Bayer process liquors present a difficult and complex matrix to the analytical chemist, and the h... more Bayer process liquors present a difficult and complex matrix to the analytical chemist, and the history of the application of modern analytical techniques to this problem is a case study in innovation. All Bayer process liquors contain organic compounds, in amounts varying from traces to several grams per litre. The total organic carbon content of Bayer liquors may be less than 5 g/L up to as much as 40 g/L. The presence of these organic impurities is of concern to Bayer technologists because they can have significant impacts on the economics of the process and the quality of the product. This review examines the history and current state-of-the-art of the analysis of organics in Bayer process liquors, and provides guidance on the applicable techniques matched to a comprehensive list of the compounds most likely to be present.
Organic impurities in Bayer liquor cause significant losses in productivity and hence the develop... more Organic impurities in Bayer liquor cause significant losses in productivity and hence the development of improved processes for removing these impurities from this unique solution is of great interest to the alumina industry. Of the various organics removal processes that have been ...
This review is the first of a series examining the history and current state of knowledge of the ... more This review is the first of a series examining the history and current state of knowledge of the science related to organic compounds in the Bayer process for the extraction of alumina from lateritic bauxites. Part 1 covers the origins, nature and chemistry of organic compounds in ...
Organic compounds with adjacent hydroxyl groups inhibit gibbsite (“hydrate”) precipitation in the... more Organic compounds with adjacent hydroxyl groups inhibit gibbsite (“hydrate”) precipitation in the Bayer process for the production of alumina. These hydrate yield inhibitors can be degradation products from the breakdown of larger organic molecules extracted from bauxite ore in digestion. Wet oxidation can be used to remove organics from Bayer liquor, but the nature and amounts of products are difficult
ABSTRACT Organic matter in Bayer liquor from an alumina production facility in Australia was char... more ABSTRACT Organic matter in Bayer liquor from an alumina production facility in Australia was characterized in terms of its molecular weight distribution and molecular structure using a suite of complementary chromatographic, spectroscopic, and thermal and chemical degradation methods. The organic matter was characterized using high-performance size-exclusion chromatography with UV–vis detection (HPSEC–UV), Fourier transform infrared (FTIR) spectroscopy, and solid-state 13C nuclear magnetic resonance (13C NMR) spectroscopy. These techniques provided information on the apparent molecular weight distribution of the organic matter contained in the Bayer liquor, its alkyl/aromatic characteristics, and the presence of specific functional groups. The techniques of microscale sealed vessel (MSSV) pyrolysis–gas chromatography–mass spectrometry (GC–MS), flash pyrolysis–GC–MS, and online tetramethylammonium hydroxide (TMAH) thermochemolysis–GC–MS provided detailed information at a molecular level. Information on individual low-molecular-weight organic acids in the sample was also obtained using liquid chromatography–tandem mass spectrometry (LC–MS–MS). The novelty of this work is the molecular identification of nitrogen compounds, pyridines, pyrenes, quinolones, benzoquinolines, indoles, carbazoles, bipyridines, and phenylpyridines that derive from organic matter in the bauxite or its transformation products. The results from the other analysis techniques largely confirm the high aromatic content of the liquor, with varying degrees of alkyl (predominantly methyl), carboxylic, ketone, nitrile, and hydroxyl substitution. Aromatic acids were found to be abundant, although they were poorly detected using pyrolysis methods, highlighting the importance of using a suite of complementary techniques for the analysis of Bayer liquor samples.
Bayer process liquors present a difficult and complex matrix to the analytical chemist, and the h... more Bayer process liquors present a difficult and complex matrix to the analytical chemist, and the history of the application of modern analytical techniques to this problem is a case study in innovation. All Bayer process liquors contain organic compounds, in amounts varying from traces to several grams per litre. The total organic carbon content of Bayer liquors may be less than 5 g/L up to as much as 40 g/L. The presence of these organic impurities is of concern to Bayer technologists because they can have significant impacts on the economics of the process and the quality of the product. This review examines the history and current state-of-the-art of the analysis of organics in Bayer process liquors, and provides guidance on the applicable techniques matched to a comprehensive list of the compounds most likely to be present.
Organic impurities in Bayer liquor cause significant losses in productivity and hence the develop... more Organic impurities in Bayer liquor cause significant losses in productivity and hence the development of improved processes for removing these impurities from this unique solution is of great interest to the alumina industry. Of the various organics removal processes that have been ...
This review is the first of a series examining the history and current state of knowledge of the ... more This review is the first of a series examining the history and current state of knowledge of the science related to organic compounds in the Bayer process for the extraction of alumina from lateritic bauxites. Part 1 covers the origins, nature and chemistry of organic compounds in ...
Organic compounds with adjacent hydroxyl groups inhibit gibbsite (“hydrate”) precipitation in the... more Organic compounds with adjacent hydroxyl groups inhibit gibbsite (“hydrate”) precipitation in the Bayer process for the production of alumina. These hydrate yield inhibitors can be degradation products from the breakdown of larger organic molecules extracted from bauxite ore in digestion. Wet oxidation can be used to remove organics from Bayer liquor, but the nature and amounts of products are difficult
ABSTRACT Organic matter in Bayer liquor from an alumina production facility in Australia was char... more ABSTRACT Organic matter in Bayer liquor from an alumina production facility in Australia was characterized in terms of its molecular weight distribution and molecular structure using a suite of complementary chromatographic, spectroscopic, and thermal and chemical degradation methods. The organic matter was characterized using high-performance size-exclusion chromatography with UV–vis detection (HPSEC–UV), Fourier transform infrared (FTIR) spectroscopy, and solid-state 13C nuclear magnetic resonance (13C NMR) spectroscopy. These techniques provided information on the apparent molecular weight distribution of the organic matter contained in the Bayer liquor, its alkyl/aromatic characteristics, and the presence of specific functional groups. The techniques of microscale sealed vessel (MSSV) pyrolysis–gas chromatography–mass spectrometry (GC–MS), flash pyrolysis–GC–MS, and online tetramethylammonium hydroxide (TMAH) thermochemolysis–GC–MS provided detailed information at a molecular level. Information on individual low-molecular-weight organic acids in the sample was also obtained using liquid chromatography–tandem mass spectrometry (LC–MS–MS). The novelty of this work is the molecular identification of nitrogen compounds, pyridines, pyrenes, quinolones, benzoquinolines, indoles, carbazoles, bipyridines, and phenylpyridines that derive from organic matter in the bauxite or its transformation products. The results from the other analysis techniques largely confirm the high aromatic content of the liquor, with varying degrees of alkyl (predominantly methyl), carboxylic, ketone, nitrile, and hydroxyl substitution. Aromatic acids were found to be abundant, although they were poorly detected using pyrolysis methods, highlighting the importance of using a suite of complementary techniques for the analysis of Bayer liquor samples.
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