EXTRACTION-ATOMIC-ABSORPTION DETERMINATION OF GOLD IN MARINE FERROMANGANESE FORMATIONS AFTER ITS CONCENTRATION WITH DIBUTYL SULPHIDE IN TOLUENE

Abstract

The relevance of the study is caused by the need to develop methodological solutions for the quantitative determination of gold content in ferromanganese formations and other geological objects due to the chemical and analytical difficulties that exist here and the insufficient number of certified reference materials of ferromanganese formations with a reliably certified gold content in them. The main aim is verification of the applicability of the gold extraction technique using petroleum sulfides (dibutyl sulfide in toluene) for determining gold in ferromanganese formations with electrothermal atomic absorption termination, along with the gold extraction method by its co-precipitation with tellurium. Objects: samples of ferromanganese formations from various regions of the North Pacific Ocean, as well as the Russian certified reference materials with a certified gold content OOPE 603 (SDO-6) and the USGS standard NOD-A-1. Methods. Gold was concentrated during its determination in ferromanganese formations by the methods of extraction with dibutyl sulfide in toluene and co-precipitation with tellurium and electrothermal atomic absorption analysis. Processing of the obtained results was carried out using the methods of mathematical statistics. Results. The method of gold extraction with dibutyl sulfide in toluene has shown its advantage for the purposes of analysis of ferromanganese formations in comparison with the procedure of co-precipitation with tellurium, due to its high selectivity, which makes it possible to get rid of the influence of matrix components, primarily iron, which forms an interfering superposition of spectral lines during atomic absorption determination of gold. The technique of gold extraction with dibutyl sulfide was tested for the analysis of ferromanganese formations samples from various regions of the North Pacific Ocean, as well as for the analysis of ferromanganese formations samples – the Russian OOPE 603 ​​(SDO-6) and the American standard NOD-A-1. The use of an air-dry sample of 2 g of the sample gave a satisfactory result in the analysis of the standard sample SDO-6, with a certified gold content of 10±6 ng/g, but did not allow successful analysis of the NOD-A-1 sample, for which irreproducible results were obtained. In this regard, the use of even larger weights is recommended for defining gold in this standard. Atomic absorption determination of gold in the studied ferromanganese formations samples using the proposed method gave results that meet the requirements of geochemical analysis, including in comparison with the ICP-MS method. However, an earlier electron microscopic study of ferromanganese crusts in the northwestern part of the Pacific Ocean showed the presence of native gold particles in them, which, in its turn, can cause methodological difficulties in the process of taking a representative sample and the procedure for preparing ferromanganese formations samples for analysis.

Keywords

• atomic absorption analysis
• gold
• extraction
• dibutyl sulfide
• nugget effect
• ferromanganese formations
• certified reference materials