The Leaching Characteristics Of Heavy Metals From Fly Ash And Experimental Study On Cement Solidification

The property of fly ash in a medical waste incineration and solidification effect of cement are studied in this paper. Leaching characteristics of all of particle size of heavy metal and different particle size of heavy metal are studied. And influence of heavy metal leaching is studied at different factors such as leaching time. L/S ratio, pH value and additives. The results shows that the content of heavy metals in fly ash can increase with decrease of the particle size, but small size particles(<100μm) account for little among total amount of fly ash so the content of heavy metals in fly ash is relatively low. Heavy metals in the fly ash are very easy to leach in acid condition, while hardly leach in alkaline condition.Solidification characteristics of fly ash are studied by using cement 425 as solidification after solidification effect of cement 325 and cement 425 is compared. Influence of heavy metals leaching is analyzed in different mixed proportions of fly ash and cement and solidified time so that appropriate parameter on solidification of fly ash with cement is determined. The results show that leaching ratio of heavy metals can increase with increase of the content of fly ash and can reduce with the increase of solidified time. 50% cement ratio in mixed proportions should be appropriate because of solidification effect and leaching characteristics of heavy metal.It is considered that additives such as NaOH,Na₂S and so on are added in the mixtures of fly ash and cement because leaching ratio of heavy metals such as Zn,Pb and Cd in fly ash and solidified products is much more than the other heavy metals. Stabilization effect in the additives of same adding amount and influence of heavy metals leaching in different adding amount of several kinds of additives after solidification of fly ash with cement are researched. The results show that the best stabilization effect of heavy metals in solidified products is and leaching ratio of heavy metals is lower than 4%. Leaching consistence of heavy metals in solidified products can reduce with the increase of adding amount. The adding amount of the additive should be appropriate, generally about 5% because of stabilization effect and economic benefits.So it is that the cement solidification and the additive stabilization combined to obtain a better effect. The experiment results shed some light in the future research on solidification/stabilization treatment of fly ash, and it is significant to application of engineering.