Bratislav Ž. Todorović

Cretaceous-Paleogene boundary (KPB) Fish Clay at Højerup (Stevns Klint, Denmark): Ni, Co, and Zn of the black marl

The black marl of the Fish Clay at Hojerup is mainly made up of biogenic calcite and cheto-Mg-smectite. We suggest that the formation of the smectite occurred during the latest Maastrichtian (or earlier) and that it represents a short period of rapid redeposition through coastal erosion occurring at the Cretaceous-Paleogene boundary (KPB) sea level lowstand. The smectite of the black marl shows enhanced concentrations of Ni, Co, and Zn. The predominant source of these metals was probably the impact-ejecta fallout deposited on the top of nearby soil which was leached by the impact-induced-acidic surface waters. Most of the content of Ni and Co in the smectite is derived from the chondritic component of the fallout, but the ultimate origin of Zn may have been the impact-target rocks. Incorporation of the metals into the smectite took place during the KPB but before its redeposition at the Fish Clay site. The biogenic calcite-rich fraction of the black marl also shows high concentrations of Ni, Co, and Zn. The ultimate source of the metals was also probably the impact-ejecta fallout on the nearby soil at Stevns Klint. Enrichments of Ni in the biogenic calcite-rich/smectite fractions of the black marl represent the sudden input of the metal into the seawater at the KPB.

Thermal Energy Storage of Composite Materials Based on Clay, Stearic Acid, Paraffin and Glauber’s Salt as Phase Change Materials

Thermal protection and insulation are important problems in many fields such as industry, agriculture and medicine. New composite materials with good thermal storage capacities have become important in the last few decades. The role of these materials is reflected in their ability to store energy and allow it to be reused in some other thermal systems. The aim of this study was to create a new material based on the basically activated bentonite clay. First, the clay was basically activated, resulting in a thick gel. Afterwards, stearic acid, Glauber’s salt and active carbon were added, and a heterogeneous gel was obtained as a finished final product. In order to obtain the best heterogeneous gel with satisfactory storage properties, the amount of stearic acid and Glauber’s salt was varied. The characterization of the resulting heterogeneous gel was performed by measuring the cooling rate of the gel samples. Compared with stearic acid, Glauber’s proved to be more effective. Heterogeneous gel cooling tests have shown that there was a certain proportional dependence between the concentration of stearic acid and the Glauber salt. However, it has been noticed the reduction in the cooling rate. Namely, the increase in stearic acid and Glauber’s salt concentration lead to slowing down the cooling rate of the gel. Adding active carbon to the heterogeneous gel also reduced the cooling rate, which indicated that the presence of active carbon in the heterogeneous gel should not be excluded in the future. The advantage of this system is the improvement of the gel thermal characteristics by the presence of water and clay. The gel was reversibly cooled and heated up to 100 °C without changing the homogeneous structure. This system can be used as a heat recovery pad, due to its flexible body pillow. It can be very quickly warmed up in a microwave oven if it is packaged in polyethylene packaging.

Scaling potential of geothermal water from the well A-2 at Vranjska Banja: Serbia

Geochemical and physicochemical characteristics of geothermal water from A-2 well are investigated in order to estimate its tendency towards the formation of scale in the pipe installation. Based on the geochemiocal analysis of major elements and groups, as well as triangular plots, this geothermal water can be classified as NaAlk·SO4 type. The ternary diagram classifies it as steamheated-peripheral water. A-2 has a good utilization capacity of 1 L s-1 at the water temperature of 84 °C. Regarding this, SI values are determined as the measure of tendency to form deposits. A positive SI value of calcite (0.14) and aragonite (0.03) at the temperature of 84 °C suggests a very low tendency to form scale, as well as the possible occurrence of a minor proportion of carbonate minerals. XRD mineralogical and SEM analyses of the scale have confirmed its calcite composition. SI values for the temperature of 25 °C indicate the safe silicate minerals deposition due to the positive temperature coefficient. The obtained SI values indicate that the A-2 geothermal water in Vranjska Banja is suitable for use in piping installations because it shows poorly pronounced tendency to form deposits.