Slags from the Pb/Ag medieval (14th century) smelting plant located at Bohutín, Příbram district, Czech Republic, were studied from the mineralogical and geochemical points of view. Two types of slags were distinguished: (i) quenched slags formed mainly by Pb‐rich glass and unmelted residual grains of SiO2 and feldspars, and (ii) crystallized slags mainly composed of Fe‐rich olivine (fayalite) and glass. The mean log viscosity value of the slags calculated for 1200°C was 2.119 Pa s. The morphology of olivine crystals was used to estimate the cooling rates of the melt, for some slags indicating rates > 1450°C/h. The projection of the bulk composition of slags onto the SiO2–PbO–FeO ternary system was used for rough temperature estimates of slag formation, lying probably between 800 and 1200°C.

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The present work is focused on the study of strontium transport through crushed granite in the presence of bentonite colloids under dynamic arrangement. The aim of the experiments was to investigate the effect of bentonite colloids on strontium migration in crushed granite. The tracer behaviour was studied in a column set-up under aerobic conditions with a continuous inlet of the liquid phase of a constant tracer concentration (activity) and flow rate. Defined volumes of liquid phase were sampled at periodic time intervals at the column outlet for the measurements of tracer concentrations (activity). The transport was described by breakthrough curves. The stepwise approach included these steps: (1) an evaluation of the hydrodynamic column properties by the non-sorbing tracer 3 H; (2) a column experiment with bentonite colloids in deionized water was performed; (3) migration of 85 Sr solution in two liquid phases (deionized and synthetic granitic water); and (4) the transport of a radiocolloid suspension in deionized water was studied. Results showed different behaviour of bentonite colloids and strontium in the column. Bentonite colloids behaved as a non-sorbing tracer: conversely, strontium showed strong sorption on granitic material. The strontium transport in the presence of bentonite colloids differed from strontium transport itself. The strontium transport in the presence of colloids was faster than transport without the bentonite colloids. The observed retention of strontium on granite suggests a higher affinity of strontium towards granitic rock than towards bentonite colloids, and showed the reversibility of the sorption of strontium on bentonite colloids.

Humic substances / Complexation / Cation exchange / Charge neutralization model / Ruprechtov site / Czech Republic / U(VI)Summary. The extent of complexation between natural humic acid (HA) and uranium(VI) has been investigated at the Ruprechtov natural analogue site, Czech Republic. Natural HA was extracted from the clay sediments enriched by organic matter and then characterized for their elemental composition, UV/Vis and infrared spectroscopic properties, exchange capacity and protonation constants. Moreover, the reference sample HA-leonardite was selected and studied for comparison. Complexation between natural HA and U(VI) was studied using the cation exchange technique at pH 5-6. The experimental work was focused on study dependence of U(VI) complexation with HA: i) on the concentration of HA 1-40 mg/l, and ii) on the concentration of U(VI) 1 × 10 −5 -1 × 10 −7 M. The charge neutralization model (CNM) was used for evaluation of the experimental data, modified in a way, that the total charge was divided among the individual U(VI) species in solution under given conditions. The stability constant value was determined to be log β = 4.32 ± 0.50, LC = 50-60%, being independent on the HA concentration at U(VI) concentrations of 1 × 10 −4 M. On the other hand, a dependence on the stability constant for the different U(VI) concentrations was observed. At close to real conditions of the site (U(VI) = 1 × 10 −7 M and mHA = 5 mg/l) the stability constant log β = 6.16, LC = 50.3-52.7%.

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Modification alloy is an important part of the metallurgical process, and this also applies, of course, for aluminum alloys, particularly for Al-Si (silumins). As a modification of the material we can use the modification using the selected element or heat treatment of alloys, or a combination of both processes. One of the elements that it is possible to modify the alloy of Al-Si used is antimony (Sb). The paper examines the possible effect of the modification that element and heat treatment on the final structure of the alloy AlSi9CuMnNi. In the experiments were made three castings from the alloy AlSi9CuMnNi without modification, three castings with the modification and without heat treatment, three castings with modification and without heat treatment, and three castings with modification and heat treatment too. The described experiment and analysis are part of extensive research, focusing on a Faculty of Production Technology and Management, J. E. Purkyne University in Usti nad Labem.