Exploration of interactions of modified sodium lignosulfonate with coal pitch in coal pitch–water slurry based on experiments and simulations

Abstract

Large amounts of coal pitch (CP) are utilized insufficiently. To realize resource utilization, CP was employed for preparing high-performance coal pitch-water slurry (CPWS). In this study, the influences of three sodium lignosulfonate (LS) dispersants with different sulfonation degrees and relative molecular weights (modified LS (MLS), sulfomethylated LS (SLS), and condensed LS (CLS)) on the characteristics of CPWS were investigated. The adsorption behaviors of dispersants and the surface properties of CP were also analyzed. Results showed that compared with SLS and CLS, the viscosity-reducing and stabilizing capability of MLS were best in CPWS, and the saturated adsorption quantity of MLS was the largest (4.37 mg/g). After adsorbing dispersants, the wettability and Zeta potential of CP were improved in the order of MLS > SLS > CLS. Furthermore, the molecular dynamics (MD) simulation and density functional theory (DFT) calculation were employed to elucidate the interactions between CP and dispersants. Results showed that the adsorption energy of MLS with CP was the most prominent (−1516.04 kJ/mol), and the mobility of water molecules reduced. According to the DFT calculation results, the order of ΔELUMO-HUMO was Unit 3 > Unit 1 > Unit 4 > Unit 2, which were the four structure units of CP. The interactions between CP and MLS had not only hydrogen bonds but also π-π interactions in slurry. The findings were beneficial to understand the interactions between dispersants and CP and design the efficient dispersant for CPWS.