Simultaneous immobilization of several heavy metals in naturally contaminated soils using waste and recycled materials

The water leachable amounts of heavy metals including arsenic (As), lead (Pb), and cadmium (Cd) can be found in relatively higher concentrations in surplus soils from construction activities. There is a potential risk to human health and negative impacts on the soil and water environment. One of the cost-effective and efficient strategies for remediation techniques is the immobilization of heavy metals based on natural and artificial materials. The objective of this study is therefore to use five waste and recycled materials such as fly ash and recycled concrete. It tries to achieve simultaneous immobilization of several heavy metals in naturally contaminated soils. Two representative natural soils containing relatively higher concentrations of water leachable As, Pb, and Cd were selected and tested for a simple batch immobilization experiment in the laboratory. The weight percent of each waste and recycled material added to each soil was 2.5%, 5%, and 10%. After 24 hours of curing at 20^oC, 10 times the volume of ultrapure water was added and shaken for 6 hours. The supernatants were filtered through a 0.45 µm filter and the concentrations of heavy metals were measured by ICP-MS. Generally, the immobilization rate of As, Pb, and Cd increased with increasing additive weight of waste and recycled materials. Recycled concrete especially demonstrated simultaneous immobilization of these heavy metals above with its addition of 2.5% to 5%, suggesting a better immobilization performance compared to other waste and recycled materials.