阅读说明：本技术 一种加压锌粉净化硫酸锌溶液的方法 (Method for purifying zinc sulfate solution by using pressurized zinc powder ) 是由 罗永光 张利波 李静 曲洪涛 张侯文 夏洪应 谢庭芳 王仕兴 顾利坤 杨大锦 杨 于 2018-08-06 设计创作，主要内容包括：本发明公开了一种净化硫酸锌溶液的方法,以除去硫酸锌溶液中铜、镉、钴和镍等金属杂质,步骤包括：将锌粉调浆加热,通过加压设备加压,形成热压锌粉以喷射流体射入硫酸锌溶液中进行净化处理,锌粉耗量为待处理金属杂质总质量的1.2～2.5倍,经反应-固液分离后,获得净化后的硫酸锌溶液。根据本发明提供的净化方法,有效地优化了锌粉-溶液之间的固-液传热过程,保证反应界面温度高于溶液温度,促进化学反应热力学过程,能够在高效除杂的同时有效的降低锌粉耗量和缩短置换反应时间,减少渣量的产生及提高后续渣中有价金属的回收；同时避免硫酸锌整体溶液温度的增加,降低生产过程能耗；综合实现了经济效益和环境效益。(The invention discloses a method for purifying a zinc sulfate solution to remove metal impurities such as copper, cadmium, cobalt, nickel and the like in the zinc sulfate solution, which comprises the following steps: and (2) mixing and heating the zinc powder, pressurizing the mixture through a pressurizing device to form hot-pressed zinc powder, injecting a jet fluid into the zinc sulfate solution for purification treatment, wherein the consumption of the zinc powder is 1.2-2.5 times of the total mass of the metal impurities to be treated, and carrying out reaction-solid-liquid separation to obtain the purified zinc sulfate solution. According to the purification method provided by the invention, the solid-liquid heat transfer process between zinc powder and a solution is effectively optimized, the temperature of a reaction interface is higher than the temperature of the solution, the thermodynamic process of chemical reaction is promoted, the consumption of the zinc powder can be effectively reduced while the impurities are efficiently removed, the replacement reaction time is shortened, the generation of slag amount is reduced, and the recovery of valuable metals in subsequent slag is improved; meanwhile, the increase of the temperature of the whole zinc sulfate solution is avoided, and the energy consumption in the production process is reduced; the economic benefit and the environmental benefit are comprehensively realized.)

1. A method for purifying a zinc sulphate solution, which method comprises introducing zinc powder in the form of a spray stream into the zinc sulphate solution for a purification reaction.

2. The method as defined in claim 1, characterized in that the zinc powder is passed through a spraying device, using a non-oxidizing gas as a protective gas and a pressurizing medium, to form a spray jet at a set pressure, to be passed into the zinc sulphate solution;

the set pressure is 0.1 to 4.4MPa, preferably 0.3 to 3.5 MPa.

3. The method of claim 1, further comprising heating the zinc powder to raise the temperature of the zinc powder so that the zinc powder is added to the zinc sulfate solution as a high temperature zinc powder.

4. A method according to claim 3, characterized in that the zinc dust is at a temperature of 50-255 ℃, preferably 80-200 ℃, and above the temperature of the zinc sulphate solution to be purified and below the melting point of the metallic zinc.

5. A method as claimed in claim 4, characterized in that a protective measure against oxidizing gases and/or liquids is used during the heating to ensure that the zinc powder is not oxidized; the non-oxidizing gas is an inert gas including nitrogen or a noble gas such as argon; the non-oxidizing liquid is an inert liquid, and the inert liquid comprises water or the same liquid as the purification system;

the heating mode of the zinc powder comprises a direct heating method and an indirect heating method, wherein the direct heating method adopts non-oxidizing gas alone to protect the zinc powder; the indirect heating method adopts non-oxidizing liquid or the combination of non-oxidizing gas and non-oxidizing liquid to protect the zinc powder.

6. The method as claimed in claim 3, characterized in that the zinc powder is added in an amount of 1.2 to 2.5 times, preferably 1.5 to 2 times, the total mass of the metal impurities to be removed in the zinc sulphate solution;

the metal impurities to be removed in the zinc sulfate solution are metal impurities with weaker reducibility than zinc elements, such as one or more of copper, cadmium, cobalt, nickel, arsenic, antimony and germanium.

7. The method according to claim 3, wherein the reaction temperature during the purification of the zinc sulfate solution is 50-80 ℃, preferably 50-70 ℃, i.e. when the zinc sulfate solution is a leachate produced by zinc hydrometallurgy, the temperature of the leachate does not need to be raised during the purification reaction.

8. The method according to claim 3, characterized in that the time of the zinc sulfate solution purification treatment is 10-60 minutes, preferably 20-50 minutes.

9. A method according to claim 3, characterized in that the zinc powder is sprayed into the zinc sulphate solution continuously during the operating time or intermittently, preferably intermittently, and more preferably 2-4 times.

10. A method according to claim 3, characterized in that no activator is involved in the method in combination with the zinc powder.

Technical Field

The invention relates to the field of fine chemical engineering, in particular to a method for purifying zinc sulfate solution by using pressurized zinc powder.

Background

The zinc sulfate solution in the zinc hydrometallurgy often contains impurities such as copper, cadmium, cobalt, nickel, arsenic, antimony, germanium and the like, which are extremely harmful to the electrolytic deposition process of zinc, and the excessive content of the impurities can reduce the electrolytic current efficiency and influence the quality of cathode zinc. Therefore, all impurities that are detrimental to zinc electrowinning must be removed by solution purification, which yields a qualified zinc sulfate solution.

The purification of zinc sulfate solution usually adopts zinc powder adding displacement method, and is assisted by adding additives, including zinc powder-arsenic salt method, zinc powder-antimony salt method, alloy zinc powder method and other purification methods. In the actual production process, according to different requirements of various impurity elements to be removed on temperature, the purification process is divided into two or more sections, the purification time is more than 2.5 hours, wherein the integral temperature of the zinc sulfate solution in at least one section of high-temperature impurity removal process needs to be maintained at more than 78 ℃, and the time reaches 1-2 hours.

In the existing purification operation, electric furnace zinc powder (or metal zinc powder) under the condition of normal temperature (room temperature) is added into a zinc sulfate solution, or the zinc powder is simply made into high pulp by using liquid and then added into the zinc sulfate solution. The added zinc powder absorbs the heat of the solution, so that the surface temperature reaches the thermodynamic condition of the reaction and then the replacement reaction starts to occur. In the heat absorption-heat transfer process, the temperature inside the zinc powder is slowly increased to be balanced with the temperature of the solution, in the temperature balancing process, a reaction interface is in a low-temperature stage, the replacement reaction is slow, the zinc powder rapidly reacts with acid in the solution to cause the pH value on the surface of the zinc powder to be rapidly increased, hydroxide is formed to wrap the zinc powder, and the electronic transfer in the replacement process is blocked. Therefore, the traditional zinc sulfate solution purification process has the problems of low utilization efficiency of zinc powder, large consumption of zinc powder (generally, the addition amount is 3-5 times or even higher than the total mass of copper, cadmium, cobalt and nickel), strict temperature condition of the zinc sulfate solution, more than two times of liquid-solid separation required in the process, large energy consumption in the whole production process and high production cost. Therefore, the purification method of zinc sulfate solution is to be further improved.

The invention aims to overcome the defects in the prior art and provide the method for purifying the zinc sulfate solution by using the hot-pressing zinc powder, which is the zinc sulfate solution purification method with simple process flow, easy implementation, reduced energy consumption and capability of realizing economic benefit and environmental benefit.

Disclosure of Invention

In order to solve the above problems, the present inventors have conducted intensive studies and have provided a method for removing at least one metal impurity of copper, cadmium, cobalt, nickel, arsenic, antimony, etc. from a zinc sulfate solution by heating zinc powder under pressure by a pressurizing device using a non-oxidizing gas and/or a non-oxidizing liquid as a protective medium to form high-temperature zinc powder by heating, and injecting the high-temperature zinc powder into the zinc sulfate solution by a jet flow to purify the zinc sulfate solution, thereby obtaining a purified and qualified zinc sulfate solution. The method for purifying the zinc sulfate solution can obviously reduce the consumption of zinc powder and the temperature of the zinc sulfate solution, shorten the purification time, reduce the filtration times, save the purification power consumption and energy consumption, obviously reduce the treatment cost and avoid the deterioration of the operating environment, thereby completing the invention.

The invention aims to provide the following technical scheme:

(1) a method for purifying a zinc sulphate solution, which method comprises introducing zinc powder in the form of a spray stream into the zinc sulphate solution for a purification reaction.

(2) The method according to the above (1), further comprising heating the zinc powder to raise the temperature of the zinc powder so that the zinc powder is added to the zinc sulfate solution as a high temperature zinc powder.

(3) According to the method in the (2), the adding amount of the zinc powder is 1.2-2.5 times, preferably 1.5-2 times of the total mass of the metal impurities to be removed in the zinc sulfate solution;

the reaction temperature is 50-80 ℃, and preferably 50-70 ℃;

the time for the purification treatment is 10 to 60 minutes, preferably 20 to 50 minutes.

The method for purifying the zinc sulfate solution by using the pressurized zinc powder provided by the invention has the following beneficial effects:

(1) the method comprises the steps of introducing zinc powder into a zinc sulfate solution in a pressurized jet flow mode for purification reaction, and damaging coating hydroxides formed on the surface of the zinc powder by friction with solid particles and liquid to expose fresh surfaces to promote replacement reaction.

(2) The method can also comprise the step of adding the zinc powder into the zinc sulfate solution in the form of high-temperature zinc powder, the problem of zinc powder agglomeration can be effectively solved by the high-temperature zinc powder, and the method has long-term development in the aspects of improving the reaction efficiency, reducing the usage amount of the zinc powder, improving the impurity residue grade and the like.

(3) The method of the invention adopts hot-pressed zinc powder to purify the zinc sulfate solution, the consumption of the zinc powder is greatly reduced compared with the prior art, the treatment time is obviously shortened, the slag amount is greatly reduced, the increase of the temperature of the whole zinc sulfate solution is avoided, the energy consumption in the production process is reduced, and the improvement of economic benefit and environmental benefit is comprehensively realized.

Drawings

FIG. 1 shows a flow chart of the purification of zinc sulfate solution by hot-pressed zinc powder provided by the invention.

Detailed Description

The features and advantages of the present invention will become more apparent and appreciated from the following detailed description of the invention.

In the leaching process of zinc sulfate, most of the metal impurities entering the solution are removed from the solution along with the neutralization hydrolysis during leaching, but a part of the impurities remain in the solution, mainly copper (Cu), cadmium (Cd), nickel (Ni), which have a redox potential greater than that of zinc, and a small amount of cobalt (Co), arsenic (As), antimony (Sb), germanium (Ge), and the like. The presence of these impurities not only poses a great hazard to the zinc electrowinning process, but also makes it absolutely necessary to separate them from the overall resources. Therefore, the neutral leachate obtained in the leaching process is purified. The purification is a process of removing impurities in the neutral supernatant after leaching and filtration to a predetermined limit or less to increase the purity thereof so as to satisfy the requirement of the leachate in the electrodeposition.

In the present invention, the redox potential is a relative value, which is 1X 10⁵The potential difference between the platinum sheet saturated with hydrogen gas in pa and the hydrogen ion solution having a concentration of 1 mol/liter is specified to be zero, that is, the equilibrium potential of the following reduction reactions is specified to be equal to zero:

in the present invention, the leachate satisfying the electrolytic deposition, i.e. the qualified leachate, includes but is not limited to the following conditions: the copper content is lower than 0.2 mg/L; the cadmium content is lower than 0.3 mg/L; the cobalt content is lower than 0.8 mg/L; the content of nickel is lower than 0.1 mg/L; the arsenic content is lower than 0.001 mg/L; the content of antimony is lower than 0.002 mg/L; the content of germanium is less than 0.06 mg/L.

The present inventors have conducted a great deal of research on the purification process of leachate, and found that zinc powder put into leachate can react with hydrogen having a higher oxidation-reduction potential to produce insoluble zinc hydroxide on the surface of the zinc powder; and because the temperature of the added zinc powder is low, heat absorption is needed to achieve the thermodynamic conditions of the reaction, and then the replacement reaction begins to occur; in the heat transfer process, the temperature of the solution in the zinc powder is slowly increased to be balanced with the temperature of the solution, and in the temperature balancing process, a reaction interface is in a low-temperature stage, the replacement reaction is slow, so that the zinc powder is further promoted to rapidly react with acid in the solution to rapidly increase the pH value on the surface of the zinc powder, the zinc powder is wrapped by hydroxide, and the purification reaction efficiency is reduced.

In order to solve the above problems, the present invention provides a method for purifying a zinc sulphate solution, which comprises introducing zinc powder in the form of a jet into the zinc sulphate solution for a purification reaction.

In the invention, the zinc sulfate solution is leachate of zinc hydrometallurgy or zinc sulfate solution with pH of 4.5-5.4.

In the invention, the particle size of the zinc powder is 0.08-0.4 mm, preferably 0.12-0.18 mm. From the viewpoint of increasing the specific surface to accelerate the substitution reaction, it is naturally better that the particle size of the zinc powder is smaller, but if it is too small, it will cause it to float on the surface of the solution, and it is apparently not favorable for the effective use of the zinc powder. The inventor finds that when the particle size is 0.08-0.4 mm, particularly 0.12-0.18 mm, zinc powder can be suspended in a zinc sulfate solution to be treated and is surrounded by liquid, the reaction efficiency is high, and the reaction requirement can be met.

In a preferred embodiment, zinc powder is passed into the zinc sulphate solution by means of a spraying device, which forms a spray at a set pressure, using a non-oxidising gas as protective gas and a pressurizing medium.

Further, the non-oxidizing gas is an inert gas including nitrogen or a noble gas such as argon.

Further, the set pressure is the injection pressure of the injection equipment for the zinc powder, and the set pressure is 0.1-4.4 MPa, preferably 0.3-3.5 MPa.

In the present invention, the reason why the set pressure is 0.1 to 4.4MPa is determined as follows: if the injection pressure is lower than 0.1MPa, the injection capability is insufficient, and hydroxide formed on the surface of the zinc powder cannot be effectively removed through solid-liquid friction; if the injection pressure is more than 4.4MPa, the impact force on the zinc sulfate solution in the reaction container is extremely large, which brings more challenges to the production safety and the reaction container and is not beneficial to production control.

In the invention, zinc powder formed at high pressure is injected into zinc sulfate solution (including leachate) at high speed, and coated hydroxide formed on the surface of the zinc powder is damaged by friction with liquid to expose fresh surface so as to promote replacement reaction, thereby improving the contact interface area of the zinc powder and the zinc sulfate solution; meanwhile, zinc powder is injected at a high speed to react with impurity ions in the solution to generate a multi-element metal simple substance, and the metal simple substance collides to form multi-element alloy, so that the displacement reaction is further promoted.

The inventor further discovers in research that the existing zinc sulfate purification process is generally to add zinc powder at room temperature (normal temperature) into the leaching solution, or add zinc powder-activating agent (such as zinc powder-antimony salt) at room temperature into the leaching solution in a batch manner or in batches, wherein the temperature of the zinc sulfate leaching solution is 50-80 ℃ which is far higher than the temperature of the added zinc powder or zinc powder-activating agent. This causes the following problems: after the normal-temperature zinc powder is added into the hot leaching liquid, the agglomeration effect is very easy to occur just like adding coffee powder into hot water, but the agglomeration effect is more obvious because of the water insolubility of the zinc powder, and the agglomeration is difficult to disintegrate even through a stirring mode.

The problem of zinc powder agglomeration can cause at least four negative consequences:

(i) hydroxide encapsulation, affecting the displacement process:

the zinc powder forming the aggregate is lower than the leachate, and the surface temperature of the zinc powder reaches the reaction thermodynamic condition and starts to generate a replacement reaction by absorbing the heat of the leachate; in the temperature balancing process, a reaction interface is in a low-temperature stage, the replacement reaction is slow, the zinc powder rapidly reacts with acid in the leachate to cause the pH value on the surface of the zinc powder to be rapidly increased, hydroxide coated zinc powder is formed, and the electronic transfer in the replacement process is blocked; compared with dispersed zinc powder, the zinc powder forming the aggregates has slower heat transfer speed and stronger resistance to electron transfer;

(ii) the zinc powder has low utilization rate and high reaction cost:

the agglomerated zinc powder reacts with metal impurities with higher oxidation-reduction potential in the leachate, the zinc powder is wrapped by the replaced impurities in a precipitation mode, the agglomerates wrapped by the impurity precipitates are difficult to open even if stirring is carried out, the internal zinc powder cannot participate in the reaction, the waste of the zinc powder is caused, the additional use amount of the zinc powder is required because part of the zinc powder cannot participate in the reaction, and the cost of the zinc powder is increased;

(iii) the reaction area is not uniform, and the replacement process is influenced:

the inevitable agglomeration of zinc powder can cause uneven reaction areas in the leachate, the concentration of the zinc powder in some areas is increased rapidly, the reaction is severe, and metal impurity ions tend to diffuse towards the areas, but the diffused metal impurity ions cannot participate in the reaction due to the factors such as coating or complete consumption of the surface of the zinc powder, and the concentration of the metal impurity ions in the areas with lower concentration of the zinc powder is also lower, so that the uneven 'hot spot' effect in the reaction areas hinders an ion replacement channel, and the process of replacement and impurity removal is slowed down on the whole;

(iv) influence the grade of the precipitate (slag):

after the reaction is finished, precipitate (slag) is obtained through solid-liquid separation, during industrial production, valuable metals with larger oxidation-reduction potential, such as copper, cadmium, cobalt and nickel, in the slag can be recovered, and the wrapped zinc powder serving as impurities in the slag can influence the grade of the metals, so that the further comprehensive recovery is not facilitated, and the overall economic benefit is reduced.

Aiming at the problems caused by the zinc powder at normal temperature, the inventor conducts a great deal of research and finds that the agglomeration phenomenon of the zinc powder or the adverse consequences caused by the agglomeration phenomenon of the zinc powder is slightly improved by increasing the stirring strength in the reaction process, increasing the reaction time, replacing the pure zinc powder method with a zinc powder-activating agent, changing the components of the activating agent and the like.

The inventors have surprisingly discovered that by heating zinc powder to raise the temperature of the zinc powder, the zinc powder is added to the zinc sulfate solution as high temperature zinc powder, effectively solving the problem of zinc powder agglomeration.

In a preferred embodiment, the temperature of the zinc powder is 50-255 ℃, preferably 80-200 ℃, and is higher than the temperature of the zinc sulfate solution to be purified and lower than the melting point of the metal zinc. The inventors have found that the minimum temperature of the zinc powder is higher than the temperature of the zinc sulphate solution to avoid heat transfer from the zinc sulphate solution to the zinc powder; when the temperature of the zinc powder is 50-255 ℃, the temperature difference between the zinc powder and a zinc sulfate solution can reach 0-205 ℃, the temperature difference can avoid the agglomeration of the zinc powder and other problems, and the more difficult the agglomeration of the zinc powder is generated along with the increase of the temperature difference; the temperature difference is higher than 205 ℃, and the method does not improve the zinc powder agglomeration and the reaction efficiency.

The method for solving the problem of zinc powder agglomeration is simple, but the zinc powder pretreatment process has the following technical effects:

(a) the adverse consequences of at least four aspects (i to iv) caused by the zinc powder agglomeration are effectively solved;

(b) the replacement reaction in the purification process needs to be carried out at a certain temperature, the temperature of the zinc powder is increased, the zinc powder is dissolved and dispersed in the zinc sulfate solution to be purified, the contact area between the surface of the zinc powder and the zinc sulfate solution is increased, and meanwhile, the zinc powder is used as a dispersed heat source to meet the temperature of the replacement reaction, so that the purification reaction process is accelerated;

(c) the temperature of the zinc powder is increased, the heat transfer process from the zinc sulfate solution to the zinc powder does not exist, and the purification reaction process is accelerated.

In the invention, non-oxidizing gas and/or non-oxidizing liquid protection measures are adopted during the heating process to ensure that the zinc powder is not oxidized. The non-oxidizing gas is an inert gas including nitrogen or a noble gas such as argon; the non-oxidizing liquid is an inert liquid comprising water or the same liquid as the purification system (which may be a pure zinc sulphate solution or a zinc sulphate leach solution).

In one embodiment, the zinc powder is heated by a direct heating method. The direct heating method is that a heat source directly heats zinc powder without a heating medium (such as water or steam), and non-oxidizing gas is used for protection during heating; the zinc powder is heated, for example, by a heating device such as an oven and protected with nitrogen gas.

In one embodiment, the zinc powder is heated by an indirect heating method. The indirect heating method is that a heat source heats the zinc powder through a heating medium to achieve the purpose of increasing the temperature of the zinc powder, and at the moment, the heating medium is non-oxidizing liquid; for example, the zinc powder is slurried with water and then heated; optionally, inert gas may also be passed in for further protection.

As can be seen from the above heating method, the direct heating method is to use a non-oxidizing gas alone; the indirect heating method may employ a non-oxidizing liquid, or a combination of a non-oxidizing gas and a non-oxidizing liquid.

Preferably, the zinc powder is heated by an indirect heating method; compared with a direct heating method, the indirect heating method is more beneficial to controlling the temperature of the zinc powder, and the non-oxidizing liquid is evaporated to increase the pressure in the heating process, so that the zinc powder is sprayed into the zinc sulfate solution.

In the present invention, zinc powder is pretreated in a combination of pressurization and heating and then used for subsequent purification treatment, and the pretreated zinc powder is called hot-pressed zinc powder. And (3) injecting the high-temperature zinc powder formed after heating into the zinc sulfate solution at a high speed through a nozzle of injection equipment under the propelling of non-oxidizing gas for purification treatment to obtain the purified zinc sulfate solution.

In the present invention, the injection equipment and the pressurizing equipmentThe equipment is not particularly limited and conventional injection equipment and pressurization equipment may be used, but is preferably an integrated equipment. The injection equipment mainly utilizes an air compressor to inject and blow zinc powder, and the air quantity produced by the air compressor meets 100m³H, the highest exhaust pressure meets 8kg/cm²。

In the invention, when hot-pressing zinc powder is adopted for purifying the zinc sulfate solution, the addition amount of the zinc powder is 1.2-2.5 times, preferably 1.5-2 times of the total mass of metal impurities to be removed in the zinc sulfate solution.

In a preferred embodiment, the metal impurities to be removed in the zinc sulphate solution are metal elements that are less reducing than the zinc element, such as copper, cadmium, cobalt, nickel, arsenic, antimony, germanium, etc. The reducibility of the metal is represented by an oxidation-reduction potential, and if the oxidation-reduction potential is large, the reducibility is weak, and if the oxidation-reduction potential is large, the reducibility is strong. Wherein, Zn²⁺The redox potential of/Zn is-0.76V, Cu²⁺The redox potential of/Cu is +0.34V, Cd²⁺The redox potential of/Cd is-0.40V, Co²⁺The redox potential of/Co is-0.28V, Ni²⁺The redox potential of/Ni is-0.25V, As³⁺/AsH₃Has a redox potential of-0.23V, Sb³⁺The redox potential of/Sb is +0.21V, Ge⁴⁺The redox potential of/Ge was + 0.12V. It is known that zinc has a stronger reducibility than copper, cadmium, cobalt, nickel, arsenic, antimony, and germanium.

Compared with the using amount (generally 3-5 times or even higher than the total mass of the metal impurities) in the prior art, the consumption amount of the zinc powder is remarkably reduced, the slag amount is reduced, the grades of valuable metals such as copper, cadmium, cobalt, nickel and the like in the slag are increased, further comprehensive recovery is facilitated, and the economic benefit is improved.

In the invention, when hot-pressed zinc powder is adopted for purifying the zinc sulfate solution, the reaction temperature is 50-80 ℃, preferably 50-70 ℃, namely when the zinc sulfate solution is a leaching solution produced by zinc hydrometallurgy, the temperature of the leaching solution does not need to be raised in the purification reaction process, the temperature of the leaching solution can be directly used for meeting the purification reaction requirement, and the energy consumption in the purification process is further reduced.

In the invention, when the hot-pressed zinc powder is used for purifying the zinc sulfate solution, the purification treatment time is 10-60 minutes, preferably 20-50 minutes, so that the hot-pressed zinc powder and impurities in the zinc sulfate solution can completely and fully react.

Correspondingly, in the existing practical production process, no matter the one-stage reaction or two-stage or more than two-stage purification process, the purification time is more than 2.5 hours. The purification mode greatly reduces the purification time, improves the purification efficiency, reduces the energy consumption and saves the treatment cost.

In a preferred embodiment, the zinc powder can be continuously sprayed into the zinc sulfate solution in the operation time or intermittently sprayed for a plurality of times, and the two spraying modes can realize effective removal of impurity metals in the operation time to obtain qualified zinc sulfate solution.

Preferably, the zinc powder is intermittently sprayed into the zinc sulfate solution for multiple times for purification treatment, so that the mixing of the zinc powder and the solution is promoted, and the reaction efficiency is accelerated; on the other hand, a small amount of zinc powder is added for many times, so that the agglomeration of the zinc powder is avoided.

More preferably, the zinc powder is introduced into the zinc sulfate solution 2 to 4 times for the convenience of production operation.

The inventor finds that in the actual production process, according to different requirements of various impurity elements for removing temperature, the purification process is divided into two or more sections so as to make up the problem that one-section reaction cannot fully remove various elements, so that correspondingly, solid-liquid separation is needed after each section is finished, and generated dregs are removed, so that the filtration frequency is relatively high.

Meanwhile, from thermodynamic analysis, the zinc powder is adopted to replace copper, cadmium, cobalt, nickel, arsenic, antimony and germanium, which can be purified completely, but in practice, the zinc powder is adopted to replace and purify copper and cadmium more easily, but the cobalt and nickel are not purified easily. Copper can be easily removed by precipitation with a theoretical amount of zinc powder, cadmium can be removed with several times the theoretical amount of zinc powder, but cobalt is difficult to remove with a large amount of zinc powder, even several hundred times the theoretical amount of zinc powder, to the extent required for zinc electrowinning (deep purification of leachate, required Co²⁺The concentration is reduced to below 1-2 mg/L. The reason why cobalt is difficult to remove is explained as Co in more documents at home and abroad²⁺The overvoltage is high during reduction and precipitation.

In order to improve the removal effect and efficiency, the purification method of the leachate can be roughly divided into two types, one is to add zinc powder to remove copper and cadmium and then remove cobalt and nickel under the condition of the existence of an activating agent, the other is to add zinc powder to remove copper and cadmium and then add special medicaments to react with cobalt to generate insoluble solid for removing cobalt, the former comprises a zinc powder-antimony salt purification method, a zinc powder-arsenic (arsenate) purification method, an alloy zinc powder method and the like, and the latter comprises a zinc powder-xanthate purification method, a zinc powder- β -naphthol method and the like.

Through a large number of verification tests, the inventor surprisingly finds that when hot-pressed zinc powder is used for purifying zinc sulfate solution, the effective removal of various metal elements including copper, cadmium, cobalt, nickel, arsenic, antimony and germanium including cobalt can be realized by adopting a one-stage reaction within the purification treatment time (10-60 minutes).

The purification treatment of the invention can achieve the effective removal of the impurity metal through one-stage reaction, but is not limited to one-stage reaction, and can also be a multi-stage hot zinc powder purification combination mode according to the production requirement.

Fig. 1 shows the specific operation steps of zinc sulfate solution purification using hot-pressed zinc powder according to a preferred embodiment of the present invention:

the method comprises the steps of mixing zinc powder with non-oxidizing liquid, carrying the mixed slurry into a pressurizing device through a pressurizing pump, heating to 50-255 ℃, using non-oxidizing gas as a pressurizing medium, injecting hot zinc powder into a zinc sulfate solution through an injection fluid by means of pressure in the device to purify the hot zinc powder, wherein the consumption of the zinc powder is 1.2-2.5 times of the total mass of metal impurities with weaker reducibility than that of zinc, such as copper, cadmium, cobalt and nickel, the temperature of the zinc sulfate solution is 50-80 ℃, reacting for 10-60 minutes, and finally performing solid-liquid separation to obtain a purified qualified zinc sulfate solution and solid impurities.