Accelerated screening of lead fractions and bioavailability in coal and its combustion products by ultrasound and microwave assistant procedure

Coal-fired power plant is one of the main anthropogenic sources of lead emission and most of lead in coal can be transferred to its combustion products (fly ash, desulfurization gypsum and slag) after burning. The fraction distribution of lead in coal, fly ash (FA), desulfurization gypsum and slag can reveal their environmental stability and migration ability. However, the conventional sequential extraction method (CSE) for screening lead fractions is time-consuming and labor-intensive. In this paper, two high efficiency methods including ultrasonic-assisted sequential extraction (UASE) method and microwave-assisted sequential extraction (MASE) method were developed. The working parameters were optimized by comparing the concentration obtained from the UASE and MASE with the optimized BCR method. The whole extraction time shorten from 48 h to 20 min. The recoveries of the first three fractions were on average of 85% for the UASE method and 95% for the MASE method in coal, fly ash, desulfurization gypsum and slag. The accuracies of the developed methods were verified by the analysis of the coal CRM (GBW11156) and FA CRM (GBW08401). The high reproducibility and applicability of the methods were demonstrated by analyzing lead in coal, fly ash, desulfurization gypsum and slag samples from 12 different power plants in China. The developed UASE and MASE were more efficient methods for accelerated screening of lead fractions in coal and its combustion products.