Gypsum-based products

The permissible level of iron in the gypsum is limited, as iron can cause discolouration of gypsum-based products. This, in turn, imposes a limit on the amount of Fc203 in the limestone. Nevertheless, some iron is desirable as it accelerates the rate of oxidation of the calcium sulfite. 

D. Neuschiitz, R. Nino, Mixing it right — the K.M.A. integrated dry mortar plant for gypsum, lime and cement-based products . Gypsum Lime and Building Products, April, 1996, 33-36. 

Experiments in the production of sulfuric acid dating from the 1920s, which had been abandoned, were resumed. The development of a large gypsum-based sulfuric acid plant at the Farbenfabrik Wolfen and another facility in Coswig/A. began in 1936. This was intended to make German industry independent of imports of sulfuric raw materials. ... 

Table 10 shows that special shortages occurred in basic chemistry. Sulfuric acid production, which was underrepresented in the SBZ, fell still farther behind. The sole gypsum-based sulfuric acid facility in the Wolfen plant was completely dismantled. Complete dismantling occurred also in Doberitz (37,800 tons), Leuna (20,000 tons) and Magdeburg (53,800 tons). A total of 231,600 tons were taken out of production. This dismantling affected the textile industry especially. 

Gypsum-based plaster >- Cement- or gypsum-based vermiculite >- Mineral or glass fibre > Ceramic-based products... 

Wallboard - The use of gypsum-based wallboard, once common only in the US and Canada, has spread to virtually all developed countries. The gypsum core provides a strong, fire-resistant, and inexpensive construction material. The -100 mesh stucco (hemihydrate) form is used. Japan is the largest user of synthetic gypsmn products in wallboard, because it lacks natural gypsum resources. The other major source of synthetic (FGD-based) product for this market is Germany, which serves all of Emope. Most of current US wallboard production is based on natural soinces. 

Nitric Phosphate. About 15% of worldwide phosphate fertilizer production is by processes that are based on solubilization of phosphate rock with nitric acid iastead of sulfuric or phosphoric acids (64). These processes, known collectively as nitric phosphate or nitrophosphate processes are important, mainly because of the iadependence from sulfur as a raw material and because of the freedom from the environmental problem of gypsum disposal that accompanies phosphoric acid-based processes. These two characteristics are expected to promote eventual iacrease ia the use of nitric phosphate processes, as sulfur resources diminish and/or environmental restrictions are tightened. 

Some commonly used primary nutrient fertilizers are incidentally also rich sources of calcium. Ordinary superphosphate contains monocalcium phosphate and gypsum in amounts equivalent to all of the calcium originally present in the phosphate rock. Triple superphosphate contains soluble monocalcium phosphate equivalent to essentially all the P2 5 product. Other fertilizers rich in calcium are calcium nitrate [10124-37-5] calcium ammonium nitrate [39368-85-9] and calcium cyanamide [156-62-7]. The popular ammonium phosphate-based fertilizers are essentially devoid of calcium, but, in view of the natural calcium content of soils, this does not appear to be a problem. 

A major consequence of the activities associated with the exploitation of mineral deposits (i.e., exploration, the development of mines and processing facilities, the extraction and concentration, which is also called beneficiation, of ores containing the desired minerals, and the decommissioning or abandonment of mine facilities) is the production of extremely large volumes of unwanted materials. Waste volumes vary from ca. 30% of the mass of the ore in the case of gypsum and other non-metals, to about 50% for base metals to more than 80% for strip-mined... 

Xylene Solvent, dyes, insecticides, polyester fibres, adhesives, wallpaper, varnish, carpeting, wet-process photocopying, pressed-wood products, gypsum board, water-based adhesives, grease solvents, paints, carpet adhesives. 2.9 3... 

Various well-known industrial and municipal waste products particularly those from the base metal industry, contain appreciable amounts of Fe oxides which may make them suitable for remediation purposes. Two examples from industry are the residues from the alumina and the titanium industries. The extraction of either Al or Ti from the natural ores (bauxite and ilmenite/rutile, respectively) leaves behind an alkaline and acidic (sulphuric) residue, respectively, in which Fe oxides are enriched, as indicated by their names Red Mud and Red Gypsum . A sample of Red gypsum is reported to contain ca. 35% of Fe oxide consisting of goethite and hematite, half of which was oxalate soluble (Fauziah et al., 1996). As expected, this material had an appreciable adsorption capacity for phosphate and heavy metals and, if added to soils, could confer these properties on them (Peacock Rimmer, 2000),... 

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