Development of a quick leaching test for monolithic materials by using factorial design

A quick leaching test procedure for monolithic waste materials has been developed by a Nordic expert group using experimental factorial design. The Dutch quick leaching test proposal in which the wetting time of the test specimen is reduced by applying vacuum was chosen as a starting point. The influence of the following parameters were studied: vacuum, stirring, open or closed vessel, water renewal frequency, leachant quality and laboratory or batch differences. The study was performed with test specimens prepared from a cement stabilised soil containing As, Cr and Cu. The test specimens were immersed in water and the water was renewed at certain time intervals. The study clearly showed that the use of vacuum had a strong effect on the release rate and that the open vessel lowered the pH-values of the eluates due to uptake of carbon dioxide in the water. The results also indicate higher emissions when stirring was applied. The following test conditions are recommended: application of vacuum prior to testing, use of closed test vessel, use of stirring, a test time of 3 days with four water renewals after 15 min vacuum steps, and then after e.g. 2 h, 23 h and 3.2 days, use of demineralised water as leachant. The amount of water must be selected according to the size of the test specimen. A liquid to surface (L/A) ratio of 5-10 ml cm(-2) is recommended. All four eluates collected are filtered and analysed.