Sulphides, oxidation

The kinetics of the processes of oxidation of these complex sulphides have not been established quantitively, but the rate of advance of the oxides into sulphide particles of inegular shapes were always linear. This suggests tlrat the oxide films were rupmred during growth thus permitting the gas phase to have relatively unimpeded access to tire sulphide-oxide interface in all cases. 

In general, greatly reduced rates of attack are observed for impure or dilute nickel alloys compared with pure nickel when exposed to SO2 + O2 atmospheres. Haflan et al. have attributed this to the segregation of impurities at the sulphide/oxide interface causing breakup of the sulphide network. For example in the case of silicon additions, it has been shown that silicates form and it has been proposed that these alter the wetting characteristics of the sulphide and prevent the establishment of an interconnected sulphide network. 

Although not strictly included within the scope of the present review, decompositions have been considered in the context of related rate processes including sulphide oxidations, sulphidation of oxides and/or metals and diffusion in sulphide phases [689],... 

In 1960, Montanari and Balenovic and their coworkers described independently the first asymmetric oxidation of sulfides with optically active peracids. However, the sulphoxides were formed in this asymmetric reaction (equation 130) with low optical purities, generally not higher than 10%. The extensive studies of Montanari and his group on peracid oxidation indicated that the chirality of the predominantly formed sulphoxide enantiomer depends on the absolute configuration of the peracid used. According to Montanari the stereoselectivity of the sulphide oxidation is determined by the balance between one transition state (a) and a more hindered transition state (b) in which the groups and at sulphur face the moderately and least hindered regions of the peracid,... 

The appropriate ratio between chiral Schiff bases and Ti(Oi-Pr)4 from catalytical point of view has been recommended. On the basis of the 1H NMR measurements at — 20 °C, the kinetic scheme for sulphide oxidation has been proposed. 

Ritchie, A.I.K. 1994. Sulphide oxidation mechanisms-controls and rates of oxygen transport. In Alpers, C.N. Blowes, D.W. (eds.), Environmental Geochemistry of Sulphide Oxidation, ACS Symposium Series 550. Washington DC. 

Mixed copper sulphide oxide ores. These contain varieties of both sulphide and oxide minerals, and are the most complex copper-bearing ores from a beneficiation point of view. The major copper minerals present in this ore type include bomite, chalcocite, covellite, malachite, cuprite and chrysocolla. In some cases, significant amounts of cobalt minerals are also present in this ore. 

This method is the most commonly used in beneficiation if oxide copper-bearing ore. The reagent schemes used to treat oxide copper ores, mixed copper sulphide oxide ores and oxide copper cobalt ores varies from one ore type to the next, mainly by type of collector and sulphidizer used. 

The mixed sulphide oxide ores usually contain two or more oxide minerals, including cuprite, malachite and tenanntite. The sulphide copper minerals are represented by covellite and bomite. Examples of this type of operation are located in the former Republic of Zaire (Komoto, Dima 1 and 2 plants), and the Nchanga open pit plant in Zambia. 

There are only slight differences in the reagent schemes used to treat the mixed sulphide oxide ores. The type of sulphidizier and collectors are the main variance in the reagent... 

Reagent schemes used in beneficiation of mixed sulphide oxide ores... 

Industrial Practice in Beneficiation of Mixed Sulphide Oxide Ores... 

The plant metallurgical results achieved in these concentrators are presented in Table 19.12. In most cases, the results obtained on mixed copper sulphide oxide ores are better than those obtained on oxide ores. The floatability of oxide copper from mixed ore is usually better than the floatability of copper from oxide ores. 

Ser, F., Sulphydric Flotation of Previous Sulphidized Oxide Copper Minerals of Nachanga Consolidated Copper Mines Limited (Zambia), Rudy, Vol. 5, pp. 169-174, 1970. 

Bulatovic, S., and Jessup, T., Evaluation of New Line of Collector on Zambian Sulphide/Oxide Ore and the Chilean Oxide Ore, R D Report 87, 1993. 

Flotation of Mixed Lead Zinc Sulphide Oxide and Oxide Lead and Zinc Ores... 

SULPHIDE OXIDE AND OXIDE LEAD ZINC ORES... 

There are a variety of mixed sulphide oxide ores and oxide lead zinc ores, and these ores cannot be classified into any specific group due to the vast differences in geology and mineral compositions. Only limited literature is available on the geological and miner-alogical characteristics of these ores. From a processing point of view, these ores can be classified into the following groups ... 

Mixed sulphide oxide lead zinc ores... 

The beneficiation of mixed lead zinc sulphide oxide ores is a complex process and is dependent on gangue composition of the ore. There are two basic types of mixed sulphide oxide ores that have been extensively studied. These include (a) ores with dolomitic and... 

Treatment of mixed lead zinc sulphide oxide ores with dolomitic and calcite gangue... 

Continuous locked cycle test results from mixed lead zinc sulphide oxide ore... 

There are only few operations treating mixed lead zinc sulphide oxide ores that contain barite-calcite gangue minerals. A typical example of such an operation is the Tynagh oxide complex in Ireland [11]. In this deposit, the oxide ores are generally located at the bottom and at the ends of the sulphide mud ores. The major gangue mineral is barite (large quantities) and minor amounts of clay. This ore assays 8.5% Pb(total), 6% Pb(oxide), 6.8% Zn(total) and 5% ZnO. 

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