Effect of microwave pretreatment on oxidized coal flotation

The oxidized coal should be well recovered as the demand for energy is increasing. But the hydrophobicity of oxidized coal is much lower than that of fresh coal, the improvement in floatability of oxidized coal is a key issue. Microwave pretreatment is used to improve the floatability of oxidized coal in this investigation. FTIR was used to show the changes in the main functional chemical groups of microwave treated oxidized coal at different times. The moisture content of microwave treated oxidized coal at different times was also measured. The results of FTIR and moisture content measurements show that microwave pretreatment seems to have weak effect on the chemical properties of oxidized coal surface but can reduce the moisture content. The results of flotation tests show that the combustible recovery increases with microwave pretreatment time. The mechanism of microwave pretreatment improving the floatability of oxidized coal is discussed in this investigation.

The combustible matter recovery of oxidized coal increases with the increase of microwave pretreatment time and/or the decrease of moisture content. The main purpose of microwave pretreatment, enhancing the oxidized coal flotation may be, to reduce the moisture content of oxidized coal and weaken the peak at 3450 cm− 1 as observed from FTIR spectrums.Figure optionsDownload as PowerPoint slideHighlights
► Microwave pretreatment is used to improve the flotation of oxidized coal.
► Microwave pretreatment can reduce the moisture content.
► Combustible matter recovery increases with microwave pretreatment time.