Dissolution Behavior Of Low-Calcium Fly Ash In Alkaline Solution

As one of the industrial solid wastes,fly ash can be used for road backfilling,concrete admixture,extraction of valuable elements,selection of float beads,preparation of mineral aggregate materials,etc.There are many studies on alkaline conditions,in-depth understanding of the phase and morphology of fly ash in the alkaline dissolution process is conducive to improving the comprehensive utilization rate of fly ashTaking low-calcium fly ash as raw material and taking the dissolution rate of silicon,aluminum and calcium as the evaluation index,the influence rule of element dissolution was studied emphatically.By means of XRD,IR,and SEM morphology observation,the change behavior of the phase and structure of fly ash in the process of alkaline solution was clarified.On this basis,the kinetics of alkali solution process of fly ash is studied,and the reaction energy and reaction type of this kind of reaction are obtained.The results show that in the sodium-alkali system,the highest dissolution rate of silicon ions is 33.64%,and the highest dissolution rate of aluminum ions is 3.56%.In the potash system,the dissolution rate of silicon and aluminum increased with the addition of potassium water glass,and the highest dissolution rates of silicon and aluminum ions were 27.62%and7.66%,respectively.In the potassium-sodium mixed alkali system,the dissolution rate of silicon ions reaches the maximum value in the Na OH+K₂Si O₃ system,which is 30.06%;while the dissolution rate of aluminum reaches the maximum value in the KOH+Na₂Si O₃system,which is 5.73%.The dissolution rule of elements showed that the sodium-alkali system was favorable for the dissolution of silicon。The phase study of low-calcium fly ash in the alkaline dissolution process shows that hydroxysodalite and Linde Type F（K）are formed in sodium-alkali system or potassium-alkali system.Na OH and KOH solutions conforms to the solid-liquid kinetic model,which is controlled by the mixed reaction and has a good linear fit.The reaction activation energies of silicon and aluminum obtained from the two solutions are 15.75k J/mol and 12.16k J/mol,respectively;15.60k J/mol,12.55k J/mol.Figure 64;Table 12;Reference 90...