基于流动注射分析测定催化剂共浸液中高浓度CoO的研究

Study on determination of high-concentration CoO in co-impregnating solution based on flow injection spectrophotometry

为了监测钴钼催化剂浸渍液中高浓度Co(Ⅱ)含量,基于Co(Ⅱ)/KSCN反应体系,建立了一种能测定上述离子的流动注射分光光度系统。研究发现:Co(Ⅱ)与KSCN络合物是由K_2Co(SCN)_4和K_4Co(SCN)_6构成,利用第二种物质可以定量Co(Ⅱ);共浸液实样在碱性或强酸性条件下能形成稳定均一的溶液,而在中性和弱酸性条件下则会出现大量溶质析出的问题。利用硫酸将样品酸化至pH≈0.38,可以实现实样的测定。另外,本研究对相关影响因素进行了优化,得到的测定条件为:显色剂由37.5%(w/V)KSCN和0.1 mol/L Na Ac-HAc(pH 5.8)组成,载流为1.0 mol/L硫酸,系统出口总流量为2.0 m L/min,样品定量环体积为90μL,显色剂定量环体积为220μL,测定波长为620 nm。本方法的线性范围5.0~50.0 g/L,检出限1.3 g/L。系统的RSD<1.2%(n=11),回收率为96.0%~102.7%,分析速度为20样/h。

For determinating the content of cobalt in co-impregnating solution of Co-Mo catalysts,based on flow injection spectrophotometry and Co（II）/KSCN reaction system,a new automatic analysis system was proposed. This study found that： the reaction product of Co（II） and KSCN consisted of K2Co（SCN）4 and K4 Co（SCN）6,and the second one could be used to quantify Co（II）; on alkaline or strongly acidic condition,the sample of co-impregnating solution was stable and homogeneous,but on neutral and weakly acidic conditions,a serious problem of solute precipitation appeared. For solving the problem,the sample was acidized by H2SO4 to pH≈0. 38. The optimized conditions for determination of cobalt were as follows： mixed solution of 37. 5%（w/V） KSCN and 0. 1 mol/L Na Ac-HAc（pH 5. 8）was used as chromogenic reagent; carrier was 1. 0 mol/L H2SO4; total flow rate was 2. 0 m L/min; the volumes of quantitative loop were 90 μL for samples and 220 μL for chromogenic reagent; detection wavelength was 620 nm. The calibration curve was linear from 5. 0 to 50. 0 g/L,and the limit of detection was 1. 3 g/L. The relative standard deviations（RSD） was less than 1. 2 %（n = 11）,the recoveries were in the range of 96. 0% ~ 102. 7%,analysis speed was 20 samples per hour.