TVEX-DIOMP

The Sc extraction process by TVEX-TBP and TVEX-DIOMP from hydrochloric, nitric, and sulfuric is endothermic in hydrochloric solutions and exothermic for sulfuric and nitric solutions (Table 8.6). Additionally, the extraction rates showed diffusion coefficients 1 to 2 orders of value higher (K jf of Sc + ions into TVEX granule mVs) than for phosphorus-containing ion-exchange resins. 

During scandium extraction by TVEX-DIOMP resins an increase of DIOMP capacity in TVEX matrix is observed at lower Sc concentrations as compared with TVEX-TBP due to the higher DIOMP donor abilities in comparison with TBP. 

Isotherms of Ga extraction by TVEX-TBP, TVEX-DIOMP as well as by liquid TBP andDIOMP from 3,5, and 8 mol/L HCl solutions show (Figure 8.25 and Figure 8.26) that extractant equilibrium capacity increases with aqueous phase acidity increase extractant capacity in TVEX matrix is 1.3 to 1.5 times higher as compared with solvent extractant. Enthalpy of gallium extraction from 3 mol/L HCl is -11.7 kJ/mol for TBP and -12.0 kJ/mol for TVEX-TBP. Diffusion coefficient of gallium extraction is 4.210-" mVs for TVEX-TBP (3mol/L HCl) and 5.410-" mVs for TVEX-DIOMP (6 mol/L HCl) [27]. 

V. Korovin and Y. Shestak, Scandium extraction hy TVEX-DIOMP from hydrochloric media, Ukrainian Chem. J., 62, 22-26 (1996). 

TVEX industrial batches are nowadays produced based on the following extractants tri-butylphosphate (TBP), diisooctyl methyl phosphonate (DIOMP), and phosphine oxide (POR) (with different radicals R,(R2)(R3)P = O Rj - R3 are alkyl radicals, 85 to 90% CgHi7,10 to 15 % C5H, - CgH,) (Figure 8.1). These extractants act as a base due to its phosphoryl group (P = O). The alkoxy oxygenes do not play any direct role on the metal extraction process. 

FIG U RE 8.3 Integral and differential curves of pore volume distribution on radiuses for the matrix of TVEX-50%DIOMP-25%DVB. 

MINERAL ACIDS EXTRACTION BY SOLID POLYMERIC EXTRACTANTS TVEX CONTAINING NEUTRAL ORGANOPHOSPHORUS COMPOUNDS (TBP, DIOMP)... 

Scandium extraction capacity of TBP and DIOMP in TVEX porous matrix is higher as compared with corresponding solvent extractant capacity [10,19-22]. Isotherms of Sc extraction from hydrochloric solutions by TBP, TBP 50% solution in CCI4 and TVEX-TBP almost coincide (Figure 8.16) at low Sc concentration ... 

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