Chai Jin-Chun, Onitsuk Katsutada, Hayashi Shigenori
Department of Civil Engineering, Saga University, Saga, Japan.
J Hazard Mater. 2009 Jul 15;166(1):67-73. doi: 10.1016/j.jhazmat.2008.11.010. Epub 2008 Nov 17.
Batch contact, tank leaching and column percolation tests were conducted to investigate the Cr(VI) concentration in the solution/leachate from two fly ashes (fly ash A and B) with additives. The additives used were cement, low alkalinity additive and Ariake clay. There are several factors influencing Cr(VI) concentration in solution/leachate, namely (1) properties of solid/liquid mixture (chemical composition, pH value, etc.), (2) cementation effect, (3) amount of water in contact with the solid mass (solid/liquid ratio in case of batch contact test), and (4) adsorption characteristics of the solid particles to Cr ions. The test results indicate that fly ash A has less cementation component (CaO of 1.92%) and the amount of water in contact with the fly ash played an important role. As a result, Cr(VI) concentration from the column percolation test was much higher than that of the batch contact test. Adding Ariake clay had more effect on reducing Cr(VI) concentration for fly ash A than B because the pH value of the solution from fly ash A was lower, which provided a favorable condition for Cr(VI) ions to be reduced to Cr(III) and possibly to be adsorbed by clay particles. Fly ash B has more cementation component (7.15%) and for column percolation test, curing the sample for 1 week reduced Cr(VI) concentration significantly. The test results indicate that in engineering practice, a method which closely simulates the field condition should be selected to assess possible environmental effects and corresponding countermeasure methods.
进行了批量接触、槽浸和柱渗透试验，以研究两种添加了添加剂的粉煤灰（粉煤灰A和B）溶液/浸出液中的六价铬浓度。所使用的添加剂为水泥、低碱度添加剂和有明黏土。有几个因素会影响溶液/浸出液中的六价铬浓度，即（1）固液混合物的性质（化学成分、pH值等），（2）胶结作用，（3）与固体物质接触的水量（批量接触试验中的固液比），以及（4）固体颗粒对铬离子的吸附特性。试验结果表明，粉煤灰A的胶结成分较少（氧化钙含量为1.92%），与粉煤灰接触的水量起了重要作用。因此，柱渗透试验中的六价铬浓度远高于批量接触试验中的浓度。添加有明黏土对降低粉煤灰A中六价铬浓度的效果比对粉煤灰B的效果更好，因为粉煤灰A溶液的pH值较低，这为六价铬离子还原为三价铬并可能被黏土颗粒吸附提供了有利条件。粉煤灰B的胶结成分较多（7.15%），对于柱渗透试验，将样品养护1周可显著降低六价铬浓度。试验结果表明，在工程实践中，应选择一种能紧密模拟现场条件的方法来评估可能的环境影响及相应的对策方法。
