Treating processes lead sulfide

Catalytic removal. In this process, lead sulfide serves as the catalyst for the following reaction when the oil is treated with sodium hydroxide ... 

Alternatively, low-grade stibnite ore is converted to its oxide which is then reduced with carbon. Tetrahedrite may be treated with sodium sulfide solution. The solution containing thioantimonate formed is then electrolyzed in a diaphragm cell using a steel cathode and lead anode. The metal is further refined by oxidation or electrorefining process. 

Zinc and lead usually occur together in nature as sulfides. Earlier separation processes involved the fine grinding of the combined sulfides and then treating the particles with chemical reagents to cause one sulfide to be preferentially wetted and rhns the two sulfides separated by the froth flotation process. In a first stage, the lead sulfide is floated while the zinc sulfide sinks to the bottom of the tank. In the second stage, the process is reversed and the zinc sulfide is floated. Gangue and other nonmetals collect at the bottom of the tank. The separated sulfides are dewatered to a 6-7% moisture content and are referred to as the zinc concentrate and the lead concentrate. 

Bender process a chemical treating process using lead sulfide catalyst for sweetening light distillates by which mercaptans are converted to disulfides by... 

The Dowa Mining Company (K9) in Kosaka, Japan has developed a hydrometallurgical process shown in Fig. 15 to treat 2400 metric tons/ month of copper-zinc sulfide flotation concentrates. The microscopically fine mixture of copper and zinc sulfides was separated from lead sulfide and barite by flotation. The flotation concentrate analyzed 8.7% Cu,... 

It can be chopped and fed with suitable nutrients to an anaerobic digester wherein 95% of the carbohydrate is converted to a mixture of carbon monoxide and carbon dioxide. In the process the lead precipitates as lead sulfide and is centrifuged to separate it from the residual carbohydrate and water. The aqueous layer is recycled to the digester after taking a suitable purge to bleed off salts. The aqueous waste can be treated with lime to precipitate the salts. As with alternative 2, the lead sulfide can be sold to a lead smelter at 50% of the price for pure lead. 

The flotation process was developed in Australia at the turn of the century to treat the primary sulfidic silver/lead/zinc ore at Broken Hill, New South Wales, following the mining of the overlying secondary ore. Oxidation to form the secondary zone had resulted in a concentration of silver and lead, and this section of the ore body could be smelted directly. The underlying sulfide zone, which comprised the bulk of the resource, was less amenable to treatment in the smelters of that era, and a method was required to recover the zinc values if the potentiality of the primary ore was to be realized. Many approaches were pursued to solve the sulfide problem before selective flotation was developed. The flotation process was then rapidly adopted by mining companies throughout the world. 

Although silver is not treated by solvent extraction in any of the flow sheets, silver is recovered from aqueous solution in several other situations. For these processes, Cytec developed reagents with donor sulfur atoms to extract this soft element. For example, tri-isobutylphosphine sulfide (CYANEX 47IX) extracts silver from chloride, nitrate, or sulfate media selectively from copper, lead, and zinc [32]. The silver is recovered from the loaded organic phase by stripping with sodium thiosulfate, and the metal recovered by cementation or electrolysis. Silver can also be extracted from chloride solution by a dithiophosphinic acid (CYANEX 301) [33]. 

Sulfide ores of silver and lead are also treated by the Parkes process, which is described later, in discussion of the metallurgy of lead. 

In one example the process involves loss of nitrogen and a sulfur atom. Thus cyclohexanone is treated with hydrazine and hydrogen sulfide to give the tetra-hydrothiadiazole (1) in quantitative yield. This is then oxidized with lead tetraacetate at 0° to give the azo sulfide (2) in 95% yield. When (2) is heated with triphenylphosphine (1.1 moles) at 100° for one hour, biscyclohexylidene (4) is obtained in 77% yield. The thiirane (3) is an intermediate it has been obtained by pyrolysis of (2).6... 

Ore mining presents matty of the same dangers of harmful chemical modification ofthe environment as does fossil fuel recovery. Sulfur-containing minerals frequently ac-compaity ores and, unless properly recovered and treated, promote the formation of acid waters and contamination of the atmosphere with sulfur dioxide (SO2) and hydrogen sulfide (H2S). Acidic sludges and slurries are produced in conjunction with the recovery and processing of iron, copper, zinc, and lead cyanide salts are used in the recov-... 

A novel approach in treating paste in order to provide feed for a paste lead electrowinning process is proposed by Engitec, in which all lead containing salts are converted into PbS by using anaerobic bacteria. This follows the successful commercial application of sulfate reducing bacteria to treat smelter waste waters for the separation and recovery of heavy metals as sulfides. Reactions are as in Equations 10.9 to 10.11 ... 

The assumed configuration of the sample plant is illustrated in Figure 17.1 and covers current practice for a plant treating average sulfide concentrates by sintering and processing of sinter in a blast furnace to produce aude lead bullion. Refining of the crude lead bullion is considered in a separate section. 

Besides the main reactions, several side reactions (mostly leading to the formation of undesirable sulfur compounds) occur in the process. These side reactions depend on the operating conditions and the composition of the gas to be treated. Usually a certain amount of thiosulfate formation is inevitable. In some cases it may even be desirable to operate these processes so that hydrogen sulfide is quantitatively converted to thiosulfate according to the following equations ... 

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