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  • Author: S. Banerjee x
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Abstract

The extraction behaviour of Th(IV) from aqueous nitric acid medium employing 2-hydroxy-1-naphthaldehyde thiosemicarbazone has been studied in the presence of various donors, like trioctyl phosphine oxide (TOPO), calix[3]OH[3]OMe[6]arene, trioctyl amine (TOA), dimethyl sulphoxide (DMSO) in ethylacetate solvent. The constants (log k ex) for the binary complex in organic phase [Th(A)(NO3)3], where A is the ligand, was found to be 3.99, which was by far the largest amongst the corresponding values known for the other thiosemicarbazones. The overall equilibrium constants (log K) for the ternary species [Th(A)TOPO(NO3)3], [Th(A)TOA(NO3)3], [Th(A)Calix[3]OH[3]OMe[6]arene(NO3)3], [Th(A)DMSO(NO3)3] were estimated to be 8.287, 8.862, 8.415, 6.921 respectively. The trend in equilibrium constants were in accordance with the substitution of the donor. The extraction of Th4+ by the ligand–donor combination was maximum at pH=1 and extraction decreases with increase in pH. It has been found that the extent of extraction of Th4+ in the organic phase as the binary as well as ternary complex [Th(A)(NO3)3] and [Th(A)(NO3)3S], where S is the donor, increases with increase in the concentration of the ligand. Similar trend is obtained in the extraction by donors in absence of ligand. In case of ternary extraction, using different donors, amines are found to perform best compared to the other donors. The trend is as follows: TOA > calix[3]OH[3]OMe[6]arene > TOPO > DMSO. In addition, the effect of different diluents on extraction was also studied and the observed trend was methyl salicylate > ethyl acetate > methyl isobutyl ketone > ethyl benzoate.

Abstract

A heat transfer model for estimating pinene emissions from hot-pressing strand for the manufacture of flake-board has been constructed from first principles and validated. The model predicts α-pinene emissions of 0.4 kg/1000 kg from a 0.95-cm board, which is within the 0.3–0.6 kg/1000 kg range reported for commercial operations. Most of the emissions originate from the hot 1-mm layer of wood adjoining the platen surface. As a result, residual pinene in the board is depleted at the surface for both commercial and laboratory-prepared boards. Emissions are drastically reduced when the mat is surfaced with a layer of aspen, which prevents the hot platen from directly contacting softwood.