Effect Of Surfactants On The Wettability Of Coal

Wettability is one of coal’s key parameters, and is significant to not only dust suppression in coal mining, flotation technology, but also coal slime water treatment, coal water slurry preparation. There are kinds of surfactant suitable for coal flotation technology and slime water treatment, and surfactant can effectively increase the solution’s wettability in coal’s surface, therefore increase the operating efficiency of coal.This paper focus on both wettability and surfactant. Main factor that affect coal’s wettability has been studied and surfactant’s influence on wettability has been explored through experiments. Firstly, contact angle of coal dust, industrial analysis, elemental analysis, infrared spectrum, particle size analysis, density analysis and zeta potential is conducted to analyze influence factors of coal’s wettability, and regression equation of coal dust’s physicochemical properties and coal’s wettability is also established; secondly, different type of surfactants are selected to measure variation of surface tension, zeta potential, contact angle and adsorption, to explore surfactant’s influence on wettability and verify result by filtration test in laboratory and semi-commercial filter pressing test.By researching relationship between coal’s physicochemical properties and its wettability, influence factors of coal’s wettability is analyzed. Research shows that there are large amount of hydrophobic groups like aliphatic hydrocarbon and aromatic in coal’s surface, which makes coal with a strong hydrophobicity, however, oxygen-containing functional groups like carboxyl, hydroxyl and carbonyl in coal’s surface also make it with certain hydrophilicity. Electrical property of coal’s surface reflex ionizing property of hydrophilic groups in coal’s surface. The higher coal’s moisture content, ash content and oxygen content is, the better coal’s wettability would be; The higher coal’s fixed carbon content, volatile content, carbon content, and hydrogen content is, the worse coal’s wettability would be; sulfur and nitrogen content has little influence on coal’s wettability, and the lower coal dust’s size and density, the better coal’s wettability would be. Finally, optimal regression equation about coal dust’s wettability is concluded by stepwise linear regression.Conclusion is drawn by researching surfactant’s influence on wettability:as the concentration of surfactant rises, coal’s contact angle increases and then decreases slowly; solution’s surface tension decreases rapidly, and then decreases slowly to horizon. SDS makes Zeta potential of coal sample decreases rapidly, and then slowly to the horizontal line. OP-10 has little obvious influence to coal sample’s Zeta potential; surfactant’s absorption on coal’s surface increases rapidly, and then slowly increases to the horizontal line. The conclusion shows that coal’s zeta potential changing caused by solution’s surface tension and surfactant is not the main factor that influencing coal’s wettability, and absorption is the most significant factor of surfactant’s influence on wettability. Three surfactants are selected as filter aid to filter coal samples in filtration test of laboratory and semi-commercial filter pressing test. Curves are draw based on test results, moisture content of filter cake decreases as contact angle of coal rises, which verifying correctness of mechanism analysis.