Silver is recovered from the leaching solution of the spent Ag/α-Al2O3 catalyst by solvent extraction. Most of the silver in the spent catalyst was dissolved by using HNO3 solution. The parameters such as concentration of lixiviant, reaction temperature, pulp density, and stirring speed, which might affect the dissolution of silver from the spent catalyst, were investigated. McCabe-Thiele plots predicted that complete extraction of Ag from the leaching solution could be obtained with LIX63 at an O/A ratio of 1 in 3 stages, while complete stripping of Ag from the loaded LIX63 could be obtained with thiourea at an A/O ratio of 1 in 2 stages. Countercurrent extraction and stripping simulation tests were carried out to confirm this prediction. More than 99.89% of Ag with purity of 99.91% was recovered from the leaching solution. Finally, a complete flow sheet of the process for separation and recovery of Ag from the spent catalyst was demonstrated.

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The separation of Ag(I) and Zn(II) from nitrate solutions using 5,8-diethyl-7-hydroxy-dodecan-6-oxime (LIX63) as the extractant was investigated as a function of nitric acid (HNO 3 ) and extractant concentrations. Selective extraction of Ag(I) over Zn(II) was achieved with LIX63 when HNO 3 concentration was in the range 0.001-1 mol/dm 3 . Quantitative stripping of Ag(I) from loaded LIX63 was accomplished using 5 mol/dm 3 of HNO 3 . The McCabe-Thiele diagrams for the extraction and stripping of Ag(I) with LIX63 were constructed, and the results were veri ed by simulated cross-current extraction and stripping experiments. Finally, Ag(I) and Zn(II) solutions of high purity (> 99.95%) were obtained.

Pt and Rh in HCl solutions were separated by adsorption with strong basic resins (Diaion SA10A, Diaion SA20A, and Diaion PA308) in the HCl concentration range 0.15 mol/dm 3 . The molar ratio of Pt to Rh in the feed solution was fixed at 5 : 1, based on the composition of spent automobile catalysts. The resins used had selectivity for Pt over Rh, and the adsorptions of both metals were clearly affected by the acid concentration. Batch experiments indicated that it is possible to separate Pt from Rh at low acid concentrations with these resins; Diaion SA10A was the most effective. The feasibility of separation of Pt and Rh with Diaion SA10A was verified using continuous column experiments. The loaded Diaion SA10A resin was regenerated by elution with a mixture of HCl and thiourea.

A new method was developed to synthesize uniform anatase TiO2 nanocrystals by the hydrolysis of titanium tetraisopropoxide in nitric acid-isopropyl alcohol aqueous solutions at 353 K. The samples were characterized by XRD, TEM, FE-SEM, and specific surface area determination. In this work, the photocatalytic degradation of 2,4-dinitrophenol in the presence of TiO2 using ultraviolet (UV) light source was investigated in a batch reactor. The effects of various factors, namely TiO2, pH, temperature and concentration, on the degradation performance of 2,4-DNP were studied. The photocatalytic degradation of 2,4-DNP follows the pseudo-first-order kinetics. In acidic or alkaline conditions, the photocatalytic degradation efficiency of 2,4-DNP was greater than that in neutral conditions. Thermodynamic studies have also been carried out and values of standard free energy (deltaG degrees), enthalpy (deltaH degrees) and entropy (deltaS degrees) were calculated.