生活垃圾焚烧飞灰固化体重金属动态浸出规律

Dynamic leaching rule of heavy metals in solidified body of fly ash from MSW incineration

为研究实际生活垃圾卫生填埋场中渗滤液长期作用于飞灰固化体的浸出行为,分别采用pH值为5.5的醋酸-醋酸钠溶液和pH值为7.0的去离子水作为初始浸提液,建立飞灰固化体的动态浸出试验.初始浸提液pH值的差异会影响飞灰固化体的结构完整性和固化体表面晶体的生成情况,当初始浸提液为醋酸-醋酸钠溶液时,实验过程中飞灰固化体会破碎;当初始浸提液为去离子水时,飞灰固化体表面生成的CaCO_3晶体可能会抑制重金属浸出.当实验进行至约120d时,2组实验浸出液的pH值和重金属浓度基本稳定,且pH值相差不大;但采用去离子水浸提时,Pb、Cr的累计浸出量明显更高,且Pb的浸出浓度(0.29mg/L)甚至一度超过填埋场入场限值,其潜在风险应受到关注.

A dynamic leaching experiment was established using CH3COOH-CH3COONa solution with a pH of 5.5 and deionized water with a pH of 7.0 as initial leach liquor,aiming at studying the long-term leaching behavior of fly ash solidified body in the domestic waste sanitary landfill site.The difference in pH of the initial leach liquor would affect the structural integrity and the formation of crystal on the surface of fly ash solidified body.When CH3COOH-CH3COONa solution was used,the fly ash solidified body would be broken during the experiment.While deionized water was used,CaCO3 crystals formed on the surface of fly ash solidified body would inhibit the leaching of heavy metals.Both pH value and heavy metal concentration of the two groups’leachate tended to be stable until the experiment lasted about 120 days,and the final pH value of them were close to each other.However,in the group of deionized water,the amount of cumulative leaching of Pb and Cr were significantly higher than that of CH3COOH-CH3COONa solution,and the leaching concentration of Pb(0.29mg/L)even once exceeded the landfill entry limit,which should be concerned for the potential risk.