碱性水热法同步稳定城市垃圾/医疗废物焚烧飞灰与废水中重金属的研究

研究了碱性水热法同步稳定城市垃圾/医疗废物焚烧飞灰与废水中重金属的稳定化效果和稳定化机制.结果表明,在碱性水热条件下,城市垃圾/医疗废物焚烧飞灰均对废水中重金属具有很强的去除作用,并且经反应后,飞灰重金属渗滤毒性不仅没有上升反而大大降低.原始医疗废物焚烧炉飞灰中6种重金属渗滤毒性为:Mn 17 300μg/L,Ni 1 650μg/L,Cu 2 560μg/L,Zn 189 000μg/L,Cd 1 970μg/L,Pb 1 560μg/L;原始城市垃圾焚烧飞灰中6种重金属渗滤毒性为:Mn 17.2μg/L,Ni8.32μg/L,Cu 235.2μg/L,Zn 668.3μg/L,Cd 2.81μg/L,Pb 7 200μg/L.这2种飞灰分别与重金属废水(浓度Cu、Pb为50mg/L,Mn、Zn、Ni、Cd为25 mg/L)在275℃条件下,碳酸钠添加量为1/10(5 g碳酸钠/50 g干灰),液固比为10/1,经10 h反应后,医疗垃圾焚烧炉飞灰对重金属去除率达86.2%～97.3%,城市垃圾焚烧飞灰对重金属去除率达94.7%～99.6%.反应后飞灰经重金属渗滤毒性测试均远远低于国家标准值.重金属稳定化机制主要是由于在硅铝酸盐晶体形成过程中对重金属化学吸附,物理包裹作用,老化期重金属空间几何位置迁移,高pH值对稳定化起到一定辅助作用.

Novel Process Utilizing Alkalis Assisted Hydrothermal Process to Stabilize Heavy Metals both from Municipal Solid Waste or Medical Waste Incinerator Fly Ash and Waste Water

An alkalis assisted hydrothermal process was induced to stabilize heavy metals both from municipal solid waste or medical waste incinerator fly ash and waste water. The results showed that alkalis assisted hydrothermal process removed the heavy metals effectively from the waste water, and reduced leachability of fly ash after process. The heavy metal leachabilities of fly ash studied in this paper were Mn 17,300 microg/L,Ni 1650 microg/L, Cu 2560 microg/L, Zn 189,000 microg/L, Cd 1970 microg/L, Pb 1560 microg/L for medical waste incinerator fly ash; Mn 17.2 microg/L, Ni 8.32 microg/L, Cu 235.2 microg/L, Zn 668.3 microg/L, Cd 2.81 microg/L, Pb 7200 microg/L for municipal solid waste incinerator fly ash. After hydrothermal process with experimental condition Na2CO3 dosage (5 g Na2CO3/50 g fly ash), reaction time = 10 h, L/S ratio = 10/1], the heavy metal removal efficiencies of medical waste incinerator fly ash were 86.2%-97.3%, and 94.7%-99.6% for municipal solid waste incinerator fly ash. The leachabilities of both two kinds of fly ash were lower than that of the Chinese national limit. The mechanism of heavy metal stabilization can be concluded to the chemisorption and physically encapsulation effects of aluminosilicates during its formation, crystallization and aging process, the high pH value has some contribution to the heavy metal removal and stabilization.