JSCS Vol 66, No. 10
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J.Serb.Chem.Soc. 66(10)647–670(2001)
UDC 550.4:552.61
JSCS – 2894
Original scientific
paper
The Cretaceous-Tertiary boundary Fiskeler at
Stevns Klint, Denmark: the geochemistry of the major trace metals
PAVLE I. PREMOVIC*, NIKOLA D. NIKOLIC, MIRJANA S. PAVLOVIC*,
BRATISLAV Z. TODOROVIC, DRAGAN M. DJORDJEVIC, RUZICA S. NIKOLIC, LILIANA
LOPEZ** and SALVADOR LOMONACO**
Laboratory for Geochemistry and
Cosmochemistry, Department of Chemistry, Faculty of Science, University of Nis,
P. O. Box 91, YU-18000 Nis, Yugoslavia,
*Vinca Institute of Nuclear Sciences, P. O. Box 522, YU-11001
Belgrade,Yugoslavia and
**Instituto de Ciencias de la Tierra Facultad de Ciencias,
Universidad Central de Venezuela, Aptdo. 3895, Caracas 1010-A, Venezuela
(Received
17 April 2001)
Trace
metals in the four discrete layers of the Cretaceous-Tertiary boundary
(Fiskeler) at Stevns Klint (Denmark) are relatively well studied, yet much
remains to be learned about them. Therefore, an integrated study of the trace
(meteoritic Ir, partly meteoritic Cr/Ni/Co/Au and terrestrial
Zn/Cu/La/Ce/Nd/Sm/Eu/Tb/Yb/Ta/Th) metals in the basal black marl of Fiskeler
and in its (carbonate, HCl-soluble, smectite, HCl-insoluble, silicate and
kerogen) fractions was undertaken. The mineralogy of the marl is comparatively
simple, authigenic calcite (mainly derived from planktonic marine algae:
coccoliths), detrital Mg-smectite and quartz being the principal components,
with lesser amounts of kerogen, Fe3+-oxides,
pyrite, ilite and feldspar. Selective leaching procedures were used to
establish geochemical associations and specific mineralogical locations of the
trace metals. The results identified the main locations of the major trace
metals (Cr/Ni/Co/Zn/Cu/Ir/Au). They occur mainly in the smectite and, to a
lesser extent, in the biogenic calcite (Ni/Co/Zn) and kerogen (Ir/Au). The
trace metal data are in accordance with the hypothesis that substantial
proportions of Cr/Ni/Co/Zn/Cu/Ir/Au were probably contained in the detrital
smectite arriving at the site of the deposition. In a general discussion of the
results, a geochemical model describing the incorporation of trace metals in
the smectite is presented, based on the weathering/trasport of the clay by
(impact-induced) acid surface waters and the adsorption of trace metal ions by
the smectite particles/colloids in the acidic solution of nearby oxic soil. The
distribution/enrichment patterns of Cr/Ni/Co/Zn of the basal black marl and
higher Fiskeler layers indicate, on the other hand, that notable proportions of
these metals were incorporated into the smectite structure during the formation
of the clay. The trace metal data are also considered in light of previously
published paleoecological and geochemical information for Fiskeler. It is
proposed, for example, that the local (impact-induced) superacid rainfall and
wildfires played an important role in providing appropriate humics (i.e.
appropriate organics of decaying land green plants) having porphyrin stuctures
for the formation of kerogen (enriched with Cu2+-porphyrins).
In addition, it has been suggested that the biogenic calcite with high Ni is
probably a product of the metabolic uptake of boundary seawater (enriched with
this metal) by the coccoliths. The metal enrichment of the seawater was created
by a sudden and high influx of (apparently mainly meteoritic) Ni: airborne and
laterally redeposited (by the acid surface/river waters) from a nearby soil.
Lastly, the lateral distribution of kerogen (enriched withCu2+-porpyhyrins)
supports an earlier interpretation presented by Hultenberg that the alleged
(Nye Kløv/Dania) boundaries in northwestern Denmark represent erosion and
subsequent redeposition of Fiskeler in eastern Denmark.
Keywords:
geochemistry, Cretaceous-Tertiary boundary, trace metals, smectite, kerogen.
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J.Serb.Chem.Soc. 66(10)671–683(2001)
UDC 536.7+543.54
JSCS –2895
Original scientific
paper
Influence of the composition of the
stationary and mobile phase on the retention factors and solvent strength
parameters in RP chromatographic systems in which the Everett equation is valid
T. J. JANJIC, G. VUCKOVIC and M. B. CELAP
Faculty of Chemistry, University of
Belgrade, P. O. Box 158, YU-11001 Belgrade, Yugoslavia
(Received
28 May 2001)
It
is shown how in RPchromatography the Everett equation for ideal phase
equilibriums can be used to estimate SP values (SP = log xs/x1, xs and x1 denoting
the modifier mole fractions in the stationary and mobile phases, respectively)
which are in a linear dependence with the log k values. The described
procedure includes the determination of the approximate phase equilibrium
constant K. By analysis of the Everett equation it was found that in the
field of x1/K there are regions of linear dependence of the SP
parameter or log k values and the mole fraction of modifiers or its
logarithm. Consequently, only in these regions it is possible for two different
chromatographic systems to have the same solvent strength scale: x1 or log x1.
Keywords:
Everett equation, RP column chromatography, capacity factor, SP parameter.
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J.Serb.Chem.Soc.
66(10)685–695(2001)
UDC 661.847.321+661.183.8:541.128
JSCS – 2896
Original scientific
paper
Alumina/silica aerogel with zinc
chloride as an alkylation catalyst
ALEKSANDAR M. ORLOVIC, DJORDJE T. JANACKOVIC, SASA DRMANIC,
ZORICA
MARINKOVIC* and DEJAN U. SKALA
Faculty of Technology and
Metallurgy, University of Belgrade, Karnegijeva 4, P. O. Box 3503, YU-11120
Belgrade and
*Center for Multidisciplinary Studies, University of Belgrade,
Kneza Viseslava 1a, YU-11000 Belgrade, Yugoslavia
(Received
5 April 2001)
The
alumina/silica with zinc chloride aerogel alkylation catalyst was obtained
using a one step sol-gel synthesis, and subsequent drying with supercritical
carbon dioxide. The aerogel catalyst activity was found to be higher compared
to the corresponding xerogel catalyst, as a result of the higher aerogel
surface area, total pore volume and favourable pore size distribution. Mixed
Al–O–Si bonds were present in both gel catalyst types. Activation by thermal
treatment in air was needed prior to catalytic alkylation, due to the presence
of residual organic groups on the aerogel surface. The optimal activation
temperature was found to be in the range 185–225°C, while higher temperatures
resulted in the removal of zinc chloride from the surface of the aerogel
catalyst with a consequential decrease in the catalytic activity. On varying
the zinc chloride content, the catalytic activity of the aerogel catalyst
exhibited a maximum. High zinc chloride contents decreased the catalytic
activity of the aerogel catalyst as the result of the pores of the catalyst
being plugged with this compound, and the separation of the alumina/silica
support into Al-rich and Si-rich phases. The surface area, total pore volume,
pore size distribution and zinc chloride content had a similar influence on the
activity of the aerogel catalyst as was the case of xerogel catalyst and
supported zinc chloride catalysts.
Keywords:
aerogel catalyst, Friedel-Crafts alkylation catalyst, sol-gel derived
catalyst.
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J.Serb.Chem.Soc.
66(10)697–708(2001)
UDC 546.815+628.312.5+66.061
JSCS –2897
Original scientific
paper
Lead distribution in water and its
association with sediment constituents of the “Barje” lake (Leskovac,
Yugoslavia)
Z. TODOROVIC, P. POLIC*, D. DJORDJEVIC** and S. ANTONIJEVIC***
Faculty of Technology, University
of Nis, Bulevar Oslobodjenja 124, Leskovac (E-mail: todoroviczoran@yahoo.com),
Faculty of Chemistry, University of Belgrade, P. O. Box 158,
Belgrade, (E-mail: ppolic@helix.chem.bg.ac.yu),
Institute of Chemistry, Technology and Metallurgy, P. O. Box 815,
YU-11001 Belgrade and
Hemofarm Concern, Beogradski put bb, YU-26300 Vrsac, Yugoslavia
(Received
28 November 2000, revised 19 July 2001)
The
lead concentrations in the water of the “Barje” lake are presented for the
years 1995 to 1998. Sequential extraction was applied to estimate the chemical
association of lead in the sediments of the “Barje” lake. Several lead
fractions showed highly significant correlations with the corresponding
substrate (step II: Mn-oxyhydroxides; step III: Fe-oxyhydroxides) suggesting
that lead carbonates were incorporated with amorphous iron and manganese
hydroxides. An explanation for this relation can be in the same anthropogenic
source of these elements.
Keywords:
lead, sediments, sequential extraction, correlation analyses.
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J.Serb.Chem.Soc.
66(10)709–721(2001)
UDC 546.683+546.57:543.31:628.1.033
JSCS –2898
Original scientific
paper
ETAAS determination of thallium and
silver from water matrix after colloidal precipitate flotation using lead(II)
hexamethylenedithiocarbamate
KATARINA CUNDEVA, GORICA PAVLOVSKA and TRAJCE STAFILOV*
Institute of Chemistry, Faculty of
Natural Sciences and Mathematics, St. Cyril and Methodius University, P. O. Box
162, 91000 Skopje, Macedonia
(Received
6 March, revised 18 June 2001)
Afast
method for the preconcentration of thallium and silver in nanogram quantities
in fresh drinking waters (source, well, tap) and waters for irrigation using
colloidal precipitate flotation is described. Lead(II)
hexamethylenedithiocarbamate, Pb(HMDTC)2 played the
role of flotation collector. The experimental conditions for the successful
separation of thallium and silver (mass of Pb, amount ofHMDTC-, pHof
the system, induction time, type of surfactant etc.) were optimized.
After flotation separation from the mother liquor, the solid sublate containing
traces of thallium and silver was dissolved and the analytes were determined by
electrothermal atomic absorption spectrometry (ETAAS). The results of the ETAAS
analysis are compared with those obtained by inductively coupled plasma-atomic
emission spectrometry. The detection limit for thallium by this method is 0.027
mg/l, and
for silver 0.005 mg/l.
Keywords:
thallium, silver, determination, water, colloidal precipitate flotation,
ETAAS, lead(II) hexamethylenedithiocarbamate.
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J.Serb.Chem.Soc.
66(10)723–727(2001)
UDC 681.7.062+669.228
JSCS – 2899
Note
N O TE
The
STM analysis of a silver mirror surface
NEBOJSA D. NIKOLIC, ZLATKO RAKOCEVIC* and KONSTANTIN I. POPOV**
ICTM-Institute of Electrochemistry,
Njegoseva 12, Belgrade,
*Vinca Institute of Nuclear Sciences, Belgrade and
**Faculty of Technology and Metallurgy, Karnegijeva 4, Belgrade,
Yugoslavia
(Received
23 May 2001)
In
this work, the structure of a silver mirror surface was examined by the STM technique.
It was shown that the structural characteristics which enable a high degree of
mirror reflection from this surface, which is very close to the ideal
reflectivity of silver, are: flat and mutually parallel parts of the surface
which are smooth on the atomic level, and distances between adjacent flat parts
which state several atomic diameters.
Keywords:
silver mirror, STM technique.
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Copyright & copy; SHD 2001.
Updated
October 8, 2001.
For
more information contact: SHD@elab.tmf.bg.ac.yu