Calcium sulfate Concentration

The solution was dried over anhydrous calcium sulfate, concentrated under reduced pressure, and the polymer precipitated by methanol. The polymer was redissolved in methylene chloride, reprecipitated with methanol, and dried overnight at 100°C (0.01 mm Hg). 

U of immobilized B-glucosidase were added to 50 ml of wine or fruit juice. The enzymatic reactions were run in stoppered glass bottles at 30°C, with shaking. After addition of 4-nonanol (190 pg) as standard, both the wine and the fruit juice were passed through a solvent washed Amberlite XAD-2 colunm (1 cm i.d. x 35 cm) with a flow rate of 2.0 ml/min [5]. The column was then rinsed with 100 ml of distilled water to eliminate sugars, acids and other water-soluble compounds. The fractions containing free aroma was eluted by 50 ml of pentane/dichloromethane (2V/1V). The eluate was dried over anhydrous calcium sulfate, concentrated to 50 pi under reduced pressure (rotavapor) and then subjected to GC analyses. 

Xanthan gum interacted with calcium sulfate Buspirone HCl Bioadhesive buccal disc Increase in calcium sulfate concentration resulted in faster drug release and decreased bioadhesive strength of the designed discs and decreased viscosity of xanthan gum. [155]... 

In our opinion the reaction mechanism can be described as follows First calcium sulfide is being formed. Depending on the temperature and the amount of calcium sulfate available around the formed calcium sulfide the consecutive reaction between calcium sulfate and calcium sulfide (3) takes place. Sorbents with a low calcium sulfate concentration and a relatively high surface area, like Duwa C Normal or Carmeuse Engis do not have a high concentration of calcium sulfate at this location for the consecutive reaction. For this reason their selectivity is low. 

Production Technology. Processes for extraction of P2O3 from phosphate rock by sulfuric acid vary widely, but all produce a phosphoric acid—calcium sulfate slurry that requires soHds-Hquid separation (usually by filtration (qv)), countercurrent washing of the soHds to improve P2O3 recovery, and concentration of the acid. Volatilized fluorine compounds are scmbbed and calcium sulfate is disposed of in a variety of ways. 

Cation exchangers are regenerated with mineral acids when used in the form. Sulfuric acid [8014-95-7] is preferred over hydrochloric acid [7647-01-0], HCl, in many countries because it is less expensive and less corrosive. However, the use of hydrochloric acid is the best method of overcoming precipitation problems in installations which deionize water with high concentrations of barium or calcium compared to other cations. A 4% acid concentration is common, although sulfuric acid regenerations may start as low as 0.8—1% to minimize calcium sulfate [7718-18-9] precipitation. 

Excess calcium hydroxide is precipitated by usiag carbon dioxide and the calcium carbonate, calcium hydroxide, and calcium phosphite are removed by filtration. The filtered solution is treated with an equivalent amount of sodium sulfate or sodium carbonate to precipitate calcium sulfate or carbonate. Sodium hypophosphite monohydrate [10039-56-2] is recovered upon concentration of the solution. Phosphinic acid is produced from the sodium salt by ion exchange (qv). The acid is sold as a 50 wt %, 30—32 wt %, or 10 wt % solution. The 30—32 wt % solution is sold as USP grade (Table 12) (63). Phosphinic acid and its salts are strong reduciag agents, especially ia alkaline solution (65). 

As of 1993—1994, over 70% of sulfuric acid production was not sold as such, but used captively to make other materials. At almost all large fertilizer plants, sulfuric acid is made on site, and by-product steam from these sulfur-burning plants is generally used for concentrating phosphoric acid ia evaporators. Most of the fertilizer plants are located ia Florida, Georgia, Idaho, Louisiana, and North Carolina. In the production of phosphate fertilizers, the primary role of sulfuric acid is to convert phosphate rock to phosphoric acid and soHd calcium sulfates, which are removed by filtration. 

Obtaining maximum performance from a seawater distillation unit requires minimising the detrimental effects of scale formation. The term scale describes deposits of calcium carbonate, magnesium hydroxide, or calcium sulfate that can form ia the brine heater and the heat-recovery condensers. The carbonates and the hydroxide are conventionally called alkaline scales, and the sulfate, nonalkaline scale. The presence of bicarbonate, carbonate, and hydroxide ions, the total concentration of which is referred to as the alkalinity of the seawater, leads to the alkaline scale formation. In seawater, the bicarbonate ions decompose to carbonate and hydroxide ions, giving most of the alkalinity. 

A very complete separation of the calcium sulfate may be effected by adding to the concentrated solution 1000 cc. of alcohol, allowing the mixture to stand for 24 hours, and filtering. The alcohol is then distilled from the filtrate and the procedure followed as indicated above. 

Calcium sulfate (anhydrous). (Prepared by heating the dihydrate or the hemihydrate in an oven at 235° for 2-3h it can be regenerated.) Available commercially as Drierite. It forms the hemihydrate, 2CaS04.H20, so that its capacity is fairly low (6.6% of its weight of water), and hence is best used on partially dried substances. It is very efficient (being comparable with phosphorus pentoxide and concentrated sulfuric acid). Suitable for most organic compounds. Solvents boiling below 100° can be dried by direct distillation from calcium sulfate. 

The degree of concentration that can be achieved by RO may be limited by the precipitation of soluble salts and the resultant scaling of membranes. The most troublesome precipitate is calcium sulfate. The addition of polyphosphates to the influent will inhibit calcium sulfate scale formation, however, and precipitation of many of the other salts, such as calcium carbonate, can be prevented by pretreating the feed either with acid or zeolite softeners, depending on the membrane material. 

The moist cells were suspended in 750 parts of volume of ethanol and extracted by warming at 60°C for 1 hour. A total of 3 extractions were carried out in a similar manner and the extracts were pooled, diluted with water and further extracted three times with 1,000 parts of volume portions of n-hexane. The n-hexane layer was concentrated to dryness under reduced pressure to recover 4.12 parts of a yellow oil. This oily residue was dissolved in 6 parts by volume of benzene and passed through a column (500 parts by volume capacity) packed with Floridil (100 to 200 meshes). Elution was carried out using benzene and the eluate was collected in 10 parts by volume fractions. Each fraction was analyzed by thin-layer chromatography and color reaction and the fractions rich in ubiquinone-10 were pooled and concentrated under reduced pressure. By this procedure was obtained 0.562 part of a yellow oil. This product was dissolved in 5 parts by volume of chloroform, coated onto a thin layer plate of silica gel GF254 (silica gel with calcium sulfate) and developed with benzene. The fractions corresponding to ubiquinone-10 were extracted, whereby 0.054 part of a yellow oil was obtained. This oil was dissolved in 10 parts by volume of ethanol and allowed to cool, whereupon 0.029 part of yellow crystals of ubiquinone-10 were obtained, its melting point 4B°to 50°C. 

Five hundred grams of mesquite gum (Note i) is dissolved (Note 2) in 3 1. of cold water in a 5-1. round-bottom flask a cold solution of 125 g. of concentrated sulfuric acid in 80 cc. of water is added and the mixture warmed at 8o° for six hours (Note 3) in a large water bath. The acid is neutralized by gradual addition of 140 g. of powdered calcium carbonate (Note 4), and the solution with excess calcium carbonate is heated in a boiling water bath for an hour to complete the neutralization. The calcium sulfate is filtered off and washed with about 2 I. of hot water. The filtrate is concentrated in an evaporating dish (Note 5) on the boiling water bath to a volume of 650-700 cc. 

This time the trial product, 4 X 10-4, is greater than Klp = 2.4 X 10 s so a precipitate does form. Solid calcium sulfate, CaS04, will continue to form, lowering the concentrations [Ca+2] and [SO -2] until they are low enough that the ion product equals Kcp. Then equilibrium exists and no more precipitation occurs. 

Sulfates in surface MU water sources usually are present at lower concentrations (typically 20-60 ppm) but this level may rise to several hundred ppm in subsurface waters. The maximum solubility of calcium sulfate is dependent on temperature but is in the range of 1,800 to 2,000 ppm in cold water. This rate is significantly less in hot BW where boiler deposits occur, the sulfate scale normally is present as anhydrite (CaS04). Sulfate scales are hard and very difficult to remove, so treatment programs employed must be carefully controlled to avoid risks of scaling. 

NOTE The calcium carbonate limit that RO system designers typically require is +1.6 to 1.8 LSI in the concentrate or reject water, and the calcium sulfate design limit typically calls for a maximum reject water saturation ratio of 1.6 to 1.8 times solubility product. 

Fig. 12 Tensile strength of calcium sulfate tablets as a function of magnesium stearate concentration (solid fraction = 0.57). (From Ref. 29.)...

Common pollutants in a titanium dioxide plant include heavy metals, titanium dioxide, sulfur trioxide, sulfur dioxide, sodium sulfate, sulfuric acid, and unreacted iron. Most of the metals are removed by alkaline precipitation as metallic hydroxides, carbonates, and sulfides. The resulting solution is subjected to flotation, settling, filtration, and centrifugation to treat the wastewater to acceptable standards. In the sulfate process, the wastewater is sent to the treatment pond, where most of the heavy metals are precipitated. The precipitate is washed and filtered to produce pure gypsum crystals. All other streams of wastewater are treated in similar ponds with calcium sulfate before being neutralized with calcium carbonate in a reactor. The effluent from the reactor is sent to clarifiers and the solid in the underflow is filtered and concentrated. The clarifier overflow is mixed with other process wastewaters and is then neutralized before discharge. 

An ASTM standard recommends the use of 0.005 normal calcium sulfate as the standard permeating water, because of its medium range electrolyte concentration. Calcium sulfate, with divalent calcium, will usually not reduce hydraulic conductivity. 

Chlorine (BOC Gases, 99.5%) was dried with concentrated sulfuric acid and anhydrous calcium sulfate. Purging was done with 99.998% pure argon (BOC Gases). 

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