Temperature leaching

Effect of Leaching Temperature The quantity of alkali extracted in a fixed time increases with increasing temperature. Depending upon the composition of the glass coating and the alkali present (ions of different size behave characteristically), the amount leached approximately doubles for each rise in temperature of 10°C. This temperature dependence can be expressed by the equation (Arrhenius)... 

Leaching temperature also impacts the surface area and size of the crystallites. Kagan and coworkers212 214 found that, by leaching at 18 °C, the crystallites were between 14 and 34 nm but were between 16 and 80 nm when leaching was carried out at 80 °C. Similar results were obtained by Pearce and Lewis211). 

They usually suppose that the mobility of atoms at leaching temperature is too low to rearrange for the phase transformation. However, transformation has clearly occurred except in a few cases. One of the motivations for our research studies on Raney catalysts is to clarify what happens during the leaching process. 

As stated earlier, lower leaching temperatures result in increased surface areas of skeletal catalysts. Furthermore, slowing the leaching process by the addition of sodium zincate to the leach solution leads to higher surface areas. Thus leaching of CuA in 6.1 M NaOH containing 0.62 M sodium zincate at 274 K leads to a catalyst of surface area of 58.1 m2 g 1 compared with a surface area of 28.0 m2 g 1 when no sodium zincate is present. 

Forward and Halpem (F7) described extraction of uranium by generating sulfuric acid directly from the sulfide minerals present in the ore at elevated temperatures and pressures. The optimal conditions found for most of the ores studied are a grind of 50-65% — 200 mesh, a pulp density of 65% solids, leaching temperature of 130°C, and an oxygen partial pressure of 10 psi to give 90-95% uranium dissolution in 4-6 hr. This... 

Effect of leaching temperature on the composition and the activity of Raney Cu/Zrf) leached with aqueous solution of NaOH and zincate... 

For the leaching experiments, a weighed amount of finely divided coal or mineral matter was mixed with 120 ml. of alkaline solution in a 300-ml. stainless steel (Type 316) autoclave equipped with a turbine agitator. The system was flushed with nitrogen and then heated to the desired leaching temperature. The mixture was stirred continuously while leaching was conducted at constant temperature and pressure for a specified period. After this treatment, the autoclave... 

When kaolin was leached with 1.0 M sodium carbonate at 200 C for 1 hr., most of the kaolinite was converted to the sodalite-type natrodavyne (NS) while the quartz and illite impurities were not affected noticeably (Table IV). Increasing the leaching temperature to 250 C resulted in the converion of the kaolinite to a mixture of mixed-type natrodavyne (NCS) and analcime (A) and complete dissolution of the quartz impurity. The illite impurity was not affected. Leaching at 300 C and above resulted in the conversion of the... 

When pyrite was leached for 1 hr. with 1.0 M sodium carbonate at 250 C, only 12.7% of the pyrite was converted to iron oxide and soluble sulfur species (Table V). Increasing the leaching temperature to 300 C raised the conversion to 26.4%, and increasing the temperature to 350°C raised the conversion to 44.8%. In each case the solid residue consisted principally of hematite and unreacted pyrite. 

Concentrated sulfuric acid is added directly to limonite ore slurry. This substantially dissolves the nickel containing goethite matrix causing over 90% of the nickel and cobalt to leach along with substantial amounts of iron. Leach temperatures close to the boiling point of the liquor are attained, due to the heat of dilution of the acid. The goethite dissolution reaction is represented by equation 1. 

The decomposition of the ore sample by leaching and the liberation of rare earth elements to the leach liquor depends mainly on leaching temperatures as well as sulfuric acid concentration. Performing the leaching experiments at room temperature dissolve only 50% of the rare earth contents at 5M and 15M acid concentrations. The XRD analysis of the residue showed that relatively equal amounts of anhydrite and yttrium-fluorite were identified at 5M H2SO4. Increasing the acid concentration to 15M enhanced the formation of anhydrite to be double that of the yttrium fluorite in the sepai ated residue. This indicates that the reaction was not sufficient for complete decomposition of the ore sample. 

The influencing factors of alumina leaching rate are leaching temperature, leaching time, the content of sodium hydroxide and sodium carbonate. The alumina leaching rate was described as the leaching rate of calcium aluminate and unieacted A1 powder in residue. The experiments results are shown in Fig. 5-8. 

Fig.5 Effect of leaching temperatures on alumina leaching rate...

Leaching temperature/°C Leaching time/h Whether stirring TFe/% S/%... 

It was known that there was almost no reaction between sulfur and hydrochloric acid in room temperature 20°C. When leaching temperature was up to 70 , sulfur started... 

Effect of stirring on the Lead Content of Leached Concentrate Under conditiorrs the dilute hydrochloric acid mass fraction of 5%, pulp density of 30%, leaching time of 2 hours, leaching temperature of 20°C, the tests were divided into two part, the first with a stirring speed of 200r/minutes, flie second without stirring. 

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