原子吸收光谱法间接测定钼精矿中钼的研究

对于钼精矿中钼的测定，标准方法采用钼酸铅重量法，该方法需要将钼酸铅沉淀反复多次洗涤、过滤，以保证沉淀物中夹带的铅离子洗涤完全，再对沉淀物进行灰化、灼烧等多步操作，步骤较繁琐，分析费时，不能快速配合选矿、冶金的科学研究。应用原子吸收光谱法间接测定钼，建立了钼精矿中钼的快速分析方法。钼精矿样品经硝酸、氯酸钾、硫酸加热溶解后，用酚酞和盐酸调节pH值，加入乙酸-乙酸铵缓冲溶液调节pH值至5～7，再加入一定量且过量的铅标准溶液。基于在室温下，钼酸铅为难溶电解质，难溶电解质在一定温度下能否沉淀完全，通常比较离子积Q_c与溶度积常数K_sp的相对大小，当Q_c>K_sp，溶液过饱和，沉淀物完全析出，钼精矿中钼的含量为40～60%，铅的加入量为0.125 0～0.150 0 g，取最小值计算出溶液中钼酸铅的离子积，Q_c＝[Pb2+][MoO2-₄]=2.51×10-5，K_sp＝1.0×10-13，Q_cK_sp，因此钼酸铅沉淀可以完全析出，待钼酸铅沉淀完全后干过滤，用原子吸收光谱法测定滤液中过量的铅离子，用差减法计算得出钼精矿中钼的含量。文中分别考察了乙酸-乙酸铵缓冲溶液的加入量及其浓度、铅标准溶液的加入量、钼酸铅沉淀完全的时间、加热时间以及常见共存离子如W6+，Sn4+和Cu2+等的最大允许量诸多因素对原子吸收光谱法间接测定钼的影响。与钼酸铅重量法相比，该方法省去了对钼酸铅沉淀反复多次的洗涤、灰化以及灼烧等步骤，操作简便易掌握，分析时间缩短一半，并用钼酸铅重量法与本方法进行对照实验，分析结果进行数理统计，得出结论：本方法具有很好的准确度和精密度，可用于选矿、冶金钼精矿样品中钼的快速分析检测。

Study on Determination of Molybdenum in Molybdenum Concentrate by Atomic Absorption Spectrometry Indirectly

For the determination of molybdenum in molybdenum concentrate,lead molybdate gravimetric method was considered as standard method .In order to ensure the lead ions to be washed thoroughly from the entrained precipitate,lead molybdate precipitate was washed,filtered repeatedly,then ashed and burned .This method cann ot satisfy the rapid measurement demand of mineral processing and metallurgy sci entific research due to its time consuming .In the present work,molybdenum was determined by atomic absorption spectrometry indirectly and a rapid analysis method for molybdenum in molybdenum concentrate was proposed .The sample was dissolved by nitric acid,potassium chlorate and sulfuric acid,pH was adjusted by ace tic acid and ammonium acetate buffer solution to pH 5～7,then a certain amount and excess of lead standard was added .Based on lead molybdate was considered as undissolved electrolyte on room temperature,the solubility of lead molybdate w as 116×10-5g,far less than 001 g,was considered as the undissolved electrolyte,the electrolyte insoluble at a certain temperature can complete precipitation,usually compared with the solubility production product Qc and the relative size of constant Ksp,when Qc＞Ksp,solution was supersaturated,precipitation was precipitate completely,the content of molybdenum in molybdenum concentrate was 40％～60％,the amount of lead was 0125 0～0150 0 g,took the minimum calculated solution lead molybdate ion product,Qc=[Pb2+][MoO2-4]=251×10-5,Ksp=10×10-13,QcKsp,Therefore lead molybdate precipitate can be precipitated completely,after dry filtered,the excess of lead ions were determined by atomic absorption spectrometry,the content of molybdenum was calculated by subtraction method .In this paper,the amount of acetic acid-ammonium acetate buffer solution,the amount of lead standard,time of lead molybd ate precipitation,heating time and maximum amount of coexisting ions such as W6+,Sn4+,Cu2+,etc were investigated .Compared with lead moly bdate gravimetric method,repeatedly washing,ashing and burning with lead molyb date were eliminated by proposed method,which was simple,easy to master and was able to cut the analysis time in half .The control experiments were conducted by lead molybdate gravimetric method and proposed method .After the results were implemented by mathematical statistics,it can be concluded that it had good ac curacy and precision for the proposed method,which can be applied to rapid analysis of molybdenum in molybdenum concentrate for mineral processing and metallurgy .