Membrane fouling affecting factor

As a result of these improvements in membrane performance, the major factors determining system performance have become concentration polarization and membrane fouling. All membrane processes are affected by these problems, so... 

The main factors that affect the separation efficiency and yield in the membrane separation of beer are beer composition, membrane characteristics, process parameters, and membrane fouling. 

The efficiency of UF in whey processing is limited by a few factors, the most significant of which are concentration polarization and membrane fouling [6,39 1]. While both factors, which adversely affect permeate flux, may be aggravated by protein-protein and membrane-protein interactions [23,40,42-44], they may also be minimized by choosing suitable membrane material and configuration as well as the appropriate process conditions such as TMP, feed velocity or recirculation rate, temperature, and the chemical environment of whey [42,45,46]. 

As noted by Matthews ( ), the studies on membrane fouling published so far would suggest that some of the protein components causing fouling are affected by such factors as pH, ionic strength and ionic composition (particularly calcium concentration). Interactions between the various solutes are also Important, as shown by Peri and Dunkley (18). Their results on the reverse osmosis of solutions of whey components showed little Indication of fouling only whole whey gave a steady decline In flux rate with time. 

Membrane fouling was not a significant factor affecting UF flux periodic cleaning with sodium hypochlorite effectively removed any foulants present on the membrane surface. 

The main factors affecting the severity of membrane fouling by T1O2 particles were found to be (Table 6.2) ... 

Zhang, W Park, B. C., Chang, Y. K., Chang, H. N., Yu, X. J., Yuan, Q. (1998). Factors affecting membrane fouling in filtration of Saccharomyces cerevisiae in an internal ceramic filter bioreactor. Bioprocess Engineering, 18, 317—322. 

Solute properties (conformation, hydrophobic interactions, charge, etc.), operating conditions (cross-flow velocity, pressure and temperature) and membrane material are all factors which affect membrane fouling. 

Factors that affect fouling with NOM-calcium complexes include permeate flux and cross flow rate (see Chapters 3.3 and 9.4). At higher flux though the membrane, the concentration of calcium increases in the concentration polarization boundary layer at the membrane surface, as described above. Lower cross flow rates also increase the concentration of calcium in the boundary layer. The increases concentration of calcium at the membrane surface enhances the fouling of the membranes by the NOM-calcium aggregates.5... 

Another factor that has been shown to significantly affect flux and fouling is the hydrophilic character of the membranes [4,8-12]. Water spreads over the surface of a hydrophilic membrane but not on a hydrophobic membrane. The membrane material determines its hydrophilicity, which is typically evaluated by measuring the contact angle at a membrane-water-air interface. Cellulose and hemicelluloses, which form the main part of wood and paper, are extremely hydrophilic. Wood extractives such as fatty and resin acids, on the other hand, have hydrophobic characteristics and, therefore, they are found more on fouled and used hydrophobic membranes than on hydrophilic ones (Figure 35.1) [9,13]. 

B. A. Winfield, A study of the factors affecting the rate of fouling of reverse osmosis membranes treating secondary sewage effluent. Water Research 13, 565-569 (1979). 

Conventional enzyme electrodes employ disorete-maorosoopio membranes to overcome problems associated with interferences, enzyme immobilization, and electrode fouling. While these types of enzyme electrodes have been commercially developed, there are some limitations with this approach. Some sensors use three relatively thick membranes, resulting in a slow smd complex diffusion path for reactants reaching the enzyme and hydrogen peroxide reaching the electrode. Slow diffusion in this type of system adversely affects the response and recovery time, decreasing sampling rate. Each sensor must be individually constructed, and this construction technique is limited to two-dimensional surfaces. In addition, for sensors that have complex and slow diffusion paths, rates of diffusion must remain constant, otherwise calibration of the biosensor, and more important the maintenance of calibration, are difficult. A variety of factors can influence rates of diffusion, and consequently the performance of the enzyme layer and the performance of the sensor. These complicated, and most often uncharacterizable, properties have made the development of roost biosensors difficult. 

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