Sliming

Anode slimes Anodization Ano diz ed aluminium Anodizing Anodizingaluminum... 

In both the sulfuric and nitric acid processes, the dorn metal must be in shot form prior to treatment to secure a reasonably rapid reaction. A number of steps also may be required in processing the dorne metal to remove miscellaneous impurities, particularly in treating material from copper-anode slime (31). 

Production. Indium is recovered from fumes, dusts, slags, residues, and alloys from zinc or lead—zinc smelting. The source material itself, a reduction bullion, flue dust, or electrolytic slime intermediate, is leached with sulfuric or hydrochloric acid, the solutions are concentrated, if necessary, and cmde indium is recovered as 99+% metal. This impure indium is then refined to 99.99%, 99.999%, 99.9999%, or higher grades by a variety of classical chemical and electrochemical processes. 

Electrolytic Eefming. Electrolytic refining (26,27), used by Cominco Ltd. (Trad, B.C., Canada) and Cerro de Pasco Corp. (La Oroya, Pern), as weU as by several refineries in Europe and Japan, removes impurities in one step as slimes. The impurities must then be separated and purified. Before the development of the Betterton-KroU process, electrolytic refining was the only practical method of reducing bismuth to the required concentrations. 

Slimes Treatment. After the corroded anodes are washed, and the adhering slimes scraped off, filtered, and dried, approximately 8% moisture is left to prevent dusting. The general practice is to smelt the slimes in a small reverberatory furnace, which produces a slag 10—12% by weight of the slimes (Eig. 

Fig. 16. Electrolytic refining slimes treatment flow diagram. See text.

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. 

Sodium sihcate (41°Bh, 1 3.22 ratio Na20 Si02) is added in the milling operation to disperse the slime, mosdy kaolin. Dispersion also aids the grinding process. The rod mill serves to grind the ore to 0.833 mm (—20 mesh) or to the point where mica, quart2, feldspar, and iron minerals are Hberated. Cyclones, or rake, hydrauhc, or other types of classifiers, are used after grinding to produce coarse and fine mica fractions that are treated separately. 

The slime, consisting of kaolin, fine quart2, and feldspar, is sometimes used as is after being dewatered. This material may be used in the manufacture of light-colored brick or may be further processed to produce a high grade ceramic kaolin used in the manufacture of dinnerware, electrical porcelain, or sanitary-ware (see Ceramics). Floes of kaolin may be sold in bulk from the drier or pulveri2ed and sold in a powdered form. 

Glass-grade siUca can be produced from most mica operations with additional beneficiation of the quart2. Ceramic-grade kaolin can be produced from some mica flotation plants by selective mining and additional processiag of the clay slime removed prior to mica flotation (see Clays). 

The products are an oversize (underflow, heavies, sands) and an undersize (overflow, lights, slimes). An intermediate size can also be produced by varying the effective separating force. Separation size maybe defined either as a specific size in the overflow screen analysis, eg, 5% retained on 65 mesh screen or 45% passing 200 mesh screen, or as a d Q, defined as a cut-off or separation size at which 50% of the particles report to the oversize or undersize. The efficiency of a classifier is represented by a performance or partition curve (2,6), similar to that used for screens, which relates the particle size to the percentage of each size in the feed that reports to the underflow. 

Holmans slimes table 2.0 X 4.6 0.01-0.06 for particles too fine for conventional table also for... 

Barfles cross-belt vanner 2.75 X 2.4 0.5 similar appHcations to slimes table... 

Flocculants and surfactants (qv) are used frequently as filter aids, particularly when slimes are present or when the particles to be filtered are very fine and difficult to filter. Low molecular weight polymers are more commonly used. These form small, dense floes which provide higher cake porosity. 

Blinding of the filter cloth by fine particles or slimes is reduced. Surfactants are also used to enhance flow through the filter cake pores. 

The use of these sHmicides may result in an appreciable increase in the cost of producing paper. However, thein use often reduces downtime that is caused by slime and, therefore, increases production which more than compensates for the initial cost of the sHmicides. White water systems also often contain proteolytic microorganisms which attack the machine felts and reduce thein useful life. Control of this problem may be accompHshed by treating the felts with a sHmicide foUowed by cleaning with a mild acid (see INDUSTRIALANTIMICROBIALAGENTS). 

Precipitate formation can occur upon contact of iajection water ions and counterions ia formation fluids. Soflds initially preseat ia the iajectioa fluid, bacterial corrosioa products, and corrosion products from metal surfaces ia the iajectioa system can all reduce near-weUbore permeability. Injectivity may also be reduced by bacterial slime that can grow on polymer deposits left ia the wellbore and adjacent rock. Strong oxidising agents such as hydrogen peroxide, sodium perborate, and occasionally sodium hypochlorite can be used to remove these bacterial deposits (16—18). 

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