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铑、铱是铂族金属中最难分离的一对元素,一般都是放在其他金属基本分离后,再进行分离、提纯。早期,工业上铑、铱分离是基于用 H_2S 或 Na_2S 从亚硝基络合物溶液中沉出铑。后改用(NH_4)_2S。但过滤困难,不能达到有效分离。多数工厂采用的是 KHSO_4熔融,使铑转入溶液,然后用亚硝酸盐络合法精制,得99.9%的铑粉。含铱渣,碱熔转入溶液,用(NH_4)_2IrCl_6反复结晶、煅烧,制得99.9%的铱粉。溶液中的铑铱,通常是在氧化剂存在下,使(NH_4)_2IrCl_6沉淀与铑分离。这些方法的主要缺点是:过程冗长,操作复杂,劳动条件差,直收率低,试剂消耗大。
Rhodium, iridium is the most difficult separation of platinum group metals in a pair of elements, are generally placed on the other metal after the basic separation, and then separation, purification. In the early days, industrial rhodium and iridium separation was based on the precipitation of rhodium from nitroso complex solutions with H 2 S or Na 2 S. After the switch to (NH_4) _2S. However, filtration is difficult and can not achieve effective separation. Most factories use KHSO_4 melt, turn rhodium into solution, and then use nitrite complex refining, 99.9% rhodium powder. Containing iridium residue, the alkali melt into the solution, with (NH 4) _2IrCl_6 repeated crystallization, calcined to obtain 99.9% iridium powder. Rhodium iridium in solution, the (NH 4) _2IrCl_6 precipitate is separated from rhodium, usually in the presence of an oxidizing agent. The main drawbacks of these methods are: lengthy process, complex operation, poor working conditions, low direct yield and heavy reagent consumption.