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镍—铁基合金中含有大量铁、铝、镍、铬和钛等干扰元素。因此用比色法测定其中微量稀土元素时,一般均需事先除去共存的干扰元素。对于微量稀土元素的分离,目前广泛采用 PMBP溶剂萃取法及氟化物、铜试剂、氟化物-铜试剂,氢氧化物等沉淀分离法。氟化物沉淀法的选择性较高,但氟化物沉淀不易过滤和洗涤,并需要聚乙烯器皿进行操作,故实际应用时很不方便。铜试剂沉淀分离法简便,已为一些生产单位所采用。但我们认为当沉淀分离大量干扰元素时,微量的稀土元素难免由于共沉淀现象而造成损失,使分析结果偏低。至于氟化物-铜试剂沉淀法,由于采用两次沉淀分离,操作过于麻烦。氢氧化物沉淀法的选择性差,通常只用来分离碱金属和碱土金属。但它具有操作简便,适于大批操作及工作环境较好等优点。所以只要能选择适当的掩蔽剂,提高其选择性,就能很好地满足生产上的要求。
Nickel - iron-based alloys contain a lot of iron, aluminum, nickel, chromium and titanium interference elements. Therefore, the colorimetric determination of trace rare earth elements, the general need to remove co-existence of interference elements in advance. For the separation of trace rare earth elements, PMBP solvent extraction and fluoride precipitation, copper reagent, fluoride-copper reagent, hydroxide and other precipitation methods are widely used. Fluoride precipitation method of higher selectivity, but the fluoride precipitation is not easy to filter and wash, and the need for polyethylene containers for operation, so the practical application is not convenient. Copper reagent precipitation separation method is simple, has been used for some production units. However, we believe that when a large number of interfering elements are precipitated and separated, trace amounts of rare earth elements are inevitably lost due to coprecipitation, resulting in low analytical results. As for the fluoride-copper reagent precipitation method, the operation was too troublesome due to the use of two precipitation separations. The selectivity of the hydroxide precipitation method is poor and is usually only used to separate alkali and alkaline earth metals. But it has the advantages of easy operation, suitable for a large number of operations and better working environment. So long as can choose the appropriate masking agent, improve its selectivity, can well meet the production requirements.