Characterising Electron Transfer Mechanism in Tribo-Electrification of Pyrite Through Contact Angle Measurements

Coal beneficiation by tribo-electrostatic method depends on tribo-charging attributes of coal and ash forming minerals. The tribo-electrification behaviour of pyrite mineral contacted with different materials has been investigated through charge measurements and the charge acquisition is probed through surface energy calculations from liquid contact angle data. Liquid contact angle on pyrite powder after tribo-electrification is determined by Kruss tensiometer using Washburn's equation. The sample holder in tensiometer is specially fabricated with different materials serving the purpose of tribo-electrification and contact angle measurement. The acid and base parameters of pyrite surface determined with van Oss acid-base approach using liquid contact angle data after tribo-electrification with different materials revealed the charging phenomena and electron transfer mechanism. The results showed an explicit correlation between the charge generated by pyrite powder and surface acceptor (acid)-donor (base) electronic state underlying the work functions of contacting surfaces. Thus a method for characterising the changes in surface energetic structure of solids during contact electrification in terms of surface acid-base parameters has been illustrated for the first time.