铅试金重量法结合原子吸收光谱法测定银钯精矿中银

采用硝酸、盐酸、高氯酸分解样品,加入盐酸与银反应形成氯化银沉淀后过滤,采用铅试金重量法对沉淀中银量进行了测定,并扣除了钯产生的干扰,同时采用原子吸收光谱法(AAS)对滤液中的银量进行了测定,将沉淀与滤液中的银量相加后除以样品量得到样品中银的含量,实现了铅试金重量法联合原子吸收光谱法对银钯精矿中银的测定。考虑到在沉淀形成的过程中,氯化银沉淀对铂和钯有严重的吸附作用,因此考察了铂和钯对沉淀中银量测定的影响。试验表明,采用铅试金法对沉淀中贵金属进行捕集后,贵金属合粒中的铂对银测定的干扰可忽略不计,但钯的干扰不可忽略。实验采取用10mL硝酸(1+1)低温溶解贵金属合粒,以原子吸收光谱法测定合粒溶液中钯量,从铅试金重量法所得结果中扣除合粒中钯量的方法消除了沉淀中钯对测定的干扰。干扰试验表明,滤液中的主要共存元素钯、铜、铋、金、铂对样品中银测定的干扰可忽略不计。按照实验方法,对钯银精矿样品中银平行测定11次,相对标准偏差(RSD)为0.028%~0.059%,同时加入高纯硝酸银进行加标回收试验,回收率为98%~102%。将实验方法应用于银钯精矿样品中银的测定,其测定结果与碘化钾电位滴定法基本一致。

Determination of silver in silver-palladium concentrate by lead fire assaying gravimetry combined with atomic absorption spectrometry

The sample was decomposed with nitric acid, hydrochloric acid and perchloric acid. Hydrochloric acid was added to react with silver ions to form silver chloride precipitate. After filtration, the content of silver in precipitate was determined by lead fire assaying gravimetry. The interference of palladium was eliminated. Meanwhile, the content of silver in filtrate was determined by atomic absorption spectrometry (AAS). Thus the content of silver in sample could be obtained by summing the silver content in precipitate and filtrate. Therefore, the determination of silver in silver-palladium concentrate by lead fire assaying gravimetry combined with AAS was realized. Since the silver chloride precipitate had serious adsorption effect on platinum and palladium in precipitate formation process, the influence of platinum and palladium in precipitate on the determination of silver content was investigated. The results showed that after capture of precious metals in precipitate by lead fire assaying, the interference of platinum in precious metal particles could be ignored. However, the influence of palladium on the determination of silver could not be ignored. The precious metal particles was dissolved with 10mL of nitric acid (1+1) at low temperature. The content of platinum in precious metal particles was determined by AAS. The interference of palladium in precipitate could be eliminated by deducting the amount of palladium in precious metal particles from the results of lead fire assaying method. The interference tests indicated that the interference of coexisting elements in filtrate including palladium, copper, bismuth, gold and platinum could be ignored. The silver-palladium concentrate sample was determined according to the experimental method, and the relative standard deviations (RSD, n=11) were between 0.028% and 0.059%. High-purity silver nitrate was added for recovery test, and the recoveries were between 98% and 102%. The proposed method was applied for the determination of silver in silver-palladium concentrate sample, and the found results were basically consistent with those obtained by potassium iodide potentiometric titration.