(V) were studied; they included the initial arsenic concentration, the applied potential, pH of the feed, the cross-flow filtration pressure and the presence of different salts in the feed. Among those parameters, the pH of the feed greatly affected As(V) rejection; As(V) ([As(V)]_o = 1000 ppb) rejection was increased from 72.3 to 98.5% when pH of the feed was changed from 3.0 to 10.0. This might be due to the fact that higher pH enhanced the formation of negative divalent anion like HAsO₄²⁻ which should be rejected more effectively by the negative surface charge of the NF membrane. Beside the effect of the negative surface charge of the membrane, applied potential increased the As(V) rejection by 48.2% when the applied potential was increased from 0 to 2.0 V for a feed containing 1000 ppb initially. For the same change of applied potential rejection of As(III) was increased from 52.3 to 70.4%; this might be the result of the formation of anionic species like H₂AsO₃⁻ from the neutral molecule of H₃AsO₃ by the applied potential.