Solvent extraction in analytical geochemistry : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy at Massey University of Manawatu
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Date
1966
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Massey University
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Abstract
A procedure conbining solvent extraction enrichment techniques and spectrographic analysis was developed
for the quantitative determination of many trace elements
in a wide range of silicate rocks and in a series of highly
saline Antarctic lake waters.
Since a great deal of the work depended on spectrographic
analysis, an investigation was carried out to
improve the precision and sensitivity of existing methods.
An improved method for the determination of spectralline
intensities was developed. This was based on the author's
nodification of the partial Seidel function, referred to as
B-functions. A conversion table for these is given. A
scale calibrated in B-functions was incorporated into a
Hilger microphotometer enabling such values to be obtained
directly without the use of conversion tables. B-values
can be plotted directly onto the linear ordinate of semilog
paper if the self-calibration method is used for evaluating
line intensities. This results in a straightening
of the characteristic curve with an attendant time saving
and an improvement in the accuracy of the background
extrapolation. A nomographic technique was also developed
for use in conjunction with this scale and resulted in a
rapid evaluation of line intensities but with some loss
in precision.
Cathode excitation as distinct from cathode layer
was compared with anode excitation under the same
conditions. Data on 33 elements were used to study relative
self-absorption effects, absolute sensitivities, volatilisation curves,
times for complete combustion and background
effects. Data on14 elements and 35 line pairs were used
to study reproducibilities in the three matrices, NaCl, CaCl2
and carbon. It was shown that cathode excitation in a
carbon matrix afforded the greatest precision for a number
of the more volatile elements. Anode excitation provided
generally better precision if a NaCl matrix was used.
CaCl2 was a very unsatisfactory rnatrix. For the more
volatile elements cathode excitation provided a higher
sensitivity than anode excitation but with increased background
and cyanogen emission.
The extraction of the elements Au,Zn,Cd,Hg, Ga, In,Tl,Sn,Pb,As,Sb
and Bi from hydrochloric acid into the three solvents cyclohexanone, cyclohexanol and cyclohexane was studied as a function of acid concentration.
Cyclohexanone is a more efficient, but less selective
extractant, than cyclohexanol. Cyclohexane has little
extracting power for these elements.
Solvent extraction of hydrochloric acid solutions of a series of highly saline Antarctic lake waters into cyclohexanone was used to enrich the elements Zn,Pb,
In, Bi, Fe, Mn, Mo prior to spectrographic analysis. For
this, the percent extraction of Fe, Mn and Mo into cyclohexanone
from 3N hydrochloric acid was obtained. This
investigation has shown that one of these lakes, Lake Bonney,
has most probably had a seawater origin. It is also
possible that another of these lakes, Lake Fryxell, may also
have contained seawater in the past. From the relative
abundance of the various elements in the other lakes, it
was possible to conduct a geochemical reconnaissance of the
areas surrounding the lakes. This suggested that the two
most likely areas for mineralisation in the McMurdo Oasis
area of Antarctica are the region surrounding and feeding
water to Lake Hoare and the region surrounding Lake Joyce.
A consideration of the theory of discontinuous
counter current liquid-liquid extraction has shown that
it is possible to simultaneously determine the extraction
characteristics of a large number of elements for a given
solvent system. If this technique is coupled with spectrographic
analysis the determination is particularly rapid.
The extraction of the elements Ti, V, Cr, Mn, Fe, Co, Ni,
Zn, Ga, As, Nb, Mo, Ru, Rh, Pd, Ag, Cd, In, Sn, Sb, La, W,
Re, Os, Ir, Pt, Au, Hg, Tl, Pb and Bi from hydrochloric
acid into methyl isobutyl ketone was studied as a function
of acid concentration. The data were obtained by studying
spectrographically the distribution patterns of the
elements after equilibration on a discontinuous counter current
liquid-liquid extraction apparatus. A comparison
of some of the data so obtained with results for the same
system as reported by other workers showed that the technique
is valid and accurate.
Using these data it was possible to devise a
scheme which could separate Fe from the majority of the
trace elements extracted by cyclohexanone from a hydrochloric
acid solution of a rock. By a combination of batch extraction with
cyclohexanone and counter current distribution with
methyl isobutyl ketone it was possible to obtain quantitative
data for Zn and Ga and semiquantitative data for In in a
wide range of silicate rocks by spectrochemical analysis.
By the use of extraction into cyclohexanone coupled with
atomic absorption spectrometry it was possible to determine
the concentration of Pb, Cd and Bi in the same suite of rocks.
By the use of these techniques it wa spossible
to obtain fresh abundance data for the above elements in
the four standard rocks,G-1, W-1 CAAS syenite and CAAS
sulphide.
The cyclohexanone/hydrochloric acid extraction
system provides a satisfactory enrichment technique for
the spectrographic analysis of trace elements in material
with a low Fe content. For material containing a high
concentration of Fe, it is necessary to combine this technique
with discontinuous counter current liquid-liquid
extraction to separate the Fe before spectrographic analysis.
However, under these conditions, certain elements can be
determined by direct atomic absorption spectrometry of the
cyclohexanone extract.
Description
Content removed due to copyright restrictions:
Boswell, C. R., & Brooks, R. R. (1965). Improved Methods for the Measurement of Spectral Line Intensities. Applied Spectroscopy, 19(5), 147.
Brooks, R. R., & Boswell, C. R. (1965). A comparison of cathode and anode excitation in the d.c. arc. Analytica Chimica Acta, 32(C), 339-345.
Boswell, C. R., & Brooks, R. R. (1965). The extraction of elements with cyclic solvents and its application to geochemical analysis. Analytica Chimica Acta, 33(C), 117-122.
Boswell, C. R., & Brooks, R. R. (1965). The application of discontinuous, countercurrent, liquid-liquid extraction to the study of the distribution of metal ions between hydrochloric acid and methyl isobutyl ketone. Mikrochimica Acta, 53(5-6), 814-821.
Keywords
Solvent extraction, Silicate rocks, Geochemistry