Removal from water column

Surface water half-lives for removal from water column at 25°C in midsummer sunlight were, t,/2 = 10.5 h for deep, slow, somewhat turbid water t,/2 = 21.6 h for deep, slow, muddy water t,/2 = 8.5 h for deep, slow, clear water t,/2 = 3.5 h for shallow, fast, clear water and t,/2 = 1.4 h for very shallow, fast, clear water (Southworth 1977, Herbes et al. 1980) ... 

Column Extraction. Aqueous samples and distillates were added to glass chromatographic tubes or plastic syringe barrels containing 0.5 g Celite 560 per g of sample. After 20 to 30 min of equilibration, the columns were eluted with 100 ml of DCM [for NDMA, NPYR and N-nitrosomorpholine (NMOR) or ethyl acetate (for NDELA and BHP)]. Residual solvent was removed from the columns by applying nitrogen pressure. Extracts were dried with Na S0, and concentrated to 1 ml in a Kuderna-Danish apparatus (NuMA, NPYR, and NMOR) in a 50 C water bath or in a rotary evaporator for NDELA and BHP, using a 30 C water bath. 

We obtained the best results with the Carbopack B-DA/4% Carbowax 20M, 80-120 mesh Supelco column, 2000 x 2 mm. It was initially conditioned for 21 h at 245°C, but the normal running temperature is 175°C. The injector/detector temperature is 200°C and a flame ionization detector is used. A glass sleeve is fitted to the injector and the glass wool plug removed from the column inlet. The carrier gas is nitrogen with a flowrate of 40 ml min at 310 kN m. The sample solution (9 ml) is mixed with 1 ml of pivalic acid solution (1.5% m/v) as internal standard. Then 1 ml of this solution is mixed with 1 ml 0.3 M oxalic acid solution and 3 ml deionized water before injecting 1 pi into the septum. 

Note. (1) Alternatively the (Z)-isomer may be removed from the column by changing the eluting solvent to one of light petroleum, b.p. 40-60 °C, containing 1 per cent of methanol. The eluate fraction is then washed with water to remove the methanol in the manner described in the main text. 

The first evaporation step was limited to a factor of 25 to limit the HNO3 concentration to 9M. The white solids product plugged the ion exchange columns, but could be removed from the column with a water wash. 

This precipitate is dissolved and loaded onto a Sr resin column. The date and time of Y removal from the column is recorded. All the column eluents are collected for further Ca purification, and the Sr fraction is eluted using water, and counted by Cerenkov... 

Acetone is being removed from water by contacting with toluene in a packed extraction column. Water is the continuous [heavy] phase, and toluene is the dispersed [light] phase. Calculate the overall mass transfer coefficient for this process. 

Since the column/HPLC and shake-flask methods are also the main source of solubility values, the evaluation of error for KQW is very similar. Loss of solute to walls or the atmosphere are still of concern, as are the extraction efficiencies for solute removal from water. Equilibration of each of the three phases involved (instead of two for solubility) is of concern. 

The reactor effluent pressure is reduced and adiabatically flashed to recover acetic acid as vapor. The liquid phase contains the homogeneous catalyst which is pumped back to the reactor. The flashed vapor enters the light ends column where low molecular weight hydrocarbons are removed and a heavy fraction including water and hydrogen iodide is condensed and recycled to the reactor flash tank. The acetic acid product is removed from the column as a liquid side draw and further purified in downstream distillation columns. 

Water or other liquids should be adequately removed from the column prior to a vacuum leak test. Evaporation of liquids may cause a rise in pressiire during the test. 

We have now successfully employed Amberlite XAD-2 (11) and XAD-16 resin in the purification of our conjugates. After applying the 3.74 g of residue from the aqueous phase to the XAD-16 column better than 92% of the impurities were removed from the column with water (Fig. 3) and the partially purified conjugates were eluted with ethanol. The Cig SEP-PAK fractionation removed additional impurities. Final purification can now be achieved by ion suppression RP-HPLC followed by desalting on SEP-PAK. 

M. Bhaumik, K. Setshedi, A. Maity, M. S. Onyango, Chromium(VI) removal from water using fixed bed column of polypyrrole/Fe O nanocomposite. Sep Purif Technol 2013,110,11-19. 

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