ISO/TC 27/SC 5/WG 8 - Major, minor and trace elements in coal and coal residues

This document specifies a method for the determination of total fluorine in coal, coke and fly ash. From measurement of the total fluorine alone, it is not possible to estimate the amount of fluorine released to the environment by utilization of the coal and subsequent disposal of the ash residue.

ISO 11723:2016 specifies a method using Eschka's mixture during ashing, extraction of the ash residue with acid, and hydride generation atomic absorption spectrometry or hydride generation atomic fluorescence spectrometry, for the determination of arsenic and selenium in solid mineral fuels.

ISO 622:2016 specifies a reduced molybdophosphate photometric method for the determination of the total phosphorus content of hard coal, lignites and coke. Two methods for taking the phosphorus into solution are specified, namely extraction from the coal or coke ash with acid or by repeated oxidation of the coal or coke, by acid, to remove carbonaceous matter.

ISO 15238:2016 specifies a procedure for the determination of the total cadmium content of coal. This procedure has not been validated with coals that spontaneously ignite. Prior to use with such sample types, users should validate the method.

ISO 15237:2016 specifies a procedure for the determination of the total mercury content of coal.

ISO 602:2015 specifies a method of determining the amount of mineral matter in all types of coal, including brown coals and lignites.

ISO 23380:2013 provides guidance on the selection of methods used for the determination of trace elements in coal. The trace elements of environmental interest include antimony, arsenic, beryllium, boron, cadmium, chlorine, chromium, cobalt, copper, fluorine, lead, manganese, mercury, molybdenum, nickel, selenium, thallium, vanadium, and zinc. The radioactive trace elements thorium and uranium can be added to this list.

ISO 8983:2007 covers the determination of beryllium, chromium, copper, manganese, nickel, lead, strontium, vanadium and zinc by atomic absorption spectrometry, following acid digestion of a laboratory-prepared ash.

ISO 11724:2016 specifies a method for the determination of total fluorine in coal, coke and fly ash. From measurement of the total fluorine alone, it is not possible to estimate the amount of fluorine released to the environment by utilization of the coal and subsequent disposal of the ash residue.

ISO 23380:2008 provides guidance on the selection of methods used for the determination of trace elements in coal and coal ash. The trace elements of environmental interest include arsenic, beryllium, boron, cadmium, chlorine, chromium, cobalt, copper, fluorine, lead, manganese, mercury, molybdenum, nickel, selenium, vanadium and zinc. To this list can be added the radioactive trace elements, thorium and uranium. ISO 23380:2008 does not prescribe the methods used for the determination of individual trace elements. The analysis of appropriate CRMs is essential to confirm the accuracy of any method used.

ISO 11724:2004 specifies a method for the determination of total fluorine in coal, coke and fly ash.

ISO 11723:2004 specifies a method using Eschka's mixture during ashing, extraction of the ash residue with acid, and hydride generation atomic absorption spectrometry or hydride generation atomic fluorescence spectrometry, for the determination of arsenic and selenium in coal and coke ash.

ISO 15238:2003 specifies a procedure for the determination of the total cadmium content of coal. This procedure has not been validated with coals that spontaneously ignite. Prior to use with such sample types, users should validate the method.

ISO 15237:2003 specifies a procedure for the determination of the total mercury content of coal.

A sample of the coal is partially demineralized by treatment with hydrochloric and hydrofluoric acids under such conditions that coal substance remains unaffected. The loss in mass of the coal due the acid treatment is recorded and the undissolved part of the mineral matter is determined by ashing the partiallay demineralized coal. The iron copntent of the ash is determined so that the pyrites present in the extracted coal can be calculated. In addition the amount of hydrochloric acid absorbed by the coal substance is determined.

The sample is oxidized by nitric and sulphuric acids or by the use of Eschka mixture. Then, using the method specified in ISO 2590, the arsenic is reduced by zinc in sulphuric acid or hydrochloric acid medium. The arsine formed is absorbed in a solution of silver diethyldithiocarbamate in pyridine. The purplish-red colour produced by the colloidally dispersed silver is measured photometrically at the maximum of the adsorption curve (wavelength approximately 540 nm). Feste mineralische Brennstoffe; Bestimmung des Arsengehalts nach dem Standardverfahren von ISO 2590 mit Silberdiethyldithiocarbamat

For taking the phosphorus into solution the following two methods are specified: The carbonaceous material is removed by ashing in amuffle furnace under specified conditions and the phosphorus is extracted by treatment with hydrofluoric and sulphuric acids. The carbonaceous material is removed by repeated oxidation with nitric acid in the presence of sulphuric acid. The determination is carried out by adding ammonium molybdate and ascorbic acid solution and measuring the absorbance of the resulting blue solution by a siutable optical instrument.