CN102453926A - Method for obtaining high-purity zinc by electrolyzing zinc chloride - Google Patents

Abstract

The invention discloses a method for obtaining recyclable chlorine and high-purity metal zinc by electrolyzing zinc chloride in an aqueous solution system. According to the method, an anode adopts a RuTi coated electrode with low chlorinated overpotential, a cathode adopts a polished aluminum electrode or a pure zinc sheet, an electrolyte adopts a zinc chloride aqueous solution system, a proper amount of sodium chloride and ammonium chloride are added as conductive salts, and deposited zinc with the Zn content of more than 99.99% can be obtained by controlling proper electrolysis conditions. The method is suitable for recycling zinc from zinc-containing waste and directly producing zinc chloride waste, and realizes the recycling of zinc and chlorine.

Description

A method for obtaining high-purity zinc by zinc chloride electrolysis

technical field

The invention relates to a method for recycling non-ferrous metal zinc and chlorine gas from zinc chloride by electrolysis.

Background technique

Zinc is a non-ferrous metal, ranking fourth in the earth's crustal metal reserves, and its appearance is silvery white. The zinc electrode potential is -0.7630, which ranks in front of hydrogen in the metal activity sequence table and belongs to active metals. Although zinc reserves are abundant, as a non-renewable resource, with the increase of zinc consumption, the recycling method of zinc has been paid more attention.

The application of zinc is very extensive. Galvanizing on metal products can slow down the rate of metal oxidation and corrosion; by hot-dip plating materials and products that need protection in molten metal tanks, zinc can be used for corrosion protection. In the galvanizing industry, generally Chloride galvanizing is used, and the electroplating wastewater and plating solution contain a large amount of zinc chloride. Pollution has always been the biggest problem in the electroplating industry.

Zinc is widely used in the anti-corrosion protection of steel structural parts and the production of zinc alloys. The annual consumption of zinc in the world is 10 million tons, and the amount of recycled zinc is 3 million tons. The electrochemical method realizes the zinc recovery technology of zinc-containing waste, which can improve the recovery rate of zinc and comprehensively utilize resources.

Metal zinc has an indelible position in battery manufacturing in modern industry. It is a very important metal. Zinc/manganese dioxide dry batteries are widely used in primary batteries, alkaline zinc/manganese dioxide batteries with high energy density, zinc /Mercury oxide, button zinc/air batteries, etc. use zinc electrodes; zinc/silver oxide reserve batteries have high discharge rate and high volume specific energy and are used in missile and aviation fields; zinc/nickel batteries can also be used in many commercial applications In general, it is designed as a mechanically rechargeable zinc/air battery for use in the field of electric vehicles. The battery can be replaced with the used zinc negative electrode at the service station, and the discharged negative electrode can be electrochemically regenerated with zinc through electrolysis. The high-efficiency recovery and regeneration of zinc in the zinc electrode discharge product in zinc/air batteries is one of the key technologies for the promotion and application of zinc/air batteries.

The photovoltaic industry uses a large amount of polysilicon materials, and the improved Siemens method technology is used to produce polycrystalline materials to produce a large amount of SiCl ₄ by-products. Using metal zinc to reduce SiCl ₄ can obtain polysilicon and by-product zinc chloride. Combined with zinc chloride electrolysis process, The recycling of zinc and chlorine in the polysilicon production process can be realized, which not only has huge commercial value, but also has environmental protection benefits.

At present, there are two types of zinc smelting at home and abroad: pyrometallurgy and hydrometallurgy. Hydrometallurgy has the advantages of large production capacity, high efficiency, good operating conditions, low environmental pollution and comprehensive recovery of valuable metals, and has been widely used. Since hydrometallurgy zinc was put into industrial production at the beginning of the 20th century, its technology has been continuously developed and improved. At present, more than 80% of the world's total zinc production is produced by this process. At present, the wet zinc smelting in various countries in the world is zinc salt electrolysis, that is, electrolysis is carried out with a solution of sulfate, chloride or zincate. Industrial production uses zinc sulfate electrolysis. However, there have been no reports on the use of chloride electrolytic hydrometallurgy. The basic reaction principle of chloride electrodeposition zinc:

Electrode reaction:

Anode: 2Cl ^- -2e ^- ＝Cl ₂

Cathode: Zn ²⁺ +2e ^- = Zn

There are side effects:

Anode: 2OH ^- -4e ^- ＝O ₂ +2H ⁺

Cathode: 2H ⁺ -2e ^- = H ₂

Contents of the invention

In view of the defects in the prior art that zinc reduces silicon tetrachloride to generate solar-grade polysilicon to generate a large amount of zinc chloride and a large amount of zinc oxide in zinc/air batteries, the technical problem to be solved in the present invention is to propose a method of using an aqueous solution system to chlorinate A method for generating zinc and chlorine gas by zinc electrolysis, so as to realize the recycling of zinc and chlorine and the effective comprehensive utilization of resources.

The main contents _{of the technical solution of the present invention are: the by-product zinc chloride (ZnCl 2 )} formed by the reduction of the collected zinc to SiCl is dissolved with deionized water, or the collected zinc/air battery zinc electrode reaction product zinc oxide is dissolved with chlorine Chlorine gas generated by zinc electrolysis reacts to form a zinc chloride solution, and then add analytically pure ammonium chloride (NH ₄ Cl) and analytically pure sodium chloride (NaCl) to the zinc chloride solution as conductive salts. The electrolyte is electrolyzed with a small current to remove other heavy metal ions, then the electrolyte is injected into the electrolytic cell, the RuTi coated electrode is used as the anode, the polished pure aluminum sheet is used as the cathode, and direct current electrolysis, chlorine gas is obtained at the anode, and chlorine gas is obtained at the cathode. metal zinc.

The specific technical scheme proposed by the present invention to solve the technical problems is: a method for recovering high-purity zinc by electrolysis of zinc chloride, dissolving zinc chloride with deionized water, and maintaining the concentration of zinc chloride at 80-160g/L , add sodium chloride with a concentration of 80-140g/L and ammonium chloride with a concentration of 40-80g/L as conductive salt; the electrolyte is electrolyzed with a small current with a current density of 0.1A/dm ² to 1A/dm ² For heavy metal ions, RuTi-coated electrodes are used as anodes, high-purity aluminum is used as cathodes, electrolyzed in the above electrolyte at 25-35°C, and the cathode current density is controlled at 5-15A/dm ² to obtain high-purity zinc and chlorine gas. Specific steps are as follows:

The first step is to configure the initial electrolyte. According to the above electrolyte formula, dissolve conductive salts such as ammonium chloride and sodium chloride with deionized water, and then dissolve zinc chloride in it. Add the electrolyte prepared according to the formula into the buffer tank, electrolyze with a small current, and inject the electrolyte that removes heavy metal ions into the electrolytic tank to ensure that the electrolyte in the electrolytic tank is full to the overflow port, and at the same time submerge the bottom of the chlorine gas collection cover into the electrolytic tank In the liquid, use the electrolyte to seal. The electrolyte in the buffer tank is kept at half tank level, and the electrolyte seals the bottom of the chlorine gas collection cover.

The second step is to start electrolysis and continuously add zinc chloride to realize continuous electrodeposition of zinc. There can be one or more pairs of electrolytic electrodes in the electrolytic tank. According to the number of electrolytic electrodes and the size of the electrolytic current density, the amount of zinc chloride consumed by electrodeposition per unit time is calculated, and the amount of zinc chloride consumed is replenished in the buffer tank. Plus, keep the zinc chloride content of the electrolyte within the range required by the formula. In order to ensure the purity of zinc samples obtained by electrodeposition, it is necessary to appropriately increase the current density of heavy metal ions in the buffer tank by electrolysis with low current according to the speed of adding zinc chloride, or increase the number of electrode pairs for electrolysis with low current. Zinc chloride is mainly consumed in the electrolysis process, and because the zinc formed by electrodeposition on the cathode has a relatively large surface area, part of the electrolyte is taken out when collecting the cathode deposited zinc, and a small amount of conductive salt is lost, which will clean the electrodeposited product zinc. The solution returns to the buffer tank, which can keep the conductive salt stable in the formula of the above electrolyte for a long time.

In the present invention, a polished aluminum sheet is used as a cathode, and a 99.99% zinc sample can be obtained through a one-step electrolysis method.

In the present invention, a zinc sheet with a zinc content of 99.99% is used as a cathode, and high-purity zinc with a zinc content of 99.995% can be obtained by one-step electrolysis.

Beneficial effects of the present invention:

1. Through one-time electrodeposition, zinc samples with a purity of 99.99% can be obtained, which can be directly used for zinc reduction of silicon tetrachloride.

2. Collecting chlorine gas and drying it with concentrated sulfuric acid can also realize recycling.

3. The electrodeposition process can be carried out at room temperature.

4. After zinc chloride is electrolyzed, the recycling of zinc and chlorine is realized, and the problem of post-treatment of zinc chloride is solved.

Description of drawings

Fig. 1 is a structural schematic diagram of an electrolysis system that electrolyzes zinc chloride to generate zinc and chlorine.

Among them: 1 is acid and chlorine corrosion resistant glass and plastic electrolytic cell; 2 is polished pure aluminum cathode (zinc is deposited on this electrode); 3 is the power supply system used for electrodeposition (it can be DC power supply or pulse power supply); 4 is The insoluble anode used in the electrolysis system (it can be graphite anode, glass carbon anode or RuTi-coated DSA anode); 5 is the anode chlorine gas collection port; 6 is the anode cover (for collecting the anode chlorine gas); 7 is the electrolyte overflow Orifice (the position is slightly higher than the bottom of the anode cover to ensure that the bottom of the anode cover can be submerged in the electrolyte by 1-2cm during normal electrolysis); 8 is the chlorine gas collection port; 9 is the chlorine gas collection cover; 10 is the stirring device (one is to stir and dissolve and add 11 is the high-purity zinc anode for small current electrolysis; 12 is the DC power supply for small current electrolysis; ₁₃ is the aluminum cathode for small current electrolysis; 14 is the buffer tank; 15 16 is a circulation pump for electrolyte circulation; 17 is a pipeline for electrolyte to enter the electrolyzer.

Detailed ways

The present invention will be further elaborated below in conjunction with the accompanying drawings and specific embodiments. These examples should be understood as only for illustrating the present invention but not for limiting the protection scope of the present invention. After reading the contents of the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent changes and modifications also fall within the scope defined by the claims of the present invention.

A method for recovering high-purity zinc by electrolysis of zinc chloride provided by a preferred embodiment of the present invention uses an electrolysis system device as shown in Figure 1, dissolves zinc chloride with deionized water, and adds an appropriate amount of sodium chloride and ammonium chloride As a conductive salt; the electrolyte is electrolyzed with a small current to remove heavy metal ions, the RuTi coated electrode is used as the anode, and the high-purity aluminum is used as the cathode. Electrolysis is carried out in the above electrolyte to obtain high-purity zinc and chlorine gas. Wherein: the concentration of zinc chloride is controlled by means of continuous supplementation. The continuous replenishment of zinc chloride circulates the electrolyte into a buffer tank 14, adds zinc chloride solids into the buffer container, and circulates the high-concentration zinc chloride electrolyte back into the electrolytic cell 1 to control the electrolytic cell 1. Zinc chloride concentration. Lost sodium chloride, ammonium chloride and moisture are also replenished in the buffer tank. The electrolytic tank 1 is at a high position, and the side wall of the electrolytic tank is provided with an overflow tank 7 to control the electrolyte level in the tank, and the overflowed electrolyte directly flows into the low-level buffer tank 14, and the adjusted electrolyte in the buffer tank 14 is pumped by the circulation pump 16 into the electrolyzer. Small-current electrolysis uses zinc flakes with a purity of more than 99.99% as the anode 4 and high-purity aluminum as the cathode 2 . Small current electrolysis is carried out in the buffer tank 14 that adds zinc chloride. The high-purity aluminum cathode 2 needs to be degreased and polished.

Embodiment one

1. Put 80g of ammonium chloride and 100g of sodium chloride into a beaker respectively, stir and dissolve with deionized water.

2. Dissolve 160 grams of zinc chloride in the above conductive saline solution.

3. Using the electrolysis system device as shown in Figure 1, transfer the solution in the beaker to a 1L large cylinder to constant volume, and then pour it into the 1L plexiglass buffer tank 14.

4. Use a zinc sheet with a Zn99.99% content as an anode of 30×40mm, and a 30×40mm polished pure aluminum sheet as a cathode, and turn on a 0.02A direct current to electrolyze the above electrolyte for 1 hour.

5. Use a peristaltic pump to inject the electrolyte after electrolytic treatment with a small current into a 300mL glass electrolytic cell 1, use a RuTi-coated DSA anode of 40×60mm, a polished aluminum cathode of 40×60mm, and control the distance between electrodes to 4cm, and pass 2A DC current for electrolysis .

6. After 1 hour of electrolysis, 2.2015 g of the zinc product was collected. The analysis results of the deposited zinc element are shown in Table 1, and a 99.99% zinc product can be obtained.

Table 1

Sample name Analytical elements Analytical results (%)

Al 0.0004

As <0.0002

Ca 0.0002

Cd 0.001

Cu 0.0008

                                                            

                                                                 

Zn-like Pb 0.002

                                                                          

Bi <0.0005

                                           

                                                                         

                                      

Zn >99.99

Embodiment two

1. Put 80g of ammonium chloride and 100g of sodium chloride into a beaker respectively, stir and dissolve with deionized water.

2. Dissolve 160 grams of zinc chloride in the above conductive saline solution.

3. Using the electrolysis system device as shown in Figure 1, transfer the solution in the beaker to a 1L large cylinder to constant volume, and then pour it into the 1L plexiglass buffer tank 14.

4. Use a zinc sheet with a Zn99.99% content as an anode of 30×40mm, and a 30×40mm polished pure aluminum sheet as a cathode, and turn on a 0.02A direct current to electrolyze the above electrolyte for 1 hour.

5. Use a peristaltic pump to inject the electrolyte after electrolytic treatment with a small current into the 300mL glass electrolytic cell 1, use RuTi-coated DSA anode 40×60mm, use zinc sheet cathode with Zn99.99% content 40×60mm, and control the electrode distance to 4cm , Through 2A DC current electrolysis.

6. After 1 hour of electrolysis, 2.2236 g of the zinc product was collected. The analysis results of the deposited zinc element are shown in Table 2, and a 99.99% zinc product can be obtained.

Table 2

Name of sample Analysis element Analysis result (%)

                                                                    

                                             

Cd 0.0002

                                                 

                                                 

Zn-like Pb <0.001

                                                                            

Bi <0.0005

Sn ＜0.0003

Total ＜0.0034

                        ＞ 99.995

Claims (8)

1. the method for a zinc chloride electrolytic recovery high purity zinc; It is characterized in that: zinc chloride is dissolved with deionized water; And to keep zinc oxide concentration be 80～160g/L, adds concentration and be the sodium-chlor of 80～140g/L, ammonium chloride that concentration is 40～80g/L as conducting salt; It is 0.1A/dm that electrolytic solution adopts current density ²～1A/dm ²Little current electroanalysis remove heavy metal ion, adopt the RuTi coated electrode to do anode, rafifinal is done negative electrode, carries out electrolysis at above-mentioned electrolytic solution under 25～35 ℃, cathode current density is controlled at 5～15A/dm ², obtain high purity zinc and chlorine.

2. the method for zinc chloride electrolytic recovery high purity zinc as claimed in claim 2 is characterized in that, the concentration of zinc chloride, sodium-chlor and ammonium chloride is able to keep through the mode of adding continuously.

3. the method for zinc chloride electrolytic recovery high purity zinc as claimed in claim 3; It is characterized in that; Zinc chloride add continuously through with circulation of elecrolyte in a dashpot; The zinc chloride solid is added in the dashpot, and high density chlorination zinc electrolyte is circulated back in the electrolyzer, zinc oxide concentration in the control electrolyzer.

4. the method for zinc chloride electrolytic recovery high purity zinc as claimed in claim 4; It is characterized in that; Electrolyzer is in a high position; Cell sidewall has overflow groove control flume electrolyte inside liquid level, and the effusive electrolytic solution that overflows flows directly into the low level dashpot, and the electrolytic solution of adjusting in the dashpot is squeezed in the electrolyzer through recycle pump.

5. the method for zinc chloride electrolytic recovery high purity zinc as claimed in claim 1 is characterized in that, little current electroanalysis adopts the zinc metal sheet of purity more than 99.99% to make anode, and rafifinal is done negative electrode.

6. like the method for any one described zinc chloride electrolytic recovery high purity zinc in the claim 1～5, it is characterized in that little current electroanalysis carries out in the dashpot that adds zinc chloride.

7. the method for zinc chloride electrolytic recovery high purity zinc as claimed in claim 1 is characterized in that, the rafifinal negative electrode is through oil removing and polished finish.

8. the method for zinc chloride electrolytic recovery high purity zinc as claimed in claim 1 is characterized in that, the electrolysis cathode current density is 7～9A/dm ²

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