CN106636651B - The separation method of chromium and iron aluminium in a kind of sulfuric acid system solution of aluminium containing ferrochrome - Google Patents

Abstract

The invention belongs to the technical field of hydrometallurgy and relates to a method for separating chromium and iron and aluminum in a sulfuric acid system solution containing chromium, iron and aluminum. The method comprises the following steps: 1) adding an oxidizing agent for pretreatment; 2) adjusting the solution to a specific pH value, adding phosphate and reacting at a specific temperature to obtain iron-aluminum phosphate composite precipitation and filtrate mainly composed of iron phosphate; 3) Adjust the filtrate to a specific pH value, add phosphate again and react at a specific temperature to obtain iron-aluminum phosphate composite precipitation mainly composed of aluminum phosphate and chromium sulfate solution to complete the separation of chromium and iron-aluminum. The method has short flow, simple operation, and is easy to be applied on a large scale; adopting the step-by-step precipitation method of phosphate has strong selectivity and ideal separation effect; the recovery rate of metal chromium is greater than 98%, and the economic benefit is remarkable; the whole separation process No chemical substances that may cause harm to the environment are used, which meets the requirements of green environmental protection.

Description

A kind of separation method of chromium and iron and aluminum in sulfuric acid system solution containing chromium, iron and aluminum

technical field

The invention belongs to the technical field of hydrometallurgy.

Background technique

In the process of resource utilization of electroplating sludge, sulfuric acid is a commonly used hydrometallurgical leaching solvent, which has high leaching efficiency and good leaching effect, so it is widely used. Sulfuric acid leaching uses PAC (polyaluminum chloride) as a flocculant to form a mixed solution containing chromium sulfate, aluminum sulfate, and ferrous sulfate. Since the atomic radii of chromium, iron, and aluminum are similar and their chemical properties are similar, there is a problem of difficulty in separation.

The separation method of chromium and iron in the sulfuric acid system that has been developed at present mainly comprises the following several: (1) solvent extraction method: this method has characteristics such as equipment is simple, process is easy to control and reagent can be recycled, through phosphine extraction agent (such as P204, P507) extraction, although the extraction rate of iron can reach more than 99%, the co-extraction rate of chromium is also up to 25%, the separation effect is not good, and the loss of chromium is obvious; (2) Mohr's salt crystallization method: this method is based on sulfuric acid Ferrous, chromium sulfate reacts with ammonium sulfate, and there is an obvious solubility difference between the chromammonium alum and ferrous ammonium alum, and the ferrous ammonium alum crystallizes out, while the chromium stays in the solution to achieve the purpose of separating ferrochrome, and the chromium The loss rate of ferrous oxalate is relatively low, but the method is complicated in operation and strict in operation requirements, and is not easy for large-scale industrial application; (3) ferrous oxalate precipitation method: this method is based on the principle of low solubility product of ferrous oxalate, and precipitates iron by adding oxalic acid Elements, in order to achieve the purpose of separating chromium and iron, but the iron removal rate is extremely sensitive to factors such as the amount of oxalic acid added and temperature, the operation requirements are strict, and the optimal reaction pH value is about 4.0, the initial solution has a large neutralization load, and it is not easy Large-scale promotion and use; (4) goethite method: this method removes iron and reclaims chromium from the mixed solution, although the iron removal rate is as high as 99%, the loss rate of chromium is also higher, about 15%; (5) Phosphate chromium precipitation method: This method realizes the separation of chromium and ferrous phosphate based on the solubility difference between chromium phosphate and ferrous phosphate. Although a chromium recovery rate of 98% can be achieved, the reaction requires heating, and the products are chromium phosphate and hydrogen Composite deposits of chromium oxide that subsequently require regeneration.

The currently developed separation method of chromium and aluminum mainly oxidizes trivalent chromium to hexavalent chromium under alkaline conditions, while aluminum exists in the form of metaaluminate, adding acid to adjust the pH value to 8.0, aluminum can Separation from ionic chromium is achieved in the form of aluminum hydroxide precipitates.

The Chinese invention patent with application number 200710041574.3 discloses a phosphate stabilization treatment method for electroplating sludge. The main steps are as follows: (1) drying the electroplating sludge at 102° C., and then grinding it into powder for later use; (2) ) in the temperature range of 30-70°C, mix the analytically pure soluble phosphate with the above-mentioned electroplating sludge in a weight ratio of 1:70-90, and stir vigorously in a mixer for 4 hours to make it fully react, during the reaction process Control the pH value in the range of 8 to 11; (3) After the reaction, cool naturally to obtain a solid sample of sludge containing heavy metal compound phosphate, and the test shows that the sludge can meet the national hazardous waste landfill standard. However, this method only stabilizes electroplating sludge, and does not realize the resource utilization of valuable metals.

The Chinese invention patent with application number 201310008199.8 discloses a selective separation method for chromium and iron in a sulfuric acid system solution, the main steps of which are as follows: (1) adding a reducing agent to the sulfuric acid system solution containing chromium and iron for pretreatment (2) adjust the pH value of the solution; (3) add soluble phosphate, carry out selective phosphoric acid chromium precipitation reaction, form the composite precipitate of chromium phosphate and chromium hydroxide; (4) carry out filtration separation, obtain chromium phosphate chromium hydroxide Composite precipitate and solution containing ferrous sulfate to achieve selective separation of ferrochromium. Although this method can achieve a chromium recovery rate of more than 98%, the applicable chromium ion concentration is low (0.1-30g/L), which leads to a large processing scale and is difficult for large-scale industrial application.

Contents of the invention

Aiming at the problems existing in the above-mentioned prior art, the present invention aims to provide a step-by-step selectivity of chromium and iron-aluminum in the sulfuric acid system solution containing chromium-iron-aluminum with short process flow, simple operation, environmental friendliness and easy large-scale application. Separation method.

Specifically, the present invention adopts the following technical solutions:

A method for separating chromium and iron and aluminum in a sulfuric acid system solution containing chromium, iron and aluminum, comprising the steps of:

1) Add an oxidizing agent to the sulfuric acid system solution containing Cr ³⁺ , Fe ²⁺ , and Al ³⁺ until the chromium, iron, and aluminum elements in the solution only exist in the form of Cr ³⁺ , Fe ³⁺ , and Al ³⁺ ;

2) Add lye to the solution in step 1) until pH = 1 to 3, and add soluble Phosphate, and insulated and stirred at 5-60°C, filtered to obtain iron-aluminum phosphate composite precipitation and filtrate mainly composed of iron phosphate;

3) Add lye to the filtrate in step 2), until pH=2～4, according to the molar ratio of phosphate ion and aluminum ion in the filtrate is the ratio of 0.6～1.6:1, add soluble phosphate, and in Keep stirring at 5-60°C, filter to obtain iron-aluminum phosphate composite precipitation mainly composed of aluminum phosphate and chromium sulfate solution, and complete the separation of chromium and iron-aluminum in the sulfuric acid system solution containing chromium-iron-aluminum.

In the above separation method, the sulfuric acid system solution containing Cr ³⁺ , Fe ²⁺ , and Al ³⁺ in step 1) is an electroplating sludge sulfuric acid leaching solution.

In the above separation method, the mass concentration of Cr ³⁺ in the sulfuric acid system solution containing Cr ³⁺ , Fe ²⁺ , and Al ³⁺ in step 1) is 10-80 g/L, and the mass concentration of Fe ²⁺ is 0.5 ~4g/L, the mass concentration of Al ³⁺ is 0.5~4g/L.

In the above separation method, the oxidant in step 1) is waste liquid containing Cr ⁶⁺ . Utilizing the redox reaction between Cr ⁶⁺ and Fe ²⁺ , not only can Fe ²⁺ in sulfuric acid system solution be oxidized to Fe ³⁺ , but also Cr ⁶⁺ in industrial waste liquid can be reduced to Cr ³⁺ , and ^then Subsequent selective separation is carried out together with Cr ³⁺ in the sulfuric acid system solution.

In the above separation method, the alkaline solution in step 2) is a saturated aqueous solution of sodium hydroxide or potassium hydroxide.

In the above separation method, the soluble phosphate in step 2) is sodium phosphate or potassium phosphate.

In the above separation method, the linear velocity of the stirring in step 2) is 50-400 m/min, and the time is 5-120 min.

In the above separation method, the lye described in step 3) is a saturated aqueous solution of sodium hydroxide or potassium hydroxide.

In the above separation method, the soluble phosphate in step 3) is sodium phosphate or potassium phosphate.

In the above separation method, the linear velocity of the stirring in step 3) is 50-400 m/min, and the time is 5-120 min.

The separation method of the present invention utilizes the solubility differences of phosphates corresponding to Cr ³⁺ , Fe ³⁺ , and Al ³⁺ respectively, and realizes the selective separation of chromium and iron and aluminum in the sulfuric acid system solution. Since the solubility product (Ksp) of CrPO ₄ ·2H ₂ O is 2.4×10 ^-23 , the solubility product of FePO ₄ ·2H ₂ O is 9.9×10-16, and the solubility product of AlPO ₄ is 6.3×10-19 Therefore, by adjusting the pH value and temperature, carrying out chemical precipitation reaction, filtration and separation and other process steps, the iron-aluminum phosphate composite precipitation and chromium sulfate solution can be obtained, and the final separation of chromium and iron-aluminum can be realized.

Compared with the prior art, the present invention adopting the technical solution has the following advantages:

(1) The process flow is short, the operation is simple, the cost is low, and it is easy to realize large-scale industrial application;

(2) Using phosphate to precipitate iron and aluminum step by step can have strong selectivity and ideal separation effect in a wide range of ion concentration;

(3) Metal chromium in the sulfuric acid system solution is effectively recovered, the recovery rate is greater than 98%, and the economic benefit is remarkable;

(4) In the pretreatment process of sulfuric acid system solution, industrial waste liquid containing hexavalent chromium can be used as oxidant, which can not only realize the secondary utilization of high-valent chromium waste liquid, but also recover the chromium element in high-valent chromium waste liquid , kill two birds with one stone;

(5) The entire separation process does not use chemical substances that may cause harm to the environment, which meets the requirements of green environmental protection.

Detailed ways

The technical solutions of the present invention will be further described below in conjunction with specific embodiments. Unless otherwise stated, the instruments, materials and reagents used in the following examples can be obtained through conventional commercial means.

Example 1: Separation of chromium and iron and aluminum in the sulfuric acid system solution containing chromium, iron and aluminum.

(1) to the sulfuric acid system solution containing chromium, iron and aluminum (wherein the mass concentration of Cr ³⁺ is 49.3g/L, the mass concentration of Fe ²⁺ is 2.1g/L, and the mass concentration of Al ³⁺ is 2.13g/L) Add waste liquid containing Cr ⁶⁺ into the solution, oxidize Fe ²⁺ to Fe ³⁺ through oxidation-reduction reaction, and reduce Cr ⁶⁺ to Cr ³⁺ at the same time, until the chromium, iron, and aluminum elements in the mixed solution are only composed of Cr Exist in the form of ³⁺ , Fe ³⁺ , Al ³⁺ ;

(2) Add saturated sodium hydroxide solution to the mixed solution in step (1) until pH=2.0, according to the mole of n(PO ₄ ^3- ):n(Fe ³⁺ +Al ³⁺ )=0.5:1 Add sodium phosphate, keep stirring at 5°C for 10 minutes, control the stirring line speed at 150m/min, filter to obtain iron-aluminum phosphate composite precipitation and filtrate mainly composed of iron phosphate; after testing, Cr ³⁺ , The mass concentrations of Fe ³⁺ and Al ³⁺ are 48.8g/L, 0.2g/L and 1.4g/L respectively;

(3) Add saturated sodium hydroxide solution to the filtrate in step (2) until pH=3.0, according to the molar ratio of n(PO ₄ ^3- ):n(Al ³⁺ )=1.2:1, add sodium phosphate , and kept stirring at 5°C for 10 minutes, the stirring line speed was controlled at 150m/min, and filtered to obtain iron-aluminum phosphate composite precipitation and chromium sulfate solution mainly composed of aluminum phosphate; after testing, Cr ³⁺ and Fe ³⁺ in the filtrate , Al ³⁺ mass concentrations are 48.4g/L, 0.003g/L, 0.141g/L respectively.

After the above three steps of operation, the chromium and iron and aluminum in the sulfuric acid system solution containing chromium, iron and aluminum have been effectively separated, and the chromium element is mainly dissolved in the solution in the form of chromium sulfate, and the chromium recovery rate is 98.16%; The iron-aluminum phosphate composite precipitation mainly composed of iron phosphate can be recovered, and the iron recovery rate is 99.85%; the aluminum element is mainly recovered through the iron-aluminum phosphate composite precipitation mainly composed of aluminum phosphate, and the aluminum recovery rate is 93.38%.

Example 2: Separation of chromium and iron and aluminum in the sulfuric acid system solution containing chromium, iron and aluminum.

(1) In the sulfuric acid system solution containing chromium, iron and aluminum (wherein the mass concentration of Cr ³⁺ is 30g/L, the mass concentration of Fe ²⁺ is 1.29g/L, and the mass concentration of Al ³⁺ is 1.25g/L) Add waste liquid containing Cr ⁶⁺ , oxidize Fe ²⁺ to Fe ³⁺ through oxidation-reduction reaction, and reduce Cr ⁶⁺ to Cr ³⁺ at the same time, until the chromium, iron and aluminum elements in the mixed solution are only composed of Cr ^{3+ +} , Fe ³⁺ , Al ³⁺ forms;

(2) Add saturated sodium hydroxide solution to the mixed solution in step (1) until pH=2.1, according to the mole of n(PO ₄ ^3- ):n(Fe ³⁺ +Al ³⁺ )=0.53:1 Add sodium phosphate, keep stirring at 10°C for 8 minutes, control the stirring line speed at 200m/min, filter to obtain iron-aluminum phosphate composite precipitation and filtrate mainly composed of iron phosphate; after testing, Cr ³⁺ , The mass concentrations of Fe ³⁺ and Al ³⁺ are 29.6g/L, 0.11g/L and 0.63g/L respectively;

(3) Add saturated sodium hydroxide solution to the filtrate in step (2) until pH=3.3, according to the molar ratio of n(PO ₄ ^3- ):n(Al ³⁺ )=1:1, add sodium phosphate , and kept stirring at 10°C for 8 minutes, the stirring line speed was controlled at 200m/min, and filtered to obtain iron-aluminum phosphate composite precipitation and chromium sulfate solution mainly composed of aluminum phosphate; after testing, Cr ³⁺ , Fe ³⁺ in the filtrate , Al ³⁺ mass concentrations were 29.4g/L, 0.002g/L, 0.065g/L, respectively.

After the above three steps of operation, the chromium and iron and aluminum in the sulfuric acid system solution containing chromium, iron and aluminum have been effectively separated, wherein the chromium element is mainly dissolved in the solution in the form of chromium sulfate, and the chromium recovery rate is 98.15%; The iron-aluminum phosphate composite precipitation mainly composed of iron phosphate can be recovered, and the iron recovery rate is 99.84%. The aluminum element is mainly recovered through the iron-aluminum phosphate composite precipitation mainly composed of aluminum phosphate, and the aluminum recovery rate is 94.8%.

Example 3: Separation of chromium and iron and aluminum in the sulfuric acid system solution containing chromium, iron and aluminum.

(1) To the sulfuric acid system solution containing chromium, iron and aluminum (wherein the mass concentration of Cr ³⁺ is 10.5g/L, the mass concentration of Fe ²⁺ is 0.56g/L, and the mass concentration of Al ³⁺ is 0.51g/L) Add waste liquid containing Cr ⁶⁺ to the mixture, oxidize Fe ²⁺ to Fe ³⁺ through oxidation-reduction reaction, and reduce Cr ⁶⁺ to Cr ³⁺ at the same time, until the chromium, iron, and aluminum elements in the mixed solution are only composed of Cr Exist in the form of ³⁺ , Fe ³⁺ , Al ³⁺ ;

(2) Add saturated potassium hydroxide solution to the mixed solution in step (1) until pH=1.0, according to the mole of n(PO ₄ ^3- ):n(Fe ³⁺ +Al ³⁺ )=0.2:1 Add potassium phosphate, keep stirring at 30°C for 20 minutes, control the stirring line speed at 400m/min, filter to obtain iron-aluminum phosphate composite precipitation and filtrate mainly composed of iron phosphate; after testing, Cr ³⁺ , The mass concentrations of Fe ³⁺ and Al ³⁺ are 10.25g/L, 0.06g/L and 0.26g/L respectively;

(3) Add saturated potassium hydroxide solution to the filtrate in step (2) until pH=2.0, according to the molar ratio of n(PO ₄ ^3- ):n(Al ³⁺ )=1.2:1, add sodium phosphate , and kept stirring at 30°C for 20 minutes, the stirring line speed was controlled at 400m/min, and filtered to obtain iron-aluminum phosphate composite precipitation and chromium sulfate solution mainly composed of aluminum phosphate; after testing, Cr ³⁺ , Fe ³⁺ in the filtrate , Al ³⁺ mass concentrations are 10.29g/L, 0.001g/L, 0.046g/L respectively.

After the above three steps of operation, the chromium and iron and aluminum in the sulfuric acid system solution containing chromium, iron and aluminum have been effectively separated, and the chromium element is mainly dissolved in the solution in the form of chromium sulfate, and the chromium recovery rate is 98.03%; The iron-aluminum phosphate composite precipitation mainly composed of iron phosphate can be recovered, and the iron recovery rate is 99.82%; the aluminum element is mainly recovered through the iron-aluminum phosphate composite precipitation mainly composed of aluminum phosphate, and the aluminum recovery rate is 90.98%.

Example 4: Separation of chromium and iron and aluminum in the sulfuric acid system solution containing chromium, iron and aluminum.

(1) to the sulfuric acid system solution containing chromium, iron and aluminum (wherein the mass concentration of Cr ³⁺ is 81.3g/L, the mass concentration of Fe ²⁺ is 4.56g/L, and the mass concentration of Al ³⁺ is 4.23g/L) Add waste liquid containing Cr ⁶⁺ to the mixture, oxidize Fe ²⁺ to Fe ³⁺ through oxidation-reduction reaction, and reduce Cr ⁶⁺ to Cr ³⁺ at the same time, until the chromium, iron, and aluminum elements in the mixed solution are only composed of Cr Exist in the form of ³⁺ , Fe ³⁺ , Al ³⁺ ;

(2) Add saturated potassium hydroxide solution to the mixed solution in step (1) until pH=3.0, according to the mole of n(PO ₄ ^3- ):n(Fe ³⁺ +Al ³⁺ )=0.7:1 Add potassium phosphate, keep stirring at 60°C for 40 minutes, control the stirring line speed at 200m/min, filter to obtain iron-aluminum phosphate composite precipitation and filtrate mainly composed of iron phosphate; after testing, Cr ³⁺ , The mass concentrations of Fe ³⁺ and Al ³⁺ are 80.6g/L, 0.42g/L and 2.24g/L respectively;

(3) Add saturated potassium hydroxide solution to the filtrate in step (2) until pH=4.0, according to the molar ratio of n(PO ₄ ^3- ):n(Al ³⁺ )=1.2:1, add potassium phosphate , and kept stirring at 60°C for 40 minutes, the stirring line speed was controlled at 200m/min, and filtered to obtain iron-aluminum phosphate composite precipitation and chromium sulfate solution mainly composed of aluminum phosphate; after testing, Cr ³⁺ and Fe ³⁺ in the filtrate , Al ³⁺ mass concentrations are 79.6g/L, 0.01g/L, 0.246g/L respectively.

After the above three steps, the chromium and iron-aluminum in the sulfuric acid system solution containing chromium-iron-aluminum have been effectively separated, wherein the chromium element is mainly dissolved in the solution in the form of chromium sulfate, and the chromium recovery rate is 97.92%; The iron-aluminum phosphate composite precipitation mainly composed of iron phosphate can be recovered, and the iron recovery rate is 99.78%; the aluminum element is mainly recovered through the iron-aluminum phosphate composite precipitation mainly composed of aluminum phosphate, and the aluminum recovery rate is 94.18%.

The above examples are only used to explain and illustrate the specific implementation of the present invention, and are not intended to limit the protection scope of the present invention. It should be understood that any modification or replacement made by those skilled in the art within the technical scope disclosed in the present invention shall fall within the protection scope of the present invention.

Claims (10)

1. the separation method of chromium and iron aluminium in a kind of sulfuric acid system solution of aluminium containing ferrochrome, it includes the following steps：

1) to containing Cr³⁺、Fe²⁺、Al³⁺Sulfuric acid system solution in add oxidant, until solution in chromium, iron, aluminium element difference Only with Cr³⁺、Fe³⁺、Al³⁺Form exists；

2) lye is added into the solution in step 1), until pH=1~3, according to the iron ion in phosphate anion and solution Molar ratio with the sum of aluminium ion is 0.2~0.7:1 ratio, adds soluble phosphate, and is kept the temperature under the conditions of 5~60 DEG C Stirring, is obtained by filtration ferric phosphate aluminium composite precipitation and filtrate based on ferric phosphate；

3) lye is added into the filtrate in step 2), until pH=2~4, according to the aluminium ion in phosphate anion and filtrate Molar ratio be 0.6~1.6:1 ratio, adds soluble phosphate, and the insulated and stirred under the conditions of 5~60 DEG C, filters To the ferric phosphate aluminium composite precipitation and chromium sulfate solution based on aluminum phosphate, complete in the sulfuric acid system solution of the aluminium containing ferrochrome chromium with The separation of iron aluminium.

2. separation method according to claim 1, it is characterised in that：

Contain Cr described in step 1)³⁺、Fe²⁺、Al³⁺Sulfuric acid system solution be electroplating sludge sulphuric leachate.

3. separation method according to claim 1, it is characterised in that：

Contain Cr described in step 1)³⁺、Fe²⁺、Al³⁺Sulfuric acid system solution in Cr³⁺Mass concentration be 10~80g/L, Fe²⁺'s Mass concentration is 0.5~4g/L, Al³⁺Mass concentration be 0.5~4g/L.

4. separation method according to claim 1, it is characterised in that：

Oxidant described in step 1) is containing Cr⁶⁺Waste liquid.

5. separation method according to claim 1, it is characterised in that：

Lye described in step 2) is sodium hydroxide or the saturated aqueous solution of potassium hydroxide.

6. separation method according to claim 1, it is characterised in that：

Soluble phosphate described in step 2) is sodium phosphate or potassium phosphate.

7. separation method according to claim 1, it is characterised in that：

The linear velocity stirred described in step 2) is 50~400m/min, and the time is 5~120min.

8. separation method according to claim 1, it is characterised in that：

Lye described in step 3) is sodium hydroxide or the saturated aqueous solution of potassium hydroxide.

9. separation method according to claim 1, it is characterised in that：

Soluble phosphate described in step 3) is sodium phosphate or potassium phosphate.

10. separation method according to claim 1, it is characterised in that：

The linear velocity stirred described in step 3) is 50~400m/min, and the time is 5~120min.