Dithiophosphate collectors

Aetivators. These are used to make a mineral surface amenable to collector coating. Copper ion is used, for example, to activate sphalerite (ZnS), rendering the sphalerite surface capable of absorbing a xanthate or dithiophosphate collector. Sodium sulfide is used to coat oxidized copper and lead minerals so that they can be floated by a sulfide mineral collector. 

Tellurides, on the other hand, are readily floatable in the presence of small quantities of collector, and it is believed that tellurides are naturally hydrophobic. Tellurides from Minnesota (USA) were floated using dithiophosphate collectors, with over 9% gold recovery. 

The type of collector and flowsheet configuration play an important role in gold recovery from these ores. With a flowsheet that uses bulk Cu-Pb flotation followed by Cu-Pb separation, the gold recovery is higher than that achieved with a sequential Cu-Pb flotation flowsheet. In laboratory tests, and Aerophine collector type, in combination with xanthate, had a positive effect on gold recovery as compared to either dithiophosphate or thionocarbamate collectors. Table 17.10 compares the metallurgical results obtained with an Aerophine collector to those obtained with a dithiophosphate collector. 

Xanthates and dithiophosphates dominate sulfide flotation usage, though several other collectors including more recently developed ones are gaining acceptance rapidly (43). As of this writing, this is an active area of research. Many of the sulfide collectors were first used ia the mbber iadustry as vulcanizers (16). Fatty acids, amines, and sulfonates dominate the nonsulfide flotation usage. The fatty acids are by-products from natural plant or animal fat sources (see Fats and fatty oils). Similarly petroleum sulfonates are by-products of the wood (qv) pulp (qv) iadustry, and amines are generally fatty amines derived from fatty acids. 

The pH of the pulp to the flotation cells is carefliUy controlled by the addition of lime, which optimizes the action of all reagents and is used to depress pyrite. A frother, such as pine oil or a long-chain alcohol, is added to produce the froth, an important part of the flotation process. The ore minerals, coated with an oily collected layer, are hydrophobic and collect on the air bubbles the desired minerals float while the gangue sinks. Typical collectors are xanthates, dithiophosphates, or xanthate derivatives, whereas typical depressants are calcium or sodium cyanide [143-33-9] NaCN, andlime. 

Figure 2.28 Critical pH curves for flotation with sodium dithiophosphate as collector for some sulfidic minerals.

Flotation was carried out at an alkaline pH, controlled by lime. A xanthate collector with cyclic alcohol further (pine oil, cresylic acid) was shown to be the most effective. The use of small quantities of a dithiophosphate-type collector, together with xanthate was beneficial. 

The reagent schemes used in commercial operations treating porphyry copper-gold ores vary considerably. Some operations, where pyrite rejection is a problem, use a dithiopho-sphate collector at an alkaline pH between 9.0 and 11.8 (e.g. OK Tedi/PNG Grasberg/ Indonesia). When the pyrite content in the ore is low, xanthate and dithiophosphates are used in a lime or soda ash environment. 

The primary collector used in PGM flotation is xanthate. As a choice of secondary collectors, dithiophosphates and mercaptans are used in some operating plants. 

Laboratory studies conducted on Falconbridge ores, also from the Sudbury Region, during 1980 [16] showed that PGM recovery can be improved with the use of a secondary collector. Figure 18.5 shows the effect of level of secondary collector on PGM recovery in a Cu-Ni bulk concentrate. The highest PGM recoveries were achieved using isobutyl dithiophosphate (Minerec 2087) as the secondary collector. 

The consumption rate of sulphidizer also depends on the type of collector used. When using xanthate only, the sulphidizer rate is much higher than when using certain secondary collectors, such as dithiophosphates. 

During oxide lead flotation, the choice of collector is rather limited to xanthates, which are used in operating plants. Dithiophosphates and mercaptans are used as secondary collectors. This is due to the fact that natural ores contain a variety of floatable gangues, for which the anionic flotation process is not applicable. The use of chelating agents as flotation collectors for oxide lead flotation have been extensively examined [5,6], Oximes/fuel oil... 

Suitable collectors can render hydrophilic minerals such as silicas or hydroxides hydrophobic. An ideal collector is a substance that attaches with the help of a functional group to the solid (mineral) surface often by ligand exchange or electrostatic interaction, and exposes hydrophobic groups toward the water. Thus, amphi-patic substances (see Chapter 4.5), such as alkyl compounds with C to C18 chains are widely used with carboxylates, or amine polar heads. Surfactants that form hemicelles on the surface are also suitable. For sulfide minerals mercaptanes, monothiocarbonates and dithiophosphates are used as collectors. Xanthates or their oxidation products, dixanthogen (R - O - C - S -)2 are used as collectors for... 

Amphipathic substances such as we have discussed throughout this chapter are used as collectors. Alkyl compounds with C8 to C18 chains are widely used with carboxylate, sulfate, or amine polar heads. For sulfide minerals, sulfur-containing compounds such as mercaptans, monothiocarbonates, and dithiophosphates are used as collectors. The most important collectors for sulfides are xanthates, the general formula for which is... 

Collectors arc chemical reagents that selectively coat the particles to be floated with a water-repellanl surface that will adhere to air bubhlcs. Collectors generally are classified as cationic, anionic, or nonionic. Examples of collectors include the xanlhales, dithiophosphates. thiocarbonilides. and ihionocarbonales, all of which are anionic collectors... 

Fig. 99. Production diagram of bis(octylphenoxy)dithiophosphate 1 - sulfiding reactor 2, 3 - batch boxes 4, 8- absorbers 5, 13 - containers 6 - pumps 7- phos-phorisation reactor 9- collector 10- settling box 11 - neutraliser 12 - ultracentrifuge...

Promoters or collectors provide the substances to be separated with a water-repellent air-avid coating that will adhere to air bubbles. Typical collectors for flotation of metallic sulfides and native metals are dithiophosphates and xanthates. Fatty acids and their soaps, petroleum sulfonates, and sulfonated fatty acids are widely used as collectors in flotation of fluorspar, iron ore, phosphate rock, and others. Fuel oil and kerosene are used as collectors for coal, graphite, sulfur, and molybdenite. Cationic collectors such as fatty amines and amine salts are widely used for separation of quartz, potash, and silicate minerals. 

Alkoxyl group exists in the non-polar position of some xanthates and dithiophosphates, which have properties similar to those of alkyl group and produce more froth. For example, etheralkyl carboxylate (ECA), R ,-(OC2H4) 2-OCH2COOH, has been reported as a collector where ni is Cg ig chain and W2 is the number of alkoxyl groups (0-16). Since its Ca or Mg salts with ni = 10, 12, 14, 17 and h2 = 10, 20 30 are soluble in water, ECA is suitable under hard water and low pH (<6) conditions for the flotation of calcium or magnesium minerals, chalcopyrite and beryl with better selectivity. FloatabiUty of Ca minerals is found to linearly decrease with n values and increase with h2 values. 

Hostaflot L. [Hoechst AG] Aliphatic dithiophosphates flotation collectors for sulfide minerals. 

PbosokresoL [Hoechst AG] Aromadc dithiophosphates flotation collectors for sui de minerals. 

Potassium amyl xanthate Potassium ethyl xanthate Sodium isobutyl xanthate Sodium isopropyl xanthate flotation collector, gold ore Sodium di-s-butyl dithiophosphate flotation collector, iron sulfide Ammonium dibutyl dithiophosphate flotation collector, lead Ammonium dibutyl dithiophosphate Sodium diethyidithiocarbamate... 

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