CN106119545B - A kind of cleaning detoxification treatment of chromium slag and the extracting method of chromium - Google Patents

Abstract

The invention discloses a cleaning and detoxification treatment of chromium slag and a method for extracting chromium, belonging to the fields of cleaning treatment of chromium slag and recycling of resources. The specific steps of the method are: 1) add water to the waste residue containing hexavalent chromium, and mix evenly; 2) add hydrogen peroxide into the solution obtained in step 1), and stir thoroughly to obtain a mixed solution; 3) adopt the hydrothermal method or directly Heat the mixed solution; 4) After the heat treatment, let the solid-liquid mixture cool to room temperature naturally, and let it stand still; 5) Separate the solid residue from the chromium-containing supernatant, wash the filter residue with water and then dry it; 6) Dilute the chromium-containing solution Recycled and returned to the plant, or processed for recycled chrome. The mineralizer adopted in the invention is green and pollution-free, the treated supernatant can be directly reused in the process of chromium salt production or chromium salt use, and the filter residue can be comprehensively utilized. The method has the advantages of clean and simple process, small investment, quick effect, recyclable hexavalent chromium, and effectively controls chromium pollution without causing secondary pollution.

Description

Cleaning and detoxification treatment of chromium slag and extraction method of chromium

technical field

The invention belongs to the field of cleaning treatment of chromium slag and recycling of resources, and in particular relates to a method for cleaning and detoxification treatment of chromium slag and chromium extraction.

Background technique

Chromium residue refers to the waste residue containing hexavalent chromium produced in the production and application of chromium salts. Hexavalent chromium is highly toxic and can cause cancer, and is listed as one of the eight most harmful chemicals to humans. my country's chromium salt production and consumption rank first in the world, and it is also the country that produces the most chromium slag. Millions of tons of chromium slag have been piled up to be treated urgently, which has brought serious pollution to soil and groundwater. However, my country's chromium ore resources are relatively poor, and the current proven reserves only account for 0.825% of the world's total reserves, which is a shortage of resources in terms of meeting the demand. Therefore, detoxification of chromium slag and recovery of chromium resources have become an ideal way to deal with chromium slag.

For the treatment of chromium slag, the method of detoxification and then landfill is usually used. The core is to reduce and fix the highly soluble and highly toxic hexavalent chromium into low-toxic trivalent chromium. Not only chromium resources cannot be recovered and utilized, but also chromium is still discharged in the environment. With the long-term action of the natural environment, trivalent chromium will be oxidized to hexavalent chromium, causing secondary pollution. The ideal method is to extract and separate the chromium in the chromium slag from the slag, recycle and reuse it, and recover chromium resources while detoxifying the chromium slag.

Chinese patent "A method for recovering hexavalent chromium resources from chromium slag" (CN102191390A) uses sulfuric acid or hydrochloric acid at room temperature to leach water-soluble and acid-soluble hexavalent chromium, and then adds a reducing agent to the leached hexavalent chromium solution and precipitant to recover chromium, and recover 60% to 80% of hexavalent chromium from chromium slag. The Chinese patent "Process for Recycling and Reusing Chromium Slag and Wastewater Treatment" (CN102699006A) takes into account the recovery of chromium and the reuse of slag. Under normal temperature conditions, the chromium slag is almost completely dissolved with acid, and then different precipitants are added respectively. The mixed ions in the solution are precipitated and separated, but this method needs to consume a large amount of chemical reagents such as acid and precipitant, and the process is complicated and the treatment cost is high.

Therefore, aiming at the deficiencies of the prior art, there is an urgent need for a practical and scientific chromium slag treatment method to fully extract the hexavalent chromium and realize the detoxification of the chromium slag.

Contents of the invention

The purpose of the present invention is to provide a cleaning and detoxification treatment of chromium slag and a method for extracting chromium. The method is clean, simple, small in investment, quick in effect, can fully recover hexavalent chromium, detoxify thoroughly, and effectively control chromium pollution without cause secondary pollution. The chromium recovered by this method can be reused in production or used in other purposes, such as paint, pigment, papermaking, etc., turning waste into treasure. The filter residue obtained by the method can be used in rubber, plastic, fertilizer, paint, textile, papermaking and other industries.

The purpose of the present invention is achieved through the following technical solutions.

A method for cleaning and detoxifying chromium slag and extracting chromium, the steps are as follows:

1) Add water to the waste residue containing hexavalent chromium and mix well;

2) Add a mineralizer to the solution obtained in step 1), and stir thoroughly to obtain a mixed solution; the mineralizer is hydrogen peroxide;

3) The mixed solution obtained in step 2) is treated by hydrothermal method or direct heating;

4) Cool the solid-liquid mixture obtained in step 3) to room temperature naturally, and let stand;

5) Separating the solid residue from the chromium-containing supernatant, washing the filter residue with water and drying;

6) Recover the chromium-containing solution and return it to the workshop, or carry out chromium recovery treatment.

Further, after adding water to the waste residue containing hexavalent chromium in step 1), the solid-to-liquid ratio (w/w) is 1:0.5-1:10.

Further, the concentration of hydrogen peroxide in the mixed liquid in step 2) is 0.1 mol/L-5 mol/L.

Further, the temperature of the hydrothermal method or direct heating in step 3) is controlled at 50°C-250°C.

Further, the heat preservation time in step 3) is 2 to 10 hours.

Further, the standing time in step 4) is 0.5-48 hours.

Further, the specific steps of the recovery of chromium in step 6) are as follows: adding a reducing agent to the chromium-containing solution to reduce the hexavalent chromium in the solution to trivalent chromium, then adding the precipitant NaOH to produce Cr(OH) ₃ precipitation, and finally The Cr(OH) ₃ precipitate is calcined to Cr ₂ O ₃ .

A method for cleaning and detoxifying chromium slag and extracting chromium, the steps are as follows:

(1) After mixing the waste residue containing hexavalent chromium and water at a solid-to-liquid ratio of 1:0.5 ~ 1:10 (w/w), add hydrogen peroxide to make the concentration of hydrogen peroxide in the solution 0.1 mol/L ~ 5 mol/L.

(2) Stir fully to fully mix the waste residue and the solution.

(3) Set the temperature at 30°C to 250°C, and keep warm for 2 to 10 hours with or without stirring.

(4) Stop heating, let it cool down naturally, and let it stand for 0.5 to 48 hours.

(5) After the hydrothermal treatment or heat treatment, the solid waste residue is deposited at the bottom, and the supernatant contains higher concentration of hexavalent chromium.

(6) Filtrating and separating the solid slag from the chromium-containing supernatant, washing, dehydrating and drying the solid slag.

(7) The separated supernatant and the water for washing the filter residue can be reused in production or processed for recovery of chromium.

The cleaning and detoxification treatment of a kind of chromium slag provided by the invention and the extraction method principle of chromium are as follows:

The present invention adds mineralizer (hydrogen peroxide) when carrying out hydrothermal treatment or heat treatment, a small amount of trivalent chromium in the chromium slag is oxidized by hydrogen peroxide into dichromate with higher solubility under weakly alkaline conditions and is more likely to enter the solution; at the same time Under heating conditions, excess hydrogen peroxide will be decomposed into water and oxygen, and under the hydrothermal action of oxygen partial pressure, the solid particle crystal will grow and the crystal lattice will be complete, thereby reducing the specific surface area and reducing the active sites for adsorption, and realizing hexavalent chromium from The particle surface desorbs and separates.

2Cr ³⁺ + 4H ₂ O ₂ →Cr ₂ O ₇ ^2- + H ₂ O

2H ₂ O ₂ →2H ₂ O + O ₂ ↑

Compared with the prior art, the present invention has the following advantages and technical effects:

The invention solves the problem of difficult treatment of chromium slag, the adopted mineralizer is green and pollution-free, no miscellaneous ions are introduced in the treatment, and the supernatant liquid after waste slag treatment can be directly reused in the process of chromium salt production or chromium salt use , greatly reducing business costs. The treated filter residue can be used comprehensively. The method has the advantages of clean and simple process, small investment and quick effect, recyclable hexavalent chromium, and effectively controls chromium pollution without causing secondary pollution.

Detailed ways

The present invention will be further described below in conjunction with specific examples, but the embodiments of the present invention are not limited thereto.

Example 1

1) Put 0.5 kg of waste residue containing hexavalent chromium into a hydrothermal kettle, then add water to make the solid-to-liquid ratio (w/w) 1:1, stir well, add hydrogen peroxide, and make the concentration of hydrogen peroxide in the system 0.1mol /L, set the temperature at 130°C, and keep warm for 6 h.

2) After 6 h, stop heating, cool down to room temperature naturally, and let stand for 24 h.

3) After standing still, pour out the solution containing hexavalent chromium in the upper layer. Carry out centrifugal washing and dehydration to the residue after hydrothermal treatment, and dry the filter residue to obtain a white or white yellowish solid.

4) Reuse the chromium-containing solution in production, or collect it in the wastewater treatment station for reduction, recovery, and purification treatment, add reducing agents (such as sodium sulfide, sodium bisulfite) and precipitating agent (NaOH), and distill the solution six The valent chromium is reduced to trivalent chromium, and Cr(OH) ₃ precipitates are generated, and the treated water can meet the national drainage standard. Throughout the process, water can be recycled in the system.

5) The final products are slag mainly containing CaSO ₄ and chromium sludge mainly containing Cr(OH) _3. Calcium sulfate slag can be used as raw material for rubber, plastic, fertilizer, pesticide, paint, textile, paper and other industries. Chromium sludge can be calcined into Cr ₂ O ₃ to realize the recovery of chromium.

The concentration of hexavalent chromium leached from the original chromium residue in this embodiment was 272 mg/L, and the concentration of hexavalent chromium leached from the filter residue after treatment was 2.53 mg/L.

Example 2

Take 1 kg of waste residue containing hexavalent chromium and put it into a hydrothermal kettle, then add water to make the solid-to-liquid ratio (w/w) 1:0.5, stir well, add hydrogen peroxide, and make the concentration of hydrogen peroxide in the system 1 mol/L, Set the temperature at 50 °C, keep it warm for 10 h, and let it stand for 48 h after stopping heating. Other technological process is identical with embodiment 1.

The concentration of hexavalent chromium leached from the original chromium residue in this example was 269 mg/L, and the concentration of hexavalent chromium leached from the filter residue after treatment was 2.12 mg/L.

Example 3

Take 1.5kg of waste residue containing hexavalent chromium and put it into a hydrothermal kettle, then add water to make the solid-to-liquid ratio (w/w) 1:10, stir well, add hydrogen peroxide, so that the concentration of hydrogen peroxide in the system is 3 mol/L, Set the temperature at 200 °C, keep it warm for 2 h, and let it stand for 0.5 h after stopping heating. Other technological process is identical with embodiment 1.

The concentration of hexavalent chromium leached from the original chromium residue in this example was 277 mg/L, and the concentration of hexavalent chromium leached from the filter residue after treatment was 1.92 mg/L.

Example 4

Take 1 ton of waste residue containing hexavalent chromium and put it into a hydrothermal kettle, then add water to make the solid-to-liquid ratio (w/w) 1:5, stir well, add hydrogen peroxide, so that the concentration of hydrogen peroxide in the system is 5 mol/L, Set the temperature at 180 °C, keep it warm for 4 h, and let it stand for 12 h after stopping heating. Other technological process is identical with embodiment 1.

The concentration of hexavalent chromium leached from the original chromium residue in this embodiment was 265 mg/L, and the concentration of hexavalent chromium leached from the filter residue after treatment was 1.43 mg/L.

According to the scope of protection defined by the claims and the technical solutions provided in this specification, multiple implementation cases can also be given, all of which belong to the scope of protection of the present invention.

Claims (8)

1. a cleaning and detoxification treatment of chromium slag and a recovery method of chromium, containing trivalent chromium and hexavalent chromium in the chromium slag; it is characterized in that the steps of the method are as follows: 1) Add water to the chromium slag and mix well; 2) Add a mineralizer to the solid-liquid mixture obtained in step 1), and stir thoroughly to obtain a mixed solution; the mineralizer is hydrogen peroxide; 3) Using the hydrothermal method or direct heating to treat the mixed solution obtained in step 2), the trivalent chromium in the chromium slag is oxidized by hydrogen peroxide to dichromate and enters the solution. Chromium is desorbed from the surface of chromium slag; 4) Cool the solid-liquid mixture obtained in step 3) to room temperature naturally, and let stand; 5) Separating the solid residue from the chromium-containing supernatant, washing the filter residue with water and drying; 6) Recover chromium from the chromium-containing solution separated in step 5). 2. A method for cleaning and detoxifying chromium slag and recovering chromium according to claim 1, characterized in that, after adding water to the chromium slag in step 1), the solid-liquid ratio w/w is 1:0.5~ 1:10. 3. A method for cleaning and detoxifying chromium slag and recovering chromium according to claim 1, characterized in that, in step 2), the concentration of hydrogen peroxide in the mixed solution is 0.1 mol/L ~ 5 mol/L . 4. A method for cleaning and detoxifying chromium slag and recovering chromium according to claim 1, characterized in that the temperature of the hydrothermal method or direct heating in step 3) is controlled at 50°C to 250°C. 5. A method for cleaning and detoxifying chromium slag and recovering chromium according to claim 1, characterized in that the holding time in step 3) is 2 to 10 hours. 6 . The method for cleaning and detoxifying chromium slag and recovering chromium according to claim 1 , wherein the standing time in step 4) is 0.5 to 48 hours. 7. A method for cleaning and detoxifying chromium slag and recovering chromium according to any one of claims 1 to 6, characterized in that, in step 6), the specific steps of recovering chromium treatment are: adding chromium to the chromium-containing solution Add a reducing agent to reduce the hexavalent chromium in the solution to trivalent chromium, then add the precipitating agent NaOH to produce Cr(OH) ₃ precipitation, and finally calcinate the Cr(OH) ₃ precipitation into Cr ₂ O ₃ . 8 . The method for cleaning and detoxifying chromium slag and recovering chromium according to claim 7 , wherein the reducing agent is sodium sulfide or sodium bisulfite.