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The co-slurrying technology of coal and organic wastewater, which achieves the simultaneous disposal and utilization of wastewater, has attracted extensive attention in recent years. The emission of coal gasification wastewater causes serious environmental hazards, because of its large amount, high organic content, and high toxicity. In the present study, two types of wastewater, namely, gasifier wastewater (GW) and wastewater from a secondary sedimentation tank (SW), were used to prepare coal water slurry (CWS), which was labeled as coal−GW−slurry (CGS) and coal−SW−slurry (CSS), respectively, with coal−deionized water−slurry (CDS) as a reference. The surface property of coal and the dispersing mechanism were characterized using zeta potential and contact angle analyses. Results showed that the fixed viscosity loading decreased with the addition of the two types of wastewater, and the decrease was more considerable with GW. All the slurries exhibited pseudoplastic behavior and thixotropy, with the following order: CGS > CSS > CDS. Wastewater, particularly GW, strengthened the stability of CWS. The influences of ammonium and volatile phenols on slurry viscosity were also investigated. The effect of ammonium was related to the pH value of the solution. The effect of volatile phenols on the range of wastewater organic content was limited. The stability of CWS was obtained by combining the result of ammonium with organic matter. Ammonium affected the surface charge of coal particles and changed the electrostatic repulsion between coal particles. The amphiphilic organic molecules enhanced the hydrophilicity of coal, which weakened the hydrophobic interaction between particles and thickened the hydration layer. Consequently, the agglomeration of coal particles was weakened.

Organic wastewater can be used to prepare coal water slurry (CWS) for the resource utilization of organic wastewater. The components in organic wastewater are highly complex, and some of their substances can influence the properties of CWS. Here, the effects of six metal ions in organic wastewater on the properties of CWS and the interaction mechanism with a dispersant are studied. Findings show that Fe 3+ can increase while Cu 2+ can decrease the apparent viscosity of slurry, whereas Mg 2+ , Ca 2+ , K + , and Na + have no corresponding obvious effects. The stability of the slurry is improved by adding Fe 3+ and Cu 2+ , whereas those of the other ions have no considerable effects. The inductively coupled plasma optical emission spectrometer, the energy dispersive spectrometer, and the zeta potential are used to analyze the adsorption behavior of metal ions at the coal−water interface. Results show that Fe 3+ and Cu 2+ can adsorb on coal surfaces and change the properties of these coal surfaces, whereas Mg 2+ and Ca 2+ can hardly adsorb on coal surfaces, which further imply the negligible effects on the properties of the slurry. Furthermore, Fe 3+ can form a complex compound with the dispersant, which leads to the inactivation of the dispersant.

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