EDTA滴定法结合原子吸收光谱法测定镉团中锌铅镉  

Determination of zinc,lead and cadmium in cadmium cluster by EDTA titration combined with atomic absorption spectrometry

作　　者：罗开良 魏巍 LUO Kailiang;WEI Wei(Yunxi Wenshan Zinc and Indium Smelting Co.,Ltd.,Maguan 663700,China)

机构地区：[1]云锡文山锌铟冶炼有限公司,云南马关663700

出　　处：《冶金分析》2023年第4期84-89,共6页Metallurgical Analysis

摘　　要：湿法炼锌产生的副产品镉团含有较高含量的锌、铅、铜等杂质,对滴定法测定镉产生干扰;即使分离杂质后再直接滴定,其终点突跃也不明显;而使用返滴定-置换滴定法时,碘化钾置换镉后溶液的pH值难以控制,且需要预先分离铅,步骤繁琐。为了建立一种适合测定镉团中镉含量的方法,实验首先采用酸分解样品,再使用EDTA滴定法结合原子吸收光谱法(AAS)测定镉团中锌、铅、镉。在pH 5.5~6.2的六次甲基四胺缓冲溶液中,以硫脲掩蔽Cu^(2+)的干扰,用过量的EDTA标准溶液络合锌、铅、镉;以二甲酚橙为指示剂,用锌标准溶液返滴定,测得结果为锌、铅、镉合量(以锌记)。再使用原子吸收光谱法(AAS)分别测定锌、铅的含量,以锌、铅、镉合量扣除锌、铅的量即为镉量。实验发现,对于镉团化学成分分析,大称样量才能保证样品的代表性;使用AAS测定锌、铅含量时不受体系中共存离子的干扰。方法用于测定镉团中锌、铅、镉,结果的相对标准偏差(RSD,n=11)分别为0.69%~1.2%、0.65%~1.6%和0.11%~0.12%;结果和电感耦合等离子体原子发射光谱法(ICP-AES)及返滴定-置换滴定法的结果一致。The by-product(cadmium cluster)of zinc hydrometallurgy contains high contents of zinc,lead,copper and other impurities,which interferes with the determination of cadmium by titration method.The end-point jump is not obvious even if the direct titration is conducted after separating the impurities.For the back titration-displacement titration,the pH of solution after replacing cadmium with potassium iodide is hardly controlled.Moreover,the pre-separation of lead is required and the operation is complicated.In order to establish a method suitable for the determination of cadmium content in cadmium cluster,the sample was first decomposed with acid,and then the contents of zinc,lead and cadmium were determined by EDTA titration combined with atomic absorption spectrometry(AAS).In the hexamethylenetetramine buffer solution at pH 5.5-6.2,thiourea was added to mask the interference of Cu2+.Excessive EDTA standard solution was used to complex zinc,lead and cadmium.Back titration was performed with zinc standard solution using xylenol orange as the indicator.The results obtained were the total contents of zinc,lead and cadmium(in Zn).Then the contents of zinc and lead were determined by atomic absorption spectrometry(AAS).The content of cadmium could be obtained by subtraction.It was found that only large weight of sample could ensure the representativeness of samples for the analysis of chemical composition in cadmium cluster.The determination of zinc and lead by AAS was not interfered by the coexisting ions in system.The proposed method was applied for the determination of zinc,lead and cadmium in cadmium cluster.The relative standard deviations(RSD,n=11)were 0.69%-1.2%,0.65%-1.6%and 0.11%-0.12%,respectively.The found results were consistent with those obtained by inductively coupled plasma atomic emission spectrometry(ICP-AES)and back titration-displacement titration.

关 键 词：EDTA滴定法 原子吸收光谱法(AAS) 镉团 锌 铅 镉 返滴定-置换滴定法 

分 类 号：O655.2[理学—分析化学] O657.31[理学—化学] TF813[冶金工程—有色金属冶金]