废物水泥窑共处置产品中Pb释放的pH影响

STUDY ON RELEASE CHARACTERISTICS OF Pb IN CEMENT PRODUCT FROM CO-PROCESSING WASTE IN CEMENT KILN

通过模拟煅烧实验制取水泥熟料,并制取混凝土样品。参照NEN7375浸出方法,设定5种不同pH值的浸取液,研究了pH值对混凝土块中重金属Pb释放的影响.结果表明:浸取液的pH为2.00,3.50,5.00,7.35和10.0时,混凝土中Pb的累积释放量分别为0.125,0.00897,0.00687,0.00407和0.00503mg/kg;酸性范围内,累积释放量随着pH值的增大而减小,并在弱碱性条件下达到最小值,碱性范围内,随pH值的增大而呈增加的趋势。pH值对混凝土中Pb的释放过程影响较大,pH为2.00和5.00的浸取液中,混凝土中Pb的释放机制前期均为扩散控制,后期分别发生了耗竭(pH=2.00)和溶解(pH=5.00)作用;pH为7.35和10.0的溶液中,Pb的释放在前期出现了延滞现象,而后期的释放机制分别为溶解作用(pH=7.35)和扩散控制(pH=10.0);pH为3.50的溶液中,Pb在释放初期出现了表面冲刷现象,中期为扩散控制,而后期发生了溶解作用。

Clinker was produced by simulating cement calcination test,and concrete samples were also prepared.The impact of pH on the release of Pb in the concrete samples was studied using similar method of NEN 7375,with five different leachants.The results show that the measured cumulative release amount of Pb in the concrete is 0.125,0.008 97,0.006 87,0.004 07 and 0.005 03 mg/kg when the pH of the leachant is 2.00,3.50,5.00,7.35 and 10.0,separately.In the acid condition,the measured cumulative release amount decreases with the increase of pH,and reaches the minimum at weak alkaline condition.In the alkaline condition,the measured cumulative release amount increases with the increase of pH.pH could impact the release process of Pb.In the prophase,diffusion control is the major release mechanism of Pb in the leachants with pH=2.00 and 5.00,but in the prophase,depletion and diffusion control occurred,separately.Delayed diffusion is the major release mechanism of Pb in the leachants with pH=7.35 and 10.0 in the prophase,but in the prophase,dissolution and diffusion control occurred,separately.In the leachants with pH=3.50,surface wash-off occurred in the prophase,diffusion control is the major mechanism in the metaphase and dissolution occurred in the anaphase.