Technical Field

The invention relates to a method for obtaining Zn and Pb metals from Zn-Pb ores.

In particular the invention relates to a new method for obtaining Zn and Pb metals from Zn-Pb ores which is using non-aqueous solvents such as molecular organic solvents, ionic liquids, and deep eutectic solvents instead of aqueous solutions and which provides less energy consumption advantages compared to the pyrometallurgy method and higher selectivity advantages compared to the hydrometallurgy method.

Background of the Invention

Zn-Pb ores are found in nature in oxidized, sulphurous and oxidized+sulphurous mineral forms. The production of zinc and lead metals is carried out using pyrometallurgical, hydrometallurgical and pyrometallurgical+hydrometallurgical methods that differ according to the grade values of the ore.

Current applications for the obtaining Zn and Pb metals from Zn-Pb ores are generally using techniques that include metallurgical pretreatments such as roasting, known as calcination followed by flotation and heating the ore in the presence of excess air or oxygen, high temperature melting processes, leaching using hydrometallurgical methods, and electrowinning processes, being carried out.

Flotation process is an enrichment method that uses the water-loving and waterhating properties of the ore to be produced, creating bubbles in the liquid, and separating it from other materials by floating or sinking in water. It is generally used in the separation of sulfide ores. Flotation is one of the enrichment methods of copper, lead and zinc ores in the world. The calcination process is the process of breaking down carbonates and hydrates with the effect of heat in order to obtain oxide components. It is a method in which a solid chemical compound is raised to a high temperature without melting under a limited supply of ambient oxygen, generally to remove impurities or volatiles and/or to cause thermal degradation.

The fact that Zn-Pb ores are fine-grained by nature and additionally grinding the ores to obtain ultra-fine grains in order to liberate the minerals sufficiently makes the flotation process difficult. In addition, complex flotation circuits are required from production facilities.

Another problem experienced is that the use of high amounts of reagents in the flotation method increases the production cost. The separate acquisition of metals by different production techniques sends zinc during lead production and lead to waste during zinc production.

For the reasons mentioned, most of the existing techniques have low lead and zinc recoveries, high capital investment, and it is very difficult for small enterprises to use all of these techniques to produce lead and zinc metals.

Heavy metal-containing wastes released in the smelting process known as the process of separating the metal content of the ore from the rest of the ore with the help of a high-temperature reduction reaction, and SO2/CO2 gases released in the roasting/calcination processes harm the environment.

Considering the environmental and economic disadvantages of the extraction of zinc and lead metal from these ores by existing methods, it is very important to eliminate the flotation, roasting/calcination and smelting processes in such systems.

In the PCT application numbered WO2019153098A1 in the literature, “he invention, corresponding to IPC symbol B03D1/02, relates to the design of a flotation system for ultra fine particles, with a system for dissolving air in water to generate micro bubbles with a surface area greater than that obtained in conventional aeration systems for ore flotation. The increased surface area increases the probability of collision between ultra fine particles and micro bubbles, generating a particle-bubble aggregate able to rise to the surface of the liquid and be removed as a concentrate. The main field of application is flotation in metallurgical processes for the extraction of valuable minerals. In general, the majority of the industries focus on copper extraction. However, internationally, processes for the flotation of Zn, Ni, Pb and Mo, inter alia, have been developed, which all have problems with the presence of ultra fine material. The ore concentration process begins with reducing the size of the ore extracted from the mine. The ore passes through primary crushing and secondary crushing, continuing with a step of grinding in which fine particles are obtained. This step also generates overgrinding of the material. Thus, the invention is also aimed at solving a problem inherent in the conventional flotation process, as the fraction of ultra fine particles accumulates as slime at the bottom of the flotation system tanks and becomes a major consumers of reagents, owing to the large surface area thereof. A large part of the ultra fine ore fraction results in tailings. These ores demonstrate greater liberation (they are presented as individual particles of a single mineral per particle) at a lower particle size, meaning that a significant quantity of valuable mineral is lost in the process.” statements are included.

In said application, a foam flotation system is disclosed for the physical chemical separation of ultrafine ore particles.

Again, in the Polish patent application numbered PL399677A1 in the literature, " The subject of the invention is a method for the production of Zn-Pb collective concentrate with an increased silver content in the process of zinc sludge flotation. The method is carried out in such a way that the sludge from the zinc hydrometallurgy process is flotated in a flotation machine in order to produce a Zn-Pb flotation collective concentrate with an increased Ag content, and in order to filter the electrolyte residues, they are dewatered on a filter to the content of about 20% H2O and obtain a pH of 5 , 0-5.5. So cleaned, it is pumped to a flotation machine with four working sections. The sludge is introduced through the mixing chamber to the second section of the machine by preflotation at a pH value of 7.0 - 7.5, and the froth product of the second section is directed to the first concentrate chamber of the machine, from which the Zn-Pb-Ag collective concentrate is withdrawn. Sludges from the second section of the flotation machine after adding a foaming agent to them. (CuSO4 solution) and milk of lime until pH 9.5-11 .0 is fed into the third section of the machine. Foam products from the third and fourth section of the machine are fed into the mixing chamber, while the final waste from the fourth section of the machine is directed to the waste collection or settling ponds.” statements are included.

In the mentioned application, a method is described for the production of Zn-Pb bulk concentrate with higher silver content in zinc flotation sludge.

Again, in the European patent document numbered EP2597099A1 in the literature, “The present invention contains at least one phosphonium salt (I) with the formula R1 R2R3R4P+X- and (b) at least one compound (II) with the formula MYn or MYn. It is related to a deep eutectic solvent. m(H20) where R1 , R2, R3 and R4 are independently selected from H, substituted or unsubstituted, linear or branched alkyl, alkoxy, cycloalkyl, aryl or alkaryl, or where two of R1, R2, R3 and R4 are optionally substituted are alkylene groups, preferably a C4-C10 alkylene groups; X is halogen; M is selected from the group consisting of Li, Mg, Ca, Cr, Mn, Fe, Co, Ni, Cu, Zn, Cd, Sn, Pb, Bi, La or Ce; Y is selected from halide, nitrate, phosphate and/or acetate; n is from 1 to 5; m is from 1 to 10; and the molar ratio of phosphonium salt (I) to compound (II) is in the range of 2:1 to 1 :10. A method for its preparation is also provided.” statements are included.

In said patent, however, a deep eutectic solvent and a method for its preparation are disclosed.

For the reasons mentioned above, a new method was needed to obtain Zn and Pb metals from Zn-Pb ores.

Aim of the Invention

Starting from this position of the technique, the aim of the invention is to introduce a new method for the extraction of Zn and Pb metals from Zn-Pb ores, which eliminates the existing disadvantages. Another aim of the invention is to present a method in which the volume of water to be used is always lower compared to the volumes of organic solvents, and no or very little water consumption is realized.

Another aim of the invention is to present a method that eliminates the problems related to wastewater generation and wastewater treatment.

Another aim of the invention is to present a method where metal recovery from ore deposits in arid regions where sufficient water supply cannot be provided is easier.

Another aim of the invention is to present a method that allows to reduce energy consumption by providing the opportunity to work at room temperature or at low temperatures (<100), unlike melting systems with very high energy consumption.

Another aim of the invention is to present a method in which the leaching process is carried out with much lower acid consumption compared to the leaching process performed in traditional hydrometallurgical methods.

Another aim of the invention is to present a method that makes it possible to leave the carbonate structured gangue minerals in the ore in the waste at a high rate.

Another aim of the invention is to provide a method that does not require an extra process step to remove unwanted metals from leaching solutions by preventing the dissolution of unwanted metals such as iron with the leaching process.

Detailed Description of the Invention

In this detailed explanation, the innovation that is the subject of the invention is only explained with examples that will not have any limiting effect for a better understanding of the subject.

A method for direct obtaining Zn and Pb metals from Zn-Pb ores which is using nonaqueous solvents such as molecular organic solvents, ionic liquids, and deep eutectic solvents instead of aqueous solutions and which provides less energy consumption advantages compared to the pyrometallurgy method and higher selectivity advantages compared to the hydrometallurgy method characterized in that; includes method steps of; preparation of deep eutectic solvent with the help of a controlled mixer until a homogeneous and clear solution is obtained from 1 :2 mole ratio Choline Chloride (ChCI) - urea and 1 :0.5.1.5 mole ratio Choline Chloride (ChCI) - Urea- Ethylene or Choline Chloride (ChCI) - urea- organic acid or Choline Chloride (ChCI) - Organic acid, subjecting said Zn-Pb ore to deep eutectic solvent leaching under atmospheric conditions and the ore combined with the deep eutectic solvent during the leaching process becomes a slurry, obtaining solid waste and Zn-Pb loaded solution by making solid/liquid separation after the leaching process of said slurry, performing the electrowinning process by using different kinds of cathode anode from Zn-Pb loaded deep eutectic solvent obtained after the leaching process and obtaining metallic Zn/Pb or Zn and Pb metals as a result of electrowinning process.

Solvometallurgy is a new branch of extractive metallurgy that uses non-aqueous solvents such as molecular organic solvents, ionic liquids and deep eutectic solvents instead of aqueous solutions. Solvometallurgical methods provide advantages such as less energy consumption compared to the pyrometallurgical method and higher selectivity compared to the hydrometallurgical method.

Said deep eutectic solvents are commonly defined as systems consisting of a mixture of at least two components, a hydrogen bond acceptor and a hydrogen bond donor. Deep eutectic solvents are systems formed from a eutectic mixture of Lewis or Bronsted acids and bases that may contain various anionic and/or cationic species.

Deep eutectic solvents are usually a hydrogen bond acceptor such as a quaternary salt; It is a mixture of amines, carboxylic acids, alcohol and a hydrogen bond donor such as carbohydrates.

Deep eutectic solvents can basically be classified into four types (Table 1): Type I (quaternary salt and metal salt), Type II (quaternary salt and hydrated metal salt), Type III (quaternary salt and hydrogen bond donor) and Type IV (hydrated metal salt), salt and hydrogen bond donor). Deep eutectic solvents are expressed by the general formula Cat ⁺ " zX Y. Here Cat ⁺ is any ammonium, phosphonium, or sulfonium cation and X is a Lewis base, usually a halide anion. Complex anionic species are formed between X- and Y, a Lewis or Brbnsted acid (z refers to the number of Y molecules interacting with the anion). Deep eutectic solvents are used in many areas due to their low vapor pressure, non-flammability, and easy recyclability compared to other organic solvents, as well as their biodegradability.

In addition, the low cost of deep eutectic solvents, unlike ionic solvents and mineral acids used in hydrometallurgical processes, provides a great economic advantage for their use on a larger scale. In addition, expensive and complex devices are not needed for their synthesis. For example, a controlled heater or a lyophilizer may be sufficient for the synthesis of these compounds.

Table 1. Types of deep eutectic solvents

Most of the deep eutectic solvents used are Type III. Here, eutectic formation is due to strong hydrogen bond interactions between hydrogen bond acceptor and hydrogen bond donor. One of the most common Cat ⁺ X's is choline chloride (ChCI), also known as vitamin B4 with a melting point of 302°C, with the formula [(CH3)3N(CI)CH2- CH2OH], which consists of two functional groups containing a quaternary ammonium salt and alcohol. Common examples of Type III HBD are urea with the formula NH2CONH2, which is formed as a result of two -NH2 combined with a carbonyl (C=O) functional group with a melting temperature of 133 °C, which provides the formation of deep eutectic solvents, and b with a boiling temperature of 197 °C and a melting temperature of -12.9 °C. They are organics with the formula (CH ₂ OH) ₂ , such as ethylene glycol (EG) with a diol structure. Commonly used deep eutectic solvents are ChCl-urea in 1 :2 mole ratio, ChCl-EG in 1 :2 mole ratio, and ChCl-urea-ethylene glycol and ChCl-urea-organic acid and ChCl- organic acid in 1 :0.5.1.5 mole ratio. The combined organics are prepared by mixing at temperatures below their melting point (<100 °C). There are Ch+ and Cl-/urea and Cl-/urea/ ethylene glycol and organic acid ions in the solution prepared by hydrogen bonding of the Cl- ion in ChCI, which is used as a hydrogen bond acceptor, to the organics used as the hydrogen bond donor.

These solvents, which are used in many fields, will be used in the technique of the invention to dissolve metals in the leaching of Zn-Pb ores. While Cl- ions in the content of deep eutectic solvents prepared with ChCl/urea or ChCl/Ure/ ethylene glycol or ChCl/Urea/organic acid or ChCl/organic acid are effective in the metal dissolution mechanism, Ch+ ion does not participate in the dissolution mechanism. During the leaching process, Cl- ions weaken the oxygen bond in metal oxide structures, causing the metal to bind to the oxygen of urea. In this case, Cl-/urea or CI-/urea/EG or Cl-/urea/organic acid or Cl-/organic acid compound bonded by hydrogen bonding takes the metal into its body and dissolution takes place (Reaction 1)-

MO + Ch+ + Cl-/urea — [MCIO. urea]- + Ch+ (M: Cu, Zn etc.)

In this method, which is the subject of the invention, Zn and Pb are obtained in metallic form by applying electrolysis to the solution of charged deep eutectic solvents by utilizing the high electrical conductivity of deep eutectic solvents after the leaching process, and the uncharged deep eutectic solvents from which the metals are removed can be reused in the leaching system.

The process steps of the production method of the invention are basically as follows;

- Choline Chloride (ChCI) in 1 :2 mol ratio - urea and Choline Chloride (ChCI)- Urea- Ethylene Glycol or Chloride (ChCI)- Urea - organic acid or Chloride (ChCI)- organic in 1 :0.5.1.5 mol ratio Preparation of deep eutectic solvent with the help of a controlled mixer until a homogeneous and clear solution is obtained from the acid, - Subjecting the Zn-Pb ore to deep eutectic solvent leaching under atmospheric conditions and turning the ore into a slurry combined with the deep eutectic solvent during the leaching process,

- Obtaining solid waste and Zn-Pb loaded solution by making solid/liquid separation after leaching of the slurry,

- Electrowinning process using copper cathode and graphite anode from deep eutectic solvent with Zn-Pb load obtained after leaching,

- It is in the form of obtaining metallic Zn/Pb or Zn and Pb metals as a result of electrowinning process.

It is very important to prepare the aforementioned deep eutectic solvents with the help of a controlled mixer in the temperature range of 50-100 °C between 1 hour and infinite hours.

Zn-Pb ore is subjected to atmospheric deep eutectic solvent leaching at a temperature range of 50-100 °C, solid/liquid ratios of 1/5-1/25, 12-72 hours, and at a stirring rate where all solids can be mixed in suspension. In addition, the Zn and Pb loaded solution is subjected to electrowinning in the range of 0-10 V, in the range of 1 hour -infinite hour.

Before starting the leaching of the mentioned deep eutectic solvents, all equipment is cleaned in accordance with the experimental material cleaning procedure and contamination is prevented.

In order not to reduce the leaching efficiency of the organics and the physical water contained in the ore by being used in the leaching process, the physical water of the ore and the organics used is removed at 105 °C for 24 hours and stored in vacuum containers.

It is done at the voltage value at which Ch output will not occur during the electrowinning process.