Many models are proposed to predict flux decline in Membrane ultrafiltration, but since these models have limiting assumptions, they are not applicable to all solutions. The present study modeled fouling in skim milk concentration process using proposed equations for the main mechanisms of fouling, including complete blocking mechanism, intermediate blocking mechanism, standard blocking mechanism and cake filtration mechanism. These models then were compared with experimental data at 50, 100, 150, 200 and 250 kPa trans-Membrane pressures to investigate the effect of trans-Membrane pressure on flux decline.Based on the results obtained here, it was found that predictions of cake filtration model were in good agreement with experimental data, while those of standard blocking model were in poor agreement.Complete blocking mechanism was not capable of predicting flux data using CurveExpert Professional.With decreasing trans-Membrane pressure, the differences between experimental data and models decreased. The results also showed that the second mechanism responsible for flux decline was intermediate blocking model. In fact, cake filtration mechanism and intermediate blocking mechanism are the two main mechanisms responsible for fouling in skim milk concentration process. Moreover, the results obtained from modeling of resistance showed that the cake layer resistance was the main resistance to flow, which was in accordance with what we had expected from accumulation of protein and fat molecules on the surface of the Membrane. All in all, the cake filtration mechanism is the main mechanism for predicting flux decline, and it is expected that this model in combination with intermediate blocking model, would result in the best prediction of fouling phenomena in milk concentration process.

In this paper, results obtained from investigations on a polysulfon ultrafiltration Membrane fouled by precipitation of milk components have been presented. Operating conditions such as temperature, pressure and crossflow velocity, which could play an important role in the fouling processes, were selected for the studies. Results show that dimensionless fouling resistance increase with increasing temperature and pressure and decreases cleaning agents on recovery of the fouled Membrane has also been studied. Results show that a combination of sodium dodecyl sulfate and sodium hydroxide can be used as a cleaning material to reach the optimum recovery of the polysulfon Membrane used in milk concentration industries. A mixture of sodium hypocholorite and sodium hydroxide shows acceptable results, while washing with any acidic material has no considerable result.

One of the most important factors affecting Membrane formation via phase inversion method is the viscosity of the polymer solution. In this research, with the aim of providing a solution to predict the performance of polymeric Membranes based on viscosity data, the influence of dope solution temperature and casting speed on the viscosity of PVDF solution were investigated. For this purpose, the viscosity of PVDF/DMAc solution with LiCl and PEG additives was measured at the temperature range of 10-50 ° C and atmospheric pressure with a precise rheometer. The performance of PVDF ultrafiltration Membrane with composition of PEG 3 wt. % and LiCl 7 wt. % was evaluated and an empirical model using response surface methodology and central composite design was developed to predict Membrane permeability and rejection based on viscosity data and two variables of solution temperature and casting speed. Scanning electron microscopy, pure water permeability, and Membrane rejection tests were used to characterize the Membranes. The results show that the model is in good agreement with the experimental data and based on the results, the casting speed of 1. 2 m/min and the temperature of the polymer solution at 50 ° C are the optimum conditions for Membrane fabrication to obtain the Membrane with maximum flux and rejection.

Whey, as a strong environmental pollutant, is produced along the production of cheese and contains about 50% of the valuable nutrients of milk. The Membrane-based separation process is one of the most fascinating technologies for concentration and purification of whey proteins in the dairy industries; using this technology makes fewer damages to the nutrients of whey. In addition, separation of the valuable compounds of whey makes less environmental problems. In this study, three different nanostructure PES hollow fiber Membranes with different characterization and pore sizes have been used and their intrinsic resistances were measured; the effect of temperature and pressure on fouling resistances and the effect of temperature on the permeation flux, protein rejection, and lactose permeation were studied. The results showed that permeation flux increases with increase in temperature. The intrinsic resistance and fouling resistances of the Membranes increase with a decrease in pore size. The fouling resistance increases by pressure even though the intrinsic resistance of the Membrane doesn't change.

In this paper, the effect of Vapor-Induced Phase Separation (VIPS) time on the morphology and performance of poly (phenyl sulfone) Membranes was investigated. 14 wt. % dope solutions were employed for Membrane fabrication. After casting the solution, the formed polymeric film was exposed to humid air for certain times to form a porous structure. Morphology and performance of Membranes were characterized by Scanning Electron Microscopy (SEM), pore size distribution, pure water flux, and Bovine Serum Albumin (BSA) retention. Pore size distribution results showed that by an increase in VIPS time, the pore size of the Membrane was increased, and SEM images showed that with increasing VIPS time, the thickness of the dense skin top layer decreased, also the surface of the Membranes at first became smooth and then changed to rough. Moreover, by increasing the VIPS time, the pure water flux of the prepared Membranes increased from 17. 12 to 37. 61 L/m² . h. The performance of the fabricated Membranes for retention of BSA indicated that with increasing the VIPS time, the retention of BSA decreased gradually from 71. 3 to 52. 3% but the flux increased more sharply from 6. 94 to 17. 36 L/m² . h. Generally, vapor induced phase separation technique is an effective method that could be applied for fabricating Membranes with different characteristics for different applications from one dope solution. If a Membrane with antifouling features is required, low VIPS time should be applied and if a high flux Membrane is desirable, high VIPS time should be employed.

In this study, first, the water purification process was modeled by the hybrid of direct osmosis Membrane and ultrafiltration, then the current system was compared with experimental results in terms of quality control and costs. In the direct osmosis process, a highly concentrated sodium polyacrylate solution was used as the draw solution. When the FO side of the hybrid Membrane met wastewater, seawater, or saltwater, clean water was drawn through the FO Membrane into the SPA solution. Then, the clean water was removed from the SPA solution through the UF Membrane by applying pressure, which can be hydraulic or mechanical, less than 1 bar. Modeling was done to prove the validity of the design concept. Some model equations were extracted to simulate the performance of the hybrid Membrane, and the experimental data were analyzed based on the model equations. It is believed that this method allows the production of RO quality water at a UF pressure much lower than the RO pressure and thus leads to a significant reduction in energy consumption for water production. It was noticed that more water (than the calculated value) could be drawn to the SPA solution when the CSPA,0 was<15.75 wt% while less water was drawn when CSPA,0 was>15.75 wt%.