Acids such as aqua regia, a 3:1 mixture of hydrochloric acid (HCl) and nitric acid, that contain strong oxidizing agents are used in the dissolution-based recovery of platinum group metals (PGMs). However, nitrate-nitrogen emission has become subject to increasingly strict environmental regulations in recent years. Accordingly, we herein propose a dissolution process for PGMs via the formation of complex oxides using HCl alone. We prepared complex oxides of alkali metals and rhodium (Rh), which is particularly hard to dissolve, and investigated their dissolution behaviors in HCl. Rh-containing complex oxides were prepared by calcining Rh powder and alkali metal salts in air, and dissolution tests using HCl were conducted on the complex oxides obtained. It was found that Rh-containing complex oxides were completely dissolved under appropriate calcination and dissolution conditions.

中文翻译：

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用碱金属盐法在盐酸中溶解铑

诸如王水、盐酸 (HCl) 和硝酸的 3:1 混合物等含有强氧化剂的酸可用于铂族金属 (PGM) 的溶解回收。然而，近年来，硝酸盐-氮排放已受到越来越严格的环境法规的约束。因此，我们在此提出了一种通过单独使用 HCl 形成复合氧化物来溶解 PGM 的方法。我们制备了特别难溶解的碱金属和铑 (Rh) 的复合氧化物，并研究了它们在 HCl 中的溶解行为。通过在空气中煅烧Rh粉末和碱金属盐制备含Rh复合氧化物，并用HCl对得到的复合氧化物进行溶解试验。