Distillation, comparison with adsorption

Adsorption Method Iodine separation by the platinum adsorption technique was first reported by Toth (1961) and Lin et al. (1963). Oak Ridge National Laboratory has adopted an adsorption procedure (Case and Acree, 1966) for the purification of I produced from fission by a distillation process. In 1966, in comparison with other methods of L Baker (1966) has concluded that the adsorption technique is the most efficient and economical method. In this method, a metallic Pt plate or felt is used to adsorb carrier-free iodine from an acidic solution containing target materials. The Pt plate or felt with iodine activity is then removed from the solution and thoroughly washed with water. The activity is then desorbed in a slightly basic solution. Application of electrical current could enhance the desorption process. Nearly quantitatively the adsorbed iodine activity can be desorbed from the Pt surfaces. 

Finally, it is also interesting to report that in the literature it is possible to find studies dealing with esterification membrane reactor units coupled with other than distillation-based separation technologies. An example is the work of Park and Tsotsis (2004), who linked to the permeate side of the membrane reactor an adsorption step to increase byproduct extraction. Adsorption is a very powerful technology and leads to higher conversion in comparison with a conventional reactor (up to 10%). However, the cost of the adsorbent and of related equipment makes this design economically disadvantageous. 

However, in general, solvent recovery is an important step in the overall solvent extraction process. Solvent recovery from the raffinate (i.e., water phase) may be accomplished by stripping, distillation, or adsorption. The extract, or solute-laden solvent stream, may also be processed to recover solvent via removal of the solute. The solute removal and solvent recovery step may include reverse solvent extraction, distillation, or some other process. For example, an extraction with caustic extracts phenol from light oil, which was used as the solvent in dephenolizing coke plant wastewaters (4). The caustic changes the affinity of the solute (phenol) for the solvent (light oil) in comparison to water as will be explained in the equilibrium conditions section. Distillation is more common if there are no azeotropes. 

Conversion (upgrading) of bitumen and heavy oils to distillate products requires reduction of the MW and boiling point of the components of the feedstocks. The chemistry of this transformation to lighter products is extremely complex, partly because the petroleum feedstocks are complicated mixtures of hydrocarbons, consisting of 10 to 10 different molecules. Any structural information regarding the chemical nature of these materials would help to understand the chemistry of the process and, hence, it would be possible to improve process yields and product quality. However, because of the complexity of the mixture, the characterization of entire petroleum feedstocks and products is difficult, if not impossible. One way to simpHfy this molecular variety is to separate the feedstocks and products into different fractions (classes of components) by distillation, solubility/insolubility, and adsorption/desorption techniques. For bitumen and heavy oils, there are a number of methods that have been developed based on solubility and adsorption. The most common standard method used in the petroleum industry for separation of heavy oils into compound classes is SARA (saturates, aromatics, resins, and asphaltenes) analysis. Typical SARA analyses and properties for Athabasca and Cold Lake bitumens, achieved using a modified SARA method, are shown in Table 1. For comparison, SARA analysis of Athabasca bitumen by the standard ASTM method is also shown in this table. The discrepancy in the results between the standard and modified ASTM methods is a result of the aromatics being eluted with a... 

The flotation behavior of kaolin in distilled water is poor. Even with high initial concentrations, only 30 to 40% of the kaolin are recovered with the foam (Fig. 8). On the other hand, in hard water the recovery increases more strongly even at low surfactant concentrations, reaching a recovery of 75% in the plateau region. The high recovery in hard water shows that the adsorption of the surfactant on the surface predominates the precipitation in solution. A comparison of the recovery of fillers with a technical collector in hard water (Fig. 8) leads to the conclusion that it is distinctly easier to flotate calcium... 

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