The behavior of heavy metal release from sulfide waste rock under microbial action and different environmental...

The dissolution of heavy metals from the waste rock is controlled by many factors. Herein, we investigated the release behavior of iron (Fe), chromium (Cr), copper (Cu), and zinc (Zn) from sulfide waste rock under the actions of microorganisms and different environmental factors (solution pH value, particle size of waste rock, temperature, Fe³⁺ concentration). The release quantity of heavy metals was negatively correlated with pH and particle size and positively correlated with ambient temperature and Fe³⁺ concentration. Under the experimental conditions of pH value of 3.0, temperature of 35°C, and waste stone particle size of less than 0.075 mm,, the release quantity of Fe, Cr, Cu, and Zn reached 3680, 18.32, 132.20, 26.60 mg·kg^-1 after 20 days of leaching, respectively. Rising the temperature to 45 °C, Fe, Cr, Cu, and Zn release quantities increased to 89.30, 5.81, 105.08, and 28.00 mg·kg^-1. Six hundred milligrams per liter Fe³⁺ increased the release of heavy metals considerably (2.63-65.48 folds). The presence of microorganisms can significantly facilitate the release of heavy metals. Compared to the control group, the release quantities of Fe, Cr, Cu, and Zn increased 4.29, 3.17, 1.54, and 2.39 times, respectively. In addition, the waste rock under microbial action was more seriously corroded than that under chemical factors. The release behavior of these four heavy metals was consistent with the interfacial chemical reaction control model, indicating that the reactions mainly occurred on the surface of the waste rock. This study provides an essential reference for the study of heavy metal leaching behavior.