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Flotation
Published in Ko Higashitani, Hisao Makino, Shuji Matsusaka, Powder Technology Handbook, 2019
Wei Sung Ng, George Vincent Franks, Elizaveta Forbes, Luke Andrew Connal, Hiroki Yotsumoto
Depressants hamper the flotation of a targeted mineral, by rendering the surface hydrophilic or by blocking collector attachment to the surface. This can be accomplished by selective surface attachment, or by altering the pulp pH or Eh conditions to alter the mineral species present on the surface of the particles. Depressants are typically used to impede the flotation of hydrophobic gangue, as well as gangue minerals with similar chemistries as the targeted flotation mineral, to prevent dilution of the concentrate product. Examples of depressants include cyanide and sodium sulfite for sulfide minerals, and silicates, polysaccharides, starch, tannin, lignite, and xanthan gum for non-sulfide particles.
Resources and Processing
Published in C. K. Gupta, Extractive Metallurgy of Molybdenum, 2017
The function of depressants or depressing agents is to increase or assist the selectivity of one mineral from another. Originally, before the development of specific depressants, it was not possible to float minerals of one type from others where floatability was closely similar. Depressants make certain minerals hydrophilic, thereby preventing their flotation. Types of depressants are many. Their actions are complex and varied and in most cases little understood. This makes the depression more difficult to control than the use of other types of reagent in flotation. Slime coating is a fine example of a naturally occurring form of depression. Slimes in a comminuted ore adversely affect flotation. They coat the mineral particle and retard adsorption of collector. The particle size at which these results become significant depends on the flotation system. In general, however, fine particles below about 20 μm are taken to be potentially deleterious. Some form of desliming is usually carried out prior to flotation. Slimes can be removed from the mineral surfaces by vigorous agitation, or a slime dispersant may be used. Sodium silicate has quite often been used to disperse the slime layers formed on the mineral particles. That leaves the mineral surfaces clean for interaction with collector and to acquire floatability. In this respect, sodium silicate is an activator, preventing depression action by slimes. As regards sodium silicate, it may also be pointed out that it is used as a depressant in some systems, being one of the field of nonsulfide minerals flotation. As a typical example, mention may be made of minerals such as scheelite, calcite, and fluorite. In the case of flotation of these minerals, sodium oleate is the major collector. The selectivity in the separation of scheelite from calcite is often not adequate, and for this reason sodium silicate has been used to improve selectivity in this system.
Application of inverse gas chromatography to bench scale flotation of sulphide ore
Published in Canadian Metallurgical Quarterly, 2023
Shiva Mohammadi-Jam, Gilberto Rodrigues da Silva, Kristian E. Waters
In order to achieve an efficient separation of minerals through flotation, the surface of the desired minerals must be altered to obtain the necessary hydrophobicity, which leads to a strong bubble-particle interaction. In order to render the mineral hydrophobic, reagents called collectors are added. Depressants may be used to block the adsorption of the collectors onto the mineral surface or to reduce the hydrophobic nature of unwanted minerals. The development of sulphide flotation over many years has shown that sulphide mineral wettability is affected by various factors, such as surface treatment conditions, pH, electrochemical potential, chemical alteration of the surface in the pulp, galvanic interactions between different sulphide minerals, the presence of other particles and grinding by-products and wide range of particle sizes [10, 11]. In addition, sulphide minerals are highly prone to surface oxidation, which can result in both hydrophobic surfaces (rich in sulphur, metal-deficient sulphides or polysulphides) and hydrophilic surfaces (rich in oxides/oxyhydroxides/hydroxides). Therefore, the relative proportion of these species on the chemically altered surface is a key factor in flotation [11–13]. Depending on the collector concentration, hydrophobicity may or may not overcome the hydrodynamic effects of particle size [12].
Beneficiation of low-grade collophane by a novel combined enhanced gravity separation-flotation process
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2022
Xuebin Zhang, Youjun Tao, Yushuai Xian
The effect of water glass dosage on cleaner flotation was studied (conditions: collector of 0.5 kg/t ZF-1, and PH regulator of 5.5 kg/t Na2CO3) (see Figure 8a). With the increase of water glass dosage, the P2O5 grade increases at first and then decreases. When the dosage of water glass is 0.8 kg/t, the P2O5 grade reaches 26.58%. The separation efficiency gradually decreases at first and then increases rapidly, and the P2O5 recovery gradually decreases with the increased water glass dosage. On the whole, the changes of P2O5 grade, P2O5 recovery, and separation efficiency are not obvious by adjusting the dosage of water glass, which indicates that the content of silicate gangue mineral in the concentrate after the enhanced gravity pre-separation and rougher flotation is lower. That is to say, the enhanced gravity pre-separation and direct flotation have better desilication effect on low-grade collophane. Overall, 0.8 kg/t is determined as the optimal dosage of depressant in cleaner flotation.
Beneficiation of Lead-Zinc Ores – A Review
Published in Mineral Processing and Extractive Metallurgy Review, 2022
Aryasuta Nayak, M. S. Jena, N. R. Mandre
Selective flotation of valuable minerals from gangue is not feasible without the use of depressants. Standard lead depressants are starch, dextrin, dichromate, and zinc depressant is zinc sulfate, cyanide, etc. out of which zinc sulfate is the most commonly used depressant because of its low cost (Wang et al. 2019). Earlier sodium cyanide was more preferable. But, now-a-days its application has become more limited owing to its toxic nature (as it can turn into toxic gas in the presence of an acidic medium). Also, the presence of cyanide as a residual reagent in tailing dump causes environmental pollution to the surrounding watercourses through the dam or surrounding rock. Sometimes the effect of depressants is insufficient during flotation given to the mineral assemblage and surface properties of the target mineral. So, researchers investigated the development of new depressants for a complex poly-metallic sulfide mineral system (Bulatovic and Wyslouzil 1995; Bulatovic, Wysouzil and Bermejo 2001). The details are provided in Table 4. The selectivity of collector adsorption on the mineral surface is usually regulated by depressants (Bulatovic and Wyslouzil 1995).