Study on the effect of hydrogen bonding network structure in amphoteric surfactant solution on the wettability of coal dust

Abstract

The interaction between coal, surfactant, and water molecules is a vital surface chemistry problem. The mechanism by which the type of hydrogen bonding network structure (HBNS) between H2O and surfactant molecules in solution wets the coal dust is unclear. In this study, the results of wetting tests and Raman spectroscopy were used to evaluate the wettability of Cocamidopropyl betaine (CAB) with Dodecyldimethyl betaine (BS-12) solutions at different concentrations as well as the type of HBNS inside the solution as a percentage. The analysis revealed that CAB had better wettability on bituminous coal compared with BS-12. In addition, the composition of HBNS in solution changes with increasing concentration, with the proportion of strong hydrogen bonds increasing and the proportion of weak hydrogen bonds decreasing. Molecular dynamics and quantum chemistry results are mutually validated with experiments. The hydrogen bonding coordination number (CN) of water molecules at different concentrations (CNCAB/H2O < CNBS-12/H2O), and the hydrogen bonding interaction energy between water molecules and active agent molecules were investigated. It was finally indicated that CAB binds water molecules in higher numbers and strength than BS-12. This provides a new way to determine the wettability of surfactants.