Development of Rare Earth Hydrometallurgy Technology in China

In this paper, the recent advance of processes for treating Baotou mixed-type rare earths concentrate, bastnasite, and ionic adsorption deposit in China was reviewed. The R & D circumstance and new progresses in separation and purification of individual and high purity RE compounds in China were introduced. Moreover, the development of RE hydrometallurgy was also predicted. So we suggest to enhance the research and development of products applying RE, especially Ce, Y, Gd, Sm etc., for keeping RE consumption equilibrium and extending applications, to increase enterprise's automatic control level for improving the stability and the consistency of the products, and to pay more attention to protection of environment.

EXPERT OPTIMIZED CONTROL TECHNIQUE FOR ELECTROLYTIC DEPOSITION PROCESS OF HYDROMETALLURGY OF ZINC

ＥＸＰＥＲＴＯＰＴＩＭＩＺＥＤＣＯＮＴＲＯＬＴＥＣＨＮＩＱＵＥＦＯＲＥＬＥＣＴＲＯＬＹＴＩＣＤＥＰＯＳＩＴＩＯＮＰＲＯＣＥＳＳＯＦＨＹＤＲＯＭＥＴＡＬＬＵＲＧＹＯＦＺＩＮＣ①ＹａｎｇＣｈｕｎｈｕａ，ＧｕｉＷｅｉｈｕａ，ＹｅＷｅｎｗｕＩｎｆｏｒｍａｔｉ...

Modeling, Optimization, and Control of Solution Purification Process in Zinc Hydrometallurgy

The solution purification process is an essential step in zinc hydrometallurgy. The performance of solution purification directly affects the normal functioning and economical benefits of zinc hydrometallurgy. This paper summarizes the authors' recent work on the modeling, optimization, and control of solution purification process. The online measurable property of the oxidation reduction potential(ORP) and the multiple reactors, multiple running statuses characteristic of the solution purification process are extensively utilized in this research. The absence of reliable online equipment for detecting the impurity ion concentration is circumvented by introducing the oxidationreduction potential into the kinetic model. A steady-state multiple reactors gradient optimization, unsteady-state operationalpattern adjustment strategy, and a process evaluation strategy based on the oxidation-reduction potential are proposed. The effectiveness of the proposed research is demonstrated by its industrial experiment.

Development Status and Research Progress in Rare Earth Hydrometallurgy in China

Characteristic and hydrometallurgy processes for Baotou mixed-type rare earth concentrate, bastnasite, and ionic adsorption deposit in China were reviewed. The R ＆ D circumstance and new progresses in extraction and separation of RE element in China were introduced. Moreover, the development trend of RE hydrometallurgy was predicted. The direction and emphasised fields of research and development are also brought forward as： to R ＆ D high efficient green progresses in hydrometallurgy and separation of RE ore, resolve the waste pollution problem of water, slagand gas, reduce the chemical material consumption and improve comprehensive efficiency of resources; to R ＆ D preparation technology for RE compounds with ultra high-purity and special physical property for extending application fields of RE.

Chalcocite(bio)hydrometallurgy-current state,mechanism,and future directions:A review

There has been a strong interest in technologies suited for mining and processing of low-grade ores because of the rapid depletion of mineral resources in the world.In most cases,the extraction of copper from such raw materials is achieved by applying the leaching procedures.However,its low extraction efficiency and the long extraction period limit its large-scale commercial applications in copper recovery,even though bioleaching has been widely employed commercially for heap and dump bioleaching of secondary copper sulfide ores.Overcoming the technical challenges requires a better understanding of leaching kinetics and on-site microbial activities.Herein,this paper reviews the current status of main commercial biomining operations around the world,identifies factors that affect chalcocite dissolution both in chemical leaching and bioleaching,summarizes the related kinetic research,and concludes with a discussion of two on-site chalcocite heap leaching practices.Further,the challenges and innovations for the future development of chalcocite hydrometallurgy are presented in the end.

Expert fault diagnosis system for leaching process in zinc hydrometallurgy

Leaching process is the first step in zinc hydrometallurgy, which involves the complex chemical reactions for dissolving zinc bearing material in dilute sulfuric acid. Ensuring the safe running of the process is a key point in the operation. An expert fault diagnosis system for the leaching process was proposed, which has been implemented in a nonferrous metals smeltery. The system architecture and the diagnosis procedure were presented, and the rule models with the certainty factor were constructed based on the empirical knowledge, empirical data and statistical results on past fault countermeasures, and an expert reasoning strategy was proposed which employs the rule models and Beyes presentation and combines forward chaining and backward chaining. [

Study on Extracting Low Concentration Cadmium from Zinc Hydrometallurgy System by Liquid Membrane Crystallizing Technique

The extraction of low concentration cadmium from a system containing high concentration zinc was studied and got CdS product directly. A new liquid membrane system taking DIPSA, TIBPS as carriers, (NH 4) 2S as precipitating agent was reported. Precipitating Cd 2+ in the internal aq. phase that is used to treat sulfuric acid leaching solution of zinc oxide in zinc hydrometallurgy has gotten satisfied results of extracting cadmium from high concentration zinc. After one stage of batch process under the optimum liquid membrane conditions, 98.6% transferring rate and 98.1% extracting rate of cadmium was obtained with only less than 1.0% transferring rate of zinc, and the feed solution can be purified very well.

Recovery of Gallium from Zinc Hydrometallurgy System by Emulsion Liquid Membrane

The investigation of recovery Ga 3+ by emulsion liquid membrane (ELM) using Tri alkyl oxide phosphine (TRPO) as the mobile carrier was reported. The optimum emulsion liquid membrane conditions were determinated. They were: the feed pH 1.0, organic phase consisting of 5% TRPO, 4% LMS 2 and 2% liquid paraffin in kerosene solution, 10% K 4[Fe(CN) 6] aq. solution as the stripping agent, R oi =2∶1, R ew =1∶5. At the optimum ELM operating condition, the recovery rate of gallium was 96.5%, and the oil phase can be reused for 5 times.

MA RONG JUN—AN EXPERT IN HYDROMETALLURGY AND ENVIRONMENT ENGINEERING

Professor Ma Rongjun was bron in 1931 at Dacheng County of Hebei Province. He graduated from Northeast University of Technology in 1955 and studied as a postgraduate at Kosice

Comprehensive Recycling Technology of Waste Residues in Zinc Hydrometallurgy

In order to improve the refining effect of zinc ore and promote the development of this industry,taking the hydrometallurgical zinc smelting process as an example,this paper first establishes a model for the recycling of waste residues in the hydrometallurgical process,proposes optimization measures based on proven comprehensive recycling technology for purifying residues to obtain higher valuable metal recovery rate,and provides reference for those in relevant fields.

Recovery of platinum from spent automotive catalyst based on hydrometallurgy

Platinum(Pt)is a critical raw material for automotive catalytic converters due to its high-temperature stability,corrosion resistance and catalytic activity,whereas its limited primary resources and uneven distribution make it hard to meet the growing demand of platinum.Spent automotive catalyst(SAC)is currently the most important secondary resource of platinum,of which the platinum content is much higher than that of the primary platinum resources.The recovery process of platinum from spent automobile catalyst mainly consists of pretreatment followed by enrichment and refining,involving pyro-and hydrometallurgical techniques,among which enrichment and refining processes are extremely important for platinum recovery from spent automobile catalyst.This paper provides an overview of the technologies for platinum recovery from spent automotive catalyst.The emphasis is placed on the processes of enrichment and refining based on hydrometallurgical techniques.Future directions of research and development of platinum recovery from spent automobile catalyst are also proposed.

Technology development for rare earth cleaner hydrometallurgy in China

China is the global leader in rare earth （RE） production using hydrometallurgical processes. Advantageous extraction techniques of rare earths from Baotou mixed rare earth minerals, bastnaesite, and ion-adsorption clays of rare earth deposits have been developed in China. The separation and purification technologies have also achieved rapid development. The industrial application processes for rare earth hydrometallurgy were summarized in the present paper. With the large demands and rapid development of rare earths, the issues of resources and environment are more prominent. This review gives an overview of the main processes that were developed in the past toward greener hydrometallurgy of rare earths in China. Based on the development of the rare earth industry, comprehensive utilization and cleaner production should still be focused on in the future, to support the sustainable development.

Process modeling issues arising in zinc hydrometallurgy

As typical nonferrous metallurgical processes,hydrometallurgical processes are used extensively to recover elemental zinc from raw ores.Accurate system models must be established to increase automation of hydrometallurgical zinc processes with strict energy and environmental requirements.However,the modeling of such processes is hindered by their complex production characteristics and process mechanisms.In this review,we summarize some process modeling issues arising in zinc hydrometallurgy and provide several possible solutions from the perspective of our research work.

A critical review on the recycling of copper and precious metals from waste printed circuit boards using hydrometallurgy

Currently, increasing amounts of end-of-life （EoL） electronic products are being generated due to their reduced life spans and the unavailability of suitable recycling technologies. In particular, waste printed circuit boards （PCBs） have become of global concern with regard to environmental issues because of their high metal and toxic material contents, which are pollutants. There are many environmental threats owed to the disposal of electronic waste; off-gasses, such as dioxins, furans, polybrominated organic pollutants, and polycyclic aromatic hydrocarbons, can be generated during thermal treatments. which can cause serious health problems if effective off=gas cleaning systems are not developed and improved. Moreover, heavy metals will dissolve, and release into the ground water from the landfill sites. Such waste PCBs contain precious metals which are of monetary value. Therefore, it is beneficial to recover the metal content and protect the environment from pollution. Hydrometallurgy is a successful technique used worldwide for the recovery of precious metals （especially gold and silver） from ores, concentrates, and waste materials. It is generally preferred over other methods because it can offer high recovery rates at a relatively low cost. This article reviews the recent trends and developments with regard to the recycling of precious metals from waste PCBs through hydrometallurgical techniques, such as leaching and recovery.

Centrifugal extraction of rare earths from wet-process phosphoric acid

Phosphorite ore is a potential resource of rare earths （RE） as well as phosphate; therefore, the recovery of RE from wet-process phosphoric acid （WPA） is promising. This study investigated the influence of rotational speed, extractant concentration, flow ratio and phase contact time on the centrifugal extraction of RE from WPA and the separation of RE from impurities. The results indicate that higher rotational speed, higher extractant concentration and larger flow ratio are beneficial to the extraction of RE and impurities from phosphoric acid. It is found that the phase contact time for efficiently extracting RE and that for iron are of great difference, which provides an effective method for separating RE from iron using the non-equilibrium extraction process in centrifugal contactors. Compared with equilibrium extraction, the separation factor βRE/Fe is enhanced from 0.07 to 17.6.

Investigation on microwave heating for direct leaching of chalcopyrite ores and concentrates

The use of microwave energy in materials processing is a relatively new development presenting numerous ad- vantages because of the rapid heating feature. Microwave technology has great potential to improve the extraction efficiency of metals in terms of both a reduction in required leaching time and an increase in the recovery of valuable metals. This method is especially pertinent in view of the increased demand for environment-friendly processes. In the present study, the influence of microwave heating on the direct leaching of chalcopyrite ores and concentrates were investigated. The results of microwave leaching experiments were compared with those obtained under conventional conditions. During these processes, parameters such as leaching media, temperature, and time have been worked to determine the optimum conditions for proper copper dissolution. Experimental results show that microwave leaching is more efficient than conventional leaching. The optimum leaching conditions for microwave leaching are the solid-to-liquid ratio of 1：100 g/mL, the temperature of 140℃, the solution of 0.5 M H2SOa- 0.05 M Fe：（SOa）a, and the time of I h.

Extraction and separation of nickel and cobalt from saprolite laterite ore by microwave-assisted hydrothermal leaching and chemical deposition

Extraction and separation of nickel and cobalt from saprolite laterite ore were studied by using a method of microwave-assisted hydrothermal leaching and chemical deposition. The effects of leaching temperature and time on the extraction efficiencies of Ni2＋ and Co2＋ were investigated in detail under microwave conditions. It is shown that the extraction efficiencies of Ni2＋ and Co2＋ from the ore pre-roasted at 300℃ for 5 h were 89.19% and 61.89% when the leaching temperature and time were about 70℃ and 60 min, respectively. For the separation process of Ni and Co, the separation of main chemical components was performed by adjusting the pH values of sulfuric leaching solutions using a NaOH solution based on the different pH values of precipitation for metal hydroxides. The final separation efficiencies of Ni and Co were 77.29% and 65.87%, respectively. Furthermore, the separation efficiencies of Fe of 95.36% and Mg of 92.2% were also achieved at the same time.

Recycling of mixed cathode lithium-ion batteries for electric vehicles: Current status and future outlook

Worldwide trends in mobile electrification,largely driven by the popularity of electric vehicles(EVs)will skyrocket demands for lithium-ion battery(LIB)production.As such,up to four million metric tons of LIB waste from EV battery packs could be generated from 2015 to 2040.LIB recycling directly addresses concerns over longterm economic strains due to the uneven geographic distribution of resources(especially for Co and Li)and environmental issues associated with both landfilling and raw material extraction.However,LIB recycling infrastructure has not been widely adopted,and current facilities are mostly focused on Co recovery for economic gains.This incentive will decline due to shifting market trends from LiCoO2 toward cobalt-deficient and mixed-metal cathodes(eg,LiNi1/3Mn1/3Co1/3O2).Thus,this review covers recycling strategies to recover metals in mixed-metal LIB cathodes and comingled scrap comprising different chemistries.As such,hydrometallurgical processes can meet this criterion,while also requiring a low environmental footprint and energy consumption compared to pyrometallurgy.Following pretreatment to separate the cathode from other battery components,the active material is dissolved entirely by reductive acid leaching.A complex leachate is generated,comprising cathode metals(Li+,Ni2+,Mn2+,and Co2+)and impurities(Fe3+,Al3+,and Cu2+)from the current collectors and battery casing,which can be separated and purified using a series of selective precipitation and/or solvent extraction steps.Alternatively,the cathode can be resynthesized directly from the leachate.

Sustainable recycling of titanium from TiO_(2) in spent SCR denitration catalyst via molten salt electrolysis

Spent catalyst used for denitration by selective catalytic reduction(spent SCR denitration catalysts) is one of the important urban mines due to the high content of TiO_(2)(~85 wt%) and the massive accumulation amount(over 100,000 tons),therefore,value-added reutilization of titanium in spent SCR catalysts is considerably meaningful.In this paper,a novel method is proposed for converting the titanium oxide in spent SCR denitration catalysts to metallic titanium.Specifically,titanium dioxide(TiO_(2)) was firstly obtained from spent SCR denitration catalysts after removing the impurities by hydrometallurgy process.Then,TiO_(2) is converted to Ti_(2)CO by carbothermic reduction method,and Ti_(2)CO was further purified by oleic acid capture.Finally,by utilizing the as-prepared Ti_(2)CO as the consumable anode in the NaCl-KCl molten salt,high-purity metallic titanium was deposited at cathode,all confirming the feasibility for the conversion of low-grade TiO_(2) in the spent catalysts,from 60 wt% to high-purity metallic Ti(99.5 wt%), furthermore,the energy consumption of this process is 3950 kWh tonne-1 Ti,which is lower than that of most traditional titanium metallurgy methods.The method herein can provide new insights for the value-added recycling of titanium resources in urban mines.