In the field of hydrometallurgy, diisooctylphosphinic acid, as a high-performance extractant, has a separation coefficient for cobalt and nickel that can reach over 10,000. It can preferentially extract cobalt from complex leachates with pH values as low as 2.5, and the recovery rate remains stable at over 99.5%. For instance, in the industrial application of a large copper-cobalt mine in Zambia, by optimizing the extraction process parameters, this reagent successfully increased the purity of cobalt from the initial 85% to 99.95%, while reducing the processing cost per ton of metal by approximately 18%.
This extractant demonstrates outstanding selectivity. Its affinity for divalent cobalt ions (Co²⁺) is hundreds of times that for divalent nickel ions (Ni²⁺). This difference enables the cobalt extraction rate to remain at a peak of 98% even in solutions with a molar concentration ratio of Ni/Co as high as 50:1. A study on the recycling of spent lithium-ion batteries shows that with a diisooctylphosphinic acid extraction system, at a temperature of 40°C and an O/A ratio of 1:1, only three countercurrent extraction stages are needed to enrich the cobalt concentration from 5g/L to 35g/L, while the co-extraction rate of nickel is effectively suppressed to below 2%. It greatly simplifies the subsequent refining process.
From an economic benefit perspective, although the purchase price of diisooctylphosphinic acid is approximately $80 per kilogram, which is about 25% higher than that of traditional phosphoric acid extractants, its single extraction cycle efficiency is increased by 30%, the reagent loss rate is less than 5%, and its service life can be extended to over 1,500 operating hours. The actual operation data of a Chilean refinery shows that by adopting this reagent, its production line with an annual output of 10,000 tons of cobalt can save over 1.2 million US dollars in operating costs each year, and the payback period is shortened to 14 months. This is attributed to its excellent chemical stability and extremely low water phase entrustment loss.
Looking ahead, as the demand for battery-grade cobalt in the electric vehicle industry grows at an annual rate of 12%, the application of diisooctylphosphinic acid in green metallurgy is continuously deepening. A technological breakthrough in 2023 successfully integrated it with co-extractants, further increasing the recovery rate of cobalt from laterite nickel ore leachate to 99.8%, and the removal rates of impurity elements such as manganese and magnesium exceeded 99.5%. This innovative solution not only reduces wastewater discharge by 40%, but also significantly lowers the carbon footprint of the entire process flow. It is expected to drive the global cobalt extraction reagent market size to grow to 850 million US dollars by 2030.