光度滴定法测定铜精矿中铜

铜含量的高低直接决定了铜精矿的价值,因此铜的准确测定尤其重要。采用盐酸、硝酸、溴、硫酸湿法消解样品,以氟化氢铵除硅,高氯酸除碳,经高温硫酸冒烟法进一步消解样品,实现了光度滴定法对铜精矿中铜的测定。对测定波长、搅拌方式、加液速度、缓冲溶液进行了优化,确定实验条件为:选用520nm作为测定波长;选择搅拌桨机械搅拌方式;控制加液速度为0.40mL/4s;采用pH 5的乙酸-乙酸钠溶液为缓冲溶液。实验表明,以E(电压)-V(体积)滴定曲线定量,在测定时无需进行体积校正,仪器可自动计算滴定终点;而以电位突跃自动判断终点,无需对待测液的实际电位值进行校正,简化了操作步骤。样品中共存元素的干扰试验表明,在滴定前缓慢加入0.5mL 200mg/mL氟化钾溶液可消除样品中铁对测定的干扰,样品中其他共存元素不干扰测定。选择铜精矿标准样品及铜精矿实际样品,按照实验方法对样品中铜进行测定,结果表明,测定值与标准值或标准方法GB/T 3884.1—2012测定值基本一致,测得结果的相对标准偏差(RSD,n=12)在0.11%~0.52%之间。方法满足铜质量分数范围在9.5%~65.0%之间的铜精矿检测需求。

Determination of copper in copper concentrate by photometric titration

The copper content directly determines the value of copper concentrate, so the accurate determination of copper content is particularly important. The sample was digested by wet method with hydrochloric acid, nitric acid, bromine and sulfuric acid. Silicon and carbon was removed with ammonium hydrogen fluoride and perchloric acid, respectively. The sample was further digested by sulfuric acid fuming at high temperature, realizing the determination of copper in copper concentrate by photometric titration. The measurement wavelength, stirring method, addition rate and buffer solution were optimized. The experimental conditions were obtained as follows: the measurement wavelength was 520nm; the stirring method was mechanical stirring using stirring paddle; the addition rate was controlled at 0.40mL/4s; the buffer solution was acetic acid-sodium acetate solution (pH5). The experiment showed that thevolume correction was not required in measurement if E(voltage)-V(volume) titration curve was used for quantitation, and the titration end point could be automatically calculated by the instrument. The end point could be automaticallyjudged by the sudden change of potential. It was no need to correct the actual potential of testing solution, which simplified the operation procedures. The interference tests of coexisting elements in sample showed that the interference of iron could be eliminated by slowly adding 0.5mL of 200mg/mL potassium fluoride solution before titration. Other coexisting elements in sample had no interference with the determination. The contents of copper in certified reference materials and actual samples of copper concentrate were determined according to the experimental method. It indicated that the results were basically consistent with the certified values or those obtained by standard method (GB/T 3884.1-2012). The relative standard deviations (RSD, n=12) of determination results were between 0.11% and 0.52%. The proposed method could meet the detection requirements of copper concentrate with copper content in the range of 9.5%-65.0% (mass fraction).