Ultrasound-Promoter Pretreatment for Enhancing the Yield and Combustible Matter Recovery of High-Ash Oxidized Coal Flotation

摘要

The nature of coal surfaces changes from hydrophobic to hydrophilic due to the adsorption of hydrophilic oxygenated functionalities upon weathering or natural oxidation. The presence of such oxygenated functionalities interferes in the interaction between the collector and coal particles, leading to the poor adsorption of the collector over a coal surface, and therefore reduces the floatability of coal. In order to enhance the floatability of oxidized coal, an attempt has been made to remove the oxygenated functional groups from oxidized coal by ultrasound, promoter, and combined ultrasound-promoter pretreatments. Ethanol was used as a promoter in this study. The optimized ultrasound pretreatment time during flotation was found to be 5 min wherein a maximum yield of 46.94% and combustible matter recovery of 60.39% were achieved. The effects of ethanol dosage and pretreatment time on the floatability of oxidized coal were also studied in the absence and presence of ultrasound. It was found that the combined ultrasound-ethanol pretreatment showed higher deoxidizing potential than ultrasound or ethanol pretreatment alone. Under the combined ultrasound-ethanol pretreatment, the flotation concentrate showed a maximum yield and combustible matter recovery of 65.92 and 87.55%, respectively, at 5 min ultrasonic pretreatment time, 2.5 mL/kg ethanol dosage, and 5 min ethanol pretreatment time. FTIR analysis was also employed on the different flotation concentrates to compare the deoxidizing potential of each pretreatment mode.