pH值对含砷水泥熟料制品中砷释放的影响
Impact of pH on release of As in cement clinker product containing arsenic
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摘要: 通过模拟煅烧实验制取水泥熟料，并制取混凝土样品。参照NEN-7375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As释放的影响。结果表明，浸取液的pH为2.0、3.5、5.0、7.35和10.0时，混凝土中As的观测累积释放量分别为0.0553、0.04253、0.0157、0.00939和0.0148 mg/kg；酸性范围内，观测累积释放量随着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As的释放过程有影响，在前期，pH=2.0、3.5和10.0的浸取液中，释放曲线与斜率为0.5的直线拟合较佳，并且在1～4区间修正累积释放量曲线的斜率均在0.35～0.65范围内，其释放表现为扩散控制，而pH=5.0和7.35的浸取液中，则分别发生了表面冲刷作用和延滞现象；在中后期，pH=2.0的浸取液中，As的释放出现了耗竭现象，而pH=3.5和10.0则出现了溶解现象，pH=5.0和7.35则均为扩散控制。Abstract: Clinker was produced by simulating cement calcination test，and concrete samples were also prepared. The impact of pH on the release of As 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 As in the concrete is 0.0553，0.04253，0.0157，0.00939 and 0.0148 mg/kg respectively when the pH of the leachant is 2.0，3.5，5.0，7.35 and 10.0. Under the acid condition, the measured cumulative release amounts decrease with the increase of pH, and reach the minimum under weak alkaline condition.Under the alkaline condition, the measured cumulative release amounts increase with the increase of pH. pH could affect the release process of As. In the prophase，diffusion control is the major release mechanism of As in the leachants with pH=2.0，3.5 and 10.0，and the release curves fit the standard line which slope is 0.5 very well and slopes of increments 1～4 are all between 0.35 and 0.65, but surface washoff and delayed diffusion occurred in the leachants with pH=5.0 and 7.35.In the anaphase，depletion occurred in the leachant with pH=2.0，dissolution occurred in the leachants with pH=3.5 and 10.0，and diffusion control is the major mechanism in the leachants with pH=5.0 and 7.35.
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Key words:
- concrete /
- As /
- release amount /
- release mechanism /
- cement kiln co-processing
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