Separation of Cerium Oxide Abrasive and Glass Powder in an Abrasive-Glass Polishing Waste by Means of Liquid–Liquid–Powder Extraction Method for Recovery: A Comparison of Using a Cationic and an Anionic Surfactant Collector

Applying a cerium oxide abrasive to polish glass components generates a polishing waste containing the cerium oxide abrasive and the glass powder produced during polishing. This research applied the liquid–liquid–powder extraction method to separate the cerium oxide abrasive and the polished glass powder in an abrasive-glass polishing waste for recovering the cerium oxide abrasive. Two liquids of isooctane and water were utilized. The effectiveness of using a cationic and an anionic surfactant collector, i.e., dodecylamine acetate (DAA) and sodium oleate (NaOL), respectively, in improving their extraction and separation was investigated and compared. The results indicated that NaOL addition could improve the mutual separation of cerium oxide abrasive and glass powder but DAA could not, because the former could selectively improve the extraction of cerium oxide abrasive from the water phase to isooctane phase whereas the latter could improve that of both powders. Optimal separation for the cerium oxide abrasive and the polished glass powder in an abrasive-glass polishing waste were achieved by adding NaOL of 7.5 kg/ton at pH 7; the content of cerium oxide abrasive in the solid recovered from the isooctane phase was 96.4% with a recovery of 88.1%.

Selective and Mutual Separation of Palladium (II), Platinum (IV), and Rhodium (III) Using Aliphatic Primary Amines

The selective recovery of platinum-group metals (PGMs) remains a huge challenge. Although solvent extraction processes are generally used for PGM separation, the use of organic solvents is problematic because of their toxicity and environmental concerns. Here, we have developed a new PGM recovery method by precipitation from hydrochloric acid (HCl) solutions containing Pd(II), Pt(IV), and Rh(III) using aliphatic primary amines as precipitants. Pt(IV) was precipitated using the amines with alkyl chains longer than hexyl independent of HCl concentration. The precipitation of Pd(II) required longer alkyl amines than octyl, regardless of the HCl concentration. Rh(III) was recovered by precipitation at high HCl concentrations using the amines longer than hexyl. The mutual separation of Pt(IV), Rh(III), and Pd(II), in this order, was successfully achieved by changing the HCl concentrations and alkyl chain lengths of the amines. X-ray photoelectron spectroscopy and thermogravimetric analysis evidently showed that the metal-containing precipitates were ion-pair complexes composed of metal chloro-complex anions and ammonium cations.

Separation of neptunium from actinides by monoamides: a solvent extraction study

Separation of neptunium from a mixture of actinides viz. uranium, neptunium and plutonium was evaluated using two monoamides, viz. N,N,-dihexyl octanamide (DHOA) and N,N,-dihexyl decanamide (DHDA). The extraction of actinides with these ligands followed the order: U(VI)>Np(IV)>>Pu(III). Poor extraction of Pu(III) with both the amides (DHOA and DHDA) was exploited for the mutual separation of U, Pu and Np. At 3 M HNO3, DHDA was a better extractant for all the three metal ions while Pu(III) extraction was one order magnitude lower with DHOA as compared to that seen with DHDA. Consequently, better separation factor of U(VI)/Np(IV) over Pu(III) was obtained with DHOA. In the actinide mixed solution, Pu was reduced to its +3 state followed by selective extraction of U(VI) and Np(IV). Subsequently, the mutual separation of U(VI) and Np(IV) was carried out by selective complexation and stripping of Np(IV) by acetohydroxamic acid (AHA) at 2 M HNO3, where U(VI) remained in the organic phase. The purity of the separated actinides was confirmed by alpha spectrometry. A separation scheme for the separation of Np from radioactive waste/high level waste has been proposed.