GB647350A - Recovery of salts of copper and tartaric acid from waste cuprammonium cellulose solutions - Google Patents

Abstract

Tartaric acid and copper are simultaneously recovered in the form of salts from waste acids and alkaline waste waters accumulating in the manufacture of cuprammonium cellulose products from cuprammonium cellulose solutions containing tartrate ions by the steps in sequence comprising mixing at least one waste acid containing copper and tartaric acid with at least one alkaline waste water containing copper and tartrate ions in a proportion sufficient to cause at least a partial precipitation of copper and tartrate salts in the form of a slurry, heating said slurry in the presence of a base to convert the said copper salts into copper oxide while said tartrate precipitate remains unchanged, dissolving said copper oxide and tartrate precipitate by adding an acid thereto to form a soluble copper salt and tartaric acid and then adding a base in an amount sufficient to form a precipitate comprising essentially a basic copper salt and a tartrate. The method is applicable to the "funnel stretch spinning process" wherein the spinning solution is extruded into substantially neutral water passing through funnels in which the spinnarets are mounted. The issuing "blue water" contains one or more copper salts combined with ammonia, hydroxyl ions and a salt of tartaric acid. This solution and other waste copper solutions obtained during the spinning are suitable alkaline waste waters. The extruded threads are hardened by treatment with dilute acid and washed in skeins with more dilute acid and these waste acids constitute the other source of copper and tartaric acid. According to examples: (1) blue water, waste copper solution, waste acid and skein wash acid are mixed in proportions giving a pH value of 6.4 to 7.8 and the resulting slurry comprising cupric hydroxide, basic copper sulphate and complex copper tartrates is concentrated by settling and then heated with sodium hydroxide solution at 60 DEG to 75 DEG C. and a pH of 10.5 to 11.0. The compact copper oxide and tartrate precipitate is removed and dissolved with added copper sulphate in aqueous sulphuric acid, cooled, more d-tartaric acid added, the mixture filtered and the resulting filtrate treated with sodium carbonate solution to precipitate the copper as basic copper sulphate and the tartaric acid as a tartrate; this mixture may be used in preparing a fresh spinning solution; (2) blue water is mixed with lime solution in flow rates giving a mixture of pH 10 to 10.5 and after settling, the precipitated slurry is mixed with a slurry obtained as in (1) and the mixed slurry treated as above. Hydrochloric acid, potassium hydroxide and potassium carbonate may replace the sulphuric acid and sodium hydroxide and carbonate.