Leaching behaviors of heavy metals from improved soil mixed with waste foundry sand

Under the two kinds of leaching conditions of soil-waste foundry sand mixture and soil-waste foundry sand mixture-lime mixture in neutral and acid (acid rain condition) environments, the contamination of various heavy metals is studied by use of the stirring and column leaching tests. The aim is to obtain the leaching rules of the heavy metals from the mixtures. The results show that only the ions Fe, Mn and Pb do not meet the drinking water standards among the measured by kinds of ions; when the waste foundry sand and the improved soil mixed with it are placed below the groundwater table, the concentration of Zn, Mn, Cu and Cd in soils is not lower than that in the waste foundry sand and the improved soil mixed with it; the pH value has great influence on the leaching concentration. It is largest under acid condition, and smallest when mixed with lime; the initial effluent concentration does not increase with the content of the waste foundry sand; the ion Pb in the waste foundry sand exhibits an exponential leaching.