电位滴定法测定铁矿石中氧化亚铁

Determination of ferrous oxide in iron ore by potentiometric titration method

铁矿石中氧化亚铁在检测过程中易被氧化,而采用电位滴定法测定时可直接在密闭容器中插入电极进行检测,从而避免亚铁离子被氧化,因此试验建立了电位滴定法测定铁矿石中氧化亚铁的方法。采用盐酸溶解样品,氟化铵加入量为0.5g使硅酸盐充分分解,样品分解时间为15min,无需加入硫磷混酸。以电位滴定法代替滴定法进行检测,对仪器工作条件进行了正交试验优化,设定滴定终点筛选标准(EPC)为20,最小加液量为20μL,信号漂移速率为50mV/min。实验方法用于测定4个铁矿石及岩石类标准样品中氧化亚铁,结果的相对标准偏差(RSD,n=10)不大于0.40%,测定值与认定值基本一致,相对误差(RE)不大于0.33%;分别按照实验方法和国标方法 GB/T 6730.8—2016测定9个铁矿石及岩石类标准样品中氧化亚铁,测定值与国标方法测定值相吻合。

The ferrous oxide in iron ore is easily oxidized during detection process.The determination by potentiometric titration can be conducted by directly inserting electrode into closed container,thus avoiding the oxidization of ferrous ions.Consequently the determination method of ferrous oxide in iron ore by potentiometric titration was established.The sample was dissolved with hydrochloric acid.0.5 g of ammonium fluoride was added to fully decompose the silicate.The resolving time of sample was 15 min.The addition of mixed sulfuric acid and phosphoric acid was not required.The titration method was replaced by potentiometric titration.The working conditions of instrument were optimized by orthogonal experiments.The equivalence point criterion（EPC）of potentiometric titration was 20,the minimum dosage of sample solution was 20μL,and the signal drift rate was 50 mV/min.The proposed method was applied for the determination of ferrous oxide in four standard samples of iron ore and rock.The relative standard deviations（RSD,n=10）of measured results were not more than 0.40%.The found results were basically consistent with the certified values.The relative errors（RE）were not more than 0.33%.The content of ferrous oxide in nine standard samples of iron ore and rock were determined according to the experimental method,and the found results were consistent with those obtained by national standard method（GB/T6730.8-2016）.