Effect of the Formulation Control Agent on Brightness of Modified Fly Ash and Its Potential Application in Papermaking

Abstract

Different agents were used to control the crystalline morphology of calcium carbonate on the surface of fly ash, which was then used as a papermaking filler in an attempt to improve the utilization rate of fly ash and reduce the dust pollution problem. A mixed solution of calcium hydroxide and fly ash was used as the raw materials, and then three crystal form control agents were tested: (NaPO3)6, ZnCl2, and Na2B4O7·10H2O. A certain amount of carbon dioxide was bubbled into the mixture to form a precipitated calcium carbonate deposit on the surface of fly ash. The calcium carbonate on the fly ash surface was altered by changing the amount of crystal form control agent to determine the best coating effect. The results showed that at the 0.35% ZnCl2 dosage (relative to the theoretical quantity of the calcium carbonate), the surface of the fly ash was uniformly coated with a layer of spherical calcium carbonate crystals and there was a good coating effect. The highest fly ash brightness obtained was 65.3% ISO, and when this fly ash was used as a paper filler, the paper brightness was 75.6% ISO. More importantly, this study demonstrated the potential of fly ash in papermaking.