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Water solubility

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Description of key information

The water solubility of P-slag was studied using the dissolution/transformation protocol (OECD 29). Fluor and Silicium ions are present in solution in a concentration up to 1 mg/l. Fe, Al and Mn are below the detection levels in all cases. 

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Additional information

Due to the low solubility in water the dissolution/transformation protocol was used to further evaluate the solubility of the constituents of P-slag. If the cristalline structure of P-slag would solve in water, the elements would be present as ions in solution.

Particles of P-slag (< 1mm) were added to a synthetic medium with pH 6.5 and 8.5 at loading rates of 1, 10 and 100 mg/liter and the concentrations were measured after 7 days. In a similar way 1 mg/l was added to water with pH 5.5 and 8.5 and concentrations were measured after 28 days.

In the solution containing 100 mg P-slag per liter, Si is the element detected at the highest level, around maximum 1 mg/l. Fluor is detected as well, at concentrations maximum circa 0.5 mg/l. With pH 8.5 the solved concentrations are almost half of the concentrations at pH 6.5. In the lower P-slag loading, Si and F concentrations were below detection levels.

Concentrations of other elements were below the detection level (Fe < 0.25 mg/l, Al < 0.05 mg/l, Mn < 0.01 mg/l) in all P-slag loadings.