Stabilization treatment method for iron-arsenic waste residues

Abstract

The invention relates to the technical field of waste treatment, in particular to a stabilization treatment method for iron-arsenic waste residues. The method comprises the following steps: mixing iron-arsenic waste residues or pretreatment residue liquid of the iron-arsenic waste residues with a bicarbonate solution to obtain a turbid liquid; and adjusting the pH value of the turbid liquid to 4-9, and then carrying out normal-pressure and constant-temperature culture. According to the method, the amorphous iron-arsenic waste residues are subjected to normal-pressure and constant-temperature culture, so that the amorphous iron-arsenic waste residues are converted into stable minerals (hematite and maghemite), and the stability and magnetic separability of the iron-arsenic waste residues are improved. In the process of converting the amorphous iron-arsenic waste residues into the stable-state minerals, the arsenic which originally exists mainly in an adsorption form enters a crystal structure of the minerals, so that the stability of the arsenic in the iron-arsenic waste residues is improved, and secondary pollution caused by the arsenic is avoided.

Description

Technical Field

[0001] The invention relates to the technical field of waste treatment, and in particular to a stabilization treatment method for iron-arsenic waste residue. Background Art

[0002] Arsenic is one of the main associated elements in non-ferrous metal ores, and is bioaccumulative and carcinogenic. Arsenic is mainly associated with mineral resources such as tin (Sn), lead (Pb), zinc (Zn), gold (Au), and copper (Cu) in nature. For example, the arsenic content in high-arsenic copper and gold concentrates can be as high as 20-30%. During the mining and smelting process of non-ferrous metal ores, arsenic in the raw materials will be enriched in the solution, producing a large amount of arsenic-containing waste liquid, which must be de-arsenified. Common methods for de-arsenicizing arsenic-containing waste liquid include iron-arsenic co-precipitation, sulfide precipitation, and calcium arsenate precipitation. Among them, the iron-arsenic co-precipitation method is widely used due to its simple operation, high arsenic removal rate, and low cost.

[0003] However, the iron-arsenic coprecipitation method produces a large amount of arsenic-containing waste slag, and the arsenic element in the waste slag mainly exists in the form of iron-arsenic coprecipitation and iron hydroxide adsorption. Iron is mainly an amorphous colloid, and its thermodynamic properties are very unstable. Direct storage or landfill of iron-arsenic waste slag will cause arsenic to be released into the environment, and there is basically no resource market for iron-arsenic waste slag. Although it has a certain degree of stability, its safe and long-term solidification and stabilization treatment and disposal is still a major problem that needs to be solved in the current smelting and chemical industries. Summary of the invention

[0004] The object of the present invention is to provide a stabilization treatment method for iron-arsenic waste slag. The present invention can convert amorphous iron-arsenic waste slag into stable iron minerals that can be magnetically separated, thereby improving the stability and separability of the iron-arsenic waste slag and avoiding secondary pollution caused by arsenic seepage during the waste slag stacking process.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0006] The invention provides a stabilization treatment method for iron-arsenic waste residue, comprising the following steps: mixing the iron-arsenic waste residue or pre-treated residue liquid of the iron-arsenic waste residue with a bicarbonate solution to obtain a suspension; and adjusting the pH value of the suspension to 4-9 and then culturing at normal pressure and constant temperature.

[0007] Preferably, the temperature of the normal pressure constant temperature culture is 60-95°C.

[0008] Preferably, the normal pressure and constant temperature culture time is 0.5 to 20 days.

[0009] Preferably, the content of pentavalent arsenic in the iron-arsenic waste slag is 1 to 300 g / kg.

[0010] Preferably, the molar ratio of trivalent iron to pentavalent arsenic in the iron-arsenic waste slag is 5 to 500:1.

[0011] Preferably, the bicarbonate in the bicarbonate solution includes sodium bicarbonate and / or potassium bicarbonate.

[0012] Preferably, the molar ratio of ferric iron to bicarbonate in the suspension is 0.5 to 5:1.

[0013] Preferably, the concentration of iron-arsenic waste residue in the suspension is 1 to 50 g / L.

[0014] Preferably, the reagent used to adjust the pH value of the suspension to 4-9 is acid and / or alkali.

[0015] Preferably, the acid solution includes a hydrochloric acid solution; and the alkali solution includes a sodium hydroxide solution.

[0016] The present invention provides a stabilization treatment method for iron-arsenic waste residue, comprising the following steps: mixing the iron-arsenic waste residue or the pre-treated residue liquid of the iron-arsenic waste residue with a bicarbonate solution to obtain a suspension; adjusting the pH value of the suspension to 4-9 and then culturing at normal pressure and constant temperature. The present invention transforms the amorphous iron-arsenic waste residue into stable minerals (hematite and hematite) by culturing the amorphous iron-arsenic waste residue at normal pressure and constant temperature, thereby improving the stability and magnetic separability of the iron-arsenic waste residue. In the process of transforming the amorphous iron-arsenic waste residue into stable minerals, the arsenic that initially exists mainly in the form of adsorption enters the crystal structure of the mineral, thereby improving the stability of the arsenic in the iron-arsenic waste residue and avoiding secondary pollution caused by arsenic. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 Process flow chart for arsenic-containing wastewater treatment, stabilization and magnetic separation of waste residue;

[0018] Figure 2 This is a TEM image of the initial iron-arsenic waste slag in Example 1;

[0019] Figure 3 The SEM images of the stabilized iron-arsenic waste slag prepared in Examples 1 to 5 and Comparative Examples 1 to 4 are shown;

[0020] Figure 4 The XRD diagrams of the initial iron-arsenic waste residue in Example 1 and the stabilized iron-arsenic waste residues prepared in Examples 1 to 5 and Comparative Examples 1 to 4;

[0021] Figure 5 The magnetic properties of the initial iron-arsenic waste slag (left) and the iron-arsenic waste slag after stabilization treatment (right) in Example 1 are compared;

[0022] Figure 6This is a magnetic comparison diagram of the initial iron-arsenic waste slag (left) and the iron-arsenic waste slag after stabilization treatment (right) in Example 3. DETAILED DESCRIPTION

[0023] The invention provides a stabilization treatment method for iron-arsenic waste residue, comprising the following steps: mixing the iron-arsenic waste residue or pre-treated residue liquid of the iron-arsenic waste residue with a bicarbonate solution to obtain a suspension; and adjusting the pH value of the suspension to 4-9 and then culturing at normal pressure and constant temperature.

[0024] In the present invention, unless otherwise specified, the raw materials used are commercially available products well known in the art.

[0025] The invention mixes the iron-arsenic waste residue or the pre-treated residue liquid of the iron-arsenic waste residue with the bicarbonate solution to obtain a suspension.

[0026] In the present invention, the iron-arsenic waste residue is preferably obtained by an iron-arsenic coprecipitation method; the present invention has no special requirements for the iron-arsenic coprecipitation method, and any iron-arsenic coprecipitation method known in the art can be used. The conventional iron-arsenic coprecipitation method is to first oxidize the trivalent arsenic in the waste acid to pentavalent arsenic with an oxidant, then add a relatively pure iron-containing agent to the arsenic-containing waste acid, and use lime to adjust the pH value of the system, so that the arsenic in the arsenic-containing waste acid is removed from the waste liquid in the form of arsenic-iron coprecipitation (iron-arsenic waste residue), and the iron-arsenic waste residue is obtained after solid-liquid separation. If no solid-liquid separation is performed, it is a pre-treated slag liquid of the iron-arsenic waste residue.

[0027] In an embodiment of the present invention, a pretreatment slag liquid of iron-arsenic waste slag is specifically simulated by experiment, and the simulation method includes the following steps: dissolving sodium arsenate in water to obtain simulated arsenic-containing wastewater; dissolving a trivalent iron salt in water to obtain a trivalent iron ion solution; mixing the trivalent iron ion solution with the simulated arsenic-containing wastewater to obtain a mixed solution; adding an alkali solution to the mixed solution to form an iron-arsenic co-precipitation to obtain a suspension, and adjusting the pH value of the suspension to 8-9 to obtain a pretreatment slag liquid simulating iron-arsenic waste slag.

[0028] In the present invention, the content of pentavalent arsenic in the iron-arsenic waste slag is preferably 1 to 300 g / kg. In a specific embodiment, the content of pentavalent arsenic in the iron-arsenic waste slag can be 1 g / kg, 10 g / kg, 20 g / kg, 30 g / kg, 40 g / kg, 50 g / kg, 60 g / kg, 70 g / kg, 80 g / kg, 90 g / kg, 100 g / kg, 150 g / kg, 200 g / kg, 250 g / kg or 300 g / kg. In the present invention, the molar ratio of trivalent iron to pentavalent arsenic in the iron-arsenic waste slag is preferably 5 to 500:1; in a specific embodiment, the molar ratio of trivalent iron to pentavalent arsenic in the iron-arsenic waste slag can be 10:1, 30:1, 50:1, 80:1, 100:1, 200:1, 300:1, 400:1 or 500:1.

[0029] In the present invention, the bicarbonate in the bicarbonate solution preferably includes sodium bicarbonate and / or potassium bicarbonate. The present invention has no special requirements on the concentration and dosage of the bicarbonate solution, as long as the molar ratio of trivalent iron to bicarbonate in the suspension is 0.5 to 5:1, and the iron-arsenic waste residue can be completely immersed. In a specific embodiment, the molar ratio of trivalent iron to bicarbonate in the suspension can be 0.5:1, 1:1, 2:1, 3:1, 4:1 or 5:1.

[0030] In the present invention, the concentration of iron-arsenic waste residue in the suspension is preferably 1-50 g / L. In specific embodiments, it can be 1 g / L, 5 g / L, 10 g / L, 15 g / L, 20 g / L, 25 g / L, 30 g / L, 40 g / L or 50 g / L.

[0031] In the present invention, the role of the bicarbonate is to stabilize the pH value, prevent the pH value of the iron and arsenic co-precipitation from decreasing during the subsequent constant pressure and temperature culture process, and hinder the crystallization conversion.

[0032] After obtaining the suspension, the present invention adjusts the pH value of the suspension to 4-9 and then performs constant pressure and constant temperature culture.

[0033] In the present invention, the reagent used to adjust the pH value of the suspension to 4-9 is preferably an acid solution and / or an alkali solution; the acid solution preferably includes a hydrochloric acid solution; the alkali solution preferably includes a sodium hydroxide solution; the concentration of the hydrochloric acid solution is preferably 0.5-1.5 mol / L; the concentration of the sodium hydroxide solution is preferably 0.5-1.5 mol / L.

[0034] In a specific embodiment, after obtaining the suspension, the pH value of the suspension may be adjusted to 4, 5, 6, 7, 8 or 9.

[0035] In the present invention, the temperature of the normal pressure constant temperature culture is preferably 60-95°C. In a specific embodiment, the temperature of the normal pressure constant temperature culture can be 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C or 95°C; the time of the normal pressure constant temperature culture is preferably 0.5-20 days. In a specific embodiment, the time of the normal pressure constant temperature culture can be 0.5 days, 3 days, 5 days, 7 days, 9 days, 12 days, 15 days, 17 days or 20 days. In the present invention, the normal pressure constant temperature culture is preferably carried out under sealed conditions. The present invention is cultured under sealed conditions to prevent water loss.

[0036] Arsenic in the iron-arsenic waste residue mainly exists in the form of iron-arsenic coprecipitation and iron hydroxide adsorption. Iron is mainly an amorphous colloid, and its thermodynamic properties are very unstable. In the process of constant temperature cultivation at normal pressure, the metastable amorphous waste residue is converted into crystalline hematite or magnetic hematite. The crystalline hematite or magnetic hematite will store arsenic in the crystal structure of the mineral, inhibiting the release of arsenic; the formed magnetic hematite is a ferromagnetic mineral with high magnetism; the formed hematite also has a certain magnetism due to the distortion of the crystal structure caused by arsenic doping, and can be magnetically separated. After being treated by the present invention, the stability of the iron-arsenic waste residue is improved, and magnetic separation can be performed at the same time.

[0037] The present invention stabilizes the pH value at 4-9, which is conducive to ensuring that the waste residue is converted into hematite and magnetic hematite instead of being converted into goethite with weaker arsenic fixation ability.

[0038] After the cultivation, the present invention preferably performs magnetic separation, and the separated waste residue is dried or air-dried to obtain stabilized iron-arsenic waste residue; the stabilized iron-arsenic waste residue can be directly landfilled or solidified, and the wastewater obtained after separation can be directly discharged or treated secondary.

[0039] The stabilization treatment method of iron-arsenic waste slag provided by the present invention is described in detail below in conjunction with the embodiments, but they should not be understood as limiting the scope of protection of the present invention.

[0040] Example 1

[0041] according to Figure 1 The process shown is processed as follows:

[0042] Dissolve sodium arsenate in water to obtain an arsenic stock solution;

[0043] 27 g of FeCl3·6H2O and 500 mL of deionized water were stirred at room temperature and a rotation speed of 100 r / min for 30 min to obtain a trivalent iron ion solution;

[0044] Arsenic stock solution was added at a molar ratio of trivalent Fe to pentavalent As of 100:1 to obtain a mixed solution, wherein the content of pentavalent arsenic in the mixed solution was 150 mg / L;

[0045] Pour 270 mL of 1 mol / L NaOH solution into the mixed solution, and then drop 30 mL of 1 mol / L NaOH solution into the mixed solution at a drop rate of 50 drops / min to obtain a turbid solution;

[0046] The pH value was adjusted to 8-8.5 using 1M NaOH and 1M HCl solutions, the turbid solution was diluted to 2000 mL with deionized water, and the pH value of the mixed suspension was adjusted to stabilize the pH value of the suspension at about 8.5, and stabilized for 4 hours to obtain a pretreated slag solution of simulated iron-arsenic waste slag, wherein the content of pentavalent arsenic in the simulated iron-arsenic waste slag was 9.3 g / kg;

[0047] The pretreated slag solution was mixed with 50 mL of sodium bicarbonate solution to obtain a suspension (with a bicarbonate concentration of about 3 g / L), wherein the molar ratio of trivalent iron to bicarbonate ions in the simulated iron-arsenic waste slag in the suspension was 2:1;

[0048] After mixing the suspension with the sodium bicarbonate solution, the pH value was readjusted to 8.5;

[0049] The adjusted suspension was cultured at normal pressure and constant temperature for 10 days;

[0050] After the cultivation is completed, magnetic separation is carried out, and the separated waste residue is dried to obtain stabilized iron-arsenic waste residue, which can be landfilled or solidified. The wastewater obtained after separation can be directly discharged or treated for a second time.

[0051] Example 2

[0052] The pretreated slag liquid of simulated iron-arsenic waste slag was prepared according to the method of Example 1, except that the molar ratio of trivalent iron to pentavalent arsenic was 80:1, the content of pentavalent arsenic in the mixed liquid was 187.5 mg / L, and the content of pentavalent arsenic in the simulated iron-arsenic waste slag was 11.6 g / kg.

[0053] Arsenic-containing wastewater treatment and stabilization and magnetic separation waste residue treatment were carried out according to the method of Example 1.

[0054] Example 3

[0055] The pretreated slag liquid of simulated iron-arsenic waste slag was prepared according to the method of Example 1, except that the molar ratio of trivalent iron to pentavalent arsenic was 40:1, the content of pentavalent arsenic in the mixed liquid was 375 mg / L, and the content of pentavalent arsenic in the simulated iron-arsenic waste slag was 25.3 g / kg.

[0056] The simulated iron-arsenic waste slag stabilization treatment was carried out according to the method of Example 1.

[0057] Example 4

[0058] The pretreated slag liquid of simulated iron-arsenic waste slag was prepared according to the method of Example 1, except that the molar ratio of trivalent iron to pentavalent arsenic was 20:1, the content of pentavalent arsenic in the mixed liquid was 750 mg / L, and the content of pentavalent arsenic in the simulated iron-arsenic waste slag was 47.6 g / kg.

[0059] The simulated iron-arsenic waste slag stabilization treatment was carried out according to the method of Example 1.

[0060] Example 5

[0061] The pretreated slag liquid of simulated iron-arsenic waste slag was prepared according to the method of Example 1, except that the molar ratio of trivalent iron to pentavalent arsenic was 10:1, the content of pentavalent arsenic in the mixed liquid was 1500 mg / L, and the content of pentavalent arsenic in the simulated iron-arsenic waste slag was 88.9 g / kg.

[0062] The simulated iron-arsenic waste slag stabilization treatment was carried out according to the method of Example 1.

[0063] Comparative Example 1

[0064] A mixed solution of pentavalent arsenic and trivalent iron was prepared according to the method of Example 1, with the same molar ratio of trivalent iron to pentavalent arsenic (80:1) as in Example 2, the pentavalent arsenic content in the mixed solution was 187.5 mg / L, and the pentavalent arsenic content in the simulated iron-arsenic waste slag was 11.6 g / kg, except that no sodium bicarbonate solution was added.

[0065] The simulated iron-arsenic waste slag stabilization treatment was carried out according to the method of Example 1.

[0066] Comparative Example 2

[0067] The pre-treated slag solution of simulated iron-arsenic waste slag was prepared according to the method of Example 1, with the same molar ratio of trivalent iron to pentavalent arsenic (100:1) as in Example 1, the pentavalent arsenic content in the mixed solution was 150 mg / L, and the pentavalent arsenic content in the simulated iron-arsenic waste slag was 9.3 g / kg. The difference was that the pH value was 13 during the constant temperature culture at normal pressure.

[0068] The simulated iron-arsenic waste slag stabilization treatment was carried out according to the method of Example 1.

[0069] Comparative Example 3

[0070] The pretreated slag liquid of the simulated iron-arsenic waste slag was prepared according to the method of Comparative Example 2, except that the molar ratio of trivalent iron to pentavalent arsenic was 80:1, the content of pentavalent arsenic in the mixed liquid was 187.5 mg / L, and the content of pentavalent arsenic in the simulated iron-arsenic waste slag was 11.6 g / kg.

[0071] A comparative simulation of the iron-arsenic waste slag stabilization treatment was carried out according to the method of Comparative Example 2.

[0072] Comparative Example 4

[0073] The pretreated slag liquid of the simulated iron-arsenic waste slag was prepared according to the method of Comparative Example 2, except that the molar ratio of trivalent iron to pentavalent arsenic was 40:1, the content of pentavalent arsenic in the mixed liquid was 375 mg / L, and the content of pentavalent arsenic in the simulated iron-arsenic waste slag was 25.3 g / kg.

[0074] A comparative simulation of the iron-arsenic waste slag stabilization treatment was carried out according to the method of Comparative Example 2.

[0075] Performance Testing

[0076] The initial iron-arsenic waste slag of Example 1 was observed by TEM. The results are as follows Figure 2 As shown by Figure 2 It can be seen that the initial iron-arsenic waste residue is amorphous. The stabilized iron-arsenic waste residues obtained in Examples 1 to 5 and Comparative Examples 1 to 4 were subjected to SEM, XRD and magnetic susceptibility tests, respectively. The obtained SEM images are shown in FIG. Figure 3 The obtained XRD pattern is shown in Figure 4 The obtained magnetic susceptibility is shown in Table 1, and the magnetic comparison diagram of Example 1 and Example 3 before and after stabilization treatment is shown in Figures 5-6 As shown. Combined Figure 3 and Figure 4 It can be seen that the waste residue can be converted into a substance with a certain crystal structure after being treated according to the method provided by the present invention, thereby improving the stability of the waste residue. Figures 5-6 As can be seen from the results in Table 1, the magnetic properties of the waste residue treated by the method provided by the present invention are enhanced, thereby improving the magnetic separability of the waste residue.

[0077] A sodium dihydrogen phosphate solution with a pH of 5 and a molar concentration of 1 mol / L is used as an extractant, which has a strong extraction ability for adsorbed arsenic or selenium. The leaching concentration of arsenic in the iron-arsenic waste slag is detected, wherein the volume ratio of the mass of the iron-arsenic waste slag to the leaching agent is 1 g:250 mL. Specifically, 0.1 g of the simulated iron-arsenic waste slag and the stabilized iron-arsenic waste slag prepared in Examples 1 to 5 are mixed with 25 mL of the leaching agent, respectively, and the mixture is immersed at 25° C. for 3 days. The concentration of arsenic in the solution is detected, and the results are listed in Table 1.

[0078] Table 1 Arsenic leaching in simulated iron-arsenic waste slag and stabilized iron-arsenic waste slag and magnetic susceptibility of waste slag

[0079]

[0080]

[0081] Note: In Table 1, the stabilization ratio of arsenic in the waste slag is equal to the difference between the arsenic concentration in the leaching solution of the initial iron-arsenic waste slag and the arsenic concentration in the leaching solution of the stabilized iron-arsenic waste slag divided by the arsenic concentration in the leaching solution of the initial iron-arsenic waste slag.

[0082] It can be seen from the data in Table 1 that after stabilization treatment according to the stabilization treatment method provided by the present invention, the leaching concentration of arsenic in the simulated iron-arsenic waste slag is significantly reduced, proving that the stabilization treatment method provided by the present invention improves the stability of arsenic in the iron-arsenic waste slag, converts part of the arsenic into an unextractable state, and its stabilization ratio reaches 37.1-77.8%, and the magnetism of the waste slag is enhanced, and magnetic separation can be performed. In Comparative Example 1, sodium bicarbonate is not used to stabilize the pH, and part of the iron-arsenic waste slag is converted into goethite with poor arsenic solidification ability. Compared with Example 1, the proportion of stable arsenic in the waste slag is reduced by 16.8%; Comparative Examples 2-4 are cultured at normal pressure and constant temperature under the condition of pH value of 13, and the conversion product of the iron-arsenic waste slag is mainly goethite, and the proportion of stable arsenic in the waste slag is reduced to 13.1-15.8%, and the magnetism of the waste slag is also reduced.

[0083] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for stabilizing iron-arsenic waste residue, characterized in that: The following steps are involved: The iron-arsenic waste residue or the pre-treated residue liquid of the iron-arsenic waste residue is mixed with a bicarbonate solution to obtain a suspension; the pH value of the suspension is adjusted to 4-9 and then cultured at normal pressure and constant temperature.

2. The stabilization treatment method according to claim 1, characterized in that: The temperature of the normal pressure constant temperature culture is 60-95°C.

3. The stabilization treatment method according to claim 1 or 2, characterized in that: The time of the normal pressure constant temperature culture is 0.5 to 20 days.

4. The stabilization treatment method according to claim 1, characterized in that: The content of pentavalent arsenic in the iron-arsenic waste slag is 1-300 g / kg.

5. The stabilization treatment method according to claim 1 or 4, characterized in that: The molar ratio of trivalent iron to pentavalent arsenic in the iron-arsenic waste slag is 5 to 500:

1.

6. The stabilization treatment method according to claim 1, characterized in that: The bicarbonate in the bicarbonate solution includes sodium bicarbonate and / or potassium bicarbonate.

7. The stabilization treatment method according to claim 1, characterized in that: The molar ratio of trivalent iron to bicarbonate in the suspension is 0.5-5:

1.

8. The stabilization treatment method according to claim 1, 4 or 7, characterized in that: The concentration of iron-arsenic waste residue in the suspension is 1-50 g / L.

9. The stabilization treatment method according to claim 1 or 7, characterized in that: The reagent used to adjust the pH value of the suspension to 4-9 is acid solution and / or alkali solution.

10. The stabilization treatment method according to claim 9, characterized in that: The acid solution includes a hydrochloric acid solution; the alkali solution includes a sodium hydroxide solution.

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