Study the transport properties of anion and cation exchange membranes toward various ions using chronopotentiometry
The transport properties of various anion and cation exchange membranes were studied in different electrolyte solutions using chronopotentiometry technique to get insight about the influence of the counter ion on the transport properties of the membranes. The investigated samples include heterogeneous ion exchange membranes varying in the functionality of fixed charged groups, physical properties of the polymer and the preparation procedure. Chloride and nitrate were investigated as counter-ion in their sodium salts for anion exchange membranes while sodium, calcium, potassium, and magnesium were selected as counter-ion in their chloride salts to study cation exchange membranes transport properties. First, the current – voltage curve of an ion exchange membrane in a given solution was recorded to obtain the limiting current, then a constant current above the limiting current was used for chronopotentiometry measurement. In all the studied membranes the potential across the membrane remained constant for a time interval called the transition time , when a constant current was applied. Then the potential increased rapidly to reach the steady state potential. The permselectivty and the transport number of a membrane were calculated using the corresponding transition time.
The study of dynamic milk ultrafiltration performance influenced by membrane molecular weight cut off
The effect of membrane molecular weight cut off (MWCO) at three levels (10, 20 & 50 kD) on dynamic behavior of permeate flux (JP), hydraulic resistances (total hydraulic resistance, RT; reversible fouling resistance, Rrf; irreversible fouling resistance, Rif and membrane hydraulic resistance, Rm) and milk solutes rejection (protein, RP; fat, RF; lactose, RL; minerals, RM and total solids, RTS) are studied for the ultrafiltration of milk. Experiments are carried out using the pilot plant UF membrane system equipped with a spiral wound module and a polysulfone amide membrane. A three-stage strategy based on a resistance-in-series model (boundary layer-adsorption) was used to determine the different hydraulic resistances. The results showed that the JP decreases greatly with increasing the process time, but the JP values obtained for 20 kD were considerably higher than 10 kD & 50 kD during the whole process. RT increased during operation at all levels of MWCO, but the hydraulic resistance values for 50 kD were significantly greater than 10 & 20 kD.  Results for milk solutes rejection showed that the RP and RF are almost constant with process time at the corresponding MWCO, whereas the RL, RM and RTS significantly increased.
Growth from Solutions
Growth from solutions is the crystallization of a compound whose chemical composition differs markedly from that of the initial liquid phase. Commonly used solvents are water, multicomponent aqueous or nonaqueous solutions, and melts of some chemical compounds. Differentiations are made based on growth temperatures and on the chemical nature of the solvent. In growth from low-temperature aqueous solutions, the temperatures generally do not exceed 80–90°C; in growth from superheated aqueous solutions (hydrothermal method), they reach 800°C, and in growth from salt melts (molten-salt, flux, or fluxed melt growth), they usually do not exceed 1200–1300°C, but sometimes reach 1500°C.