Research on the Preparation of Geopolymer from Red Mud-Based Fixed Fly Ash
In order to effectively handle urban waste,it is generally necessary to incinerate it,but during the incinera-tion process,a large amount of hazardous solid waste fly ash is generated.The alumina,silica,and sodium oxide in red mud could undergo geopolymerization reaction with the active alumina and silica in fly ash,and the resulting geopolymer could effectively fix heavy metals such as cadmium(Cd)and lead(Pb)in fly ash,preventing their leac-hing.The chemical composition and morphological characteristics of the experimental samples were characterized and analyzed using X-ray diffraction(XRD),thermogravimetric differential thermal analysis(TG-DTA),and scanning e-lectron microscopy(SEM)testing methods.The results showed that the activation effect of red mud was optimal un-der the conditions of 800 ℃ and 5％(mass concentration)NaOH;After activation,the red mud was mixed with fly ash(mass ratio of 1∶1,water cement ratio of 0.5);After mixing evenly,the mixture of red mud and fly ash was placed in a curing box for 14 days(d)to obtain geopolymer samples;XRD analysis showed the appearance of diffrac-tion peaks of a new mineral[Ca6 Al2(SO4)(OH)12·6H2O]in the polymer sample,indicating the occurrence of geopolymerization reaction between red mud and fly ash;The compressive strength test shows that the optimal com-pressive strength of the geopolymer sample is 1.63 MPa;The heavy metal content in the geopolymer leachate of the solidified fly ash from red mud meets the sanitary landfill standard for incineration fly ash(GB16889-2008),indica-ting that the use of red mud based materials could effectively fix heavy metals in fly ash,proving that the technology of"treating waste with waste"is feasible.
red mudfly ashsolid waste managementgeopolymerization reaction
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