Calcium sulfate precipitation

About 250 ml of a reaction mixture obtained by the electrolytic reduction of nitrobenzene in sulfuric acid solution and containing about 23 grams of p-aminophenol by assay is neutralized while at a temperature of 60° to 65°C, to a pH of 4.5 with calcium carbonate. The calcium sulfate precipitate which forms is filtered off, the precipitate washed with hot water at about 65°C and the filtrate and wash water then combined. The solution is then extracted twice with 25 ml portions of benzene and the aqueous phase is treated with 0.5 part by weight, for each part of p-aminophenol present, of activated carbon and the latter filtered off. The activated carbon is regenerated by treatment with hot dilute caustic followed by a hot dilute acid wash, and reused a minimum of three times. 

Chemically pure reagents were used. Cadmium was added as its sulfate salt in concentrations of about 50 ppm. Lanthanides were added as nitrates. For the experiments with other metal ions so-called "black acid from a Nissan-H process was used. In this acid a large number of metal ions were present. To achieve calcium sulfate precipitation two solutions, one consisting of calcium phosphate in phosphoric acid and the other of a phosphoric acid/sulfuric acid mixture, were fed simultaneously in the 1 liter MSMPR crystallizer. The power input by the turbine stirrer was 1 kW/m. The solid content was about 10%. Each experiment was conducted for at least 8 residence times to obtain a steady state. During the experiments lic iid and solid samples were taken for analysis by ICP (Inductively Coupled Plasma spectrometry, based on atomic emission) and/or INAA (Instrumental Neutron Activation Analysis). The solid samples were washed with saturated gypsum solution (3x) and with acetone (3x), and subsequently dried at 30 C. The details of the continuous crystallization experiments are given in ref. [5]. 

SYNS ALABASTER ANNAUNE C.I. 77231 C.I. PIGMENT WHITE 25 GYPSUM GYPSUM STONE LAND PLASTER UGHT SPAR MAGNESIA WHITE MINERAL W HITE NATIVE CALCIUM SULFATE PRECIPITATED CALCIUM SULFATE SATINITE SATIN SPAR SULFURIC ACID, CALCIUM(2+) SALT, DIHYDRATE TERRA ALBA... 

Regenerant. Dilute hydrochloric acid (1.4keqm ) or sulfuric acid (0.3-1.0 keqm ), the latter concentration being decided by the calcium content of the raw water thereby avoiding calcium sulfate precipitation. Regeneration levels are typically 1.3-2.0 keq m R injected over a period of about 30 minutes. 

Calcium sulfate dihydrate alabaster Cal-Tab-, Compactroh, Destab-, E516 gypsum light spar mineral white native calcium sulfate precipitated calcium sulfate satinite satin spar selenite terra alba USG Terra Alba. 

At 30 C, the solubility of calcium dithionate in water exceeds that of calcium sulfate by a factor of 105. According to the principle of Le Chatelier, under a high sulfur dioxide pressure the equilibrium of the given reaction lies on the right-hand side, while at a low pressure of sulfur dioxide essentially only calcium sulfate exists. This implies that when the digesters are depressurized, the high solubility of calcium sulfate is terminated, thus leading to calcium sulfate precipitation. 

Seawater is evaporated by concentrating the seawater in the first evaporation pool transporting to the next evaporation zone, in which calcium sulfate precipitates out and finally crystallizing sodium chloride in a further evaporation zone. The residual brine is rich in potassium and magnesium salts. The salt obtained is too impure to be used in electrolysis. Washing in special units is sufficient to increase the sodium chloride content to > 99%. I m- of seawater yields ca. 23 kg of sodium chloride. 

Also known as native calcium sulfate, precipitated cal-... 

Simple laboratory tests may not be adequate to reproduce field results. The reason for this was demonstrated in the lab with an artificial solution containing road salt and acid rain constituents. Allowing such a solution to evaporate drives off the volatile nitric acid component and hydrochloric acid formed when calcium sulfate precipitates. Hence the history of a poultice is important in determining the aggressiveness of a particular environment. 

The solubility equilibrium of calcium sulfate can also be demonstrated by supplementing portions of sodium sulfate and calcium chloride solutions (see E6.5) using highly concentrated solutions solid calcium sulfate precipitates. In addition to Ca2+(aq) ions and S042 (aq) ions, the solution also contains Na + (aq) ions and Cl (aq) ions ... 

As the concentration of sulfate increases relative to sulfite, the amount of sulfate precipitation increases. Thus, as the rate of oxidation increases, the ratio of sulfate to sulfite in solution will increase until the rate of calcium sulfate precipitation is sufficient to keep up with the rate of sulfate formation by oxidation. This self-adjustment by the system may, however, be limited by the need to maintain a high active sodium concentration which will limit sulfate concentrations (and consequently the sulfate/ sulfite ratio) simply by solution saturation considerations. Furthermore, the sulfate/sulfite ratio may also be limited by the need to ensure high limestone utilizations and good solids properties. 

Dihydrate, native calcium sulfate precipitated calcium sulfate gypsum alabaster selenite terra alba satinite mineral white satin spar light spar. Lumps or powder, d 2.32. It loses only part of its water at 100-150. Sol in water very slowly sol in glycerol. Practically insol in most organic sol -vents. 

WAG Alkalinity leakage during exhaustion cyde inadequate regeneration. Hardness leakage during exhaustion cycle regeneration fault with calcium sulfate precipitation (if sulfuric acid is the regenerant). 

Calcium sulfate precipitates from water as gypsum, the dihydrate, CaS04 2H20. If water can be taken to be at unit activity, or at least as constant, the mathematical form of our treatment is not changed. 

Lioliou, M. G., Paraskeva, C. A., Koutsoukos, P. G. Payatakes, A. C. (2006). Calcium sulfate precipitation in the presence of water-soluble polymers. Journal of Colloid and Intel face Science, 303(1), 164-170. 

Generally speaking, it can be said that in a cooling system with extreme temperatures lying between 10 C and 80°C there is no risk of calcium sulfate precipitation if ... 

This process requires that 12 of the 18 moles, or 67%, of phosphoric acid produced be recycled to treat more phosphate rock. There are other metals in the phosphate rock and upon acidification they become salts. The insoluble salts remain with the calcium sulfate precipitate but the soluble salts such as magnesium sulfate or iron sulfate remain in solution with the phosphoric acid. Generally, high purity is not required for fertilizer grade phosphoric acid. The crude phosphoric acid reacts, for example, with ammonia to make ammonium dihydrogen phosphate. 

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