Selection of Cheap Carbon Sources During Bioleaching of Heavy Metal Contaminated Soil

Soil washing is a valid and relatively inexpensive alternative in remediation of soils contaminated with heavy metals. It has been proved that organic acids produced by Aspergillus niger(A. niger) fed with sucrose had the ability to mobilize and remove heavy metal contaminants from soils. However it is still somewhat expensive to feed A. niger with sucrose. The cost for soil remediation will be significantly reduced if other cheaper alternatives can be employed. Thus,the objectives of this study were to test the feasibility of using some alternative cheaper materials as carbon sources,to evaluate the effects of these cheaper materials on heavy metal removal from a contaminated soil. Some inexpensive tree leaves or food by products,namely poplar leave,peach leave,potato peels were used as carbon sources for A. niger,respectively. The resulting mixture of A. niger solution,produced organic acids,and carbon sources were applied to the contaminated soil for heavy metal removal using one-step and two-step bioleaching processes. Results show that these materials had a good capability in helping the A. niger to remove heavy metals from the soil. Percentages of the heavy metal removals were 63.5% for Cu,100% for Cd,16.8% for Pb,and Zn for 27%,respectively,when the poplar leaves were used as carbon source;were 61.8% for Cu,100% for Cd,14.6% for Pb,and 28.5% for Zn,respectively,when the peach leaves were used;and were 61% for Cu,100% for Cd,10.6% for Pb,and 34% for Zn,respectively,when the potato peels were used. Based on this,it is concluded that the application of suitable cheaper carbon sources reduced the cost of contaminated soil remediation by means of bioleaching.