Synthesis of a novel amphoteric copolymer and its application as a dispersant for coal water slurry preparation.

Lun Du,Junguo Li,Ce Zhang,Jie Luo,Dongdong Yang,Guanghua Zhang,Wanbin Zhang,Junfeng Zhu,Yewei Liu

doi:10.1098/rsos.201480

Abstract

In this work, a novel amphoteric copolymer named Poly(sodium p-styrenesulfonate–co-acrylic acid-co-diallyldimethylammonium chloride) (P(SS-co-AA-co-DMDAAC)) was synthesized via free radical polymerization. Afterwards, P(SS-co-AA-co-DMDAAC) was explored for use as a dispersant in coal water slurry (CWS) preparation. The structure of P(SS-co-AA-co-DMDAAC) was verified by Fourier transform infrared spectroscopy and nuclear magnetic resonance. The synthetic conditions were optimized as the feed ratio of AA to SS was 1 : 1 (for Yulin coal) or 1.5 : 1 (for Yili coal), and DMDAAC dosage was 4.0 wt% (for Yulin coal) and 6.0 wt% (for Yili coal) toward total monomers. The performances of P(SS-co-AA-co-DMDAAC) as a dispersant for CWS were evaluated by various technologies, such as apparent viscosity, zeta potential, static stability and contact angle measurements. The results revealed that the optimized dosage of P(SS-co-AA-co-DMDAAC) in CWS preparation was 0.3 and 0.4 wt% for Yulin coal and Yili coal respectively. In this optimum condition, CWS prepared using P(SS-co-AA-co-DMDAAC) as dispersant showed a typical shear thinning behaviour and excellent stability, which are desired in industries. The rheological models also confirmed the pseudo-plastic characteristics of CWS. Finally, compared with the widely used anionic dispersant naphthalene sulphonate formaldehyde condensate (NSF) and poly(sodium p-styrenesulfonate) (PSS), P(SS-co-AA-co-DMDAAC) developed in this work exhibited better slurry making performance. The introduction of cationic functional groups promoted the adsorption of the dispersant, which further enhanced the electrostatic repulsion and steric hindrance among coal particles. Accordingly, the viscosity of CWS decreased and static stability enhanced.

Highlights

Over the past decades, amphoteric copolymers have attracted great attention in science and industry areas due to their special physical and chemical properties
A small amount of dispersant is critically important for the dispersion and stabilization of coal particles in Coal water slurry (CWS) system
P(SS-co-AA-co-DMDAAC) was synthesized by convenient free radical polymerization technology, which is beneficial for large-scale production

Summary

Introduction

Amphoteric copolymers have attracted great attention in science and industry areas due to their special physical and chemical properties. The most commonly used dispersants can be categorized into natural compounds and synthetic polymers according to their origins Natural compound dispersants such as lignin [6,7,8] and humic acid derivatives [9,10] possess advantages such as low cost, abundant reserve and environment friendliness. They usually exhibit poor dispersion performance, and large-scale applications have been limited. Naphthalene sulfonic formaldehyde condensate (NSF), as a synthetic dispersant, exhibits improved dispersion performance [11,12,13] Their synthetic route usually demands harsh conditions and causes environmental pollution. Various polycarboxylate dispersants with different structures and chemical composition have been reported [14,15,16]

Methods

Results

Conclusion