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Liquid-Liquid Extraction
Published in John J. McKetta, Unit Operations Handbook, 2018
The diluent, or carrier solvent, is mainly required as a diluting medium to lower the viscosity of the organic phase and facilitate contacting between the two phases. The additional important carrier properties are: The ability to retain in solution both the complexed and uncom-plexed extractant, i.e., prevent third phases forming.A low solubility in the aqueous phase.A high flash point and a consistent low rate of evaporation.High chemical stability over the range of conditions for plant operation.
Hydrometallurgy
Published in C. K. Gupta, Extractive Metallurgy of Molybdenum, 2017
The organic phase essentially consists of an extractant, a diluent, and a modifier. The extractant is primarily responsible for the transfer of metal values from the aqueous to the organic phase. An extractant should possess a number of required properties: (1) ability to extract the metal, (2) selectivity for the required metal, (3) acceptable rate of extraction, scrubbing and stripping, (4) high solubility in the organic phase and low solubility in the aqueous phase, and (5) chemical and radiochemical stability. The diluents are the carrier solvents required to dissolve or dilute the extractants in order to impart to them more mobility by reducing their viscosity. They should be insoluble in water, should have a low flash point, and should be inert to the system. The most common diluent used in commercial operations is kerosene oil. Sometimes during extraction an undesirable third phase or emulsion forms. In such situations the addition of a reagent called the modifier becomes necessary. A modifier increases the solubility of metal complexes in the organic phase and prevents the formation of the undesirable third phase. Like the diluent, the modifier should also be chemically inert to the extraction system. The modifiers in use are often long-chain alkyl alcohols like isodecanol.
Matrix Materials
Published in P. K. Mallick, Processing of Polymer Matrix Composites, 2017
Two other ingredients used in the epoxy resin mix for some composite applications are an accelerator and a diluent. Accelerators are added to increase the reaction rate and reduce gel time. Diluents are primarily added to reduce viscosity, which may be required for good resin flow and fiber wetting. One method of reducing viscosity is to increase the resin mix temperature, but it may also reduce the pot life. Because of this, instead of increasing the temperature, a low-viscosity diluent is selected. The diluents can be of either a reactive type or nonreactive type. Reactive diluents are typically monofunctional low-molecular weight epoxies. However, the addition of diluent can reduce the mechanical properties and glass transition temperature of the cured resin, and therefore, the amount to be added must be properly determined based on the application being considered.
Ionic liquids as green solvents in process industry for reaction and separation: emphasizing on protocatechuic acid recovery
Published in Chemical Engineering Communications, 2023
Fiona Mary Antony, Kailas L. Wasewar
The effect of the ILs [BMIM]OS and [HMIM][PF6] on the extraction efficiency of PCA was explored in the diluent octanol and the equilibrium results are presented in Tables 2 and 3. The effect of PCA concentration on the extraction efficiency was explored by varying the PCA concentration from 1 to 10 mmol L−1. The highest PCA concentration used was based on the yield of PCA obtained from the fermentation process (Okai et al. 2016). The effect of IL concentration was found by varying the IL concentration from 1 to 10% by volume in diluent octanol. Diluents are typically employed in extraction operations to decrease viscosity and promote diffusive mass transfer. The diluent alters the density, viscosity, and surface tension, which may impact the interphase interactions. As per preliminary research, octanol was chosen as the diluent because it increases the extraction efficiency due to the solvent’s polarity, which is regulated by the alcohol side groups, and because it also improves the solubility of the acid-extractant complex generated (Antony and Wasewar 2018a, 2018b, 2020, 2022; Antony et al. 2019a, 2019b).
Fluorinated Diluents- A Review
Published in Solvent Extraction and Ion Exchange, 2023
V. Babain, M. Alyapyshev, C. Ekberg, T. Todd
Diluents used for radiochemical processes must be resistant to radiolysis, and should be non-toxic. The cost of diluents should also be low and readily available from commercial suppliers. Obviously, the requirements for the diluent are quite stringent and partially contradict each other – for example, an increase in molecular weight leads to an increase in the boiling point and reduces solubility in the aqueous phase, but leads to an increase in viscosity. Diluent selection is an optimization problem with many variables.
Titania-silica Composite with Photocatalytic Properties and Its Application on Brazilian Granite and Sandstone
Published in International Journal of Architectural Heritage, 2023
Danielle Grossi, Dolores Ribeiro Ricci Lazar, Eliane Aparecida Del Lama, Valter Ussui
Tetraethyl orthosilicate, also known as TEOS, is one of the most commonly used products for consolidating stone, mainly sandstone and granite. It is resistant to ultraviolet radiation, which makes it ideal for use in outdoor areas (Wheeler 2005). It forms relatively strong silicon-oxygen bonds that have high thermal and oxidative stability, presenting good results on stones with moderate degradation. On very degraded stones, however, this product fails to show a good consolidation capacity (Price 2006). The deposition of silica gel via the application of TEOS causes two simultaneous reactions. The first is hydrolysis of the alkoxy group, which separates the ethanol molecules. This reaction can be accelerated by either acid or alkaline catalysis, used in the preparation of most commercial products. Water is essential to this reaction and the subsequent formation of silica gel. Due to this characteristic, TEOS is not effective in arid climates, because the water may evaporate before the gel forms. The second reaction is the condensation of unstable silanols (-Si-OH) to form an amorphous gel (Snethlage and Sterflinger 2011). A major advantage of TEOS is that the other product formed in the reaction is ethanol, which evaporates completely and causes no damage to the stone. Some types of TEOS have water-repellent properties due to the presence of alkyl groups (including methyl, ethyl, i-butyl, and n-octyl) attached directly to silicon. In general, the alkyl groups, formed by siloxanes of varying degrees of cross-linking and molecular weights, may contain reactive alkoxy groups. Diluents include water and organic solvents, such as alcohol or mineral spirits. When water-based, these products interfere with curing of joints, grouts, pointing, plastic repairs and alkoxysilane-based consolidants. Because of this, a pause time of 8 weeks is recommended between the application of the consolidant and the water repellent. The advantages of using a water-repellent consolidant include reduced maintenance time and cost (Wheeler 2005).