Characterization and environmental implications of selenate co-precipitation with barite.

This study investigated the sequestration of dissolved selenate (SeO) via co-precipitation in barite for a range of SeO concentrations (0-~8650 mg/L), as well as its release at near neutral pH conditions (pH = ~5.5-6.5).

Dissolved Selenium(VI) Removal by Zero-Valent Iron under Oxic Conditions: Influence of Sulfate and Nitrate.

Dissolved Se(VI) removal by three commercially available zero-valent irons (ZVIs) was examined in oxic batch experiments under circumneutral pH conditions in the presence and absence of NO and SO . Environmentally relevant Se(VI) (1 mg L), NO ([NO-N] = 15 mg L), and SO (1800 mg L) were employed to simulate mining-impacted waters. Ninety percent of Se(VI) removal was achieved within 4-8 h in the absence of SO and NO .

Geochemical and mineralogical characterization of sulfur and iron in coal waste rock, Elk Valley, British Columbia, Canada.

Exposure of coal waste rock to atmospheric oxygen can result in the oxidation of sulfide minerals and the release of sulfate (SO) and associated trace elements (e.g., Se, As, Cd, and Zn) to groundwaters and surface waters.

Geochemistry of arsenic in low sulfide-high carbonate coal waste rock, Elk Valley, British Columbia, Canada.

This study investigated the geochemistry of arsenic (As) in low sulfide-high carbonate coal waste rock of the Elk Valley, British Columbia, Canada. Its abundance and mineralogical associations in waste rock of different placement periods were determined in addition to its mobilization into porewater and rock-drain effluent. The mean (5.

Reservoirs of Selenium in Coal Waste Rock: Elk Valley, British Columbia, Canada.

Selenium (Se) reservoirs in coal waste rock from the Elk Valley, southeastern British Columbia, the location of Canada's major steelmaking coal mines, were characterized and quantified by analyzing samples collected from the parent rock, freshly blasted waste rock (less than 10 days old), and aged waste rock (deposited between 1982 and 2012). Se is present throughout the waste rock dumps at a mean digestible (SeD) concentration of 3.12 mg/kg.

Redox stability of As(III) on schwertmannite surfaces.

As(III)-enriched mine discharge often drains through Fe(III)-mineral abundant land covers which makes the understanding of its fate and redox behaviour extremely important. We therefore conducted batch kinetic and equilibrium studies at pH 3.0±0.

Effects of adsorbed arsenate on the rate of transformation of 2-line ferrihydrite at pH 10.

2-Line ferrihydrite, a form of iron in uranium mine tailings, is a dominant adsorbent for elements of concern (EOC), such as arsenic. As ferrihydrite is unstable under oxic conditions and can undergo dissolution and subsequent transformation to hematite and goethite over time, the impact of transformation on the long-term stability of EOC within tailings is of importance from an environmental standpoint. Here, studies were undertaken to assess the rate of 2-line ferrihydrite transformation at varying As/Fe ratios (0.

Molybdenum speciation in uranium mine tailings using X-ray absorption spectroscopy.

Uranium (U) mill tailings in northern Saskatchewan, Canada, contain elevated concentrations of molybdenum (Mo). The potential for long-term (>10,000 years) mobilization of Mo from the tailings management facilities to regional groundwater systems is an environmental concern. To assist in characterizing long-term stability, X-ray absorption spectroscopy was used to define the chemical (redox and molecular) speciation of Mo in tailings samples from the Deilmann Tailings Management Facility (DTMF) at the Key Lake operations of Cameco Corporation.

Transformation of two-line ferrihydrite to goethite and hematite as a function of pH and temperature.

Under oxic aqueous conditions, two-line ferrihydrite gradually transforms to more thermodynamically stable and more crystalline phases, such as goethite and hematite. This temperature- and pH-dependent transformation can play an important role in the sequestration of metals and metalloids adsorbed onto ferrihydrite. A comprehensive assessment of the crystallization of two-line ferrihydrite with respect to temperature (25, 50, 75, and 100 °C) and pH (2, 7, and 10) as a function of reaction time (minutes to months) was conducted via batch experiments.