| A study has been made on the recovery of nitric acid and valuable metals such as Cu, Sn and Pb from the spent nitric etching solutions. The nitric acid was extracted effectively by TBP but the heavy metals such as Fe, Cu, Sn and Pb were not extracted by TBP from the spent nitric etching solutions. From the experimental results, 95% of nitric acid in spent etching solution was extracted at O:A ratio of 3:1 in five stages by 60% TBP, and 98% of nitric acid was stripped from the loaded organic phase at O:A ratio of 1:1 in four stages by distilled water. After extraction of nitric acid, Cu was effectively recovered as a metal by electrowinning and Sn was successfully removed by precipitation methode as the form of hydroxide or hydrated oxide by adjusting pH of the raffinate solution. Finally, Pb was recovered by cementation with iron scrap at above 65℃. Parameters controlling the cementation process, such as temperature, pH and the effect of the additives were investigated. |
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