间歇浸取对废物水泥窑共处置产品中Cr和As释放的影响

Influence of intermittent wetting on release of Cr and As in cement product from co-processing waste in cement kiln

研究间歇浸取条件下废物水泥窑共处置产品中重金属Cr、As的释放,对水泥产品在实际应用中的环境安全性评价有重要意义。通过模拟煅烧实验制取含Cr和As的水泥熟料,并制取混凝土样品,采用pH影响实验和扩散浸出实验,研究了混凝土中Cr和As的溶解特性及其间歇浸取对混凝土中Cr和As释放的影响。结果表明,浸取方式对浸取液pH有较大影响,间歇碳化保存处理浸取液的pH在9.5-10.4范围内,低于连续浸泡处理浸取液pH（10.3-11.0）,而间歇自然保存处理则与连续浸泡处理相近;pH对混凝土中Cr和As的浸出影响较大,Cr的浸出量在低pH或高pH条件下较大,并且在pH=5时最低（约为5μg/L）。低pH条件下As的浸出量较大,且随pH升高而降低,并在pH=5时浸出量达到最小值,此后浸出量随pH的升高而增加,在pH=9浸出量达到最大（3 067μg/L）;间歇浸取处理Cr和As的释放量均小于连续浸取,但间歇浸取过程的碳酸化作用抑制了混凝土中Cr而促进了As的释放。

The study on influence of intermittent wetting on the release of heavy metals in product from co-processing waste in cement kiln is important for environmental safety assessment of cement product under practical scenarios.Clinker contained Cr and As was produced by simulating cement calcination test,and concrete samples were also prepared.The dissolution characteristic of Cr and As in concretes was researched by the pH-dependence test,and the influence of intermittent wetting on the release of Cr and As in concrete samples was also studied via diffusion test.The results showed that leachant pH of intermittent wetting with carbonation control was in the range of 9.5 to10.4,which was lower than that in continuous leaching control（10.3-11.0）.pH of continuous leaching control was close to intermittent wetting with non-carbonation control.Leaching amount of Cr was greater when pH was low or high,and when pH was 5,the leaching amount was minimum（about 5 μg/L）.As to As,the leaching amount was higher in low pH,and increasing with the pH descended and reached the minimum at pH=5.As pH〉5,leaching amount increased with pH increasing and arrived to the maximum at pH=9（about 3 067 μg/L）.The release amount of Cr and As in intermittent wetting both were lower than continuous leaching,but the release of Cr was restrained by the carbonation in intermittent wetting,while the release of As was promoted by carbonation.