Leaching products

FIGURE46 The leaching product (a) PrC>2 Swedish cheese and (b) the reacted site of leached Tb02. 

QCpmHBFJ RuCl2(PPh3)3 Olefms 25-40 bar, 30-60 °C <3 % catalyst leaching products [21] isolated by decantation catalyst solution remains active for at least four cycles. 

C4C im][PF6] TPPM-CCiCiim] 1-Octene 51 (2.8) No significant catalyst leaching product isolated by phase-separation. [50]... 

The stability and durability of Pt alloys, especially those involving a >d transition metal, are the major hurdles preventing them from commercial fuel cell applications. "" The transition metals in these alloys are not thermodynamically stable and may leach out in the acidic PEM fuel cell environment. Transition metal atoms at the surface of the alloy particles leach out faster than those under the surface of Pt atom layers." The metal cations of the leaching products can replace the protons of ionomers in the membrane and lead to reduced ionic conductivity, which in turn increases the resistance loss and activation overpotential loss. Gasteiger et al. showed that preleached Pt alloys displayed improved chemical stability and reduced ORR overpotential loss (in the mass transport region), but their long-term stability has not been demonstrated. " These alloys experienced rapid activity loss after a few hundred hours of fuel cell tests, which was attributed to changes in their surface composition and structure." ... 

Carbon Dioxide. As the debate of the effect of greenhouse gases rages on, the simple fact remains that carbon dioxide production is one of the known side reactions of most metal-production operations. Carbon is an effective metal reductant. Coke is used to produce pig iron from iron oxide ores and lead from sulfide ores in blast furnaces, carbon electrodes are used to produce aluminum from bauxite leaching products, and coal is used in the reduction of zinc oxide in retorting furnaces. All told, the resulting product of metal reduction is the oxidation of carbon to carbon dioxide. It is important to keep in mind that the production of carbon dioxide has been reduced dramatically since the start of the Industrial Revolution of the late nineteenth-century. This is best exemplified by the history of steel making in the world. 

To investigate the dissolution of the sodium hydroaluminosilicates produced by alkaline leaching, 3.0 g. portions of the leached product were treated with 300 ml. of acid in a stirred flask for 30 min. Either 2.0 M hydrochloric acid or 1.8 M sulfuric acid was utilized. While hydrochloric acid was always used at the boiling point, sulfuric acid was sometimes used at the boiling point and sometimes at room temperature. From XRD analysis of the solid... 

In order to demonstrate that the adsorbents perform the same way as in the case of synthetic gold bromide solution, the actual leach products were produced and used to create adsorption isotherms for both resin types and activated carbon. Furthermore, the filtrates of isotherm products... 

Roasting of the sulphide slurry feed produces a dried calcine product, in the form of oxy-sulphates of copper and sulphates of cobalt, which is highly amenable to low-temperature acid leaching. Cooled calcine product is then sent to leach tanks, where it is combined with the recycled spent electrolyte for leach. Product of leaching is then filtered prior to electrolysis. 

Because vanadium pentoxide, V Oj, which coprecipitates simultaneously with sodium uran-ate, is always present in the impure yellow cake, at levels ranging from 5 to 6 wt.%, it must be removed by roasting the impure yellow cake with sodium carbonate at S60°C for 30 min, and after cooling the solid calcinated mass is leached with water to extract the soluble sodium vanadate, NaVOj. The leached product is filtered and the washed yellow cake is dried, while the solution from which vanadium can be recovered is stored. 

Trawinski, H., Counter-current washing of leaching products in thickeners and hydrocyclones, including the mathematical calculation , Aiftbereitungs-Techrtik, 18 No. 8, 395 04 (1977)... 

Structural analyses showed that non-leached catalysts are often dominated by decomposition products [37, 38, 41, 42,104,116,164]. In such a case, with TEM, XRD, MoBbauer spectroscopy, and EXAFS analysis, mostly metal particles, carbides, nitrides, and sometimes oxides were detected. In Fig. 16.15, a Mossbauer spectrum of an as-prepared catalyst (HT 800, 2 h at 800°C in Ar) and its acid-leached product (HT 800, washed) are shown. 

Fig. 16.15 Mbbbauer spectra of a catalyst as prepared from carbon-supported FeTPPCl and pyrolyzed at 800°C for 2 h (HT 800) and its acid-leached product (HT 800, washed). The velocity scale is given relative to sodium nitroprusside (0.26 mm/s vs. a-Fe). The figure was adapted from figure 4 of [38] reproduced with permission of the American Chemical Society...

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