Lead complexes sulfide

Silver is widely distributed throughout the world. It rarely occurs in native form, but is found in ore bodies as silver chloride, or more frequently, as simple and complex sulfides. In former years, simple silver and gold-silver ores were processed by amalgamation or cyanidation processes, The availability of ores amenable to treatment by these means has declined. Most silver is now obtained as a byproduct or coproduct from base metal ores, particularly those of copper, lead, and zinc. Although these ores are different in mineral complexity and grade, processing is similar. 

Workers at PerkinElmer (Perkin Elmer Ltd., Beaconsfield, UK, Private Communication) claim that sensitivity and precision in lead determinations in spinach were both improved by using the L vov platforms as opposed to normal off the wall techniques. This is because dependence on temperature is reduced. Johns et al. [26] has described a quantitative thin-layer chromatographic procedure for the determination of lead in plant tissues. The method is based on the use of ammonium pyrrolidinedithiocarbamate for the extraction and enrichment of lead. Instead of the previously reported conversion and visualisation of the lead complex in the short wavelength region using dithizone, the lead carbamate was converted to lead sulfide with the aid of a 6% solution of sodium sulfide in methanol/water (3 1) on silica plates, after development of the plates with toluene. See also Sects. 7.34.1,7.34.4 and 7.34.5... 

In the treatment of complex sulfide concentrates containing copper, nickel, cobalt, lead, and iron, roasting with a moderate excess of sodium chloride at temperatures up to 400°C prior to leaching with hydrochloric acid has been succeasfully used by Kershner and Hoertel (K4) in the recovery of more than 95% of cobalt, nickel, and copper. The chloridized product is treated with steam at 300°C to make most of the iron insoluble before leaching at a pH of 1.0. The advantages of a salt roast prior to... 

These collectors are effective only under oxidizing conditions, and it is generally accepted that the species that confers hydrophobicity on the mineral surface is either a chemisorbed metal thio compound or the oxidized form of the collector, dithiolate. The amounts of each species formed will depend on the relative stabilities of the metal—sulfur and sulfur—sulfur bonds. The formation of four-membered chelate rings is also possible with soft metal ions such as copper(I) because the largely covalent character of the bond in this instance is able to overcome the strain within the ring by extensive electron delocalization. This could account for the >artial selectivity of some of these reagents for the copper minerals, which has been put to good use in the sequential flotation of copjrer, lead and zinc from complex sulfide ores. ... 

Complete cyanide recoveries are typically attained for the most important metal-cyanide complexes found in environmental samples. Detection limits below 0.05 pg/1 have been reported. The main drawback of this system is that the UV radiation promotes thiocyanate decomposition, what leads to sulfide and cyanide formation. To overcome this problem, it is recommended to use borosilicate glass instead of a quartz reactor, which cuts off radiation below 300 nm. 

Gold in complex sulfide ores Gold is impregnated in sulfides of copper, lead or zinc Many deposits, mined for Cu, Pb and Zn are of this type. Gold is an important by-product... 

The carbopalladation is extended to homoallylic amines and sulfides[466. Treatment of 4-dimethylamino-l-butene (518) with diethyl malonate and Li2PdCl4 in THF at room temperature leads to the oily carbopalladated complex 519, hydrogenation of which affords diethyl 4-(dimethylamino) butylmalonate (520) in an overall yield of 91%. Similarly, isopropyl 3-butenyl sulfide (521) is carbopalladated with methyl cyclopentanonecarboxylate and Li2PdCl4. Reduction of the complex affords the alkylated keto ester 522 in 96% yield. Thus functionalization of alkenes is possible by this method. 

Metals less noble than copper, such as iron, nickel, and lead, dissolve from the anode. The lead precipitates as lead sulfate in the slimes. Other impurities such as arsenic, antimony, and bismuth remain partiy as insoluble compounds in the slimes and partiy as soluble complexes in the electrolyte. Precious metals, such as gold and silver, remain as metals in the anode slimes. The bulk of the slimes consist of particles of copper falling from the anode, and insoluble sulfides, selenides, or teUurides. These slimes are processed further for the recovery of the various constituents. Metals less noble than copper do not deposit but accumulate in solution. This requires periodic purification of the electrolyte to remove nickel sulfate, arsenic, and other impurities. 

Sulfide collectors ia geaeral show Htfle affinity for nonsulfide minerals, thus separation of one sulfide from another becomes the main issue. The nonsulfide collectors are in general less selective and this is accentuated by the large similarities in surface properties between the various nonsulfide minerals (42). Some examples of sulfide flotation are copper sulfides flotation from siUceous gangue sequential flotation of sulfides of copper, lead, and zinc from complex and massive sulfide ores and flotation recovery of extremely small (a few ppm) amounts of precious metals. Examples of nonsulfide flotation include separation of sylvite, KCl, from haUte, NaCl, which are two soluble minerals having similar properties selective flocculation—flotation separation of iron oxides from siUca separation of feldspar from siUca, siUcates, and oxides phosphate rock separation from siUca and carbonates and coal flotation. 

AEROPHINE 3418A promoter is widely used ia North and South America, AustraHa, Europe, and Asia for the recovery of copper, lead, and ziac sulfide minerals (see Elotatton). Advantages ia comparison to other collectors (15) are said to be improved selectivity and recoveries ia the treatment of complex ores, higher recoveries of associated precious metals, and a stable grade—recovery relationship which is particularly important to the efficient operation of automated circuits. Additionally, AEROPHINE 3418A is stable and, unlike xanthates (qv), does not form hazardous decomposition products such as carbon disulfide. It is also available blended with other collectors to enhance performance characteristics. 

Certain of the above reactions are of practical importance. The oxidation of hydrogen sulfide in a flame is one means for producing the sulfur dioxide required for a sulfuric acid plant. Oxidation of hydrogen sulfide by sulfur dioxide is the basis of the Claus process for sulfur recovery. The Claus reaction can also take place under mil der conditions in the presence of water, which catalyzes the reaction. However, the oxidation of hydrogen sulfide by sulfur dioxide in water is a complex process leading to the formation of sulfur and polythionic acids, the mixture known as Wackenroeder s Hquid (105). 

Precipitation is affected by pH, solubiUty product of the precipitant, ionic strength and temperature of the aqueous stream, and the presence of metal complexes. For each metal precipitant, there is an optimum pH where its solubiUty is lowest and hence, the highest removals may be achieved. When an aqueous stream contains various metals, the precipitation process caimot be optimized for each metal, sometimes making it difficult to achieve effluent targets for each. SolubiUty products depend on the form of the metal compound and ate lowest for metal sulfides, reflecting the relative insolubiUty of these compounds. For example, the solubiUty product for lead sulfide [1314-87-0] is on the order of compared to 10 for lead carbonate. Metal... 

Montana. These deposits consist of stibnite and other sulfide minerals containing base metals and silver or gold. Ores of the complex deposits are mined primarily for lead, copper, 2inc, or precious metals antimony is a by-product of the treatment of these ores. 

Treatment of the primary product with a zinc salt leads to separation of a-CySj from its coproduct CSj, and multigram amounts of its complexes [NR4]2 [20(0-0385)2] and of the eorresponding -isomer s eomplexes afford convenient starting points for the synthesis of molecular binary sulfides as indicated below. 

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