Gypsum, applications

Acidic reaction Normal Saline/Calcareous Alkaline Requires liming No treatment Requires leaching of soluble salts Requires gypsum application... 

Table 14.21). Olsen and Watanabe (1979) found that on alkaline soils, iron (Fe) uptake increased as Mo concentration decreased with gypsum application (Table 14.22). 

Gypsum applications decrease bulk density of soil (Southard et al, 1988). Untreated soil by gypsum has a higher bulk density. Many of the effects of gypsum, however, are limited to shallow depths. 

Ilyas, M., Qureshi, R. H. Qadir, M. A. (1997) Chemical changes in a saline-sodic soil after gypsum application and cropping. Soil Technology , 10,247-260. 

Typical applications in the chemical field (Beaver, op. cit.) include detarring of manufactured gas, removal of acid mist and impurities in contact sulfuric acid plants, recovery of phosphoric acid mists, removal of dusts in gases from roasters, sintering machines, calciners, cement and lime Idlns, blast furnaces, carbon-black furnaces, regenerators on fluid-catalyst units, chemical-recoveiy furnaces in soda and sulfate pulp mills, and gypsum kettles. Figure 17-74 shows a vertical-flow steel-plate-type precipitator similar to a type used for catalyst-dust collection in certain fluid-catalyst plants. 

These types are most common in power station-sized boilers and process industries such as cement and gypsum, where the residual ash is absorbed in the process. As their application is at the larger end of the combustion field, on-site milling and preparation is technically feasible and... 

Special grades of gypsum hemihydrate are blended with Portland cement for types with reduced thickening time and setting time. Gypsum requires significantly more water addition. The maximal application temperatures are 70° to 80° C. Sodium silicate is used for cement slurries with diatomaceous earth. It can be used up to 7% by weight. 

The lime application and settling process treatment consists of adding a milk of lime slurry to the wastewater to precipitate the hydroxide of the heavy metals and reduce dissolved sulfate concentrations through the formation of gypsum. Sufficient lime is needed to adjust the pH to between 10 and 11.5. Also, settling may have to be aided by adding small quantities of organic polyelectrolytes. 

At this point, Lavoisier was primarily interested in doing research that would impress the academicians. He read his first paper to the Academy as a visiting scientist (that is, a non-member) on February 27,1765. It dealt with a topic that had been pursued by some of the chemists in the Academy and was titled The Analysis of Gypsum. Gypsum was the mineral from which plaster was made, so it was a topic with practical applications. The two referees appointed by the Academy to judge the paper reported favorably on it and recommended it for inclusion in the Academy s Savants etrangers collection. It is probable that some sort of behind-the-scenes deal had been made because both referees were friends of Lavoisier s father. 

Potassium sulfate is used in fertilizers as a source of potassium and sulfur, both of which are essential elements for plant growth. Either in simple form or as a double salt with magnesium sulfate, potassium sulfate is one of the most widely consumed potassium salts in agricultural apphcations. It is preferred over potassium chloride for certain types of crops such as, tobacco, citrus, and other chloride—sensitive crops. Some other applications include making gypsum cements to make potassium alum in the analysis of Kjeldahl nitrogen and in medicine. 

The sulfonated lignin products function primarily as dispersants in aqueous systems and help to form stable dispersions of a number of insoluble materials. For example, lignin dispersants find use in pigments, carbon black, gypsum, ceramics, coal slurry and water treatment systems to mention some of the more prominent applications. 

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