Synthesis of a novel dispersant with topological structure by using humic acid as raw material and its application in coal water slurry preparation

Abstract

This work reports the synthesis and performance of a novel dispersant for coal water slurry (CWS). The dispersant is derived from humic acid (HA) and has a topological structure, named humic acid-graft-poly(sodium styrene sulfonate) (HA-g-PSSNa). A series of HA-g-PSSNa with simultaneous presence of hydrophobic humic acid skeleton and hydrophilic poly(sodium styrene sulfonate) side chains were synthesized via surface acylation reaction of HA and followed by atom transfer radical polymerization. The structure and chemical composition of HA-g-PSSNa were verified by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. Scanning electron microscopy observation suggests that the incorporation of PSSNa segments onto HA skeleton remarkably affects its morphology. The performances of CWS prepared using HA-g-PSSNa, PSSNa, and naphthalene sulfonic formaldehyde condensate (NSF) as dispersants were studied and systematically compared using various technologies. The results show that the slurry-making performance of HA-g-PSSNa enhanced with the increase in the length of PSSNa side chains. In the case of HA-g-PSSNa with appropriate PSSNa chain length, the CWS prepared using HA-g-PSSNa as dispersant exhibits excellent apparent viscosity as well as static stability, even superior to those of PSSNa and NSF. The dispersing and stabilizing mechanism of HA-g-PSSNa is proposed as follows: When used as a dispersant for CWS, HA skeleton provides sufficient hydrophobic interaction to coal surface and drives the adsorption of HA-g-PSSNa molecules. Hydrophilic PSSNa side chains are oriented to water, thus forming a dense electrical layer and steric hindrance surrounding the coal particles. Accordingly, the aggregation of coal particles was suppressed.