垃圾焚烧飞灰中重金属的浸滤特性及影响因素

Leaching characteristics and impact factors of heavy metals on the flying ash due to the urban garbage incineration

以重庆市生活垃圾焚烧飞灰为研究对象,分析飞灰浸滤的初始pH值、液固比(L/S)及浸出时间对飞灰中重金属浸滤特性的影响。同时,采用分级提取法(BCR法)对浸滤进行形态分析。结果表明,飞灰浸滤呈弱碱性(飞灰浸滤pH值未超过腐蚀性鉴别标准pH≥12.5或≤2.0,不具有腐蚀性);但Pb的浸出质量浓度(5.19 mg/L)超过国家限定标准(5 mg/L),具有浸出毒性,属危险废物。飞灰中Cr、Ni和Mn主要以残渣态为主,而Cd和Cu主要以弱酸提取态为主。重金属的浸出量与初始pH值密切相关,易在酸性条件下浸出。重金属的浸出量基本上随液固比和浸出时间的增加而增加,且在浸出时间为24 h时达到最大浸出量(Cd除外)。本研究为焚烧飞灰的污染防治与合理处置提供了依据。

The present paper is aimed to introduce our research on the influence of heavy metals from the urban garbage incineration on the flying ash due in the air in Chongqing with the purpose to analyze and find the relationship between the initial pH, liquid to solid ratio （L/S）, the extraction time and leaching characteristics of heavy metals in the fly ash. The results of our investigation indicate that the leaching of heavy metals proves to be weak alkaline, whose leaching initial pH don＇t exceed corrosion standard （pH ≥ 12.5 or ≤ 2.0）, therefore, the fly ash isn＇t corrosive. But the leaching concentration of Ph （5.19 mg/L） exceeds the Chinese toxicity standard （5.00 mg/L）. Therefore, the fly ash has to be considered as a kind of hazardous waste. When BCR method is adopted to specify the samples of leaching, it can be found that, in the residual fraction, mainly exist such ingredients as Cr, Ni and Mn, with Cd, Cu existing in the acid soluble. So far as the leaching amount of heavy metals is concerned, they are mainly related to pH value, which tend to decrease with the increase of initial pH value. In addition, it has proved that the leaching amount of heavy metals except Ni reaches the maximum value when the pH value is 1. All in all, the leaching amount of the heavy metals in fly ash tends to increase with the increase of L/S and extraction time. Moreover, the leaching amount of the heavy metals except Cd reaches the maximum value when extraction time is 24 hours. Thus, it can be seen that the above investigation and analysis help to lay a basic foundation for pollution prevention and reasonable disposal for fly ash from the urban waste incineration.