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The hot-dip galvanizing sludges have been studied with the aim of establishing phase relations and chemical processes taking place during the thermal treatment. Phase relations in the sludge heated for 1-5 h between 100 and 1000°C were studied by infrared, powder X-ray, Mossbauer, and scanning electron microscopy methods. Dehydration and decomposition processes were also monitored by a thermogravimetry-mass spectrometry technique. Results of the investigations indicate that during the thermal treatment ZnFe 2 O 4 and ZnO were formed, while α- and γ-FeOOH (goethite) as well as the basic zinc chlorides were decomposed and finally cannot be detected in the 1000°C heat-treated samples. Because the major part of the zinc is present in the form of aqueous ammonia-insoluble ferrite, instead of ammoniacal leaching, another technique using, e.g., iron(II) sulfate, has to be used for recovering the zinc from these types of heat-treated samples.

Nitric acid activation of bentonite has been studied with the aim of harmonizing bleaching earth and ammonium nitrate fertilizer production, where the latter is obtained from waste acid via neutralization with ammonia. In this paper, a mathematical model is described for composition measurement of the waste acid formed during the activation of the bentonite. On the basis of the results obtained from the model, the amount of concentrated nitric acid necessary for refreshing the recycled acidic solution can easily be estimated. The amounts of the products formed during ammoniacal neutralization, such as ammonium nitrate, hydroxides of hydrolizable metals, and nitrates of nonhydrolizable metals, as well as the amount of activated bentonite, can also be calculated. It is established that, with an increase in the recycling number, the activation process becomes more economical via decreasing energy and material requirements.

A study of the utilization of aqueous decomposition of sodium amalgam for the production of deuterium-depleted water is presented. In the framework of this work the correlation between the deuterium content of the hydrogen gas and the concentration of the aqueous alkali, both formed in the reaction of sodium amalgam with water, is established. The sodium amalgam is prepared via sodium chloride electrolysis. In addition to the formation of an industrial alkaline solution containing 50% w/w sodium hydroxide, hydrogen gas with a deuterium concentration of 50 ppm is obtained. This hydrogen gas is suitable (e.g., via combustion) for the preparation of deuterium-depleted water used, e.g., in cancer therapy.