电解重量法测定混合铜矿中自由氧化铜

Determination of Free Copper Oxide in Mixed Copper Ores by Electrogravimetry

建立了用于混合铜矿石中自由氧化铜测定的方法。试样用含亚硫酸钠(6g/L)的硫酸(10%)溶液浸取2h,选择性溶解铜氧化物,过滤并煮沸滤液,用去离子水稀释后电解。溶液中的铜离子电积至阴极铂网上。用火焰原子吸收光谱法检测残余于电解后液中的铜离子;同时用硝酸(1+1)溶解铂网上的铜,并用火焰原子吸收光谱法检测与阴极铜共电积的杂质元素含量,用铂阴极差重加上电积后液残余铜含量并减去共电积的杂质元素含量可计算出氧化铜矿中酸溶铜含量。与碘量法相比,不用肉眼观察颜色变化确定终点,人为误差小,结果稳定、准确。通过对加拿大氧化铜矿标准物质AMIS0050进行测定(n=12),方法准确度可靠。并选取15批次的氧化铜矿检测,与经典碘量法比对,结果令人满意。

A method suitable for determination of free copper oxide in mixed copper ores was established. The sample was leached in the sulfuric acid solution （10%） containing （6 g/L） sodium sulfite for two hours, and copper oxide was selectively dissolved. The leaching solution was filtered and the filtrate was boiled and diluted with deionized water for electrodeposition. Copper in solution was electrically deposited to the platinum cathode. The content of the residual copper in spent electrolyte was determined by flame atomic absorption spectrophotometry. The copper deposited on the cathode was dissolved by nitric acid（1 ＋ 1）, and the content of the impurity elements which were deposited to the cathode together with the copper during the electroplate process are determined by flame atomic absorption spectrophotometry. The acid-soluble copper content in copper oxide was calculated by subtracting the content of the impurity elements on the platinum cathode from the sum of the weight difference for the platinum cathode before and after cathodic electrodeposition and the residual copper in the spent electrolyte. Compared with GB copper iodometry method, in which a titration end is determined by observation of the color change of the titration solution using naked eyes, this method has less human errors. In addition, the results measured by electrogravimetry are more stable and accurate. The results for testing Canadian Certified Reference Materials AMIS 0050 （n= 12） indicate that this method is accurate and reliable. The fifteen batches of oxide copper ores were selected and tested and the results were satisfactory compared with the classical copper iodometric method.