Phase separation other collectors

Other Aluminosilicates, Transparent mullite glass-ceramics can be produced from modified binary Al C —Si02 glasses (21). In these materials, the bulk glass phase separates into tiny alumina-rich droplets in a siliceous matrix. Further heat treatment causes these droplets to crystallize to mullite spherulites less than 0.1 Jim in size. When doped with ions such as Cr3+, transparent mullite glass-ceramics can be made to absorb broadly in the visible while fluorescing in the near-ii (22,23), thereby making them potentially useful for luminescent solar collectors. 

This type of mechanism has been considered by Barnard etal. [83]. They postulate the initiation of the charging reaction at the Ni(OH)2/current collector interface with the formation of a solid solution of Ni ions in Ni(OH)2. With further charging when a fixed nickel ion composition (Ni ) K-(Ni )i K is reached, phase separation occurs with the formation of two phases, one with the composition (Ni )i, c-(Ni ) ,c in contact with the current collector and the other... 

Flotation has been used for more than 100 years to separate sulphides, oxides and other salts from ores, as well as to obtain phosphates, barite, chromite and other materials. Up to 90% of copper, lead, nickel, zinc are extracted using flotation in the USA [152 - 153]. In Russia, flotation is widely used to additionally obtain apatite, barite and phosphates. Flotation of iron oxides is not used in practise yet, but the number of experiments carried out in this direction is rather large. The main physicochemical principles of flotation have been discussed above [59 -74]. Here, only some practical problems will be discussed. In [153], requirements are pointed out which apply to three-phase flotation foams, and the main components of the process are defined, i.e. surfactant - collector surfactant - frother activator, depressants, colligend, gangue. The peculiarities of flotation and foam separation in batch and continuous modes are outlined as well as the structure and properties of the main types of flotation agents described. As surfaces of the majority of mineral particles are hydrophilic in nature, hydrophobisation of particles is necessary for a selective separation. 

To measure the substances eluting from the column, fractions of mobile phase can be collected and the concentration of the separated components measured externally—for example, in a spectrophotometer or using a pH meter. An automatic fraction-collector which collects a defined volume of column effluent in test tubes is sometimes employed. However, it is more convenient to employ a continuous-detection device at the exit of the column. The detector can be selective (for instance, it detects ultraviolet-absorbing or fluorescent compounds only) or universal (that is, it detects all components). In some cases, two detectors placed in series are used to gain additional information. The detector output is usually displayed on a strip-chart recorder or some other data-acquisition device. For quantitative analysis, an integrator or a minicomputer are useful to automatically measure peak areas. 

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