Background
The sulfuric acid residue, also called pyrite cinder, is industrial waste residue produced in the process of producing sulfuric acid. The pyrite cinder contains rich iron and partial elements such as calcium, silicon, copper, sulfur and the like, but the pyrite cinder has low content of nonferrous metals, and metal minerals and gangue minerals are mutually wrapped, so that the comprehensive utilization of the pyrite cinder is limited. About 8000 million tons of sulfuric acid residues are discharged in China every year, and the national accumulated reserves are over hundred million tons. The accumulation of a large amount of sulfate slag wastes land resources and causes serious pollution to the environment. In addition, the utilization rate of the sulfate slag in some developed countries is close to 100%, but the utilization rate of the sulfate slag in China is less than 50%. At present, the comprehensive utilization approach of the pyrite cinder is mainly used as a raw material of sintered pellets.
However, the pyrite cinder contains a large amount of iron elements, and also contains valuable metals such as nickel, cobalt, copper and the like, for example, in the copper hilly area of Anhui, the copper content in part of the pyrite cinder is higher than 0.6%, the cobalt content is higher than 0.3%, and the pyrite cinder has extremely high recovery value. On the other hand, the pyrite cinder is directly used as a blast furnace ironmaking raw material, wherein the copper content is far higher than the requirement of blast furnace ironmaking furnace burden, and a small amount of copper element enters molten iron to influence the mechanical property of subsequent processed steel.
The lithium iron phosphate battery has the advantages of excellent charge and discharge performance, long service life, good thermal stability and the like, thereby having important market share in the market. The iron phosphate is one of the most important raw materials for preparing the iron phosphate, and the preparation method mainly comprises a solution synthesis method, wherein iron salt and phosphoric acid are used as raw materials to react to obtain a ferric phosphate dihydrate product. However, the existing iron phosphate preparation process has high cost and needs high-quality iron raw materials.
Disclosure of Invention
Aiming at the problems of comprehensive utilization of the sulfuric acid residues, low economic value of a value-added processing technology and the like in the prior art, the invention aims to provide the method for efficiently separating and extracting the valuable metals such as iron, copper, cobalt, nickel and the like in the sulfuric acid residues by adopting phosphoric acid leaching-extraction.
In order to realize the technical purpose, the invention provides a method for extracting valuable metals from sulfuric acid residues by phosphoric acid leaching-extraction.
In the preferable scheme, the sulfuric acid residue is ball-milled until the fineness meets the requirement that the mass percentage content of the fraction smaller than 0.037mm is larger than 80%. The ball milling and leaching process can adopt a common ball milling process in the prior art, such as wet ball milling, the sulfuric acid residue is subjected to ball milling mechanical action to destroy the close embedding relationship among different components in the sulfuric acid residue, and the ball milling to a proper particle size is favorable for the subsequent leaching process, so that the metal leaching rate is improved.
In the preferable scheme, the concentration of phosphoric acid in the phosphoric acid-hydrofluoric acid mixed acid is 1.5-3.8 mol/L, and the concentration of hydrofluoric acid is 0.01-0.03 mol/L. The concentration of phosphoric acid and the concentration of hydrogen ions in the whole system are controlled to ensure that iron oxide is dissolved and then converted into ferric phosphate dihydrate in the leaching process, the ferric phosphate dihydrate precipitates and is enriched in a slag phase, and other metal ions still exist in a leachate in the form of metal ions, so that the separation of the ferric phosphate and other metal ions can be realized through simple solid-liquid separation; a small amount of hydrofluoric acid is doped into phosphoric acid, so that on one hand, the effect of destroying silicate minerals in the sulfuric acid slag can be achieved, the dissociation and dissolution of metals wrapped by gangue minerals such as silicate and the like can be promoted, the leaching rate is improved, and on the other hand, partial hydrogen ion concentration is provided, and the pH value of a leaching system is maintained.
In a preferred embodiment, the leaching conditions are as follows: the liquid-solid ratio is 8-16 mL/g, the leaching temperature is 80-145 ℃, and the leaching time is 4-12 h. Higher metal leaching rates can be achieved under the preferred leaching conditions.
Preferably, the leaching residue is washed by water until the pH value is more than 6.
In a preferable scheme, the pH value of the leachate is adjusted to 4.5-6. The pH is adjusted using a common alkaline solution, such as ammonia.
Preferably, the extractant used in the extraction separation process comprises at least one of P204 and P507.
In a preferred embodiment, the extraction separation conditions are as follows: the volume percentage concentration of the extracting agent in the organic phase is 2-5%, and the diluting agent is kerosene; the volume ratio of the water phase to the oil phase is 1-3.5: 1, the extraction temperature is room temperature, and the extraction time is 30-60 min.
The sulfuric acid residue is waste residue after high-temperature oxidation roasting treatment, wherein iron mainly exists in a hematite (ferric oxide) form, other valuable metals such as copper, nickel, cobalt and the like mostly enter an iron oxide crystal lattice in an oxide form or a doping form, and silicon and aluminum elements mainly form silicate, aluminate and the like and are in a close embedding and mutual wrapping relationship. In order to realize extraction of valuable metal elements and separation of the valuable metal elements from impurity elements in the sulfuric acid slag, firstly, ball milling is carried out, mechanical energy is adopted to destroy the close embedding relationship among different components in the sulfuric acid slag, on the basis, phosphoric acid-hydrofluoric acid mixed acid is adopted for leaching, and by utilizing the solubility difference of ferric phosphate, copper phosphate, nickel phosphate and cobalt phosphate under different phosphoric acid concentrations and pH conditions, ferric oxide and other metal oxides can be promoted to be dissolved by controlling the adjustment of the phosphoric acid concentration and the pH value in the leaching process, metal ions are dissolved into a solution, iron ions are selectively precipitated in a ferric phosphate dihydrate form, and other metals still exist in a metal ion form, so that the separation of the ferric phosphate and other metal ions can be realized; a small amount of hydrofluoric acid is added into the mixed acid to destroy silicate minerals in the sulfuric acid residue, further promote dissociation and dissolution of valuable metal ions wrapped in gangue minerals, and improve the leaching rate. After leaching, the iron phosphate and other metal ions can be separated by a physical means of solid-liquid separation, and the separation, extraction and recovery of valuable metal elements are realized by subsequent combination of extraction. Therefore, the valuable metals in the pyrite cinder are separated and recovered.
Compared with the prior art, the technical scheme of the invention has the following beneficial effects:
1) according to the method, the sulfuric acid residues containing valuable metals such as copper, nickel and cobalt are taken as treatment objects, the sulfuric acid residues are subjected to acid leaching by using phosphoric acid-hydrofluoric acid mixture, the acid concentration and the pH value are regulated, the separation and recovery of the valuable metals such as iron, copper, cobalt and nickel in the sulfuric acid residues are realized, the ferric phosphate material is synchronously prepared, the comprehensive utilization and value-added processing of the sulfuric acid residues are realized, the recovery rates of the iron, the copper, the cobalt and the nickel are all higher than 90%, and the method has higher economic value compared with the traditional method.
2) The preparation method for the comprehensive utilization of the pyrite cinder, provided by the invention, has the advantages of simple operation, low energy consumption and low cost, and is easy to realize industrial production.
Detailed Description
The following examples are intended to further illustrate the present disclosure, but not to limit the scope of the claims.
Comparative example 1
Sulfuric acid slag (iron grade 57.3%, copper, cobalt and nickel contents of 0.6%, 0.3% and 0.5% respectively) of a certain sulfuric acid plant is used as a raw material to carry out phosphoric acid leaching, and leaching conditions are as follows: the concentration of phosphoric acid is 1.5mol/L, the concentration of hydrofluoric acid is 0.03mol/L, the liquid-solid ratio is 16ml/g, the leaching temperature is 80 ℃, the leaching time is 12 hours, and after the leaching is finished, the solid-liquid separation is carried out by filtering; washing the synthesized product with distilled water until the pH value of the filtrate is more than 6, and obtaining a product, namely battery-grade ferric phosphate dihydrate, wherein the purity of the ferric phosphate is 98.3%, the median particle size is 4.95 mu m, the recovery rate of the iron is 92.9%, and the content of copper and cobalt in the ferric phosphate exceeds 0.1%; adjusting the pH value of the leachate to 4.5 by using ammonia water, and then extracting valuable metal ions in the leachate by using an organic extractant, wherein the extraction conditions are as follows: the concentration of the extractant P204 is 2.0 percent, the diluent is kerosene, the water phase/oil phase ratio is 1:1, the extraction temperature is room temperature, the extraction time is 30min, and the recovery rates of valuable elements of copper, cobalt and nickel in the whole process flow are 78.2 percent, 65.3 percent and 83.9 percent respectively.
Comparative example 2
The method comprises the following steps of taking sulfuric acid residues (the iron grade is 57.3%, the contents of copper, cobalt and nickel are respectively 0.6%, 0.3% and 0.5%) of a certain sulfuric acid plant as raw materials, firstly carrying out ball milling on the sulfuric acid residues until the proportion of minus 0.037mm is higher than 80%, and carrying out phosphoric acid leaching under the leaching conditions that: the concentration of phosphoric acid is 1.5mol/L, the liquid-solid ratio is 16ml/g, the leaching temperature is 120 ℃, the leaching time is 8 hours, and after the leaching is finished, solid-liquid separation is carried out by filtering; washing the synthesized product with distilled water until the pH value of the filtrate is more than 6, and obtaining a product, namely battery-grade ferric phosphate dihydrate, wherein the purity of the ferric phosphate is 99.3%, the median particle size is 4.86 mu m, the recovery rate of the iron is 93.3%, and the content of copper, cobalt and nickel in the ferric phosphate exceeds 0.1%; adjusting the pH value of the leachate to 4.5 by using ammonia water, and then extracting valuable metal ions in the leachate by using an organic extractant, wherein the extraction conditions are as follows: the concentration of the extractant P507 is 2.0 percent, the diluent is kerosene, the water phase/oil phase ratio is 2:1, the extraction temperature is room temperature, the extraction time is 60min, and the recovery rates of valuable elements of copper, cobalt and nickel in the whole process flow are 73.2 percent, 70.3 percent and 83.3 percent respectively.
Example 1:
taking sulfuric acid slag (iron grade 57.3%, copper, cobalt and nickel contents are respectively 0.6%, 0.3% and 0.5%) of a certain sulfuric acid plant as a raw material, firstly, ball-milling the sulfuric acid slag until the proportion of-0.037 mm is higher than 80%, and the concentration of ball-milled ore pulp is 40%; then phosphoric acid leaching is carried out, and leaching conditions are as follows: the concentration of phosphoric acid is 1.5mol/L, the concentration of hydrofluoric acid is 0.03mol/L, the liquid-solid ratio is 16ml/g, the leaching temperature is 80 ℃, the leaching time is 12 hours, and after the leaching is finished, the solid-liquid separation is carried out by filtering; washing the synthesized product with distilled water until the pH value of the filtrate is more than 6, and obtaining a product, namely battery-grade ferric phosphate dihydrate, wherein the purity of the ferric phosphate is 99.3%, the median particle size is 4.86 mu m, the recovery rate of the iron is 93.3%, and the contents of copper, cobalt and nickel in the ferric phosphate are all lower than 0.005%; adjusting the pH value of the leachate to 4.5 by using ammonia water, and then extracting valuable metal ions in the leachate by using an organic extractant, wherein the extraction conditions are as follows: the concentration of the extractant P204 is 2.0 percent, the diluent is kerosene, the water phase/oil phase ratio is 1:1, the extraction temperature is room temperature, the extraction time is 30min, and the recovery rates of the valuable elements of copper, cobalt and nickel in the whole process flow are 93.2 percent, 95.3 percent and 91.9 percent respectively.
Example 2:
taking sulfuric acid slag (iron grade 57.3%, copper, cobalt and nickel contents are respectively 0.6%, 0.3% and 0.5%) of a certain sulfuric acid plant as a raw material, firstly, ball-milling the sulfuric acid slag until the proportion of-0.037 mm is higher than 80%, and the concentration of ball-milled ore pulp is 50%; then phosphoric acid leaching is carried out, and leaching conditions are as follows: the concentration of phosphoric acid is 3.8mol/L, the concentration of hydrofluoric acid is 0.01mol/L, the liquid-solid ratio is 8ml/g, the leaching temperature is 100 ℃, the leaching time is 4 hours, and after the leaching is finished, the solid-liquid separation is carried out by filtering; washing the synthesized product with distilled water until the pH value of the filtrate is more than 6, and obtaining a product, namely battery-grade ferric phosphate dihydrate, wherein the purity of the ferric phosphate is 99.2%, the median particle size is 5.03 mu m, the recovery rate of the iron is 94.1%, and the contents of copper, cobalt and nickel in the ferric phosphate are all lower than 0.003%; adjusting the pH value of the leachate to 6 by using ammonia water, and then extracting valuable metal ions in the leachate by using an organic extracting agent, wherein the extraction conditions are as follows: the concentration of the extractant P507 is 5 percent, the diluent is kerosene, the water phase/oil phase ratio is 3.5:1, the extraction temperature is room temperature, the extraction time is 60min, and the recovery rates of the valuable elements of copper, cobalt and nickel in the whole process flow are 95.1 percent, 96.2 percent and 93.8 percent respectively.
Example 3:
taking sulfuric acid slag (iron grade 54.2%, copper, cobalt and nickel contents are respectively 0.7%, 0.2% and 0.2%) of a certain sulfuric acid plant as a raw material, firstly, ball-milling the sulfuric acid slag until the proportion of-0.037 mm is higher than 80%, and the concentration of ball-milled ore pulp is 55%; then phosphoric acid leaching is carried out, and leaching conditions are as follows: the concentration of phosphoric acid is 2.6mol/L, the concentration of hydrofluoric acid is 0.02mol/L, the liquid-solid ratio is 16ml/g, the leaching temperature is 145 ℃, the leaching time is 6 hours, and after the leaching is finished, the solid-liquid separation is carried out by filtering; washing the synthesized product with distilled water until the pH value of the filtrate is more than 6, and obtaining a product, namely battery-grade ferric phosphate dihydrate, wherein the purity of the ferric phosphate is 99.2%, the median particle size is 5.32 mu m, the recovery rate of the iron is 92.1%, and the contents of copper, cobalt and nickel in the ferric phosphate are all lower than 0.003%; adjusting the pH value of the leachate to 4.5 by using ammonia water, and then extracting valuable metal ions in the leachate by using an organic extractant, wherein the extraction conditions are as follows: the concentration of the extracting agent (the proportion of P204 to P507 is 1:1) is 2.0 percent, the diluting agent is kerosene, the water phase/oil phase ratio is 2:1, the extraction temperature is room temperature, the extraction time is 30min, and the recovery rates of the valuable elements of copper, cobalt and nickel in the whole process flow are 93.2 percent, 95.3 percent and 91.9 percent respectively.
Example 4:
taking sulfuric acid slag (iron grade 54.2%, copper, cobalt and nickel contents are respectively 0.7%, 0.2% and 0.2%) of a certain sulfuric acid plant as a raw material, firstly, ball-milling the sulfuric acid slag until the proportion of-0.037 mm is higher than 80%, and the concentration of ball-milled ore pulp is 55%; then phosphoric acid leaching is carried out, and leaching conditions are as follows: the concentration of phosphoric acid is 2.6mol/L, the concentration of hydrofluoric acid is 0.02mol/L, the liquid-solid ratio is 10ml/g, the leaching temperature is 145 ℃, the leaching time is 6 hours, and after the leaching is finished, the solid-liquid separation is carried out by filtering; washing the synthesized product with distilled water until the pH value of the filtrate is more than 6, and obtaining a product, namely battery-grade ferric phosphate dihydrate, wherein the purity of the ferric phosphate is 99.2%, the median particle size is 5.32 mu m, the recovery rate of the iron is 92.1%, and the contents of copper, cobalt and nickel in the ferric phosphate are all lower than 0.003%; adjusting the pH value of the leachate to 4.5 by using ammonia water, and then extracting valuable metal ions in the leachate by using an organic extractant, wherein the extraction conditions are as follows: the concentration of the extractant P204 is 5.0 percent, the diluent is kerosene, the water phase/oil phase ratio is 3:1, the extraction temperature is room temperature, the extraction time is 45min, and the recovery rates of the valuable elements of copper, cobalt and nickel in the whole process flow are respectively 92.9 percent, 93.8 percent and 90.8 percent.