Abstract: The invention relates to methods and processes for the photoassisted oxidation of dissolved species such as arsenic, iron, phosphorous and sulphur. Each aspect of the invention involves supplying to a solution including the species to be oxidized, an oxidant and a photoabsorber, and then irradiating the resultant solution with UV/electromagnetic radiation. The resulting oxidised species can then be subsequently treated, used and/or removed (e.g. through precipation/co-precipitation).

Abstract: Copper arsenate, substantially free from impurities that will form a sludge in the process for producing wood preservatives such as chromated copper aresenate and having a water content of less than 15%, is prepared by mixing a solution of soluble arsenate and a copper sulfate solution, either or both solutions containing sludge-forming impurities, to form a copper and arsenic-containing solution without precipitating copper arsenate. The pH during the adding is controlled at a value in the range of 1.7 to 2.2 to precipitate impurities. Precipitated impurities are removed, and the copper and arsenic-containing solution is neutralized with a suitable alkaline substance, preferably dilute sodium hydroxide solution, to pH 3.2 to 4.2 to precipitate copper arsenate.