固体废物水泥窑共处置产品中Cr释放的pH影响

Impact of pH on the Release of Cr in Cement Product from Co-processing Waste in Cement Kilns

通过模拟煅烧试验制取水泥熟料,并制取混凝土样品.参照EANEN7375浸出方法,设定5种不同pH的浸取液,研究pH对混凝土样品中重金属Cr释放的影响.结果表明,在强酸性条件下,Cr的累积释放量较大,pH为2.00和3.50的条件下,Cr的累积释放量分别为64.7和21.4mg/m2,而pH为5.00,7.35和10.00的浸取液中Cr的累积释放量基本一致,分别为5.10,5.05和5.00mg/m2;浸取液pH分别为5.00,7.35和10.00的条件下,Cr的释放机理为扩散控制,释放曲线与斜率为0.5的直线拟合较佳,且不同区间释放量曲线的斜率均在0.35～0.65内;pH为2.00的浸取液中Cr的释放在前期为扩散控制,中、后期出现耗竭现象;pH为3.50的浸取液中Cr的释放在前期同样为扩散控制,但中、后期发生了溶解作用.

Clinker was prepared by simulating cement calcinations, which was used to produce concrete samples. The impact of pH on the release of Cr in the concrete samples was studied using the EA NEN 7375 method by five leachants with different pH. The results showed that the cumulative release amount of Cr in the concrete was great under the strongly acidic conditions; the release amount reached 64.7 and 21.4 mg/m^2 when the leachant pH was 2.00 and 3.50, respectively. However, the cumulative release amounts of Cr were low and similar when leachant pH was 5.00, 7.35 and 10.00, reaching and was 5.10, 5.05 and 5.00 mg/m^2 when leachant pH was 5.00,7.35 and 10.00, respectively. Diffusion control was the main release mechanism of Cr in the solutions with pH 5.00, 7.35 and 10.0. The release curves well fitted the standard line well with slope 0.5, and slopes of different increments ranged 0.35-0.65. When leachant pH was 2.00, diffusion control was the main mechanism of Cr at the early stage, while depletion occurred at the later stage. A similar phenomenon was observed at the early stage when leachant pH was 3.50, but dissolution occurred after the middle stage.