Determination of iron in copper smelting dust by titanium trichloride reduction-potassium dichromate titration method
The matrix of copper smelting dust is complex,which contains high content elements such as copper,arsenic,antimony,carbon,sulfur and silicon,which could interfere with the determination of iron in sample by potassium dichromate titration.The sample was dissolved with ammonium fluoride,hydro-chloric acid,nitric acid,sulfuric acid and perchloric acid.The interferences of arsenic and antimony were eliminated by hydrobromic acid.The excessive ammonia was added to form ferric hydroxide precipitate,realizing the separation from other elements such as copper and nickel.The precipitate was dissolved with hydrochloric acid,and the solution was reduced with stannous chloride to pale yellow.Thus,the determi-nation of iron in copper smelting dust was realized by potassium dichromate titration method.The influ-ence of some factors on the determination was discussed,including the method of sample dissolution,the duration of sulfuric acid smoke,and the interferences of arsenic or antimony,the dosage of ammonium chloride,the boiling time after adding ammonia and the type of filter paper.The optimized conditions are as follows:the duration of sulfuric acid smoke was 15-30 min after the sample was dissolved with mixed acid;When the content of arsenic in sample was higher than 1 mg or the content of antimony content was higher than 2 mg,5 mL of hydrobromic acid should be added to eliminate their interference.The dosage of ammonium chloride was 3-4 g.The boiling time after adding ammonia was 1-2 min for complete precipitati-on.The precipitates were filtered with medium speed filter paper.Two copper smelting dust samples were selected for recovery tests,and the recoveries were between 99.00％and 101.37％.Four copper smelting dust samples were determined according to the proposed method,and the results were basically consistent with those obtained by inductively coupled plasma atomic emission spectrometry(ICP-AES).The relative standard deviations(RSD,n=11)were between 0.32％and 0.56％.The proposed method was applicable for the determination of iron in dusts during all stages of copper smelting process,and it was not affected by the difference of sample matrix.
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