1,721,039 research outputs found
Discharge Composition and Concentration Profiles in a Continuosly Operating Spouted Bed (1984
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Selective ion exchangers from cross-linked alginate
No full textAlginate crosslinking with epichlorohydrin Ieads to the formation of chelating selective cation exchangers, since it insolubilises the polymer even in the basic field with no marked impairment of the exchange and swelling properties. Exchangers with different properties were
obtained on varying the preparation technique. Crosslinking of a sodium alginate powder was used to prepare a microgranular resin. This gave quantitative results in the separations of Ni2+/Cu2+, Co2+/Cu2+ and Ca2+/Ba2+ by column exchange chromatography. Its excessive swelling in basic media made this exchanger unsuitable for use in arnmonia solution. When preformed calcium alginate beads were crosslinked, exchangers suitable for column operation in basic media were obtained. Exchange tests with Cu2+ and Ni2+ complexes were performed
Explosion of a hot-oil circuit as a consequence of process, plant engineering and management shortcomings
No full textOn June 3, 1993, an explosion occurred at the Mediterranea refinery, in Milazzo, Sicily. Seven people died and eighteen people were injured with burns. An explosion in the accumulation tank 27V-16 involved hot-oil circuits subserving the refining units Topping 3, Topping 4, and HDT-RC. The explosion was caused by a sudden overpressure in the 27V-16 tank, probably as a result of the sudden vaporization of a small quantity of water. Shortcomings in the process design and in the management were at the origin of the accident, in particular: Some process choices undertaken a couple of years before the accident, such as the use of gas oil from a Topping column in place of diathermic oil and the use of a combustible gas in place of nitrogen. Some operational mistakes in the 13F-2 oven conduction and the failure (or inadequacy or exclusion) of control systems or automatic and manual safety devices. A detailed Fault Tree connects the process, design and management shortcomings identified
Effects of gamma irradiation on the degradation of dyes
No full textTo investigate the degradation kinetics of aqueous solutions of dyes of several clases, we studied the effects of gamma irradiation versus dose (up to 80 krad), dye concentration, pH and oxygen content of these solutions. To study the influence of some of the above-mentioned parameters, anthraquinonic dyes have been irradiated in a wide range of doses(up to 5 Mrad). Furthermore these dyes were acted upon
in order to investigate the complex reactions of molecular alteration through chromatographic separations and spectrophotometric analyses. Experimental results agreed with a first order kinetics for dye concentrations lower than 0.04 g/l, and with a zero order for higher concentrations. The pH was found to have a different influence according to the type of dye; for example we found that the degradation efficiency for anthraquinonic dyes has higher values for basic ranges. The disolved oxygen supports the degradation in comparison with de-aerated solutions, though its influence varies according to the dye type and the pH. The oxygen action is particularly evident with high doses; in fact, tests on anthraquinonic dyes with doses up to 5 Mrad showed a marked decrease in the kinetic constants caused by the oxygen disappearance. Radiochemical degradation yields (Gd), never greater than a few units, show that the radical reactions reponsible for the decolorizatfon effect, are limited to a few transfer sequences. COD decrease, on the other hand, confirms the presence of oxidation phenomena which correspond to computed radiochemical yields (Gox) markedly higher than those spectrophotometrically measured; such a difference is enhanced in the case of irradiation with aeration of solutions. The theoretical considerations are also described that were developed for outlining a general scheme involving the experimental results of both the kinetics and the radiochemical yield
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