Removal of heavy metals from contaminated foundry sand through repeated soil-washing

This paper presents investigations on the effectiveness of repeated washing in removing heavy metals from contaminated Foundry Sand (FS) sample collected from a recycling company in Melbourne. It is found that after repeated wash-offs, concentrations of heavy metals reduce significantly and these reductions for all the tested metals follow logarithmic trends. Results are compared with other contemporary findings on the physical separation of heavy metals from contaminated soil. Also, it is observed that higher the concentration of metals found in the initial leaching solution, higher the rate of reduction of concentration in subsequent leaching. Using logarithmic relationship, best-fit equations for the reductions of heavy metals’ concentrations through repeated wash-offs were derived. Using such equations, it is possible to work out a number of washing cycles required for a particular heavy metal to wash it up to the requirement of any particular regulatory authority. In regards to the effect of soil depth on accumulated pollutants’ concentrations, it is found that the concentrations of heavy metals in the leachate linearly vary with the depth of FS column used for testing. © 2019 Informa UK Limited, trading as Taylor & Francis Group.