Development of a quick method to test leaching for maintaining the environmental safety of recycled materials

To ensure that recycled materials such as gypsum and coal fly ash are environmentally safe, a rapid test that measures leaching from these materials was developed using the quality engineering parameter design method. Fluoride concentration in leachate is equivalent to that of Japanese regulatory leaching test 46 (JLT-46) and can be estimated rapidly by using a new method in which the samples are stirred at a high speed in a ball mill. This method greatly improved the estimation accuracy. For linear regression, the coefficient of determination between the leached amount of JLT-46 and the estimated value obtained via the quick method was R=0.95, with a standard error of 0.75 mg/L, for gypsum and R=0.98, with a standard error of 0.32 mg/L, for fly ash. This is a promising method that can be introduced as part of the inspection process for recycled materials.