Electrochemical Study of Galena Weathering in NaCl Solution: Kinetics and Environmental Implications

Abstract

Exploitation of seafloor massive sulfide deposits exposes galena and other metal sulfides to weathering factors. Galena weathering process leads to release of toxic metals into the water column. Although galena weathering has an impact on the environment, the mechanisms and kinetics of galena oxidation under seawater conditions are rarely studied. In this work, several electrochemical experimental methods were combined to examine the kinetics of galena weathering in NaCl solution to simulate the effects of Cl− in seawater, and the effects of sodium chloride concentration and pH on it were studied. The results show that galena weathering can lead to mineral surface passivation. More chloride ions can accelerate the dissolution of galena. Higher acidity and alkalinity promote the dissolution of galena in NaCl solution. Galena will release Pb2+ at a rate of 2.849 × 10−2 g m−2 d−1 in the near neutral NaCl mediums, and the amount increases to 5.705 × 10−2 g m−2 d−1 at pH 1.0 and even up to 7.569 × 10−1 g m−2 d−1 at pH 13.0. The results of polarization curves are consistent with the impedance spectrum data. Based on the dissolution kinetics of galena, the environmental significance of galena weathering is proposed.