WO2013166789A1

WO2013166789A1 - Cadmium removing process in zinc-containing solution purification and purification method of zinc-containing solution

Info

Publication number: WO2013166789A1
Application number: PCT/CN2012/079545
Authority: WO
Inventors: 高麟; 汪涛
Original assignee: 成都易态科技有限公司
Priority date: 2012-05-07
Filing date: 2012-08-02
Publication date: 2013-11-14
Also published as: JP6114381B2; KR101939433B1; JP2015516033A; CA2872927C; WO2013166789A8; KR20150007315A; CA2872927A1; CN102808083A; CN102808083B

Abstract

Disclosed are a cadmium removing process in zinc-containing solution purification with better cadmium removing effect and a purification method of zinc-containing solution with desired purification effect. The cadmium removing process in zinc-containing solution purification in the present invention includes following steps: 1) removing colloid from neutral leachate or supernatant of the neutral leachate after precipitation to obtain zinc-containing solution with colloid content less than or equal 50 mg/L; 2) performing zinc powder substitution in zinc-containing solution to at least replace cadmium; 3) carrying out solid-liquid separation to filter the zinc-containing solution containing impurity of cadmium, wherein filtering time is controlled within 60 minutes and filter precision is controlled within 10μm. In the present invention, the process of removing colloid from neutral leachate or supernatant first and then performing zinc powder substitution and filtration for solid-liquid separation is provided creatively and the selection and collocation of the key parameters such as colloid content in the zinc-containing solution after removing colloid and the filtering time and filter precision when filtering for solid-liquid separation is also provided to determine the final cadmium removing process.

Description

Cadmium removal process and zinc liquid purification method in zinc liquid purification

The invention relates to a zinc sulphate solution (hereinafter referred to as zinc liquid) purification process in the wet zinc smelting process, and specifically relates to removing impurities in the neutral leaching liquid below a prescribed limit to meet the requirements for the new liquid during electrolytic deposition.

Background technique

In the conventional zinc liquid purification method, the neutral leachate is first introduced into a thickener for concentration treatment, and then the concentrated supernatant (ie, the supernatant) is subjected to zinc powder replacement treatment. For example, Figure 1 of CN101994005A shows three stages of purification of the supernatant, the first stage of purification of copper, the second stage of removal of cobalt and nickel, and the third stage of purification of cadmium, and each stage of purification The process of removing the zinc solution after the separation by solid-liquid separation.

Some zinc plants directly replace the neutral leachate with zinc powder. For example, in the flow chart of "Zinc Liquid Cleaning Process Design of Electrolytic Zinc Plant, Yang Lian, Engineering Design and Research, No. 119, June 2006", the three-stage purification of neutral leachate is shown. One section purifies copper and cadmium, the second section purifies cobalt and nickel, and the third section purifies and removes cadmium again, and each section is cleaned and separated by solid-liquid separation to obtain the zinc solution after impurity removal.

In summary, the current trend of research on the zinc liquid purification process shows that the improvement of the zinc liquid purification process tends to focus on the zinc powder replacement process, and the neutral leachate or neutral leachate before the start of the displacement reaction. The treatment of the supernatant obtained after precipitation is rarely involved.

Even so, the problem of deep purification of cadmium has not been completely solved. Among them, the more important reason is that the existing zinc liquid purification process basically uses the filter cloth as the filter element in the solid-liquid separation and filtration, and the filter cloth generally has limited filtration precision, which easily leads to cadmium permeation; Cadmium is particularly easy to reverse. Therefore, the two reference documents given above have adopted a three-stage purification process, and the last stage of purification involves cadmium removal. It can be seen that the fundamental purpose is to improve the purification level of cadmium. Obviously, the three-stage purification process has a long process and consumes a large amount of zinc powder.

Summary of the invention

The technical problem to be solved by the present invention is firstly to provide a cadmium removal process in zinc liquid purification to achieve a better cadmium removal effect. Secondly, the present invention also provides a zinc liquid purification method which is ideal for purification and a filter residue obtained by the method, and the solid zinc having higher purity in the residue is used for subsequent use.

First, the cadmium removal process in the zinc liquid purification process of the present invention comprises the following steps: 1) removing the neutral leaching solution or the supernatant obtained by the neutral leaching solution, and removing the colloidal solution to obtain zinc having a colloid content of 50 mg/L or less. 2) Displace at least cadmium in zinc solution by zinc powder replacement method; 3) Perform solid-liquid separation and filtration on zinc solution containing impurity cadmium, wherein the filtration time is controlled within 60 minutes, and the filtration precision is controlled at Below 10 microns. The colloid in the neutral leachate or the supernatant obtained by precipitation from the neutral leachate is mainly a substance such as silica gel or iron gel, and these colloidal substances are present in the form of agglomeration in the zinc solution. Generally, the colloid content in the middle supernatant is about lg/L, while the colloid content in the neutral leachate is larger. Due to the presence of these colloidal substances, one is to reduce the effect of zinc powder replacement, and the other is to hinder the separation and filtration of solid-liquid, thus greatly affecting the effect of removing cadmium. In view of the above, the invention adopts the method of first removing the neutral leachate or the supernatant solution by colloid treatment, and then reinforcing the liquid separation by the zinc powder replacement method, and colloidal in the zinc solution after the colloid treatment. The key parameters of the content and the filtration time and filtration accuracy of the solid-liquid separation and filtration were selected and matched to determine the final cadmium removal process. Prior to the present invention, in order to remove cadmium, the neutral leaching solution or the supernatant obtained by precipitation of the neutral leaching solution is purified by a zinc powder replacement method, and then purified by solid-liquid separation and filtration. The cadmium content is generally about 20~50mg/L; the test shows that in the present invention, the neutral leaching solution or the supernatant obtained by the neutral leaching solution is purified by the zinc powder replacement method, and then separated and filtered by solid-liquid separation. The content of cadmium ions in the obtained zinc solution is 2 mg/L or less.

In the step 1) of the cadmium removal process of the present invention, the colloid removal treatment can be achieved in different ways. For example, a flocculant or electrolyte may be added to the zinc solution to precipitate the colloidal material. However, as a preferred embodiment, this step 1) is carried out by membrane filtration of a neutral leachate or supernatant. Membrane filtration not only removes the colloidal substance in the zinc liquid, but also removes solid impurities such as ZnFe0 _{2 to} better the quality of the zinc liquid before the displacement reaction, and further improves the zinc liquid purification effect. In order to avoid excessive formation of the filter cake and to reduce the filtration flux, this step 1) is preferably carried out by cross-flow membrane filtration of the neutral leachate or supernatant. Cross-flow filtration has a special effect on the colloid removal: The shear force of the cross-flow filtration can effectively prevent the colloid from adhering to the surface of the filter element, thereby reducing the thickness of the filter cake layer and ensuring the filtration flux.

The above step 3) also recommends membrane filtration. In order to facilitate rapid filtration, it is preferred to use terminal membrane filtration. The zinc liquid purification method of the present invention comprises the following steps: 1) performing a gel removal treatment on a neutral leaching solution or a supernatant obtained by precipitation of a neutral leaching solution to obtain a zinc liquid having a colloid content of 50 mg/L or less; 2) The zinc liquid is purified by the first zinc powder replacement method to remove at least copper and cadmium; 3) the zinc liquid containing solid impurities of copper and cadmium is subjected to solid-liquid separation and filtration, wherein the filtration time is controlled within 60 minutes. The filtration precision is controlled to be less than 10 microns; 4) The zinc solution after separation and filtration of the solid-liquid separation is subjected to two-stage purification to remove at least cobalt and nickel; 5) the zinc solution containing solid impurities of cobalt and nickel is subjected to solid-liquid separation and filtration. New liquid and filter residue were obtained separately.

The test shows that the weight ratio of the three solid substances of copper, cadmium and cobalt to the solid zinc in the filter residue obtained by the above method is Cu: Cd: Co : Ζη = (0· 01~0· 2 ): (0~0) · 001 ): ( 0· 5~1· 5 ): 100. It can be seen that the weight ratio of solid cadmium to solid zinc in the filter residue is less than 1 X 10—, and the cadmium content is extremely low.

In the above zinc liquid purification method, the zinc liquid may be subjected to two-stage purification of cobalt and nickel by a second zinc powder replacement method, and yellow medicine or β-naphthol may be added to remove cobalt and nickel. Based on the stated reasons, the step 1) is carried out by membrane filtration of a neutral leachate or supernatant. Based on the stated reasons, the step 1) is achieved by cross-flow membrane filtration of the neutral leachate or supernatant. As a further improvement of the above zinc liquid purification method, the filter residue obtained in the step 5) is used as the zinc powder raw material used in the zinc powder replacement method in the above step. Since the zinc liquid containing solid impurities such as copper and cadmium is subjected to solid-liquid separation and filtration through a period of purification, the content of cadmium ions in the filtered zinc liquid has been greatly reduced, and therefore, the second stage purification and cobalt containing solid impurities The slag of the nickel-zinc solution for solid-liquid separation and filtration contains only a very small amount of cadmium. In this case, the filter residue can be returned to the previous step as the zinc powder raw material used for the zinc powder replacement method. Thus, the amount of zinc powder is significantly reduced in the case of hardly any adverse effect on the zinc cleaning process (mainly, almost no impurity cadmium is introduced into the zinc liquid). Conventionally, since the cadmium content in the filter residue after the zinc liquid purification is high, it is impossible for those skilled in the art to use the filter residue as a zinc powder raw material.

Wherein, for the step 3) and the step 4), at least the step 3) uses membrane filtration.

Wherein, for the step 3) and the step 4), the terminal membrane filtration is adopted in at least the step 3).

The latter liquid zinc present invention provides purification resulting residue, wherein the solid weight ratio of solid zinc and cadmium less than 1 X 10_ ^5. This filter residue is a zinc powder raw material used as a zinc powder replacement method in zinc liquid purification.

The filter residue is obtained by the following zinc liquid purification method, and the method comprises the following steps: 1) performing a gel removal treatment on the neutral leaching solution or the supernatant obtained by precipitation of the neutral leaching solution to obtain a colloid content of 50 mg/L or less. Zinc solution; 2) Purify the zinc solution by removing the copper and cadmium at least by the first zinc powder replacement method; 3) Separating and filtering the zinc solution containing solid impurities of copper and cadmium, wherein the filtration time is controlled Within 60 minutes, the filtration precision is controlled to be less than 10 microns; 4) For the two-stage purification of the zinc solution after solid-liquid separation and filtration, at least cobalt and nickel are removed; 5) The zinc solution containing solid impurities of cobalt and nickel is solidified. One liquid was separated and filtered to obtain a new liquid and a filter residue, respectively.

Wherein, the step 1) is carried out by membrane filtration of a neutral leachate or a supernatant.

Wherein, the step 1) is carried out by performing cross-flow membrane filtration on the neutral leachate or the supernatant.

Further, in the step 1), the neutral leachate or the supernatant is subjected to a gel removal treatment to obtain a zinc solution having a colloid content of 10 mg/L or less.

Among them, the second cleaning of the zinc liquid by the second zinc powder replacement method removes at least cobalt and nickel.

The preparation method of the filter residue obtained by purifying the above zinc liquid comprises the following steps: 1) performing a gel removal treatment on the neutral leachate or the supernatant obtained by precipitation of the neutral leachate to obtain a zinc liquid having a colloid content of 50 mg/L or less. 2) Purify the zinc solution by removing the copper and cadmium at least by the first zinc powder replacement method; 3) Applying the zinc solution containing solid impurities of copper and cadmium Perform solid-liquid separation and filtration, wherein the filtration time is controlled within 60 minutes, and the filtration precision is controlled to be less than 10 micrometers; 4) the two-stage purification of the zinc liquid separated by solid-liquid separation is at least cobalt and nickel removal; The zinc solution containing solid impurities of cobalt and nickel is subjected to solid-liquid separation and filtration to obtain a new liquid and a filter residue, respectively.

DRAWINGS

1 is a process flow diagram of a specific embodiment of a zinc liquid purification method of the present invention.

detailed description

The content of copper, cadmium and cobalt ions in the supernatant obtained from the neutral leachate precipitation of a zinc plant is 400mg/L, 550 mg/L, 25mg/L, respectively. The colloid content in the solution is about lg. /L. The zinc plant currently adopts a three-stage purification process. First, the supernatant is subjected to a first purification of at least copper and cadmium by the first zinc powder replacement method; then, the solid solution is separated from the zinc solution containing solid impurities of copper and cadmium. Filtration, filter using a plate and frame filter, the filter cloth in the plate frame filter has a filtration accuracy of 40-50 microns, the filtration time is 60 minutes; Thereafter, the second zinc powder replacement method for the two-stage purification of the zinc liquid At least cobalt and nickel are removed; then, the zinc solution containing solid impurities of cobalt and nickel is subjected to solid-liquid separation and filtration, and the same plate and frame filter is used for filtration, and the filtration time is 40 minutes; thereafter, the third zinc powder is passed. The displacement method performs three-stage purification of the zinc liquid to remove at least cadmium; then, the zinc liquid containing the solid impurity cadmium is subjected to solid-liquid separation and filtration using the same plate and frame filter to obtain a new liquid and a filter residue, respectively. It has been determined that the content of copper, cadmium and cobalt ions in the zinc solution after purification and filtration is 12mg/L, 50mg/L and 20mg/L respectively _{; the} second stage purification and filtration of copper, cadmium and cobalt ions in the zinc solution The content of copper, cadmium, and cobalt ions in the zinc solution is 0. lmg / L, 0. 8mg / L, 1. 0mg/L.

As shown in Fig. 1, the present invention adopts the following method for the same supernatant, and the steps are as follows: 1) The supernatant is subjected to gel removal treatment by cross-flow membrane filtration to obtain zinc having a colloid content of 50 mg/L or less. 2) Purification of the zinc liquid by at least copper and cadmium by the first zinc powder replacement method (the process conditions for removing copper and cadmium by the existing zinc powder replacement method); 3) using a terminal membrane filtration pair containing solids Impurity copper and cadmium zinc solution for solid-liquid separation and filtration, wherein the filtration time is controlled within 60 minutes, the filtration precision is controlled below 10 microns; 4) by the second zinc powder replacement method (using existing zinc powder) Displacement method for removing cobalt and nickel) The second step of the separation and filtration of the zinc solution is to remove at least cobalt and nickel. 5) The terminal membrane filtration is used to solidify the zinc solution containing solid impurities of cobalt and nickel. The liquid is separated and filtered to obtain a new liquid and a filter residue respectively; the filter residue is returned to a purification and two-stage purification process as the zinc powder raw material used in the zinc powder replacement method in the above step; the entire zinc liquid purification process Slag produced was filtered through a membrane filter first terminal discharge outlet. The zinc liquid purification method of the present invention will be specifically described below by five sets of examples (Nos. 1 to 5), and the details are shown in Table 1.

In addition, after testing, the above five groups of examples are three solid substances of copper, cadmium and cobalt in the filter residue after the second purification process. The weight ratio of solid to solid zinc is Cu: Cd: Co: Ζη= (0·01~0·2): (0~0·001): (0·5~1· 5): 100, that is, solid in filter residue the weight ratio of solid zinc cadmium is less than 1X10- ^5, the cadmium content is very low.

Special Note:

1. The above term "filtration time" refers to the time from the start of filtration to the completion of filtration of a specific amount of zinc liquid.

2. The colloidal content of the zinc solution can be determined by the gravimetric method, spectrophotometry and the like in the turbidity measurement.

Table 1

Note: "No wave" means that the element is not detected by the polarograph.

Claims

claims

1. The cadmium removal process in zinc liquid purification includes the following steps: 1) Conduct colloid removal treatment on the neutral leachate or the supernatant obtained after precipitation from the neutral leachate, to obtain a zinc liquid with a colloid content of less than 50 mg/L ; 2) At least cadmium is replaced in the zinc liquid through the zinc powder replacement method; 3) The zinc liquid containing solid impurity cadmium is subjected to solid-liquid separation and filtration, wherein the filtration time is controlled within 60 minutes, and the filtration precision is controlled within 60 minutes. Below 10 microns.

2. The cadmium removal process in zinc liquid purification as claimed in claim 1, characterized in that: the step 1) is achieved by membrane filtration of the neutral leachate or supernatant.

3. The cadmium removal process in zinc liquid purification as claimed in claim 2, characterized in that: the step 1) is achieved by cross-flow membrane filtration of the neutral leachate or supernatant.

4. The cadmium removal process in zinc liquid purification as claimed in claim 1, characterized in that: in step 1), the neutral leachate or supernatant is subjected to a colloid removal treatment to obtain a colloid content of less than 10 mg/L of zinc liquid.

5. The cadmium removal process in zinc liquid purification as claimed in claim 1, characterized in that: membrane filtration is used in step 3).

6. The cadmium removal process in zinc liquid purification as claimed in claim 5, characterized in that: terminal membrane filtration is used in step 3).

7. A zinc liquid treated with cadmium removal. The zinc liquid is purified through a zinc powder replacement method on the neutral leachate or the supernatant obtained after precipitation from the neutral leachate, and then solid-liquid separation and filtration. The obtained product is characterized by: the content of cadmium ions in the zinc liquid is less than 2 mg/L.

8. A zinc liquid purification method, including the following steps: 1) Perform colloid removal on the neutral leachate or the supernatant obtained after precipitation from the neutral leachate, to obtain a zinc liquid with a colloid content of less than 50 mg/L; 2) Through The first zinc powder replacement method performs a stage of purification of the zinc liquid to remove at least copper and cadmium; 3) Solid-liquid separation and filtration of the zinc liquid containing solid impurities copper and cadmium, wherein the filtration time is controlled within 60 minutes, and The filtration precision is controlled below 10 microns; 4) Perform two-stage purification on the zinc liquid after solid-liquid separation and filtration to remove at least cobalt and nickel; 5) Perform solid-liquid separation and filtration on the zinc liquid containing solid impurities cobalt and nickel, respectively Obtain new liquid and filter residue.

9. The zinc liquid purification method according to claim 8, characterized in that: the step 1) is achieved by membrane filtration of the neutral leachate or supernatant.

10. The zinc liquid purification method according to claim 9, characterized in that: the step 1) is achieved by cross-flow membrane filtration of the neutral leachate or supernatant.

11. The zinc liquid purification method according to claim 8, characterized in that: in step 1), the neutral leachate or supernatant liquid is subjected to colloid removal treatment to obtain a zinc liquid with a colloid content of less than 10 mg/L.

12. The zinc liquid purification method according to claim 8, characterized in that: the filter residue obtained in step 5) is used as the zinc powder raw material used in the zinc powder replacement method in the above step.

13. The zinc liquid purification method according to claim 8, characterized in that: the zinc liquid is purified in two stages through the second zinc powder replacement method to remove at least cobalt and nickel.

14. The zinc liquid purification method according to claim 8, characterized in that: for the steps 3) and 4), at least step 3) uses membrane filtration.

15. The zinc liquid purification method according to claim 14, characterized in that: for the steps 3) and 4), terminal membrane filtration is used in at least step 3).