Cobalt molybdate

Endpoint summary

Additional information

Hydrolysis of cobalt molybdenum oxide is not expected. Cobalt molybdenum oxide is a water soluble (508 mg/L) inorganic salt of a weak Lewis base and acid. Therefore, salt hydrolysis may proceed, when it is transferred into the aquatic environment. Different aqueous cobalt and molybdate species will be formed depending on the pH and redox potential of the aquatic environment. In the aqueous environment, the aqueous cobalt speciation is dominated by hydrolysis complexes only at a basic pH range, while free Co2+ species are the most important aqueous complexes from pH up to 9. At low molybdate concentrations, dissolved molybdate exist in water predominantly as HMoO4- or H2MoO4 between pH 2 and 4.3, and MoO42- at pH > 4.3. Therefore, cobalt molybdenum oxide, cobalt and molybdate species present an equilibrium in aqueous media (pH 4-9). Under normal environmental conditions, the equilibrium is relative stable and not significantly affected by the pH condition. A pH dependent hydrolytic degradation process is not relevant for cobalt molybdenum oxide.

Biodegradation in water, sediment and soil is not an applicable endpoint for cobalt molybdenum oxide as the substance is inorganic.

No bioaccumulation data are available for cobalt molybdenum oxide, however various reliable data exist for cobalt and molybdenum (measured as environmental concentrations) and different analogue cobalt and molybdenum substances.

In general, the bioaccumulation potential of cobalt in natural ecosystems is relatively low. First of all, low BAFs have been reported in eight laboratory (steady state) studies and four field studies; five BSAF-sediment values have been found to be well below 1; and, four (out of four) average BSAF-soil values have been reported to be well below 1. In addition, results from six field investigations plus two laboratory studies indicate the absence of biomagnification of cobalt in natural food webs. Finally, cobalt is an essential micro-nutrient, the uptake of which is expected to be regulated to some extent by many organisms (Environment Canada, 2011).

For molybdenum, all of the 27 BCF/BAF reported are below 100 with the exception of one BAF measured for a mollusc exposed to background Mo water concentrations (BAF of 164). The data demonstrates that cobalt and molybdenum, like other essential elements, shows homeostatic control by organisms. Limited information on transfer of Mo through the food chain indicates that molybdenum does not biomagnify in aquatic food chains. For the terrestrial compartment, the data suggests that Mo is not significantly concentrated from soil to plants, or soil invertebrates with BCF/BAF of < 5, and that there is no further significant increase in concentration from diet to mammals or birds.

No adsorption/desorption data are available for cobalt molybdenum oxide, however various reliable data exist for cobalt and molybdenum (measured as environmental concentrations) and different analogue cobalt and molybdenum substances showing statistical or conservative partition coefficients for suspended matter, soil, STP, sediments in freshwater and in coastal waters. For Co, log Kd values for all types ranged from 0.41 to 5.83. For Mo, log Kd values for all types ranged from 2.94 to 3.45.