Temperature membrane extraction

The effect of temperature deserves special mention since it represents a major ndvanlage for the liquid-membrane process.9 9 Figure 19.4-5 compares the influence or temperature on extraction of uranium by the SX and LM techniques. In the case of liquid membraues. extraction efficiency increases with tempemiure... 

The temperature of extraction is limited by the temperature of destruction of the membrane fiber or by the temperature that allows a high solubility of water. In Ref. 28, an increase of the extraction yield with increasing temperature in the range between 10 and 50°C was observed due to the increase of the diffusion coefficients of analytes in the silicone fiber. Higher temperatures had a negative effect because higher amounts of water penetrated the membrane. 

NDSX of uranium was carried out using di-2-ethylhexylphos-phoric acid (HDEHP) as the extractant [39]. The effects of U(VI) and hydrogen ion concentrations in the feed solution, HDEHP concentration in organic phase, flow velocities of aqueous and organic phase, and temperature on extraction rate of U(VI) were examined. The extraction rate of U(V1) followed the first-order rate kinetics with respect to U(V1) concentration in aqueous phase. The extraction of U(V1) was linearly influenced by the flow velocity and its concentration in the feed solution, while a saturation effect was observed with pH and HDEHP concentration. Mass transfer resistance was mainly observed in the aqueous phase, while membrane resistance was ignored, suggesting possible application of NDSX for effective U(V1) mass transfer. 

Accelerated solvent extraction (ASE), focused microwave soxhiet extraction (FMSE), immuno affinity cleanup (im-Cu), liquid-liquid extraction (LLE), low-temperature lipid precipitation (LTLP), matrix solid-phase dispersion (MSPD), microwave-assisted extraction (MAE), nanofiltration (NF), pressurized fluid extraction (PEE), single drop microextraction (SOME), solid-phase extraction (SPE), solid-phase microextraction (SPME), steam distillation (SD), stir bar sorptive extraction (SBSE), surpercritical fluid extraction (SFE), subcritical fluid extraction (ScFE), supported liquid membrane extraction (SLME), ultra-sonication (US), size exclusion chromatography (SEC), liquid chromatography-fraction collection (LC)... 

For the accounting of promastigotes adhered to the membrane, the membrane extraction medium was performed by washing with a saline phosphate solution with pH 7.0 for the disconnection of protozoans, in a totally sterile and temperature-controlled environment. Subsequently, the membranes were reintroduced in order that the adsorption process is restarted, until the next third hour counting. 

When the enrichment factor is below 1, the prepared analyte in the sample is diluted, while a factor above 1 means that the analyte is enriched. Enrichment can be obtained simply by reducing the sample size using temperature or vacuum to evaporate the solvent. In this case, the analyte should not be thermolabile. Other more elegant techniques that both enrich the analyte and eliminate matrix components are solid-phase extraction and membrane extractions. 

Crushing canola disrupts cell membranes and brings the glucosinolates in close proximity with myrosinase enzyme, and some hydrolysis occurs until the enzyme is inactivated by heat during commercial oil extraction operations. The effect of SC-CO2 extraction conditions (temperature, pressure, extraction time and moisture content) on the myrosinase activity and glucosinolate hydrolysis in flaked and whole canola seeds was studied (Dunford and Temelli, 1996). 

Porous membranes have been prepared by leaching an additive from films and tubes of PCL (64,72). The procedure involves extrusion or casting blends of PCL and Pluronic F68, the latter being an FDA-approved oxyethylene-co-oxypropylene triblock copolymer. Treatment of the phase-separated blend with aqueous acetone or aqueous alcohols causes both swelling of the polymer and extraction of the Pluronic F68. The induced pore size and void volume may be controlled by the time, temperature, and solvent composition. 

As in the 1,2-dichloroethane case too, transient EMF and SHG responses to KSCN were observed for the nitrobenzene membranes without ionic sites. This suggests that here too not only SCN but also K ions are transferred into the nitrobenzene phase. Salt extraction into the bulk of the organic phase, in analogy to similar observations previously reported for neutral ionophore-incorporated liquid membranes without ionic sites [55], was indeed independently confirmed by atomic absorption spectrometry. Figure 15 shows the concentration of K in nitrobenzene equilibrated at room temperature with a 10 M aqueous solution of KSCN as a function of equilibration time. The presence of the ion exchanger TDDMA-SCN efficiently suppresses KSCN extraction into the organic phase but in its absence a substantial amount of KSCN enters the nitrobenzene phase. The trends of the EMF and the SHG responses are therefore very similar in spite of the different polarities of the plasticizers. 

Stability of several enzymes like proteases from thermophilic micro-organisms can be increased in aqueous-organic biphasic systems. Owusu and Cowan [67] observed a strong positive correlation between bacterial growth temperature, the thermostability of free protein extracts, and enzyme stability in aqueous-organic biphasic systems (Table 1). Enzymes, like other cell components (membranes, DNA, (RNA ribosomes), are adapted to withstand the environmental conditions under which the organism demonstrates optimal growth. 

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