Abstract
In this work, a method using microwave-induced combustion (MIC) was optimized in order to obtain a fast, simple, efficient and greener sample preparation method for coal digestion and further determination of sulfur by inductively coupled plasma optical emission spectrometry (ICP OES). Accuracy was evaluated by comparison of the results with those obtained using elemental analysis by UV-fluorescence, microwave-assisted acid digestion with determination by ICP OES and by analysis of certified reference materials of coal. Some parameters that influence MIC method, such as the type and concentration of absorbing solution, the necessity of using a reflux step as well as the cooling time were carefully optimized. No statistical difference was observed for combustion without reflux followed by 5 min of cooling, in comparison to the reference values obtained by elemental analysis. Complete digestion was obtained with this fast and simple method (total digestion program required only 6 min) and using a diluted acid solution for quantitative recovery. The feasibility of digests for sulfur determination as sulfate by ion chromatography (IC) with conductivity detection was also demonstrated. The possibility of determining other elements, commonly monitored in coals, is another advantage of this high-efficiency digestion method (MIC) combined with the multielemental capacity of ICP OES or IC instruments.
Highlights
Despite the environmental impact related to coal combustion it remains as one of the main energy sources used worldwide
The proposed microwave-induced combustion (MIC) method was optimized for coal digestion and subsequent determination of sulfur by inductively coupled plasma optical emission spectrometry (ICP OES)
The proposed MIC method was performed without reflux followed by only 5 min of cooling step, allowing to propose a method that requires only 6 min for sample digestion
Summary
Despite the environmental impact related to coal combustion it remains as one of the main energy sources used worldwide. One drawback for its use is that coal contains a variety of elements that are released to the atmosphere during coal processing.[1,2] Among these elements, sulfur is a major component and its combustion process contributes to the sulfur emission (as SO2 and SO3). In the atmosphere, those molecules can react with water resulting in acid rain, with significant environmental impacts.[3] the sulfur content impacts on the coal price, because it is directly related to the corrosion of equipment in processing power plants and defines the technology used for the desulfurization of coal.[4]. In spite of some commercial instruments available for this purpose, the method requires calibration with certified reference materials (CRMs) and can be influenced by different species of sulfur or changes in matrix composition
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
