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Properties of the Elements and Inorganic Compounds
Published in W. M. Haynes, David R. Lide, Thomas J. Bruno, CRC Handbook of Chemistry and Physics, 2016
W. M. Haynes, David R. Lide, Thomas J. Bruno
2172 Potassium perbromate 2173 Potassium percarbonate monohydrate 2174 Potassium perchlorate 2175 Potassium periodate 2176 Potassium permanganate 2177 Potassium peroxide 2178 Potassium persulfate 2179 Potassium phosphate 2157 Potassium phosphinate 2180 Potassium pyrophosphate 2181 Potassium pyrophosphate trihydrate 2182 Potassium pyrosulfate 2183 Potassium selenate 2184 Potassium selenide 2185 Potassium selenite 2186 Potassium silver cyanide 2187 Potassium sodium tartrate tetrahydrate 2188 Potassium stannate trihydrate 2189 Potassium stearate 2190 Potassium sulfate 2191 Potassium sulfide 2192 Potassium sulfide pentahydrate
Oxidation Catalysts
Published in Alvin B. Stiles, Theodore A. Koch, Catalyst Manufacture, 2019
Alvin B. Stiles, Theodore A. Koch
This catalyst family is unique in many respects, one of the most unusual being that it is often used in the molten form. This is reasonable because vanadium pentoxide and potassium pyrosulfate form a eutectic mixture that melts at a temperature approximately the same as the reaction temperature in the sulfuric acid converter (550–650°C). The catalyst is entrapped in the matrix of silica and kieselguhr, and the vanadium pentoxide and potassium pyrosulfate are molten islands in this silica matrix. This catalyst is extremely long-lived and may perform for as long as 10 years before it gradually disintegrates to powder. The catalyst is restored to usefulness by annually removing it from the converter, screening it, and replacing in the converter the portion that is retained on a 6 mesh screen, for example. Its preparation follows. A quantity of kieselguhr or diatomaceous earth is added to a kneader such as the one depicted in Fig. 27.To the kneader is also added an amount of potassium sulfate equivalent to 60% of the weight of the kieselguhr. Next are added portions of cobalt sulfate, nickel sulfate, and iron sulfate, each equivalent to 2% of the weight of the kieselguhr. Next is added sufficient ammonium meta-vanadate to be equal to 20–30% of the initial weight of the kieselguhr.Sufficient distilled water is added to produce a paste. The kneader blades are started as soon as sufficient water has been added to lubricate the powders and permit the formation of a pastelike mass. Kneading is continued until the paste becomes uniform and has a texture not quite as viscous as putty but slightly more viscous than a heavy grease. When this point has been reached, generally after a period of 45 min to 1 hr, the mixing should be continued for an additional 10 min as insurance of thorough mixing and uniformity. The kneader is then discharged.The kneaded catalyst is dried and heated to a temperature of 300°C in equipment similar to that shown in Figs. 17, 22, and 23.After drying and slight calcining, the catalyst is broken into lumps and passed 100% through a 10 mesh screen, using a granulator of the type shown in Fig. 29. The catalyst is now mixed with 1% graphite and is pilled in equipment of the type shown in Fig. 32. The ribbon mixer for the graphite mixing is shown in Fig. 31. The catalyst is now ready for use. This catalyst can also be extruded in equipment such as that shown in Fig. 28, or it can be formed into spheres using equipment of the type shown in Fig. 33. The primary requirement of the catalyst is that it have strong durability (resistance to abrasion) under long periods of exposure.
The Direct Leaching of Nickel Sulfide Flotation Concentrates – A Historic and State-of-the-Art Review Part III: Laboratory Investigations into Atmospheric Leach Processes
Published in Mineral Processing and Extractive Metallurgy Review, 2022
Nebeal Faris, Mark I. Pownceby, Warren J. Bruckard, Miao Chen
Addition of alkali metal sulfates (Na, K, and Li) are reported to enhance the recovery of Ni during sulfation roasting with lithium sulfate being the most effective and potassium the least (Fletcher and Shelef 1963; Rao, Natarajan, and Padmanabhan 2001). Fletcher and Shelef (1964) conducted sulfation roasting experiments on a Ni-containing flotation concentrate in a fluidized bed reactor (refer to Table 7). After roasting for 1 hour in the absence of sodium sulfate, Ni extraction during water leaching was only 10.5–12.5%, whilst the addition of Na2SO4 increased Ni extraction to 55.5–59.0%. Thornhill (1954) in the original patent for the process in use at the Falconbridge iron ore plant proposed that Na2SO4 improved nickel recovery during sulfation roasting by reacting with nickel ferrite releasing NiSO4, and by reaction with SO3 to form sodium pyrosulfate (Na2S2O7) which is an effective sulfation agent. Rao, Natarajan, and Padmanabhan (2001) also investigated sulfation roasting of a bulk sulfide flotation concentrate grading 7% Ni and found that the addition of an alkali metal sulfate (6 or 12 wt%) to roasting greatly improved Ni extraction during water leaching. Copper recoveries were not found to be influenced by alkali sulfate addition (92%) whilst cobalt recovery increased from 72% to 88% when an alkali sulfate was added regardless of the type of alkali metal sulfate used. Nickel extraction, however, was reported to be affected by the type of alkali sulfate used with the highest Ni extractions occurring with the use of lithium sulfate (Li2SO4); the addition of 12 wt% Li2SO4 increased Ni recoveries to above 60% when roasting concentrate at 500°C for 4 hours versus only 18.4% Ni recovery in the absence of any additive under the same conditions.