Synthesis of alkali metal platinates and their dissolution behavior in hydrochloric acid

Abstract

To decrease the environmental load due to current Pt dissolution processes that use strong acids in combination with oxidizing agents, the synthesis and dissolution of alkali metal platinates in hydrochloric acid (HCl) were examined. The alkali metal platinates were prepared by calcinating mixtures of Pt black and the alkali metal carbonates (Li, Na, K) at 600800°C in air. Li 2 PtO 3 powder was obtained through the calcination of a Pt black and Li 2 CO 3 mixture at 600°C. The formation of NaPt 3 O 4 and Na 2 PtO 3 was confirmed upon the calcination of Pt black and Na 2 CO 3 at 600800°C; however, unreacted Pt also remained in the calcined samples. The calcination of Pt black and K 2 CO 3 did not yield any Pt-containing oxides, even at 800°C. These results indicated that Li 2 CO 3 was the most active reagent among the examined alkali metal carbonates for the formation of alkali metal platinates. The dissolution of the resulting Li 2 PtO 3 in conc. HCl was monitored by inductively coupled plasmaoptical emission spectrometry. The results showed that Li ions leached into HCl prior to the Pt, and the solubilities of the metals increased with decreasing calcination temperature. The dissolution behavior of Li 2 PtO 3 was discussed based on the crystallite size and anisotropy of the crystal. A Pt dissolution process by way of these platinates is expected to benefit the establishment of recovery processes for PGMs with low environmental loads.

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Recovery of Platinum Group Metals from Spent Automotive Catalysts Using Lithium Salts and Hydrochloric Acid

“…Previously, to avoid the use and generation of toxic gases, we proposed a novel dissolution process for PGMs based on composite oxides [8][9][10][11][12][13]. This novel process enables the PGMs to be oxidized (ionized) through their calcination with alkali metal salts, thereby avoiding the requirement of highly toxic oxidizing agents in the dissolution process.…”