A study of Palladium-Tin Slag Enrichment via Acid Leaching
Abstract
The aim of this research project was to study the ability of acid leaching to enrich palladium-tin slag. The slag was submitted to a laboratory-scale acid leaching process, involving varying parameters such as pH, temperature, and time, in order to optimize enrichment yields. The results showed that the acid leaching process yielded higher enrichment recoveries than traditional smelting processes.
Introduction
Acid leaching has been shown to be a viable processing option for the extraction of valuable metals from low-grade ores, concentrates, and slags. Acid leaching is a selective process that involves the dissolution of a target metal from the host material by means of an aqueous solution of an acid or chelating agent. It is capable of selectively extracting certain metals from a given host material without the contamination of any other metals. Acid leaching can be used to increase metal recoveries in slag, for instance, by enriching the metal content of the slag, thereby increasing its economic value. This study provides an overview of the use of acid leaching to increase the economic profitability of palladium-tin slag through metal enrichment.
Materials and Methods
The slag studied in this investigation was collected from a commercial ore refinery and was composed mainly of tin, palladium, copper, and iron. The slag was prepared and sieved to a particle size of -100/+105 μm and stored in a sealed container to prevent further oxidation.
A laboratory-scale acid leaching process was used to investigate the enrichment of the palladium-tin slag. The setup was comprised of a reaction vessel, a pH meter, and a stirring device. The reaction vessel was filled with a solution of 2.0 M HCl and 100 g of slag, and the pH was adjusted to between 2.0 and 3.0. The temperature was increased gradually from 25°C to 80°C and maintained for a period of 60 minutes. The stirring speed was adjusted to 350 rpm.
The leachate was analyzed after each experiment to determine metal enrichment yields. The metal concentrations were measured using an atomic absorption spectrophotometer (AAS) and compared to the concentrations measured in the feed sample.
Results and Discussion
The results of the acid leaching experiments are presented in Table 1. The results show that the leaching process was able to increase both the tin and palladium enrichment yields significantly with respect to the feed. The highest enrichment recovery was obtained at a temperature of 80°C, where the tin and palladium recoveries were 99.6% and 99.5%, respectively. The highest recoveries of both metals were obtained at a pH of 2.5.
Table 1: Enrichment Recovery of Tin and Palladium with Acid Leaching
pH
2.0
2.5
3.0
Tin Recovery (%)
98.2
99.6
97.3
Palladium Recovery (%)
96.2
99.5
95.4
Conclusions
This study has demonstrated the ability of an acid leaching process to selectively extract tin and palladium from a palladium-tin slag. The process was able to attain higher enrichment yields for these metals than those that would be achievable by traditional smelting processes. The highest enrichment recoveries were obtained at a pH of 2.5 and a temperature of 80°C. Further investigation of parameters such as pH, temperature, and leaching time would be useful to determine the optimal leaching procedure.
