Influence of “tentacle structure” on the properties of jellyfish-like 3D dispersants based on tannic acid for preparing high-concentrated coal–water slurry

Abstract

Three kinds of jellyfish-like three-dimensional dispersants with different “tentacle structures” were designed and synthesized via polymerization reaction of tannic acid (TA) with starch, allyl polyoxyethylene ether 1200 (APEG1200), and acrylic acid (AA), respectively. These dispersants were employed for preparing high-concentrated coal–water slurry (CWS). Their structures and surfactivity were characterized using FTIR, 1H NMR and surface tension. The effects of the TA-based dispersants on the performance of CWS were fundamentally investigated. The TA-based dispersant with starch as the “tentacle structure” (TA-St) exhibited the better viscosity-reducing and stabilizing capability for CWS than those with APEG1200 (TA-APEG) or AA (TAA). The apparent viscosity reduced to 317 mPa·s at 0.5 wt% TA-St, and the maximum coal content exceeded 71 wt%. Rheological experiments showed that the CWS prepared with the three TA-based dispersants behaved as pseudoplastic fluids, and the CWS with TA-St presented the smallest yield stress. After 3.5 days of storage, the separated water ratio of CWS with TA-St reached 4.15 wt%. Meanwhile, the TA-St dispersant showed a better effect in increasing the adsorption capacity and adsorption film thickness, wettability, and absolute value of zeta potential of the coal surface compared with TAA and TA-APEG. The saturated adsorption quantity of TA-St on the coal surface was 1.77 mg/g. The excellent performances of TA-St in dispersing and stabilizing coal particles in CWS were due to the great steric hindrance and electrostatic repulsion effect derived from the starch “tentacle structure”, which effectively reduced the aggregation among coal particles.