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

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.

Synthesis and Performance of a Novel Cotton Linter Based Cellulose Derivatives Dispersant for Coal–Water Slurries

“…The rheological properties of CWS indicate that the flow characteristics of CWS are in accordance with the Herschel–Bulkley model ( ) [ 8 , 36 ]. The fitting results of the experimental data are shown in Figure 6 and Table 4 .…”

“…The introduction of carboxyl and sulfonic groups of cellulose can not only connect each monomer closely, but can also serve as the hydrophilic functional group in the dispersant system. This increases the hydrophilic ability of dispersant and resistance to metal ions in coal, making it easier to form a stable hydration film and thus, improving the dispersion stability [ 8 , 40 ].…”

“…The extent of ester, as defined by the succiniclic acid content (O-C=O %) and the sulfur content (S%), was measured using an X-ray photoelectron spectroscopy (D/max2500, Bruker AXS, Beijing, China). The DS was calculated according to Equation (1) and Equation (2), as follows [ 8 , 25 ]: where ω s and ω c are the mass fraction of the sulfonic and carboxyl groups; 122, 102 is the molar quantity of the substituted group; 162 is the molar quantity of a grape unit; 44 is the molar quantity of the O-C=O; 32 is the molar quantity of the S.…”

“…The concentration of the dispersant in the solution was determined from the characteristic absorption wavelength according to a predetermined calibration curve. The adsorption amount was calculated as follows [ 8 , 25 ]: where is the adsorption amount per unit mass coal (mg·g −1 ), and are the initial and final mass concentrations of the dispersant (mg·L −1 ), V is the total volume of the solution (L) and m is the mass of the coal sample (g).…”

“…Some dispersants have been commercialized, such as naphthalene sulfonated formaldehyde condensates, sulfonated melamine formaldehyde polymers and the aminosulfonic acid series, etc. They are in the process of synthesis or use may result in undesirable environmental effects, as they can accidentally or intentionally release formaldehyde into the environment [ 4 , 5 , 6 , 7 , 8 ]. Therefore, an environmentally friendly and biodegradable additive is urged to be developed as a new high-performance dispersant for coal–water slurries using cheap and abundant natural renewable resources as raw materials.…”