Removal of heavy metal from sediment by bioleaching combined with fenton-like reaction

Feasibility of bioleaching by Acidithiobacillus ferrooxidans combined with Fenton-like reaction to efficiently remove heavy metals from contaminated sediment was investigated. The variation of pH and ORP during the 15-day bioleaching and the removal of heavy metal Cu, Zn, Pb and Cd were studied. After 2-day bioleaching, the reaction system pH decreased to approximately 2.5, then added five different dosages of H₂O₂(1 g/L, 3 g/L, 5 g/L, 7 g/L, 9 g/L)into the system to complete the Fenton-like reaction for 3 h. The results show that the pH presented a downtrend during the 15-day bioleaching, and decreased from 5.0 to 2.0, kept stable approximately at 2.0. However, ORP increased from 250 mV to around 700 mV, then maintained at around 700 mV. Through the 15-day bioleaching, the removal efficiencies of Cu, Zn, Pb and Cd were 52.1%, 65.8%, 42.5%, 83.25%, respectively. Nevertheless, the maximal removal efficiencies of thses metals with the combination of 2-day bioleaching and 3-hour Fenton-like reaction reached: Cu-59.8%, Zn-70.0%, Pb-52.7% and Cd-85.3%. The experience demonstrates that this method can dramaticlly enhance the removal efficiency of heavy metal, and greatly reduce the reaction time, which providing a relatively effective way to remove heavy metal from sediment.