Abstract
Recently, an emerging electrodeposition-redox replacement (EDRR) method was demonstrated to provide exceptionally efficient gold recovery from cyanide-free hydrometallurgical solutions. However, the effect of electrode material and its corrosion resistance in this process was overlooked, even though the EDRR process is carried out in extremely corrosive, acidic chloride solution that also contains significant amounts of strong oxidants, i.e., cupric ions. In the current study, nickel alloy C-2000, stainless steels 316L and 654SMO, and grade 2 titanium were for the first time critically evaluated as potential cathode materials for EDRR. The particular emphasis was placed on better understanding of the effect of cathode substrate on the overall efficiency of the gold recovery process. The use of a multiple attribute decision-making method of material selection allowed reaching of a well-founded compromise between the corrosion properties of the electrodes and process efficiency of gold extraction. The 654SMO steel demonstrated outstanding performance among the examined materials, as it enabled gold recovery of 28.1 pct after 3000 EDRR cycles, while its corrosion rate (CR) was only 0.02 mm/year.
Highlights
THE recent innovation of electrodeposition-redox replacement (EDRR)[1,2,3,4,5,6] shows potential as a new method for the recovery of metals from hydrometallurgical solutions where their concentration is extremely low, i.e., at parts per billion to parts per million scale
The present study focuses on identifying the material of choice for the permanent cathode blanks to be used in the EDRR process
The results showed that the 654SMO stainless steel is the optimum cathode material for the EDRR from both corrosion resistance and gold recovery perspectives, while the 316L steel did not withstand corrosion in the process solution and was not capable of recovering gold on the cathode
Summary
THE recent innovation of electrodeposition-redox replacement (EDRR)[1,2,3,4,5,6] shows potential as a new method for the recovery of (precious) metals from hydrometallurgical solutions where their concentration is extremely low, i.e., at parts per billion to parts per million scale. Over the decades of research, a number of methods were developed to ensure that the material selected suits the needs of the process design, maximizing its performance and minimizing its cost.[23,24,25] Among these methods, the most popular are the analytical hierarchy process (AHP),[26,27] the multicriteria optimization and compromise solution (VIKOR),[28,29] the technique for order performance by similarity to ideal solution (TOPSIS),[30,31] or combinations of multiple decision making methods.[32,33] In the current study, a hybrid approach merging the AHP and TOPSIS, as described by Rao and Davim,[34] was used to rank the alternatives and make the conclusive decision on material selection This method employs the AHP to determine in a systematic way the individual weights of each attribute and the TOPSIS technique to rank the alternative materials in order of preference. The results showed that the 654SMO stainless steel is the optimum cathode material for the EDRR from both corrosion resistance and gold recovery perspectives, while the 316L steel did not withstand corrosion in the process solution and was not capable of recovering gold on the cathode
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