Experimental study of the stabilization of heavy metals in municipal solid waste incineration fly ash by chemical agent matching

Key words: 
• municipal solid wastes /
• fly ash /
• incineration /
• heavy metals /
• harmless treatment /
• chemical agents

Abstract: With taking heavy metals Pb and Zn as the target heavy metals, three agents of EDTA, Na2S and NaH2PO4 and pH value control are used to explore the efficiency of chemical agents to limit the leaching of heavy metals from fly ash. At first the agents are added into fly ash at a specific rate separately and the stabilization efficiency at a specific mass ratio to fly ash can be obtained through measuring the leaching concentration of heavy metals; then, through series experiments and sediment observation, the sequence of adding agents can be optimized; finally, based on the property of chemical agents, 4 plans of agent matching are made. After adding agents in the optimal adding sequence, the leaching concentrations of heavy metals are measured and the stabilization efficiency of each matching plan can be analyzed. It can be concluded that: when pH value stays at 10, the stabilization of heavy metals will be easier. EDTA, NaH2PO4 and Na2S can stabilize a large part of heavy metals in fly ash, and EDTA has a better efficiency than the other two in terms of the stabilization of heavy metals in fly ash; the stabilization efficiency will be the best when adding the agents in the sequence of Na2S, EDTA and NaH2PO4； the matching plan 4 has an much better stabilization of heavy metals Pb and Zn than other plans. The stabilization is much improved; meanwhile the treatment cost can be decreased by saving the usage of EDTA.