Mechanism of action of polyacrylamide in selective flocculation flotation of fine coal

The influences of anionic polyacrylamide with low molecular weight(PAM A401) on coal and kaolinite were investigated by the flocs size distribution,FTIR spectra and wettability. Flotation kinetics tests were carried out to verify the effect of PAM A401. By using 12 mg·L^-1 PAM A401 and conditioning for 11 min,at the cumulative particle size distributions of 10%,50% and 90%,the particle size of coal is 6.86,2.22 and 2.45 times that of kaolinite flocs,respectively,showing a better flocculation selectivity of coal. After PAM A401 adsorption,the peaks of hydrophilic functional groups of coal are strengthened and the coal particle surfaces become more hydrophilic. For kaolinite,both the hydrophilic and hydrophobic functional groups increase,and the kaolinite is slightly more hydrophobic. Compared with the conventional flotation,the flotation rate of selective flocculation flotation tests is higher,and 30% of collector is saved. The cumulative combustible recovery of selective flocculation flotation is 81.57%,which is 3.64% higher than the conventional flotation experiment,but the ash content of clean coal is similar. Although PAM A401 reduces the wettability of coal particle surfaces,the enlargement of apparent particle size of fine coal promotes efficient separation of fine coal.