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1

Potassium chloride recovery from mechanically activated microcline through the chlorination roasting and leaching route

Alyosif Bahaa, Uysal Turan, Erdemoğlu Murat

Physicochemical Problems of Mineral Processing

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2023

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Vol. 59, iss. 5

art. no. 167500

EN

In this study, effects of mechanical activation in the chlorination roasting and water leaching route known as CaCl2 process and developed for the production of potassium chloride (KCl) from potassium feldspar ores were studied. A microcline containing K-feldspar ore with 10.89% K2O was first intensively dry milled by a planetary ball mill and mixed with calcium chloride (CaCl2) and then roasted at temperatures up to 1000°C to obtain KCl that will be finally dissolved by the water leaching. Potassium recovery by water leaching increased rapidly up to 800°C. At higher temperatures, the recovery decreased fast due to the evaporation of KCl. According to the K recovery values per unit energy consumed, the optimum roasting temperature was determined as 750°C and the milling time was 15 min. It was concluded that intensive milling causes mechanical activation of the microcline to reduce the chlorination roasting temperature, which triggers a rise in the K recovery by the water leaching.

2

Infrared Radiofluorescence (IR-RF) of K-Feldspar: An Interlaboratory Comparison

Murari Madhav K., Kreutzer Sebastian, Frouin Marine, Friedrich Johannes, Lauer Tobias, Klasen Nicole, Schmidt Christoph, Tsukamoto Sumiko, Richter Daniel, Mercier Norbert, Fuchs Markus

Geochronometria

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2021

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Vol. 48, no.1

105--120

EN

Infrared Radiofluorescence (IR-RF) is a relatively new method for dosimetric dating of the depositional timing of sediments. This contribution presents an interlaboratory comparison of IR-RF measurements of sedimentary feldspar from eight laboratories. A comparison of the variability of instrumental background, bleaching, saturation, and initial rise behaviour of the IR-RF signal was carried out. Two endmember samples, a naturally bleached modern dune sand sample with a zero dose and a naturally saturated sample from a Triassic sandstone (~250 Ma), were used for this interlaboratory comparison. The major findings of this study are that (1) the observed IR-RF signal keeps decreasing beyond 4000 Gy, (2) the saturated sample gives an apparent palaeodose of 1265 ± 329 Gy and (3) in most cases, the natural IR-RF signal of the modern analogue sample (resulting from natural bleaching) is higher than the signal from laboratory-induced bleaching of 6 h, using a solar simulator (SLS). In other words, the laboratory sample bleaching was unable to achieve the level of natural bleaching. The results of the investigations are discussed in detail, along with possible explanations.

3

Low temperature thermochronology using thermoluminescence signals from K-feldspar

Tang S. L., Li S. H.

Geochronometria

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2017

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Vol. 44, no. 1

112--120

EN

Thermoluminescence (TL) and isothermal thermoluminescence (ITL) signals from K-feldspar were studied. The signals from K-feldspar have provided multiple thermometers for thermochronological study. Protocols of multiple aliquot (MA) additive-dose (A) and regenerative-dose (R) have been applied and tested for equivalent dose (De) determinations using TL and ITL signals (MAA-TL, MAR-TL, MAA-ITL and MAR-ITL). Single aliquot regenerative-dose (SAR) protocol was only applied for De determination using ITL signals (SAR-ITL). A 50–60°C translation of heating temperature was necessary for the ITL De values to agree with TL De values. Based on the experiment results and merits-drawbacks comparison of the five tested protocols, the MAR-TL and SAR-ITL are favorable because of their efficiency and accuracy in De determinations. These two protocols were further applied to the samples from the Nujiang River valley and both explicitly demonstrated the thermal history of the samples. They are suitable for K-feldspar thermochronology study. They, as a parallelism of the previous studies of quartz TL and ITL signals, can provide multiple measures for a rock sample with the same thermal history in geo-thermochronological studies.

4

Review and assessment of the potential of post-IR IRSL dating methods to circumvent the problem of anomalous fading in feldspar luminescence

Li B., Jacobs Z., Roberts R. G., Li S.-H.

Geochronometria

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2014

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Vol. 41, no. 3

178--201

EN

Quartz has been the main mineral used for optically stimulated luminescence (OSL) dating of sediments over the last decade. The quartz OSL signal, however, has been shown to saturate at rel-atively low doses of ~200–400 Gy, making it difficult to be used for dating beyond about 200 thou-sand years (ka), unless the environmental dose rate is low. The infrared stimulated luminescence (IRSL) from feldspars has been shown to continue to grow to higher dose levels than quartz OSL. The application of IRSL dating of feldspars, however, has long been hampered by the anomalous fading effect. Recent progress in understanding anomalous fading of the infrared stimulated luminescence (IRSL) signals in potassium-feldspar has led to the development of post-IR IRSL (pIRIR) protocols and also a multiple elevated temperature (MET) stimulation (MET-pIRIR) protocol. These procedures have raised the prospect of isolating a non-fading IRSL component for dating Quaternary deposits containing feldspars. In this study, we review the recent progress made on (1) overcoming anomalous fading of feldspar, and (2) the development of pIRIR dating techniques for feldspar. The potential and problems associated with these methods are discussed.

5

Performance of different luminescence approaches for the dating of known-age glaciofluvial deposits from northern Switzerland

Gaar D., Lowick S. E., Preusser F.

Geochronometria

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2014

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Vol. 41, no. 1

65--80

EN

Luminescence properties of two samples taken from sand lenses in proglacial outwash de-posits of a piedmont glacier that reached the Swiss midlands during the Last Glacial Maximum are investigated in detail. Deconvolution of CW-OSL decay curves shows that the fast component domi-nates the OSL signal of quartz. The chemistry of single feldspar grains, in particular the K content in different grains, is determined using wavelength dispersive spectrometry (electron microprobe), re-vealing an average 12.9 wt.% K of the grains contributing to the IRSL signal. De distributions are in-vestigated in order to gain insights into partial bleaching, and agreement is found for quartz OSL and feldspar IR50 and pIRIR225 ages for small aliquots and single grains when applying the Minimum Age Model. These ages are also consistent with independent age control. For one sample, ages determined using the Central Age Model result in highly overestimated ages for both feldspar and quartz.

6

Residual doses and sensitivity change of post IR IRSL signals from potassium feldspar under different bleaching conditions

Chen Y., Li S.-H., Li B.

Geochronometria

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2013

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Vol. 40, no. 4

229--238

EN

The residual doses and sensitivity change for potassium-rich feldspar (K-feldspar) have been studied using the post-infrared infrared stimulated luminescence (pIRIR) and multi-elevated-temperature post-IR IRSL (MET-pIRIR) protocols. Laboratory simulated poorly-bleached and well-bleached samples were those K-feldspar grains bleached using a solar simulator for 10 minutes and 8 hours, respectively. The residual doses rise with stimulation temperature and time. The poorly-bleached sample has larger residual doses than the well-bleached sample, especially at high stimula-tion temperatures. The high-temperature pIRIR signals contain a large amount of hard-to-bleach sig-nals. A decrease of luminescence sensitivity was observed after conducting a high-temperature-treatment in the measurement cycles. The sensitivity decreases significantly between the first and the second cycle. The extent of decrease in sensitivity shows a clear temperature trend. The higher the stimulation temperature of pIRIR signals is, the larger the sensitivity decreases. This decrease is more severe for the poorly-bleached sample than for the well-bleached sample, and could possibly lead to problems in sensitivity correction.

7

Aspects of Infrared Radioluminescence dosimetry in K-feldspar

Varma V., Biswas R. H., Singhvi A. K.

Geochronometria

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2013

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Vol. 40, no. 4

266--273

EN

Infrared radioluminescence (IRRL) of K-feldspar, detected at peak wavelength of 865 nm, is emerging as a potential geochronometric tool. The present study explores and attempts to optimize the IRRL dating protocols and proposes a revised protocol for estimation of palaeodose. UV light (395 nm; 700 mW/cm2) bleach of 800 s was optimum to remove the trapped charges responsible for IRRL and, reduced the interference of radio-phosphorescence due to prior irradiations. Validation of the proposed protocol was carried out by dose recovery tests on mineral and sediment K-feldspar samples of different provenances. An overestimation in dose recovery was observed and was attribut-ed to difference in sensitivity of natural IRRL and regenerated IRRL. The sensitivity changes were significant and systematic and were documented by repeating bleach–IRRL cycles. Corrections for sensitivity changes between natural and regenerated IRRL, gave reliable results and, have now been included in the proposed dating protocol.

8

Stability of IRSL signals from sedimentary K-feldspar samples

Thomsen K. J., Murray A. S., Mayank J.

Geochronometria

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2011

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Vol. 38, no. 1

1-13

EN

Recent work has identified IR stimulated luminescence signals at elevated temperature from both potassium- and sodium-rich feldspars that have much lower anomalous fading rates than the conventional signal measured using IR stimulation at 50°C. This paper examines the stability of these signals for potassium-rich sedimentary feldspars. We show that the natural post-IR IRSL (pIRIR) signal from a 3.6 Ma old sample is in apparent saturation on a laboratory generated dose response curve, i.e. it does not show detectable fading in nature although a low fading rate is observed on laboratory time scales. We show that the pIRIR signal has a greater thermal stability than the IRSL signal and that the trend in increasing thermal stability is mirrored by a decreasing fading rate. We also investigate the effect of preheat temperature and IR stimulation power on the decay shape and conclude that the data can be explained in terms of either a single- or multiple-trap model. We present evidence that may suggest that at least part of pIRIR signal is derived from a high temperature trap (~550°C thermoluminescence (TL) peak), although again the data can also be explained in terms of a single-trap model. Finally, we present dose response curves and characteristic curvature constants (D0) values for various IRSL signals and conclude that the more stable signals saturate more quickly than the less stable signals and that the initial and final signals saturate at approximately the same level.

9

Luminescence dating of young coastal deposits from New Zealand using feldspar

Madsen A. T., Buylaert J.-P., Murray A. S.

Geochronometria

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2011

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Vol. 38, no. 4

378-390

EN

A new measurement protocol has been tested on K-feldspars from Whanganui Inlet and Parengarenga Harbour, New Zealand. A Single Aliquot Regenerative (SAR) dose protocol, using two successive infrared (IR) stimulations (post-IR IR SAR protocol) is setup for these young (<1000 years) coastal sediments. Significant anomalous fading (g2days=7 %/decade) is observed using the conventional IR signal measured at 50°C. In contrast, the fading rate of the IR signal measured at elevated temperature (150°C) after the IR stimulation at 50°C (a post-IR IR signal) is not significant (g2days=7% /decade). Surprisingly low residual infrared stimulated luminescence (IRSL) signals were observed for a surface sample, suggesting that accurate ages as young as ~50 years can be obtained for these recent deposits. IRSL ages ranging between 48š6 years and 1050š50 years are obtained from six samples, indicating that sediment accumulation has occurred at the two sites during the last millennia, despite a falling trend in relative sea-level in Whanganui Inlet and a stable relative sea-level at Parengarenga Harbour.

10

Comparison of three K-feldspar luminescence dating methods for Holocene samples

Li G. Q., Zhao H., Chen F. H.

Geochronometria

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2011

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Vol. 38, no. 1

14-22

EN

The luminescence dating of the K-feldspar fraction is an alternative way for samples that cannot yield reasonable equivalent dose (De) from quartz fraction with very weak luminescence signal. For testing the reliability of the infrared stimulated luminescence (IRSL) dating of K-feldspar, luminescence dating was applied to quartz and K-feldspar fractions respectively for several Holocene samples in this study. K-feldspar apparent ages using routine single aliquot regenerative-dose (SAR) protocol, K-feldspar ages using g value correction method and ages from isochron dating method were compared with quartz ages. It is found that the g value correction method cannot give reliable ages due to the large errors induced during measurements. The isochron dating method is effective to the sample with problematically external dose rate. However, isochron dating may introduce a relatively greater error during grain sizes – De curve fitting, therefore this method could obtain lowresolution ages for Holocene samples. Even K-feldspar apparent age from routine SAR protocol is relatively younger by about 10% than the quartz age, it still could establish reasonable chronological framework for Holocene samples.

11

Chronology of Cauvery delta sediments from shallow subsurface cores using elevated-temperature post-IR IRSL dating of feldspar

Alappat L., Tsukamoto S., Singh P., Srikanth D., Ramesh R., Frechen M.

Geochronometria

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2010

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Vol. 37

37-47

EN

We present the results of luminescence dating of sediments from two cores from the Cauvery Delta in south-east India. Since all natural quartz OSL signals except one sample were in saturation, the elevated temperature post-IR IRSL protocol for K-feldspar was applied to establish a chronology. Internal dose rates of K-feldspar grains were calculated from the measured internal content of potassium, uranium, thorium and rubidium in the bulk of K-feldspar grains using solution ICP-OES and ICP-MS analysis. A substantial scatter in single-aliquot De values was observed which is most probably due to the effect of incomplete bleaching of fluvial sediments before burial. A minimum age model was applied to extract possible depositional ages. The study revealed that except an upper layer of Holocene sediments (< 5m), the majority of the upper ~50m of Cauvery delta sediments were deposited between marine isotope stage MIS-5 and MIS-10 or older. The feldspar luminescence ages also indicate the existence of a period of non deposition or erosion in the upper part of the cores.

12

Overcoming environmental dose rate changes in luminescence dating of waterlain deposits

Li B., Li S-H., Wintle A. G.

Geochronometria

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2008

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Vol. 30

33-40

EN

This study investigates lacustrine and fluvial sediments on the Sala Us River in the Mu Us Desert in central north China. Significant changes in environmental dose rate in part of the section could be shown to have occurred from measurements of the present day radioactivity and by the age reversal for some samples that had been dated by optically stimulated luminescence (OSL) measurements on quartz. These changes in dose rate can be attributed to recent uptake of radioactive elements found in the sediments; this resulted in significant underestimation of the OSL ages. In this study, the new isochron method using K-feldspar grains has been applied to overcome the effects of changes in dose rate. Calculations are used to show that changes in the environmental dose rate factors, i.e. K, U, Th, water content and cosmic ray flux, and disequilibrium in the U and Th decay chains, e.g. radon escape, have a negligible effect on the isochron age. After applying the new isochron method, the effects of changes in dose rate caused by recent uptake of radioactive elements and changes in past water content were effectively overcome and true ages are obtained; this was verified by repeating the luminescence isochron measurements on samples of overlying and underlying sediments.

13

The parameters of traps in K-feldspars and the TL bleaching efficiency

Chruścińska A., Oczkowski H. L., Przegiętka K. R.

Geochronometria

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2001

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Vol. 20

15-20

EN

The fractional glow technique (FGT) applied to the investigation of optically bleached samples of K-feldspars extracted from sediments reveals the coexistence of various groups of traps which are active in the same temperature region over 300 °C. Significant differences between the trap parameters seem to explain the diversity of TL bleaching efficiency for different trap groups.

14

The fractional glow technique as a tool of investigation of tl bleaching efficiency in K-feldspar

Chruścińska A.

Geochronometria

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2001

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Vol. 20

21-30

EN

The fractional glow technique was applied to the investigation of trap occupation in optically bleached K-feldspars separated from sediments. Various bleaching times and two spectra ranges of sunlight simulator were used. Three trap groups exhibit different sensitivities to bleaching. The influence of the spectrum range of the stimulation light on the bleaching efficiency is presented. Results of the fractional glow technique measurements simulations are presented for the case of second order kinetics.