Recently, the project led by Nanchang University, which integrates efficient and green development of ion adsorption rare earth resources with ecological restoration technology, passed the comprehensive performance evaluation with high scores. The successful development of this innovative mining technology has achieved significant results in improving rare earth recovery rate and efficient green mining, or explored a new path for the efficient and green utilization of rare earth resources in China.
Extracting leaching reagents from solid waste and recycling them
Ion adsorption rare earth is a unique resource in China. However, the existing ion adsorption rare earth mining technology restricts the mining and utilization of ion adsorption rare earth resources in China. In this context, it is urgent to develop a new generation of efficient and green mining technologies. The integrated technology of efficient and green development and ecological restoration of ion adsorbed rare earth resources has emerged. Its synergistic coupling, aluminum magnesium cycling, waste conversion, and efficient and green characteristics provide new ideas for the development of ion adsorbed rare earth resources.
The development of ion adsorbed rare earths has a history of over forty years, and how to innovate and improve the development technology of ion adsorbed rare earths has always been a challenge for rare earth researchers. In early October, the reporter met with Professor Li Yongxiu from the School of Chemistry and Chemical Engineering at Nanchang University. In his office, a “distribution map of rare earths in China” is impressive. Li Yongxiu said that the scientific research units, technologies, and talents on the distribution map are connected like a network, with countless connections between each other.
The integrated technology project of efficient green development and ecological restoration of ion adsorption type rare earth resources was led by Nanchang University, jointly developed by Jiangxi University of Technology, Changchun Institute of Applied Chemistry of Chinese Academy of Sciences and other ten units, with Li Yongxiu as the project leader.
For many years, the ammonia nitrogen pollution caused by ammonium sulfate leaching and the soil erosion caused by in-situ leaching have seriously affected the environment of mining areas. Although the recently launched leaching processes of calcium magnesium chloride and magnesium sulfate can solve the problem of ammonia nitrogen pollution, the leaching efficiency is insufficient, and the actual consumption of mines is higher, especially the eutrophication of water caused by magnesium sulfate is also very serious.
Therefore, we have developed an efficient green leaching process and material recycling technology using aluminum salts as a new generation leaching reagent. “Li Yongxiu explained that this technology first breaks through traditional mechanism understanding, shifting from a simple ion exchange theory to a leaching mechanism that is jointly constrained by ion hydration and anion coordination adsorption in a double layer mode.
Unlike in the past, we have chosen an efficient leaching system and process method using aluminum salts as the new generation leaching reagent, “said Li Yongxiu. These systems and methods include a synergistic leaching system of aluminum salts and low-priced inorganic salts, a staged leaching process of calcium magnesium salts and aluminum salts, and a staged leaching process of citrate and low concentration inorganic salts.
It is worth noting that the aluminum salts and calcium magnesium salts mentioned above are extracted and recycled from the waste residue wastewater of mining production. To this end, the team has developed a new enrichment and separation technology that can achieve the separation and recycling of rare earth ions from aluminum and other coexisting ions, coupled with precipitation, extraction, and membrane separation technologies. We convert solid waste from hydrolyzed aluminum slag into efficient leaching reagents for mining production, achieving the recycling of pollutants and significantly reducing reagent consumption and pollutant production. “Li Yongxiu said that with innovative separation technology, the once tangled rare earth and aluminum can also be treated like guests.
In this way, the aluminum content of rare earths can be controlled below one thousandth, laying the foundation for achieving high-purity rare earth separation and clean production without radioactive waste residue.
The integration of “mining leaching repair” adds green to rare earth mining
From Nanchang to Ganzhou, from rare earth mines to rare earth smelting and separation enterprises… Li Yongxiu can no longer remember the number of times she has traveled. There are too many trips back and forth in a year, I don’t know how many. With a love for the rare earth industry, Li Yongxiu led his team to constantly try and innovate on the innovative path of helping the high-quality development of the rare earth industry.
The implementation of the national “dual carbon” goal has put forward new requirements for improving the ecological environment and preventing environmental pollution, while also bringing new opportunities to the rare earth industry.
How to achieve greenery in the rare earth production process and the integration of “mining leaching repair” is another innovative point.
The core of this innovation is to use seepage prediction and control methods to couple exploration and leaching technology, as well as leaching and ecological restoration, to achieve this. “Li Yongxiu said that the significant feature of ion adsorption type deposits is their non-uniformity. Therefore, in-situ leaching mining technology lacking data on rare earth distribution and geological and hydrological conditions is not feasible. To this end, the research team will leverage the professional advantages of Jiangxi University of Technology, Nanchang University, and Wuhan University in seepage prediction and process control.
The green extraction process of ion adsorption type rare earth ore should not only comprehensively consider mining efficiency, environmental impact, product quality, and production cost, but also fully combine the geological structure of the mine, leaching solution seepage, and ecological restoration technology to optimize engineering design. “Li Yongxiu explained that in order to avoid unorganized loss of leaching solution and achieve the integration of mining, leaching, and repair.
In terms of ore leaching methods, we advocate to determine whether to adopt in-situ leaching or heap leaching based on production exploration data, or an organic combination of the two methods. “Li Yongxiu said that in terms of heap leaching technology, the research team has developed a controllable heap leaching technology characterized by growing piles to replace the previous extensive large-scale heap leaching method of simultaneous leaching. This is conducive to achieving the integration of mining, leaching, and repair, eliminating soil erosion and landslide collapse during the leaching process and subsequent tailings.
Li Yongxiu told reporters that the project focuses on key issues such as low resource recovery rate and significant environmental impact in the ion type rare earth extraction process. The basic and technical research and development work for efficient and green ion adsorption type rare earth extraction has been systematically carried out, and a series of innovative achievements have been achieved.
Technological innovation and progress will continue to ‘add green’ to the development of China’s rare earth industry, “said Li Yongxiu. The project has made new breakthroughs in basic theory, technological development, application demonstration, and other major aspects. Its large-scale promotion and application will greatly promote the scientific development and efficient application of global medium and heavy rare earth resources, and promote the high-quality development of the rare earth industry．