Abstract
Metal sulfides can stabilize toxic soluble heavy metals in anaerobic sediments. However, sediments may suspend and expose to aerobic conditions during storm events or in the estuary with tidal effects. This may cause oxidative dissolution of metal sulfides and increase metal bioavailability that can harm the ecosystem. The objective of this research is to investigate the effects of dissolved oxygen (DO), pH, natural organic matter (NOM) and salinity on the kinetics of oxidative dissolution of copper sulfide (CuS), lead sulfide (PbS) and zinc sulfide (ZnS). Batch experiments were conducted using a continuous aeration setup that can control the dissolve oxygen concentrations (0 mg/L, 5mg/L and 8.4 mg/L) for a period of 3 d. Results demonstrated that oxidative dissolution of CuS, PbS and ZnS truly occur in the presence of DO and the rate showed the following sequence: PbS >CuS>ZnS. Low pH and high salinity generally cause more and faster metal release. Humic acid can inhibit the metal release of CuS and PbS but promote the metal release of ZnS. FE-SEM analysis showed that the morphology of three metal sulfides became rounded and aggregated in the 10mg/L HA reaction, morphology change of CuS also found in brackish water reaction but PbS and ZnS had no changed.
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