Recovery of zinc(II) from HCl spent pickling solutions by solvent extraction.

Recovery of zinc(II) from HCl spent pickling solutions by solvent extraction using CYANEX921, CYANEX923, CYANEX302, tributyl phosphate, and ALAMINE336 extractants was studied. Tributyl phosphate was selected as suitable extractant. It permitted both effective zinc(II) extraction and the stripping from loaded organic phase with water. The presence of iron(II) did not affect zinc extraction, and only negligible oxidation of iron(II) was observed during extraction experiments. CYANEX reagents and ALAMINE336 extracted zinc(II) strongly, but the stripping with water was ineffective. Moreover, a significant oxidation of iron(II) to iron(III) occurred during extraction. Each of three reagents (CYANEX923, ALAMINE336 and TBP) extracted iron(III) very well. Thus, if iron(III) was present in the spent pickling solution, prior to the extraction it had to be reduced to iron(II). The oxidation was low for tributyl phosphate and high for CYANEX923 and ALAMINE336. CYANEX302 was inactive both for zinc(II) and iron(III) and could not be used for extraction of zinc(II) from spent pickling hydrochloric acid solutions.

Optical transmission of normal and atheromatous arterial wall: a spectral analysis.

In laser angioplasty one of the factors influencing the immediate damage (and therefore the risk of acute arterial perforation) is the optical absorption characteristics of the target tissue. In an attempt to evaluate the differences in optical absorptive properties, the transmission spectrograms of samples of normal and atheromatous human postmortem aortic wall were measured over the visible spectrum. Optical transmission varied inversely with sample thickness and directly with wavelength through both normal and atheromatous samples. Over the whole visible spectrum atheromatous tissue transmitted less per unit thickness than normal tissue. This differential effect was, however, most pronounced at 500 nm, where atheromatous tissue transmitted light 5-10 times less strongly than normal aortic wall. Such wavelength dependent differential optical absorption could provide a means for the selective photovaporisation of atheroma in laser angioplasty.