Recovery of nitric acid from waste etching solution using solvent extraction.
A process was developed to recover nitric acid from the waste stream of wafer industry using solvent extraction technique. Tributyl phosphate (TBP) was selected among several extractants because of its better selectivity towards HNO(3), overall superiority in operation, favorable physical properties and economics. The waste solution containing 260 g/L CH(3)COOH, 460 g/L HNO(3), 113 g/L HF and 19.6g/L Si was used as feed solution for process optimization. In the pre-treatment stage >99% silicon and hydrofluoric acid was precipitated out as Na(2)SiF(6). Equilibrium conditions for HNO(3) recovery were optimized from the batch test results as: four stages of extraction at an organic:aqueous (O:A) ratio of 3, four stages of scrubbing at O:A ratio of 5 and five stages of stripping at an O:A ratio of 1.5. The extraction of HNO(3) was suppressed by the presence of acetic acid (HAc) in the feed solution. To examine the feasibility of the extraction system a continuous operation was carried out for 200 h using a multistage mixer-settler. The concentration of pure HNO(3) recovered was 235 g/L with a purity of 99.8%.
EXTRACTION OF NITRIC AND PHOSPHORIC ACIDS WITH TRIBUTYL PHOSPHATE
ABSTRACT The extraction of nitric acid and phosphoric acid by tributyl phosphate (TBP), from solutions containing acid mixture and in the presence of nitrate salts, has been studied. The effect of the temperature on acid extraction has been also investigated. It is found that TBP extracts nitric acid preferentially to phosphoric acid, especially in the presence of nitrate salts. The coextraction of nitric acid suppresses the extraction of phosphoric acid. These results were interpreted in terms of common ion effect and variation of the activity coefficients variation in both phases. The simultaneous effects of the salts and acids on the extraction of both acids is also studied Some tests were carried out, using process solution, to evaluate the extraction of acids. Both batch experiments and continuous tests (using mixer settler) were performed. Some flowsheets were tested in order to improve the extractivity and the selectivity of phosphoric acid. The results show the limitation of TBP for the extraction...
Dating of Historical Manuscripts Using Spectrometric Methods: A Mini-Review
An overview is provided of spectrometric methods useful for age estimation of historical manuscripts (medieval ones in particular), in order to confirm their authenticity. Individual methods (infrared and Raman spectroscopy, mass spectrometry, atomic emission spectroscopy, X-ray spectroscopy, and electron scanning microscopy) are discussed and examples of their application described. The following general strategy can be recommended for dating and/or authenticating of historical manuscripts. First of all, the pigment analysis should be carried out using Raman spectroscopy (distinguishing the period and modern pigments), followed by PIXE ink analysis (solving the question of ink homogeneity). Finally, the radiocarbon dating of the writing support, potentially supplemented by the ink dating using scanning Auger microscopy should be performed.