Acid Neutralizing Capacity and Elements Leaching Behavior from MSWI Fly Ash Under Static pH Condition
定pH值下垃圾焚烧飞灰酸中和容量与元素浸出行为的研究

The acid neutralizing capacity(ANC) and elements leaching behavior from fly ash were studied using a pH_(stat) titration test.The pH value of the system was kept at 4,5,6 and 7 for 150 hours respectively.The concentration of major and heavy metals in the solution was determined.The results indicate that in the initial time of the titration,the amount of consumed acid increases rapidly.With the accumulation of the ions in the solution,the rate of the fly ash dissolution gets an inflection point after about 20 hours.With the fall of the controlled pH values,the proton buffering capacity of fly ash increases correspondingly.Elements represent different types of leaching behavior during the titration.The leaching of K,Na,Ca and Cl is not controlled by the buffing process.Si and SO~(2-)_4 reached the maximal release after several hours,followed by a decrease in concentration.The release of Cd,Zn is similar to the acid neutralizing capacity and the leaching of Cu,Pb and Cr is lower than the ANC.The result of pH static titration can provide more detailed information about the neutralizing process and the potential leachability of heavy metals,and this is useful to evaluate the long term leaching behavior of heavy metals.