Cyanide evaporation detoxification method for cyanide tailings

Abstract

The application discloses a cyanide evaporation detoxification method of cyanide tailings, which comprises the following steps: (1) pretreatment: the cyanide tailings are slurried with water, and the pH value is adjusted to 1-2; (2) cyanide dissociation: a cyanide dissociation agent is added to the slurry obtained in step (1), and the reaction is carried out in a closed state for 1-120 min; wherein the cyanide dissociation agent is one or more than two of EDDHA-Na, tin dioxide, stannous chloride, hydroxylamine hydrochloride, ascorbic acid and sodium borohydride; (3) reduced pressure evaporation: a defoaming agent is added to the slurry obtained in step (2), and reduced pressure evaporation is carried out, and the generated hydrogen cyanide gas is discharged from the slurry. Through the cooperation of the cyanide dissociation agent and the reduced pressure evaporation, the problem that the cyanide in the cyanide tailings is difficult to recover is effectively solved.

Description

Technical Field

[0001] This invention belongs to the field of hazardous waste treatment technology, specifically relating to a method for evaporation and detoxification of cyanide in cyanide tailings. Background Technology

[0002] Cyanide ore extraction has long been a primary method for gold mining companies both domestically and internationally. Depending on the type of ore being processed and the state and grade of gold within it, various cyanide processes can be employed, including heap leaching, whole-sludge cyanidation, flotation cyanidation, flotation concentrate roasting cyanidation, hot-press cyanidation, and bioleaching. Although the industry has long been committed to researching non-toxic gold extraction solvents, practice has proven that cyanide remains the most effective solvent. Due to the use of cyanide, wastewater and tailings from gold smelting often contain it. Most inorganic cyanides are highly toxic substances; even trace amounts can cause death in humans and livestock within a short time and can also lead to reduced crop yields.

[0003] The current research on the harmless treatment of cyanide tailings mainly focuses on cyanide removal technologies. Among these, cyanide destruction methods are the mainstream approach, including alkaline chlorination, INCO, hydrogen peroxide oxidation, ozone oxidation, pressurized hydrolysis, electrolytic oxidation, ferrate oxidation, peroxysulfuric acid oxidation, and high-temperature decomposition (incineration). However, cyanide destruction methods suffer from the inability to recover cyanide ions. Cyanide conversion (precipitation) and acidification recovery methods, due to process limitations, are typically used for treating cyanide-containing wastewater and are difficult to apply practically to cyanide removal from tailings. Therefore, developing a cyanide waste detoxification method suitable for cyanide tailings that can simultaneously recover cyanide ions is of great value. Furthermore, the removal of solid cyanide, especially ferrous ferrocyanide precipitates, from cyanide tailings remains a common challenge, and few ideal solutions exist in current technologies. Summary of the Invention

[0004] To address the shortcomings of the existing technology, this invention provides a method for evaporating and detoxifying cyanide in cyanide tailings, which can efficiently recover cyanide ions from cyanide tailings and is a simple process.

[0005] The specific technical solution is as follows:

[0006] A method for evaporative detoxification of cyanide in cyanide tailings includes the following steps:

[0007] (1) Pretreatment: The cyanide tailings are mixed with water to form a slurry and the pH value is adjusted to 1~2;

[0008] (2) Cyanide dissociation: Add cyanide dissociation agent to the slurry obtained in step (1) and react in a closed container for 1~120 min;

[0009] The cyanide dissociating agent is one or more of EDDHA-Na, tin dioxide, stannous chloride, hydroxylamine hydrochloride, ascorbic acid, and sodium borohydride.

[0010] (3) Reducing pressure evaporation: adding a defoaming agent to the slurry obtained in step (2) to perform reducing pressure evaporation, and discharging hydrogen cyanide gas generated from the slurry.

[0011] In step (2), continuous stirring is performed during the reaction.

[0012] Experiments prove that the cyanide dissociating agent and reducing pressure evaporation can effectively recover cyanide in cyanide tailings, and the cyanide removal efficiency is high.

[0013] Specifically, the process flow of the present application can refer to Figure 1 .

[0014] Further, in step (2), the cyanide dissociating agent preferably includes stannous chloride.

[0015] Preferably, when stannous chloride is included in the cyanide dissociating agent, the closed reaction in step (2) is 30-100 min.

[0016] Further, in step (2), the amount of the cyanide dissociating agent is 100-1000 g / t based on the slurry obtained in step (1).

[0017] Preferably, when stannous chloride is included in the cyanide dissociating agent, the amount of stannous chloride is 100-1000 g / t based on the slurry obtained in step (1).

[0018] Further, in step (1), the slurry concentration is 10wt%-40wt%.

[0019] Further, in step (1), sulfuric acid is used to adjust the pH value.

[0020] Further, in step (3), the defoaming agent preferably includes one or more of glycerol, n-octanol, isopropyl alcohol, and tributyl phosphate.

[0021] The amount of the defoaming agent is preferably 10-50 g / t based on the slurry obtained in step (1).

[0022] Further, in step (3), after reducing pressure evaporation, sodium cyanide solution is obtained by absorbing sodium hydroxide aqueous solution.

[0023] The concentration of the sodium hydroxide aqueous solution is preferably more than 10wt%.

[0024] Further, in step (3), the conditions for reducing pressure evaporation are 20-50℃, the pressure is 10-100 KPa, and the evaporation time is 1-3 hours.

[0025] Further, in step (3), the remaining slurry after the reduced pressure evaporation is subjected to pressure filtration to obtain detoxification tailings and filtrate. The filtrate can be returned to the slurry preparation process for use as slurry preparation water.

[0026] Further, the cyanide tailings are cyanide tailings generated in the gold extraction process. Preferably, the present application is suitable for sulfide ore cyanide tailings, all-slime cyanide tailings, heap leaching cyanide tailings or cyanide red slag.

[0027] The beneficial effects of the present application are as follows:

[0028] The present application effectively solves the problem of difficult recovery of cyanide in cyanide tailings by combining cyanide dissociation agent with reduced pressure evaporation, and improves the recycling value of cyanide tailings. Moreover, by using stannous chloride as a dissociation agent, the present application can solve the problem of difficult removal of cyanide in ferrous cyanide and ferric cyanide in cyanide tailings, and improve the treatment depth of cyanide removal in tailings. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 The process flowchart of the present application is described in detail. DETAILED DESCRIPTION

[0030] The principles and features of the present application are described below in conjunction with examples, which are used to explain the present application and not to limit the scope of the present application.

[0031] In each embodiment: the total cyanide content is determined by the method of Determination of Cyanide and Total Cyanide in Soil by Spectrophotometry HJ745-2015. Example 1

[0032] A certain gold concentrate cyanide tailings with a total cyanide content of 1245mg / kg were treated as follows:

[0033] (1) Pretreatment: the cyanide tailings were slurried with water to a concentration of 30wt% in a stirring tank, and the pH value was adjusted to 2 with sulfuric acid;

[0034] (2) Cyanide dissociation: under normal temperature conditions, stannous chloride was added to the slurry obtained in step (1) at an addition amount of 980g / t based on the slurry obtained in step (1), and the mixture was stirred and reacted for 60min in a sealed state;

[0035] (3) Reduced pressure evaporation: isopropyl alcohol was added to the slurry obtained in step (2) as a defoaming agent at an addition amount of 30g / t; the slurry was subjected to reduced pressure evaporation under the conditions of 50℃, 40KPa pressure and 2 hours of evaporation time.

[0036] (4) By evaporation under reduced pressure, cyanide is discharged from the slurry in the form of hydrogen cyanide gas, which is then absorbed by a 20wt% sodium hydroxide aqueous solution to obtain a sodium cyanide solution;

[0037] The remaining slurry is subjected to pressure filtration to obtain a filtrate and detoxification tailings; the total cyanide content in the detoxification tailings is 1.4 mg / kg.

[0038] The above process flow can refer to Figure 1 . Example 2

[0039] A certain total cyanide content of 460 mg / kg of cyanide slurry is treated, and the steps are as follows:

[0040] (1) Pretreatment: the cyanide slurry is slurried with water to a concentration of 40wt% in a stirring tank, and the pH value is adjusted to 1 with sulfuric acid;

[0041] (2) Cyanide dissociation: under normal temperature conditions, a mixture of stannous chloride and hydroxylamine hydrochloride is added to the slurry obtained in step (1), the mass ratio of stannous chloride to hydroxylamine hydrochloride is 2:1, and the total amount of the mixture added is 600g / t based on the slurry obtained in step (1), and the mixture is stirred and reacted for 80min under airtight condition;

[0042] (3) Evaporation under reduced pressure: add 20g / t of antifoaming agent glycerol to the slurry obtained in step (2); the slurry is evaporated under reduced pressure, the evaporation under reduced pressure is carried out at 35℃, the pressure is 60KPa, and the evaporation time is 1 hour; by evaporation under reduced pressure, cyanide is discharged from the slurry in the form of hydrogen cyanide gas, which is then absorbed by a 10wt% sodium hydroxide aqueous solution to obtain a sodium cyanide solution;

[0043] The remaining slurry is subjected to pressure filtration to obtain a filtrate and detoxification tailings; the total cyanide content in the detoxification tailings is 2 mg / kg.

[0044] The above process flow can refer to Figure 1 . Example 3

[0045] A certain total cyanide content of 653 mg / kg of cyanide slurry is treated, and the steps are as follows:

[0046] (1) Pretreatment: the cyanide slurry is slurried with water to a concentration of 10wt% in a stirring tank, and the pH value is adjusted to 1.5 with sulfuric acid;

[0047] (2) Cyanide dissociation: under normal temperature conditions, a mixture of hydroxylamine hydrochloride, ascorbic acid and sodium borohydride is added to the slurry obtained in step (1), the mass ratio of hydroxylamine hydrochloride to ascorbic acid to sodium borohydride is 1:1:1, and the total amount of the mixture added is 600g / t based on the slurry obtained in step (1), and the mixture is stirred and reacted for 80min under airtight condition;

[0048] (3) Vacuum evaporation: Add antifoaming agent n-octanol to the slurry obtained in step (2) at an amount of 50 g / t; perform vacuum evaporation on the slurry, the vacuum evaporation condition being 20℃, the pressure being 10 KPa, and the evaporation time being 2 hours; through vacuum evaporation, cyanide is discharged from the slurry in the form of hydrogen cyanide gas, which is then absorbed by 5wt% sodium hydroxide aqueous solution to obtain a sodium cyanide solution;

[0049] Perform pressure filtration on the remaining slurry to obtain filtrate and detoxification tailings; the total cyanide content in the detoxification tailings is 0.47 mg / kg.

[0050] The above process flow can refer to Figure 1 . Example 4

[0051] A historical cyanide tailings with a total cyanide content of 100 mg / kg is treated, and the steps are as follows:

[0052] (1) Pretreatment: Adjust the cyanide tailings to a slurry concentration of 40wt% with water in a stirring tank, and adjust the pH value to 2 with sulfuric acid;

[0053] (2) Cyanide dissociation: Under normal temperature conditions, add EDDHA-Na to the slurry obtained in step (1) at an amount of 200 g / t based on the slurry obtained in step (1), and stir and react for 40 min in a sealed state;

[0054] (3) Vacuum evaporation: Add antifoaming agent tributyl phosphate to the slurry obtained in step (2) at an amount of 15 g / t; perform vacuum evaporation on the slurry, the vacuum evaporation condition being 25℃, the pressure being 30 KPa, and the evaporation time being 3 hours; through vacuum evaporation, cyanide is discharged from the slurry in the form of hydrogen cyanide gas, which is then absorbed by 20wt% sodium hydroxide aqueous solution to obtain a sodium cyanide solution;

[0055] Perform pressure filtration on the remaining slurry to obtain filtrate and detoxification tailings; the total cyanide content in the detoxification tailings is 1.26 mg / kg.

[0056] The above process flow can refer to Figure 1 . Example 5

[0057] A cyanide tailings from a tailings pond with a total cyanide content of 50 mg / kg is treated, and the steps are as follows:

[0058] (1) Pretreatment: Adjust the cyanide tailings to a slurry concentration of 33wt% with water in a stirring tank, and adjust the pH value to 2 with sulfuric acid;

[0059] (2) Cyanide dissociation: tin dioxide is added to the slurry obtained in step (1) under normal temperature, the addition amount is 200 g / t based on the slurry obtained in step (1), and the reaction is stirred in a closed state for 20 min;

[0060] (3) Evaporation under reduced pressure: isopropyl alcohol is added to the slurry obtained in step (2) as a defoaming agent, the addition amount is 10 g / t; the slurry is evaporated under reduced pressure, the evaporation under reduced pressure is carried out at 30 ℃ and a pressure of 30 KPa for 1 h; through the evaporation under reduced pressure, the cyanide is discharged from the slurry in the form of hydrogen cyanide gas, and then absorbed by a 20 wt% sodium hydroxide aqueous solution to obtain a sodium cyanide solution;

[0061] The remaining slurry is filtered under pressure to obtain a filtrate and detoxification tailings; the total cyanide content in the detoxification tailings is 0.75 mg / kg.

[0062] The above process flow can refer to Figure 1 .

[0063] The above only describes the preferred embodiments of the present application and is not intended to limit the present application, and any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for cyanide evaporation detoxification of cyanide tailings, characterized by, The method comprises the following steps: (1) Pretreatment: cyanide tailings are slurried with water, and the pH value is adjusted to 1-2; (2) Cyanide dissociation: a cyanide dissociation agent is added to the slurry obtained in step (1), and the reaction is carried out in a closed state for 1-120 min; The cyanide dissociation agent is one or more of EDDHA-Na, tin dioxide, stannous chloride, hydroxylamine hydrochloride, ascorbic acid, and sodium borohydride; the amount of the cyanide dissociation agent is 100-1000 g / t of the slurry obtained in step (1); (3) Vacuum evaporation: a defoaming agent is added to the slurry obtained in step (2), and vacuum evaporation is carried out to remove the generated hydrogen cyanide gas from the slurry.

2. The cyanide evaporation detoxification process of a cyanided tailings according to claim 1, characterized in that, In step (2), the cyanide dissociation agent comprises stannous chloride.

3. The evaporation detoxification method of cyanide from cyanide tailings according to claim 1 or 2, characterized in that, In step (1), the slurry concentration is 10wt%-40wt%.

4. The evaporation detoxification method of cyanide from cyanide tailings according to claim 1 or 2, characterized in that, In step (3), the defoaming agent comprises one or more of glycerol, n-octanol, isopropyl alcohol, and tributyl phosphate.

5. The cyanide evaporation detoxification method of claim 4, wherein the cyanide tailings are selected from the group consisting of gold tailings, silver tailings, copper tailings, nickel tailings, zinc tailings, and combinations thereof. The amount of the defoaming agent is 10-50 g / t of the slurry obtained in step (1).

6. The evaporation detoxification method of cyanide from cyanide tailings according to claim 1 or 2, characterized in that, In step (3), after vacuum evaporation, a sodium cyanide solution is obtained by absorbing the hydrogen cyanide gas with a sodium hydroxide aqueous solution.

7. The evaporation detoxification method of cyanide from cyanide tailings according to claim 1 or 2, characterized in that, In step (3), the vacuum evaporation is carried out at a temperature of 20-50°C, a pressure of 10-100 KPa, and an evaporation time of 1-3 hours.

8. The evaporation detoxification method of cyanide from cyanide tailings according to claim 1 or 2, characterized in that, The cyanide tailings are cyanide tailings generated in a cyanide gold extraction process.

9. The evaporative detoxification of cyanide from cyanide tailings according to claim 8, wherein, The cyanide tailings are sulfide ore cyanide tailings, all-slime cyanide tailings, heap leaching cyanide tailings, or cyanide red slag.

Images