Study On Solution Chemistry And Effect Of Different Inorganic Electrolytes On Coal Flotation

Early in the 1930s, it was reported that inorganic electrolyte solution could promote coal floation, but the mechanism was not clear. In this paper, the floatability of coal in different electrolyte solutions and the influence of inorganic ions on the three-phase properties were investigated through experiment research, a comprehensive explanation about the effect of inorganic electrolyte on coal floation was proposed.In this study raw coal was pretreated and separated into different size–fraction and density-fraction. coal samples were analysed by IR,XRD etc., Though the research on adsorption behavior, relative contact angle and Zeta potential,it gave a further explanation on solution chemistry of coal floation.Research showed that the order of ions absorption ability,the absorption quantity of coal particles: Al3+>Ca2+>Mg2+>Na+, and ions dasorption in coal particles obeyed the Longmuir isotherm law. For different density–fraction coal, pH values also had certain effect on absorption. After the absorption of electrolyte, wettability of coal had changed. With the increasing of electrolyte concentrations, relative contact angle of coal particles also enhanced. But in high electrolyte concentrations, it would no longer affect the wettability of coal. For the -1.3 density–fraction particles, wettability of coal with pH change was relatively complex. While for the high density particles, the hydrophobicity of coal was best, was pH=6. At the same time, research found out that inorganic ions could compress electrical double-layer of coal, and reduce particles'zeta potential. However the isoelectric point was only affected by pH value of the solution, not by the types of electrolyte. Under the same conditions, compared with the particles of -1.3 density, +1.5 density had a higher absolute value of zeta potential, and it was difficult to achieve its isoelectric point.Though theoretical calculation, obtained the electrostatic repulsion,vander Waals force and the total potential energy of bubbles and particles in different solution environment. From the theoretical analysis of the role of electrolytes on the flotation of coal and found the concentration of electrolyte and acid-base environment on the flotation yield would have a certain influence on the flotation yield. With the incresae of electrolyte concentration, floation yield increased gradually,and was tend to stable at last. When the electrolyte concentration was same, the order of influence about floation yiled of ions is: Al3+>Ca2+>Mg2+>Na+. At pH 4-5, -1.3 density coal floation yield was biggest; while maximum flotation yield +1.5 density coal in the pH 5-6. Reaserch found that with electric double-layer thickness increase, the coal floation yiled was decrease. Although the adjustment of the surface electric double layer can play a role in adjusting flotation behavior of coal, but coal flotation is not entirely controlled by the surface electric double layer.Verification results showed that the floation yiled of easy-floating increased gradually with the increase of the electrolyte concentration and the propotion of ash also met the requirements; For difficult separation coal, floation yield had also increased, but the ash increased,selective reduced.