摘要
采用定pH值滴定实验研究了不同pH值条件下,垃圾焚烧飞灰的酸中和容量和元素的浸出行为.实验中将浸取液的pH值分别控制在4、5、6、7,持续滴定150 h,在不同时刻测定溶液中主要元素和重金属等多种组分的浓度.研究表明,在每个pH值条件下,在滴定最初阶段,累积的消耗酸量迅速增加,随着溶液中离子浓度的增加,酸的消耗速度逐渐下降,在20 h左右,飞灰的中和反应趋于稳定.随着滴定的pH值由7下降到4,飞灰表现出的中和能力也相应加强.由于形成机理和在飞灰中的存在形式不同,滴定过程中,各种组分表现出不同的浸出行为,K、Na、Ca和Cl的浸出不受中和反应的控制,Si和SO42-的浓度在滴定初期达到最大值,然后下降.Cd和Zn的浸出速度与酸的消耗速度基本相同,Cu、Pb和Cr的浸出慢于酸的消耗.利用定pH值滴定实验能更好地研究飞灰浸出的过程和重金属的潜在浸出性,为在较长的时间尺度上准确预测和评价重金属的浸出行为提供了手段.
The acid neutralizing capacity （ANC） and elements leaching behavior from fly ash were studied using a pHstat 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 SO4^2- 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.
出处
《环境科学》
EI
CAS
CSCD
北大核心
2008年第2期529-534,共6页
Environmental Science
基金
国家自然科学基金项目(20277024)
