Flotation performance

All DAFs are similar to each other in terms of theory, principles, design, operation, and secondary flotation performance. The authors select the circular DAF process equipment manufactured by KEC for the purpose of feasibility studies. The users should contact more than one major DAF and DAFF manufacturers for appropriate pilot plant demonstrations and cost comparisons. Rectangular DAF and DAFF clarifiers are as good as circular DAF and DAFF clarifiers. 

Ekmekci, Z., Bradshaw, D.J., Harris, P.J., and Buswel, A.M., Interactive Effect of Milling Media and CuS04 Additions on the Flotation Performance of Sulphide Minerals from the Morensky ore, Part II Froth Stability, International Journal of Mineral Processing, Vol. T8, pp. 164-174, 2006. 

In this study, the flotation performance of a series of newly developed hy-droxamate-based collectors was evaluated on different crude clays from Georgia, USA. These new collectors provide improved selectivity over the standard tall oil chemistry and the commercial hydroxamate reagent. Aero Promoter 6493 (AP 6493). The modified hydroxamates have the advantages of higher activity, easier... 

To further prove the efficacy of S-8706 and its applicability on a full-scale, a plant trial was conducted at Thiele Kaolin Company s flotation plant. The average SE value obtained with AP 6493 before the trial run was 70. Replacing AP 6493 with S-8706, the flotation performance during the trial run improved to... 

After the plant trial run with S-8706, the measured SE value for AP 6493 averaged about 68. This trial shows the improved flotation performance obtained with the use of S-8706 (Table 6). 

Gravity settling In the CPI will cnly remove free oil effective deoiling of water can, however, be achieved with gas flotation. Addition of chemical flocculant improved flotation performance, but chemical alone was not effective. 

Chemical flotation aids. There are a variety of surface active chemicals that can be used to improve flotation performance. 

K. Hadler, Z. Aktas, and J. J. Cilliers, The effects of frother and collector distribution on flotation performance. Minerals Engineering 18(2) (2005). 

Flotation performance of the collectors can also be predicted from data in Table 5.7 [4], For collectors (1) and (7), due to introducing an acceptor, the bonding power of sulfur atom to iron ion is decreased markedly, but the bonding power to copper ion stays strong. Therefore, the selectivity of separation of copper mineral from pyrite is improved. However, the reactivity of the collector (2) to the two minerals is increased because of introducing a donor group with poor selectivity in flotation. 

Non-polar groups in collector molecules play the following three roles in determining the flotation performance ... 

Flotation performance of homologous collectors reported by Wark et al. [19], it was found that contact angle of minerals treated with collector solutions depends only on the structure of the non-polar groups of the reagent, and not on any other portion. In other words, for various structures of non-polar groups, contact angle on sulfide minerals in-... 

S.2.5.3.2. Iso-alkyl chains Flotation performance of collectors with an iso-structure chain is different from that of collectors with a linear structure. This is summarized below ... 

It has been reported that in the case of flotation of galena, flotation performance depends on the micro-bubbles contained in the pulp as follows [17] (Table 5.14a). 

Typical flotation performances of Hansenula polymorpha cells from C-, N-and P-limited cultivations are shown in Table 6. The highest separation was obtained with cells cultivated under P-limitation (with 4 x 25 x 10 gP/g cell mass) S = 442 and R = 96.4 [116]. 

The cultivation medium composition and the proteins excreted by the yeast cells were determined and their influence on the flotation performance was investigated by Bahr et al. [115]. The sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAAGE) and native PAAGE measurements indicated that during the cultivation various glycoproteins were excreted, which were distributed differently between the foam and the flotation residue liquid. A... 

Table 6. Typical flotation performances of the Hansenula polymorpha cells from C-, N- and P-limited cultures as well as C-limited cultures with amino acid supplement C(AS) in the dilution range 0.1 and 0.25 h (1 Pirt unit = 0.0255 g P/g cell mass) [116]...

The flotation performances in the pilot plant were better than those achieved on a laboratory scale, probably because of the reduced wall effect in the flotation column. 

Microorganisms have a complex cell envelope structure. Their surfaces charge and their hydrophobicity cannot be predicted, only experimentally determined [131]. Several microorganisms are not hydrophobic enough to be floated. They need collectors, similar to ore flotation. In cultivation media proteins which adsorb on the cell surface act as collectors. The interrelationship between cell envelope and proteins caimot be predicted, only experimentally evaluated. The accumulation of cells on the bubble surface depends not only on the properties of the interface, proteins and cells, but on the bubble size and velocity as well [132]. On account of this complex interrelationship between several parameters, prediction of flotation performance of microbial cells based on physicochemical fundamentals is not possible. Therefore, only empirical relationships are known which cannot be generalized. Based on the large amount of information collected in recent years, mathematical models have been developed for the calculation of the behavior of protein solutions and particular microbial cells. They hold true only for systems (e.g. BSA solutions and particular yeast strains) which are used for their evaluation. In spite of this, several recommendations for protein and microbial cell flotation can be made. 

Cliek EC, YUmazer BZ. (2003) Effects of hydrodynamic parameters on entrainment and flotation performance. Miner. Eng., 16 745-756. 

Alkoxy xanthates mainly contain ethyoxyl and propoxy xanthates. In general, the flotation performances of alkoxy xanthates are similar to those of alkyl xanthates. But alkoxy xanthate has a better frothing capability. 

The flotation performance of m-cresol dithiophosphates is best. The explanation for the performance difference of three isomers had been given in Chap. 4 (Volume 1). 

These dithiophosphates are prepared from coal tar which contains various phenols. For example, the cut fractions of coal tar which are distilled, respectively, at 190-205, 205-225, 225-245, and 245-265 °C perform good flotation performance. The domestic 25 dithiophosphate is distilled from coal tar at 190-205 °C. 

According to Japanese patent, these dithiophosphates are mainly comprised of sodium salt and ammonium salt of phenol dithiophosphates. They can be applied to flotate copper pyrite, chalcocite, and copper slag. Their flotation performances are better than those of xanthates. And their solution stabilities are high comparatively. 

H.M. Bazanova also studied the effects of various nonpolar groups on flotation performance of dithiocarbamate. Those dithiocarbamates with various nonpolar groups are as follows ... 

Flotation results of Cu-Ni sulfide ore showed that the flotation performances of dialkyl dithiocarbamates are relatively better among these above reagents. And flotation results of secondary umnium ore showed that the flotation performances of monoalkyl dithiocarbamates with C4-C18 are relatively better. Meantime, the flotation performance of ammonium salt of dithiocarbamates is better than that of potassium salt of dithiocarbamates when the number of alkyl C atoms of these two reagents is 10. 

IV) The flotation performance of dithiocarbamates is better than that of xanthate when they are used to flotate PbS from Pb-Cu ore. 

Flotation results of Cu-Ni sulhde ore showed that the flotation performance of dibutyl amino ethanol dithiocarbonate is relatively better among these above reagents. Tributyl amino ethanol dithiocarbonate has good collecting capability, but low selectivity. 

The flotation performance of amino ethanol dithiocarbonates is influenced obviously by pH, especially nearby its isoelectric point. 

These new N-substituted thiocarbamides such as N, N —ethylidenethiocar-bamide and N, N —propylidenethiocarbamide are characterized by low-toxicity, good solubility, and flotation performance. 

Comparison of octyl isothiourea and dixanthogen in the flotation of copper-sulfide ore is listed in Table 1.8. The particle size of copper-sulfide ore is 10 mesh. And the mass fraction of copper in copper-sulfide ore is 4-4.5 %. It can be seen that the flotation performance of octyl isothiourea is better than that of dixanthogen. 

The flotation performance of isothiourea is influenced obviously by pulp pH. Isothiourea only performs in alkaline medium. For example, the effect of pH on the recovery rate of gold pyrite using amyl isothiourea as collector is shown in Fig. 1.5 [12]. 

The explanation for the effect of pH on the flotation performance of isothiourea lies in that isothiourea is converted rapidly to mercaptan. The hydrolytic process of isothiourea is as follows ... 

The flotation results of pyrite using various isothioureas at different pH conditions are shown in Fig. 1.6. It is shown in Fig. 1.6 that isothiourea has no collecting capability in acid medium because isothiourea does not undergo hydrolysis. The flotation performance of isothiourea is better than those of other two reagents in alkaline medium because isothiourea is converted to mercaptan. Based on these results, functional mechanism of isothiourea is that the hydrolysis product of isothiourea (mercaptan) and the oxidation product of mercaptan (organic bisulfide) are effective collectors. Therefore, the flotation performance of isothiourea depends... 

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