Materials, decomposition

If the light and heavy key components form an azeotrope, then something more sophisticated than simple distillation is required. The first option to consider when separating an azeotrope is exploiting change in azeotropic composition with pressure. If the composition of the azeotrope is sensitive to pressure and it is possible to operate the distillation over a range of pressures without any material decomposition occurring, then this property can be used to... 

The hazardous materials used in the process may be raw materials, intermediates, products, by-products, cleaning materials, decomposition, or unintended products. 

Another method of raw material decomposition is based on the fluorination of the raw material by the hydrofluoride method. No published data exists on hydrofluoride decomposition of columbite or tantalite concentrates. The interaction can, nevertheless, be discussed based on available information on the decomposition of lithium tantalate, LiTaC>3, and lithium niobate, LiNb03, using the hydrofluoride method [113,118,122]. 

In general, the process flow chart of raw material decomposition by the hydrofluoride method can be represented as shown in Fig. 117. 

The main advantages of the method can be formulated as follows. First, hydrofluoric acid is not needed for the decomposition stage the amount of fluorine required for the raw material decomposition can be calculated and adjusted as closely as possible to the stoichiometry of the interaction. Since the leaching of the fluorinated material is performed with water, a significant fraction of the impurities are precipitated in the form of insoluble compounds that can be separated from the solution, hence the filtrated solution is essentially purified. There is no doubt that solutions prepared in this way can be of consistent concentrations of tantalum and niobium, independent of the initial raw material composition. 

Nevertheless, current processes of raw material decomposition that are based on digestion of the material by highly concentrated hydrofluoric and sulfuric acids yield highly acidic solutions. 

The unique advantage of the plasma chemical method is the ability to collect the condensate, which can be used for raw material decomposition or even liquid-liquid extraction processes. The condensate consists of a hydrofluoric acid solution, the concentration of which can be adjusted by controlling the heat exchanger temperature according to a binary diagram of the HF - H20 system [534]. For instance, at a temperature of 80-100°C, the condensate composition corresponds to a 30-33% wt. HF solution. 

If solid samples are insoluble in water, some decomposition procedure must be used. For inorganic materials, decomposition with mineral acids is most often employed (for a survey of decomposition techniques see [33]). When the sample cannot be dissolved in an acid, it can either be fused (most often with alkali carbonates, hydroxides or their mixtures [157, 47]) or sintered (usually with mixtures of alkali carbonates with divalent metal oxides, sometimes in the presence of oxidants [54]). Sintering is usually preferable, because then contamination of the sample and the resultant ionic strength are lower than is the... 

The hydrazones derived from (133) and oxocarboxylic acids are thermally very sensitive and decompose immediately at 30 °C to give sulfur, nitrogen, and polymeric material. Decomposition also occurs on treatment with catalytic amounts of both acid and base. 

Figure 6.5 shows the DTA plot for the decomposition of an explosive material. Decomposition begins when the temperature T reaches the ignition temperature of the explosive material resulting in an exothermic peak. As the explosive material decomposes it releases heat which is measured on the DTA plot as AT(y-axis). AT is proportional to the rate at which the explosive material decomposes as the rate increases more heat is emitted and AT increases. Assuming that the decomposition of an explosive is a first order process, then the rate of the reaction is directly proportional to the increase in temperature AT, as shown in Equation 6.15. 

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