Role of collector polarity and size on the low-rank fine coal flotation

The nature of interaction between coal surface and collector molecule affects the yield of fine coal flotation. The interaction depends on coal surface characteristics and collector polarity as well as collector size. In this work, a detail understanding on the interaction nature of nonpolar such as dodecane (C1) and polar collectors such as tetrahydrofurfuryl oleate (C2) and 2-[2-[2-[2-[2-[2-(2-hydroxyethoxy)ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethyl(Z)-octadec-9-enoate (C3) with low-rank coal is presented using density functional theory calculations and finite temperature large scale ReaxFF molecular dynamics simulations. It has been shown that collector consisting of more electronegative elements (i.e. with larger polarity) show stronger interaction with low-rank coal. Moreover, larger aliphatic chain helps to interact via van der Walls interactions and polar functional groups through electrostatic interaction (hydrogen bond formation) due to flexibility in the collector backbone. Interestingly, the collectors did not show any spike like attachment to the low-rank coal surface, rather lies along the coal surface to maximize the possible interactions. This contrasts with commonly presented picture for collector-(low-rank) coal surface interaction. Optimal requirement of aliphatic chain length and polar functional groups was discussed by analyzing structure properties relationship.