Oxidation reactions zinc sulphide

In all reactions between sulphides and oxygen occurring at high temperatures, the sulphur produced is oxidized by an excess of oxygen, so that actually a different reaction is observed in the oxidation of zinc sulphide... 

These reactions are strongly exothermic, which is typical of these types of oxidation reactions. This means that the heat produced by the reaction will heat up the particle and further increase the reaction rate. The equilibrium constant for the oxidation of zinc sulphide is given by... 

The scorching problem is aggravated by moisture or humidity which accelerates the zinc oxide-carboxyUc acid reaction rate, and can only be overcome by either surface treatment of the zinc oxide with zinc sulphide or zinc phosphate or by the use of more costly zinc peroxide, preferably in masterbatch form. " The influence that these variations has on scorch time is illustrated in Table 6 ... 

The objective in die roasting of sulphides, such as copper sulphides and zinc sulphides, is to convert these into their coiTesponding oxides by reaction with... 

Two types of oxidation reactions are of interest in ceramics oxidation of metals and oxidation of sulfides. The oxidation of sulphides is a common extractive metallui cal process, generating an oxide ceramic powder. The oxide product is usually an intermediate product on the way to metal production but if sufficiently pure it can be used directly as a ceramic powder. A common example is the roasting of zinc sulphide to form zinc oxide,... 

Cannon, K.J. and Denbigh, K.G., Studies on gas-solid reactions—I the oxidation rate of zinc sulphide, Chem. Eng. Sci., 6, 145, 155, 1957a... 

Zinc sulphide is roasted in a current of dry air at atmospheric pressure and at a temperature of 1700 K. Determine whether zinc oxide or zinc sulphate is the more stable solid reaction product under the above conditions. In such a process the outgoing gas is found to contain 7 % by volume of sulphur dioxide. What percentage of sulphur trioxide would this gas contain if the trioxido were in equilibrium with the dioxide at the above temperature What statements could be made with regard to the mechanism of the reaction, if the actual content of sulphur trioxide in the gas was found to exceed the calculated equilibrium figure ... 

Let it be assumed, in the fimt place, that the system is prepared from zinc sulphide and from pure oxygen, in place of air. There are thus six species in all, and, since there are three independent reactions, there are three components. Assuming that the oxide, sulphide and sulphate are present as immiscible solids, there are four phases and the system is therefore univariant. 

For example, in this book the reactions which take place during the use of iron oxide or zinc oxide as absorbents for hydrogen sulphide are compared. Fresh iron oxide (Fc20s) is converted to FegO in the temperature range 340 to 400 °C when iron oxide is used as absorbent for HgS. The reactions are thus ... 

Gases which are high in FIjS are subject to a de-sulphurisation process in which H2S is converted into elemental sulphur or a metal sulphide. There are a number of processes based on absorption in contactors, adsorption (to a surface) in molecular sieves or chemical reaction (e.g. with zinc oxide). 

In the case of the alkali and alkaline earth metals, the sulphate is the sole product with copper, lead, bismuth and antimony, the product contains the metal, formed by reduction of the sulphate by unchanged sulphide. In cases where the sulphate is unstable at the temperature of reaction, as with zinc, cadmium, aluminium, tin, chromium, iron, cobalt and nickel, the oxide is the final product. The action may be catalytically accelerated by the addition of triferric tetroxide, Fe304.2... 

Other reactions readily available for the detection of a thiosulphate include reduction to hydrogen sulphide by most reducing agents, for instance by zinc and hydrochloric acid, oxidation to sulphuric add or a sulphate, and formation of a thiocyanate on warming with an alkaline solution of a cyanide 5... 

The reaction commences at a temperature above 400° C., before the melting temperature is reached, and the fused product therefore always contains some arsenious oxide.1 When heated in hydrogen, the pentoxide is reduced first to arsenious oxide and then to free arsenic. Similar reduction occurs when it is heated with carbon or phosphorus with sulphur, arsenious sulphide is formed. Arsenic and metallic arsenides result when the pentoxide is heated with alkali metals,2 zinc, lead, iron or most other heavy metals mercury and silver react only at high temperature gold and platinum do not react. 

There is a large class of industrially important heterogeneous reactions in which a gas or a liquid is brought into contact with a solid and reacts with the solid transforming it into a product. Among the most important are the reduction of iron oxide to metallic iron in a blast furnace the combustion of coal particles in a pulverised fuel boiler and the incineration of solid wastes. These examples also happen to be some of the most complex chemically. Further simple examples are the roasting of sulphide ores such as zinc blende ... 

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