In this study we compared the efficiency of four kinds of amendments (silkworm excrement, coconut husk, red mud, sepiolite) and their mixtures to immobilize the heavy metals present in a contaminated acidic soil (Pb:420 mg ·kg−1; Zn :334 mg· kg−1) and to influence several enzymatic activities. The results showed that, silkworm excrement, coconut husk and their mixtures, which had high pH and/or high content of organic matter, reduced exchangeable Pb in the soil by 18% to 46%, and reduced available Zn by 24% to 35%, which was more efficacious than single sepiolite. The complex of silkworm excrement and red mud had a great influence on soil pH, while coconut husk increased the content of organic matter in soil significantly.
The use of red mud as an immobiliser for metal/metalloid-contaminated soil: A review
