Noranda Mines Limited

Derek G Kerfoot

A novel group of corrosion inhibiting pigments has been discovered, which is based on zinc molybdate compounds selected from sodium zinc molybdate, potassium zinc molybdate, ammonium zinc molybdate and mixtures thereof, combined with a suitable carrier, so that the proportion of the zinc molybdate compound is such that the Mo content in the pigment is between about 1 and 30% by weight. Such pigments can be prepared in situ by several methods, such as a double decomposition reaction of sodium, potassium or ammonium molybdate and a solution containing dissolved zinc ion, or an addition of an appropriate acid to zinc oxide dispersed in sodium, potassium or ammonium molybdate solution, or an addition of zinc oxide to a solution which comprises molybdic oxide dissolved in an aqueous solution of sodium, potassium or ammonium molybdate. All these methods are simple, economic and lead to non-toxic pigments of essentially white colour, which have anti-corrosive properties comparable to, or better than, those of zinc yellow and other commercially available corrosion inhibiting pigments.

Corrosion inhibiting molybdate pigment and preparation thereof

A method is disclosed for removing arsenic by solvent extraction from a copper and/or nickel bearing aqueous solution containing about 100 to 600 gpl sulphuric acid. The method comprises contacting the solution with an organic solution consisting of about 5 to 80% by volume of tributylphosphate in an organic diluent, and subsequently stripping the arsenic from the loaded organic solution with a suitable stripping agent. Particularly, when the sulphuric acid concentration in the aqueous solution is lower than 300 gpl, the organic solution advantageously comprises up to about 15% of a quaternary ammonium reagent. Preferred quaternary ammonium reagents are tricaprylmethyl ammonium chloride and mixtures of tri-C.sub.8 -C.sub.10 methylammonium chlorides.

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Edgware, United Kingdom

Derek G Kerfoot