The equilibria of yttrium(III) and europium(III) (RE) extraction with PC-88A dissolved in Shellsol D70 from nitric acid solutions were studied under nonideal conditions in order to develop a chemically-based model enabling the engineering prediction of the equilibrium distribution ratios. The distribution of the extractant between the nitrate solution and the diluent was also examined. As a result, it was found that (i) the majority of PC-88A is dimerized in the organic phase, (ii) the cation exchange extraction is predominant in the low-acidity region, and (iii) solvation extraction becomes appreciable in the high-acidity region. By using a model that considers these two extraction equilibria together with the complexation of the RE with NO 3 À , the nonideality of the PC-88A dimer, and the competing extraction of HNO 3 , the extraction equilibrium constants and the coefficient for the effective concentration of the extractant were determined by the nonlinear least-squares method. The proposed model can reproduce the experimental data with good accuracy for single-metal systems over wide feed concentration ranges of RE up to 0.1 kmolÁm À3 , nitric acid (0.05 to 3 kmolÁm À3 ), and the extractant (0.25 to 1 kmolÁm À3 ). Its applicability to the prediction of the extraction from a binary metal system was also confirmed.
The condensation experiments of zinc vapor on the solid media in Zn (g) -CO-CO 2 -Ar mixtures were conducted in a flow reactor at 800°C to 1000°C under a zinc partial pressure of 0.6 to 7.9 kPa. The condensates were weighed, and the zinc contents and their morphology were analyzed to investigate the effects of various factors on the condensation. It was found that the initial temperature of the media should be as low as possible in liquid condensation for the efficient recovery of zinc. The condensation is enhanced with zinc partial pressure of the gases. The medium made of silica with a smooth surface is favorable for the efficient condensation. In the gases not oxidizing to zinc vapor, metallic zinc can be obtained on the medium with an initial temperature over the range of 120°C to 400°C. For obtaining metallic zinc, it is necessary to raise the temperature of the gases, appropriately limit the zinc partial pressure, or maintain a sufficient CO/CO 2 ratio to avoid the oxidation of zinc vapor.
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