Copper precipitation from sulfate solutions

Production and Economic Aspects. Thallium is obtained commercially as a by-product in the roasting of zinc, copper, and lead ores. The thallium is collected in the flue dust in the form of oxide or sulfate with other by-product metals, eg, cadmium, indium, germanium, selenium, and tellurium. The thallium content of the flue dust is low and further enrichment steps are required. If the thallium compounds present are soluble, ie, as oxides or sulfates, direct leaching with water or dilute acid separates them from the other insoluble metals. Otherwise, the thallium compound is solubilized with oxidizing roasts, by sulfatization, or by treatment with alkaU. The thallium precipitates from these solutions as thaUium(I) chloride [7791 -12-0]. Electrolysis of the thaUium(I) sulfate [7446-18-6] solution affords thallium metal in high purity (5,6). The sulfate solution must be acidified with sulfuric acid to avoid cathodic separation of zinc and anodic deposition of thaUium(III) oxide [1314-32-5]. The metal deposited on the cathode is removed, kneaded into lumps, and dried. It is then compressed into blocks, melted under hydrogen, and cast into sticks. 

When a strip of zinc metal is dipped in a solution of copper(II) sulfate, zinc is oxidized to 7n (a >5 )1 and q) is reduced to copper metal. The insoluble metal precipitates from the solution, hi the molecular views, water moiecuies and spectator anions have been omitted for clarity. 

Two other refining processes are also frequently employed. One involves hydrometallurgical refining in which sulfide concentrates are leached with ammonia solution to convert the copper, nickel, and cobalt sulfides into their complex amines. Copper is precipitated from this solution upon heating. Under such conditions, the sulfide-amine mixture of nickel and cobalt are oxidized to their sulfates. The sulfates then are reduced to metalhc nickel and cobalt by heating with hydrogen at elevated temperatures under pressure. The metals are obtained in their powder form. 

The three principal reactions in the precipitation of copper from sulfate, solutions by metallic iron have been established by Wartman and Roberson (W7) to be the following ... 

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. 

Aqueous ammonia also acts as a base precipitating metallic hydroxides from solutions of their salts, and in forming complex ions in the presence of excess ammonia. For example, using copper sulfate solution, cupric hydroxide, which is at first precipitated, redissolves in excess ammonia because of the formation of the complex tetramminecopper(TT) ion. 

Cadmium also may be recovered from zinc ores and separated from other metals present as impurities by fractional distillation. Alternatively, the cadmium dust obtained from the roasting of zinc ore is mixed with sulfuric acid. Zinc dust is added in small quantities to precipitate out copper and other impurities. The metal impurities are removed by filtration. An excess amount of zinc dust is added to the solution. A spongy cadmium-rich precipitate is formed which may he oxidized and dissolved in dilute sulfuric acid. Cadmium sulfate solution is then electrolyzed using aluminum cathodes and lead anodes. The metal is deposited at the cathode, stripped out regularly, washed and melted in an iron retort in the presence of caustic soda, and drawn into desired shapes. More than half of the world s production of cadmium is obtained by elecrolytic processes. 

In another industrial process, flue dusts from smelting lead and zinc concentrates are boiled in acidified water. Thallium dissolves and is separated from insoluble residues by filtration. Dissolved thallium in solution then is precipitated with zinc. Thallium is extracted from the precipitate by treatment with dilute sulfuric acid which dissolves the metal. The solution may also contain zinc, cadmium, lead, copper, indium, and other impurities in trace amounts. These metals are precipitated with hydrogen sulfide. The pure thallium sulfate solution then is electrolyzed to yield thallium. 

Alkaline-Earth Sulfides and Sulfoselenides. Activated alkaline-earth sulfides have been known for a long time their luminesence is very varied. Emission bands between the ultraviolet and near infrared can be obtained by varying the activation. They are produced by precipitation of sulfates or selenites from purified solutions, followed by reduction with Ar-H2. The addition of activators, for example, copper nitrate, manganese sulfate, or bismuth nitrate, is followed by firing for 1 - 2 h. Alkaline-earth halides or alkali-metal sulfates are sometimes added as fluxes. 

A. Preparation of Cuprous Hydroxide.—Cuprous chloride is prepared from a solution of 500 g. (2 moles) of crystallized copper sulfate and 150 g. (2.55 moles) of sodium chloride in 2.5 1. of water (Org. Syn. 3, 33) by the gradual addition of sodium sulfite (from no g. of sodium bisullite). After decanting the supernatant solution, the precipitate of cuprous chloride is added to a solution of 350 cc. of 6 N sodium hydroxide in r 1. of water contained in the 4-I. beaker in which the main synthesis is to be performed, the last portion of solid cuprous chloride being washed in with 1 1. of water. After vigorously stirring for a few minutes, the heavy precipitate of deep orange-colored cuprous hydroxide is permitted to settle and the supernatant... 

Carboxy-l -ethyl)-phenyl Methyl Tellurium3 A mixture containing 7 2 g (25 mmol) of 2-(2 -carboxy-l -ethenyl)-phenyl methyl tellurium, 50 g (1 mol) of hydrazine hydrate, 150 m/of DMSO, 2 drops of saturated aqueous copper(II) sulfate solution, and 2 drops of acetic acid is cooled to 0°. This mixture is stirred and a suspension of 30 g (0.14 mol) of sodium periodate in 250 ml of water is added slowly. The mixture is hydrolyzed with acid, the precipitate is filtered off and dissolved in aqueous sodium carbonate solution. Charcoal is added to the solution which is then filtered, acidified, and the precipitate is collected yield 5.8 g (80%) m.p. 105° (from toluene). 

Adjust your safety glasses comfortably over your eyes, and then add a tablespoon (15 milliliters) of baking soda to a half cup of water (120 milliliters) and stir. Allow the undissolved material to settle to the bottom (this should take about a minute), and then carefully pour off the clear liquid into another glass, leaving the solids. Pour a tablespoon (15 milliliters) of the copper sulfate solution described in the Shopping List and Solutions into the decanted baking soda solution. Beautiful blue flakes should immediately form and settle out of solution. You should also see some bubbles, and the supernatant, the liquid over the blue blob precipitate, should be a pastel blue. The bubbles are from excess acid in the copper solution reacting with the bicarbonate ion. 

Removal of interfering cations from the manganese(ll) sulfate solution is necessary before the subsequent electrochemical production of manganese IV) oxide (HMD) or manganese metal. Transition metal ions such as cobalt, nickel or copper and traces of arsenic are precipitated as their sulfides. 

Cobalt is produced as a coproduct of nickel or copper refining. Copper-cobalt sulfide concentrates can be processed by the RLE process. Mixed cobalt-nickel sulfides can be precipitated from ammoniacal leach solutions and as mixed nickel-cobalt hydroxide or carbonate from acid sulfate leach processes. From chloride leach solutions, cobalt can be separated by solvent extraction. Most cobalt production is associated with nickel production from sulfide and laterite ores. Pressure leaching, solvent extraction followed by the electrowinning of... 

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