Acid rejection

Activation site Larger amino acids rejected... 

Table II demonstrates all the membranes tested have amino acid rejection values over ca. 97%.

Note Distillation of concentrated sulphuric acid, rejecting the first and last 10% of the distillate, greatly improves its quality for this purpose by reducing its blank value. 

UV-grafting by employing polyelectrolyte was conducted previously for humic acid rejection test (Seman et al. 2010). Researchers found that the membranes modified through UV-grafting by employing PAA can lead to some changes in membrane... 

FIGURE 4.23 Humic acid rejections by nonmodified and UV-modified membranes when humic acid solutions at (a) pH 7 and (b) pH 3 were used. (Reprinted with permission from Seman, M. N. A. et al., J. Memb. ScL, 355, 133-141, 2010.)... 

Membrane Flux, gsfd Acid rejection, % Operating period, hr... 

The module productivity was 23 to 31 gpd with NaCl rejection of 71 to 72 % at 200 psig and 77 °F when feed NaCl concentration was 1200 ppm and feed flow rate was 0.8 to 1.0 gpm. When the module was tested with feed containing 3000 ppm acid, the flux was 32 to 38 gpd at a feed flow rate of 0.5 to 1 gpm at 75 °F. The acid rejection decreased with an increase in acid concentration as Table 5 indicates. 

H2SO4 concentration, ppm Feed flow rate, gpm Acid rejection,%... 

The acid rejection increased with an increase of feed flow rate as Table 5 indicates. When the module was operated at 600 psig, the module productivity increased from 75 to 114 gsfd, however, the rejection decreased. 

A tighter membrane was prepared from 6 % SP3O of lEC 1.5 in a solvent mixture of 5/0.9/0.1 CHCb/methanol/butanol and the composite films were tested for RO separation of acid mixtures. For the feed solution containing total 3000 ppm of H2SO4 and HNO3 the flux of 11 - 28 gsfd and acid rejection of 86 to 95 % were obtained under 600 psig at 80 to 85 °F. 

Add cautiously 15 ml. of concentrated sulphuric acid to 50 ml. of water in a 100 ml. distilling-flask, and then add 10 g. of pinacol hydrate. Distil the solution slowly. When about 40 ml. of distillate (consisting of pinacolone and water) have been collected, and no more pinacolone comes over, extract the distillate with ether. Dry the extract over sodium sulphate. Distil the dry filtered extract carefully, with the normal precautions for ether distillation (p. 164). When the ether has been removed, continue the distillation slowly, rejecting any fraction coming over below 100 . Collect the pinacolone, b.p. 106 , as a colourless liquid having a peppermint odour. Yield, 4 5-5 o g. A small quantity of higher-boiling material remains in the flask. 

Alkaline Fuel Cell. The electrolyte ia the alkaline fuel cell is concentrated (85 wt %) KOH ia fuel cells that operate at high (- 250° C) temperature, or less concentrated (35—50 wt %) KOH for lower (<120° C) temperature operation. The electrolyte is retained ia a matrix of asbestos (qv) or other metal oxide, and a wide range of electrocatalysts can be used, eg, Ni, Ag, metal oxides, spiaels, and noble metals. Oxygen reduction kinetics are more rapid ia alkaline electrolytes than ia acid electrolytes, and the use of non-noble metal electrocatalysts ia AFCs is feasible. However, a significant disadvantage of AFCs is that alkaline electrolytes, ie, NaOH, KOH, do not reject CO2. Consequentiy, as of this writing, AFCs are restricted to specialized apphcations where C02-free H2 and O2 are utilized. 

Interfdci l Composite Membra.nes, A method of making asymmetric membranes involving interfacial polymerization was developed in the 1960s. This technique was used to produce reverse osmosis membranes with dramatically improved salt rejections and water fluxes compared to those prepared by the Loeb-Sourirajan process (28). In the interfacial polymerization method, an aqueous solution of a reactive prepolymer, such as polyamine, is first deposited in the pores of a microporous support membrane, typically a polysulfone ultrafUtration membrane. The amine-loaded support is then immersed in a water-immiscible solvent solution containing a reactant, for example, a diacid chloride in hexane. The amine and acid chloride then react at the interface of the two solutions to form a densely cross-linked, extremely thin membrane layer. This preparation method is shown schematically in Figure 15. The first membrane made was based on polyethylenimine cross-linked with toluene-2,4-diisocyanate (28). The process was later refined at FilmTec Corporation (29,30) and at UOP (31) in the United States, and at Nitto (32) in Japan. 

The purified acid is recovered from the loaded organic stream by contacting with water in another countercurrent extraction step. In place of water, an aqueous alkafl can be used to recover a purified phosphate salt solution. A small portion of the purified acid is typically used in a backwashing operation to contact the loaded organic phase and to improve the purity of the extract phase prior to recovery of the purified acid. Depending on the miscibility of the solvent with the acid, the purified acid and the raffinate may be stripped of residual solvent which is recycled to the extraction loop. The purified acid can be treated for removal of residual organic impurities, stripped of fluoride to low (10 ppm) levels, and concentrated to the desired P2 s Many variations of this basic scheme have been developed to improve the extraction of phosphate and rejection of impurities to the raffinate stream, and numerous patents have been granted on solvent extraction processes. 

Propane and light ends are rejected by touting a portion of the compressor discharge to the depropanizer column. The reactor effluent is treated prior to debutanization to remove residual esters by means of acid and alkaline water washes. The deisobutanizer is designed to provide a high purity isobutane stream for recycle to the reactor, a sidecut normal butane stream, and a low vapor pressure alkylate product. 

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