Transformation/dissolution characterization of tungsten and tungsten compounds for aquatic hazard classification

Abstract

The transformation/dissolution protocol (T/DP) for metals and sparingly soluble metal compounds was applied to determine the transformation/dissolution (T/D) characteristics of yellow tungsten trioxide, WO ; blue tungsten oxide, WOx, x taken as 2.9; tungsten disulphide, WS ; tungsten metal, W; 3 samples of tungsten carbide, WC; sodium tungstate, Na WO · 2H O; ammonium paratungstate (APT), (NH ) (H W O ) · 4H O; and ammonium metatungstate (AMT) (NH ) (H W O ) · 3H O. The T/D data were used to derive aquatic hazard classification outcomes under the United Nations Globally Harmonized System of Classification and Labelling of Chemicals (UN GHS) and European Union Classification, Labelling and Packaging of Substances and Mixtures (EU CLP) schemes by comparing the data with selected acute and chronic ecotoxicity reference values (ERVs) of 31 and 3.37 mg W/L, respectively. In addition to the concentration of total dissolved tungsten (W), the T/D solutions were analyzed for the concentration of the tungstate anion, because speciation can be an important factor in establishing the ecotoxicity of dissolved metals. Results show that the tungstate anion was the predominant W-bearing species in solution for all substances examined at pH 6 and 8.5. It was found that the 100 mg/L loadings of both the yellow WO and the blue WOx exceeded the 31 mg/L acute ERV, so they would classify as Acute 3-Chronic 3 under the UN GHS scheme but they would not classify under the EU CLP. An effect of pH on the reactivity of the W metal was observed with 3% and 16% W dissolution at pH 6 and 8.5, respectively. Tungsten metal would not classify under either the UN GHS or EU CLP schemes nor would the WS . The WCs were the least reactive in terms of the 1% or less dissolution of the contained W at pH 6. A critical surface area for WC was calculated. The sodium tungstate, APT and the AMT all yielded, at pH 8.5, total dissolved W concentrations that would result in UN GHS Acute 3-Chronic 3 classifications. Integr Environ Assess Manag 2018;14:498-508. © 2018 Her Majesty the Queen in Right of Canada. Integrated Environmental Assessment and Management © 2018 SETAC.

Weight‐of‐Evidence Approach for Assessing Removal of Metals from the Water Column for Chronic Environmental Hazard Classification

“…This, together with an assessment of degradability, allows us to derive the environmental hazard classification. This approach has been successfully applied to derive environmental hazard classifications on metal concentrates, mattes, alloys, metal powders, massive metals, and metal compounds (Skeaff et al 2008(Skeaff et al , 2011(Skeaff et al , 2012Skeaff and Beaudoin 2014;Huntsman et al 2018).…”

Method Development for Determining the Removal of Metals from the Water Column under Transformation/Dissolution Conditions for Chronic Hazard Classification

“…Previous studies (Skeaff et al 2008(Skeaff et al , 2011Skeaff and Beaudoin 2014;Huntsman 2018) have demonstrated that properly equipped and operated laboratories can apply the T/DP to metal-bearing substances to yield acute and chronic aquatic hazard classification outcomes that are reliable, consistent, and in agreement with other laboratories. In the development of the T/DP-E, it was therefore important to maintain as many elements of the original T/DP as possible.…”

“…The T/DP has been included in the United Nations Globally Harmonized System (GHS) as Annex 10 (United Nations 2017). The T/DP has been successfully applied to derive hazard classifications on a wide range of metal-bearing substances including metals, metal compounds, mattes, alloys, and concentrates (Skeaff et al 2008(Skeaff et al , 2011Skeaff and Beaudoin 2014;Huntsman et al 2018).…”

Factors Controlling Tungsten Mobility in W-Cu Skarn Tailings at the Cantung Mine, Northwest Territories, Canada

“…tungsten carbide and tungsten alloys) may also become airborne, later to settle in soils and surface waters. Once settled, the W-bearing particles may leach and enter soil porewaters and surface waters, although the amount of leaching is dependent on the solubility and stability of the particle (Huntsman et al, 2018). Treated wastewater (not necessarily exclusive to mining, milling, and smelting operations) may also contain elevated tungsten concentrations, particularly in waters with alkaline pH.…”