Oxidation-reduction agent assisted adsorption of platinum group metals
Abstract
The oxidation-reduction agent assisted adsorption (ORA) of platinum group metals (PGMs) has been studied in this research to improve their recovery from dilute solutions. The ORA process can be divided into two steps: oxidation and adsorption. In the oxidation step, different oxidizing agents (e.g. hydrogen peroxide, potassium permanganate, potassium dichromate and chlorine) have been used to convert elemental PGM into soluble forms. The adsorption process involves the use of a special type of adsorbent, such as chelating resins and cation exchange resins, which have strong affinity to the metal ions. The PGM ions then can be selectively adsorbed by these resins, and the non-adsorbed substances can be removed from the solution to enrich the PGMs. This research demonstrates the ORA process for the recovery of palladium, platinum and rhodium from dilute solutions.
Keywords: Oxidation-reduction agent, Adsorption, Palladium, Platinum, Rhodium
1. Introduction
The platinum group metals (PGMs) is the collective name for elements belonging to the transition metals section in the periodic table, including Pt, Pd, Ir, Rh, Os and Au. These elements are widely used in various industries, especially in automotive catalytic converters and electronics. Their unique chemical and physical properties make them an ideal choice for applications requiring both durability and high-performance performance. At the same time, the difficulty in separating and concentrating PGMs has always been a challenge. Traditionally, their recovery from dilute solutions is very difficult, if not impossible.
Therefore, an efficient and economical method for recovering PGMs from dilute solutions is highly desired. In this research, an oxidation-reduction agent assisted adsorption (ORA) process is proposed to achieve the enrichment of PGMs from dilute solutions. This process has two major steps: oxidation and adsorption. Different oxidizing agents are used to convert elemental PGM into soluble forms, and then a special type of adsorbent is used to selectively retain the PGM ions from the solution.
2. Oxidation
The oxidation step of the ORA process involves the conversion of elemental PGM into soluble forms. Different oxidizing agents such as hydrogen peroxide, potassium permanganate, potassium dichromate and chlorine have been used for the purpose. For example, hydrogen peroxide can be used to oxidize elemental palladium into Pd(II). Likewise, potassium dichromate can be used to oxidize elemental platinum into Pt(IV). The oxidation reaction is typically carried out at elevated temperatures.
3. Adsorption
In the adsorption step, special type of adsorbents such as chelating resins and cation exchange resins are employed to selectively retain the PGM ions from the solution. These resins have strong affinity to the metal ions and can retain the PGM ions more efficiently than other compounds present in the solution. Furthermore, the non-adsorbed substances can be easily removed from the solution using various techniques such as filtration or centrifugation, thus enriching the PGM content of the solution.
4. Analysis
In order to analyze the efficiency of the ORA process, the recovery of PGM from dilute solutions was measured. Different oxidizing agents were tested and the results showed that hydrogen peroxide was the most effective in converting the PGM into soluble forms. The optimal conditions for the adsorption step were also determined and the results showed that cation exchange resins had better recovery efficiency than other adsorbents.
5. Conclusion
In conclusion, the oxidation-reduction agent assisted adsorption process can be an effective method for recovering Platinum Group Metals from dilute solutions. Different oxidizing agents can be used to convert PGM into soluble forms, and cation exchange resins have proven to be the best choice for the adsorption step. Further research is needed to optimize the process and further improve the efficiency.
