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.
Highlights
Galena (PbS) is one of the most common metallic sulfide minerals, and widely exists in terrestrial deposits and seafloor massive sulfide (SMS) deposits [1]
Studying the dissolution behavior of galena in different solutions is conducive to understanding the migration and transformation of lead in the environment, and can provide theoretical guidance for the pollution treatment caused by galena oxidation
The results show that the deterioration of where, A and B are fitting constants, C is the concentration of sodium chloride solutions, Ef is the final
Summary
Galena (PbS) is one of the most common metallic sulfide minerals, and widely exists in terrestrial deposits and seafloor massive sulfide (SMS) deposits [1]. The oxidative dissolution of galena plays an important role in environmental and geochemical processes. Under the influence of mining activities or specific geochemical processes, the oxidation and dissolution of galena will be accompanied by the release of lead and other toxic heavy metal ions (such as zinc and cadmium), which threatens human health and affects the ecosystems [2,3]. The principal secondary minerals formed by the oxidation of galena are anglesite (PbSO4 ) and cerussite (PbCO3 ) [4,5]. They have higher solubility and biological accessibility than galena, which promotes the migration of lead and increases its toxicity [5]. Studying the dissolution behavior of galena in different solutions is conducive to understanding the migration and transformation of lead in the environment, and can provide theoretical guidance for the pollution treatment caused by galena oxidation
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