How to compare the cost-effectiveness of various precious metal refining processes?

Comparison of the cost-effectiveness of precious metal refining processes is a complex issue that requires comprehensive consideration of multiple factors. Different refining processes have their own advantages and disadvantages in terms of cost and benefit. The following will analyze several common precious metal refining processes in detail.

1. Wet leaching technology of precious metals in waste circuit boards

Cost: The wet treatment process of waste circuit boards is mature, with the advantages of short process and high efficiency. However, in the process of precious metal leaching, some chemical reagents such as thiourea and iodizing agents may need to be used, and the cost of these reagents needs to be considered. In addition, cost factors such as equipment investment and energy consumption need to be considered.

Benefit: It can effectively recover precious metals such as gold in waste circuit boards, which has considerable recycling value and environmental benefits. By reasonably selecting the leaching method, the leaching efficiency of precious metals can be improved, the environmental pollution in the disposal process can be reduced, and the efficient recovery of resources can be achieved.

2. Process for recovering precious metals from anode mud of scrap copper refining
   Cost: The process includes steps such as NaOH roasting, water leaching, and coordinated acid leaching, which consume certain chemical reagents and energy. At the same time, equipment investment and operation and maintenance costs also need to be considered. However, by optimizing process parameters, costs can be reduced.
   Benefit: It can efficiently remove base metals from anode mud of scrap copper refining and enrich precious metals at the same time. Under the preferred process conditions, the removal rates of Cu, Ni, Sb, Pb, Sn, As and S are high, while the retention rates and enrichment multiples of precious metals Ag, Au, and Pd are also high. In addition, valuable metals in the leachate can be recovered to improve the comprehensive utilization rate of resources.
3. Silver nitrate-based electrorefining process and methanesulfonic acid leaching method
   Cost: The traditional silver nitrate-based electrorefining process has some technical and ecological disadvantages. The methanesulfonic acid leaching method is expected to become an alternative process with its low environmental toxicity and highly water-soluble silver salt characteristics. The process needs to consider the cost of reagents such as methanesulfonic acid and hydrogen peroxide, as well as equipment investment and energy consumption in laboratory-scale stirred leaching experiments.
   Benefits: At elevated temperatures (65°C or 80°C), solid concentrations of 500g/L and a stoichiometric ratio of H₂O₂:Ag = 3:1, the leaching rate of silver can exceed 90%. At the same time, the process has a high selectivity for the leaching of Pd, which can improve the recovery efficiency of precious metals.
4. Kell hydrometallurgical extraction process
   Cost: The Kell process is a hydrometallurgical treatment method for recovering platinum group metals, gold, silver and base metals from flotation concentrates. Compared with traditional smelting and refining processes, the Kell process has capital expenditures of 18% – 33% of smelting, operating costs of 51% – 66%, and electricity consumption of 13% – 46%.
   Benefits: The process has high extraction efficiency (extraction efficiency of valuable metals and minor metals is greater than 95%), is cyanide-free, reduces the emission of toxic substances such as sulfur dioxide and arsenic trioxide, and has significant environmental benefits. In addition, it can work in conjunction with smelters to utilize recycled acid and excess capacity of precious metal refineries.

V. Nickel Refining Process
Cost: The traditional nickel sulfide soluble anode electrolytic refining process has some key technical difficulties. The new nickel refining processes such as sulfuric acid leaching extraction separation electrolytic refining, concentration crystallization, chlorination leaching extraction purification electrolytic refining and carbonyl refining have different costs. The carbonyl refining process has the advantages of the shortest process flow, the easiest to automate, and the most environmentally friendly, but its equipment investment and technical requirements may be high.
Benefits: The carbonyl refining process has the advantages of the highest selectivity and significant energy saving and consumption reduction, and is the top priority direction for the improvement of nickel refining processes of large nickel refining enterprises. Other new nickel refining processes have also improved the refining efficiency and resource utilization of nickel to varying degrees.

VI. Process for recovering refined iridium from titanium anode stripping material
Cost: This process recovers precious metal iridium from titanium anode stripping material dissolution solution through oxidation precipitation, reduction dissolution and other steps. The cost of reagents such as ammonium chloride, as well as equipment investment and energy consumption during operation, need to be considered.
Benefit: When the redox potential is greater than 900mV and the amount of ammonium chloride is more than 1 times that of iridium, the precipitation rate of iridium is greater than 98%. When the reduction pH value is 3, a small amount of platinum, palladium, rhodium and ruthenium impurities in iridium can be well separated. This method is suitable for the treatment of iridium-containing waste with iridium as the main body and low content of precious metal impurities. It is easy to operate and the product purity can meet the national standard requirements.
In summary, different precious metal refining processes differ in cost-effectiveness. When comparing cost-effectiveness, it is necessary to comprehensively consider multiple factors such as reagent cost, equipment investment, energy consumption, extraction efficiency, and environmental impact. At the same time, with the continuous advancement of technology, new refining processes are constantly emerging, and more efficient, environmentally friendly and economical precious metal refining processes may appear in the future.