A method for simultaneously removing ruthenium and zinc from wastewater

Abstract

The present invention relates to a method for simultaneously removing ruthenium and zinc from wastewater. The method adjusts the pH value of the wastewater to convert zinc into a precipitate; a ruthenium binder is used to bind the ruthenium-containing groups in the wastewater to the precipitate; then the precipitate is removed from the wastewater, and the ruthenium element is removed together with the precipitate. The present invention can simultaneously remove ruthenium and zinc from the wastewater through a single-step precipitation, so that the ruthenium concentration and zinc concentration in the treated wastewater are both < 2.0 mg / L, and the color of the wastewater is eliminated, meeting the requirements for ruthenium and zinc elements in the direct discharge of wastewater. The method of the present invention is simple to operate and easy to implement industrially.

Description

Technical Field

[0001] The present invention relates to a wastewater treatment method, and particularly to a method for simultaneously removing ruthenium and zinc from wastewater. Background Art

[0002] In recent years, ruthenium has shown unique and stable catalytic properties in industrial catalysis and organic synthesis, which has attracted the attention of many scholars. The research and application of ruthenium-based catalysts in the chemical industries such as the utilization of by-product hydrogen chloride, ammonia synthesis, Fischer-Tropsch synthesis, and selective hydrogenation of benzene have emerged in an endless stream. Since ruthenium-containing groups generally have colors, colored ruthenium-containing wastewater will be generated during the preparation of ruthenium-based catalysts. The ruthenium in the wastewater must be removed to eliminate the color of the wastewater and meet the requirements for direct discharge of the wastewater. At the same time, the wastewater generated during the preparation of the above catalysts often contains not only ruthenium but also other metal elements that must be removed.

[0003] Taking the catalyst for selective hydrogenation of benzene to cyclohexene as an example, the catalyst is a ruthenium-zinc bimetallic catalyst. The alkaline wastewater generated during the catalyst preparation process contains both ruthenium and zinc elements, and the concentrations of ruthenium and zinc in the wastewater are relatively low, ≤50.0 mg / L and ≤500.0 mg / L respectively. Although the ruthenium concentration in the wastewater is relatively low, the wastewater is still significantly colored. As the ruthenium concentration in the wastewater increases, the color of the wastewater changes from light yellow to brownish yellow. The research results show that when the ruthenium concentration ≤2.0 mg / L, the wastewater chromaticity (dilution multiple) ≤50, and it can basically be considered colorless, meeting the requirements of the national standard GB 8978-1996 Comprehensive Wastewater Discharge Standard; when the ruthenium concentration >2.0 mg / L, the wastewater chromaticity (dilution multiple) >50, and the wastewater cannot be directly discharged. Therefore, to meet the requirements for direct discharge of the wastewater, the ruthenium concentration in the treated wastewater needs to be ≤2.0 mg / L. At the same time, according to the requirements of the national standard GB 8978-1996, the zinc concentration in the treated wastewater needs to be ≤2.0 mg / L. In summary, the ruthenium and zinc concentrations in the treated wastewater are both ≤2.0 mg / L to meet the requirements for direct discharge of the wastewater.

[0004] There are many studies on removing zinc from zinc-containing wastewater, but there is no report on the in-depth removal of ruthenium from ruthenium-containing wastewater from the perspective of wastewater treatment, especially to achieve a ruthenium concentration ≤2.0 mg / L in the treated wastewater. There are many studies on the field of ruthenium recovery and purification, such as recovering ruthenium from ruthenium-containing solutions. The focus of these studies is on the ruthenium recovery rate, and the ruthenium concentration in the treated solution is still relatively high, making the treated solution still colored and unable to be directly discharged.

[0005] As described in the patent application CN103380219A, a method for recovering ruthenium or ruthenium compounds discloses a method for recovering ruthenium from a ruthenium compound solution. In this method, an inorganic adsorbent is added to the ruthenium compound solution, then an acid is added to dissolve the inorganic adsorbent, and then the pH value is adjusted to above 7 with an alkaline solution to precipitate the inorganic adsorbent, and ruthenium or ruthenium compounds are adsorbed onto the inorganic adsorbent. The inorganic adsorbent described is one or a mixture of calcium phosphate compounds, talc compounds, and amorphous aluminosilicates. Examples show that the ruthenium concentration in the solution before treatment is 650 ppm to 810 ppm, and the ruthenium concentration in the solution after treatment is 3.7 ppm to 9.5 ppm.

[0006] As described in the patent application CN111235395A, a method for recovering ruthenium from a ruthenium-containing solution discloses a method for recovering ruthenium from a ruthenium-containing solution. By adding an alkali to adjust the pH value of the prepared ruthenium-containing solution to be alkaline, then adding a sodium hypochlorite solution for reaction, and finally adding a precipitant, filtering, and washing the precipitate until there are no impurity ions, and the filter cake is treated with hydrochloric acid to be converted into a ruthenium chloroacid solution. Examples show that the ruthenium concentration in the solution before treatment is 0.25%, and the ruthenium concentration in the solution after treatment is 5 ppm to 18 ppm.

[0007] The information disclosed in the foregoing background art section is only used to strengthen the understanding of the background of the present invention, and it may include information that is not known to those of ordinary skill in the art. Summary of the Invention

[0008] The object of the present invention is to provide a method for treating wastewater containing ruthenium and zinc, which can simultaneously treat the ruthenium concentration and zinc concentration to below 2.0 mg / L by one-step precipitation.

[0009] The present invention provides a method for simultaneously removing ruthenium and zinc from wastewater, including: adjusting the pH value of the wastewater to convert zinc into a precipitate; binding the ruthenium-containing groups in the wastewater to the precipitate through a ruthenium binder; removing the precipitate from the wastewater; the pH value of the wastewater > 12, and ruthenium exists in anionic groups.

[0010] According to the method of the present invention, after removing the precipitate, wastewater from which ruthenium and zinc have been removed is obtained.

[0011] According to the method of the present invention, the pH value of the wastewater is adjusted to 10 - 11 to convert zinc into a precipitate.

[0012] According to the method of the present invention, a ruthenium binder can be added to the wastewater before or after adjusting the pH value of the wastewater.

[0013] According to an embodiment of the present invention, a ruthenium binder is first added to the wastewater, then the pH value of the wastewater is adjusted. After precipitation appears, stirring is continued, and then the precipitate is separated and removed.

[0014] According to another embodiment of the present invention, after adjusting the pH value of the wastewater, a ruthenium binder is added to the wastewater; preferably, after precipitation occurs, the ruthenium binder is added. Preferably, after adding the ruthenium binder, stirring is continued, and then the precipitation is separated and removed.

[0015] According to the above two embodiments, before separating and removing the precipitate, the system can be left to stand, and after separating the supernatant, conventional solid-liquid separation methods can be used to remove the precipitate, such as filtering, sedimentation or centrifugal separation. One or more methods of removing the precipitate.

[0016] According to the treatment method of the present invention, the wastewater contains ruthenium in the form of or substantially in the form of [RuCHO 3 ] - 、[RuC 2 H 3 SO 5 ] - 、[RuC 4 H 5 OCl 2 ] - and [RuC 3 H 4 O 4 Cl] - The "substantially" means that, except for [RuCHO 3 ] - 、[RuC 2 H 3 SO 5 ] - 、[RuC 4 H 5 OCl 2 ] - and [RuC 3 H 4 O 4 Cl] - Except for one or several forms of ruthenium in the wastewater, the total content of other forms of ruthenium in the wastewater is less than 1.0 mg / L.

[0017] According to the treatment method of the present invention, the pH value of the wastewater is greater than 12. In the wastewater, zinc is present in anionic groups (such as ZnO 2 2- ).

[0018] According to the treatment method of the present invention, the ruthenium concentration in the wastewater before treatment, calculated on the mass of ruthenium element, is preferably ≤50.0 mg / L, more preferably 5.0 mg / L to 50.0 mg / L, and further preferably 5.0 mg / L to 30.0 mg / L.

[0019] According to the treatment method of the present invention, before treatment, in the wastewater, calculated by the mass of zinc element, the zinc concentration is preferably ≤ 500.0 mg / L, and more preferably 10.0 mg / L - 500.0 mg / L.

[0020] According to the treatment method of the present invention, before treatment, in the wastewater, the sodium concentration is generally 800.0 mg / L - 16000.0 mg / L.

[0021] According to the treatment method of the present invention, before treatment, in the wastewater, the chloride ion concentration is generally 90.0 mg / L - 6000.0 mg / L.

[0022] According to the treatment method of the present invention, before treatment, in the wastewater, the sulfate ion concentration is generally 20.0 mg / L - 1700.0 mg / L.

[0023] According to the treatment method of the present invention, the wastewater is the wastewater generated during the preparation of the benzene selective hydrogenation catalyst. The benzene selective hydrogenation catalyst is a ruthenium and zinc bimetallic catalyst. In this wastewater, the sodium concentration is generally 800.0 mg / L - 16000.0 mg / L; the chloride ion concentration is generally 90.0 mg / L - 6000.0 mg / L; the sulfate ion concentration is generally 20.0 mg / L - 1700.0 mg / L.

[0024] According to the treatment method of the present invention, this method can be carried out at ambient temperature, for example, at 10°C - 35°C.

[0025] According to the method of the present invention, the ruthenium-containing group in the wastewater is combined with the precipitate through a ruthenium binder, and then the precipitate is removed from the wastewater, so that the ruthenium-containing group is removed along with the precipitate.

[0026] According to the method of the present invention, the ruthenium binder is a cationic organic polymer, preferably cationic polyacrylamide. Cationic polyacrylamide is a water-soluble linear polymer, and its synthesis method is a mature technology. The present invention has no special limitation on the molecular weight of cationic polyacrylamide, and its molecular weight can be several thousand, several ten thousand, several hundred thousand, several million, or even up to tens of millions. The cationicity of the cationic polyacrylamide can be 10% - 60% (the measurement method can refer to GB / T31246-2014). In the present invention, the ruthenium binder is preferably a cationic polyacrylamide flocculant. As a flocculant, the molecular weight of cationic polyacrylamide is generally 8 million - 12 million. The cationic polyacrylamide can be conveniently obtained through commercial purchase; it can also be synthesized according to known existing methods. In the present invention, the cationic polyacrylamide is preferably quaternary ammonium type cationic polyacrylamide. The so-called quaternary ammonium type cationic polyacrylamide means that its cation is a quaternary ammonium cation.

[0027] Further, the mass ratio of the ruthenium binder to the wastewater is preferably (10 -6 ~10 -5 ):1.

[0028] Further, the cationic polyacrylamide can be made into an aqueous solution with a mass fraction of 0.01% to 0.5% for use, and is preferably made into an aqueous solution with a mass fraction of 0.05% to 0.3% for use.

[0029] According to the treatment method of the present invention, the ruthenium concentration and zinc concentration in the treated wastewater are both < 2.0 mg / L, the color of the wastewater is eliminated, and the requirements for direct discharge of wastewater for ruthenium and zinc elements are met.

[0030] The beneficial effects of the present invention are: it can remove ruthenium and zinc in the wastewater simultaneously through one-step precipitation, so that the ruthenium concentration and zinc concentration in the treated wastewater are both < 2.0 mg / L, the color of the wastewater is eliminated, and the requirements for ruthenium and zinc elements for direct discharge of wastewater are met. The method of the present invention is simple to operate and easy to implement industrially. Specific Embodiments

[0031] The present invention will be described in detail below in conjunction with specific embodiments. However, it should be noted that the protection scope of the present invention is not limited by these specific embodiments and theoretical explanations, but is determined by the claims.

[0032] In the present invention, except for the clearly stated content, any matters or things not mentioned directly apply to those known in the art without any change. Moreover, any embodiment described herein can be freely combined with one or more other embodiments described herein, and the technical solutions or technical ideas formed thereby shall be regarded as a part of the original disclosure or record of the present invention, and shall not be regarded as new content not disclosed or anticipated herein, unless those skilled in the art consider that the combination is obviously unreasonable.

[0033] All the features disclosed in the present invention can be combined arbitrarily. These combinations should be understood as the content disclosed or recorded in the present invention. Unless those skilled in the art consider that the combination is obviously unreasonable, they should all be regarded as specifically disclosed and recorded in the present invention. The numerical points disclosed in this specification, unless otherwise clearly stated, not only include the specific numerical points disclosed in the embodiments, but also include the endpoints of each numerical range in the specification. The ranges formed by any combination of these numerical points should be regarded as the ranges disclosed or recorded in the present invention.

[0034] For the technical and scientific terms in the present invention, those with definitions shall be subject to their definitions, and those without definitions shall be understood in accordance with the common meanings in the art.

[0035] Unless otherwise clearly stated, the numerical ranges defined in the present invention include the endpoints of the numerical ranges.

[0036] It should be understood that in the ruthenium- and zinc-containing wastewater described in the present invention, the ruthenium concentration and the zinc concentration are both greater than 2.0 mg / L, based on the mass of ruthenium element and the mass of zinc element respectively.

[0037] In the examples, for the ruthenium- and zinc-containing wastewater, the concentrations of ruthenium and zinc elements are measured by a Baird PS-4 type ICP-AES inductively coupled plasma atomic emission spectrometer according to the standard curve method.

[0038] In the examples, the detection of ruthenium-containing groups is analyzed by ultra-high performance liquid chromatography-quadrupole electrostatic field orbitrap mass spectrometry (UPLC-Orbitrap) from Thermo Fisher Scientific, USA. The analysis conditions are as follows: mobile phase A is water, mobile phase B is methanol, and the PDA detection wavelength is 210 - 800 nm. After detection, in the wastewater of the examples, the ruthenium-containing groups exist in one or more forms of 3 - [RuCHO 2 H 3 SO 5 - [RuC 4 H 5 OCl 2 - [RuC 3 H 4 O 4 Cl - and so on.

[0039] In the examples, the cationic polyacrylamide is a quaternary ammonium type cationic polyacrylamide flocculant and is commercially available.

[0040] Example 1

[0041] Take 100 g of ruthenium- and zinc-containing wastewater (the wastewater generated during the preparation of the benzene selective hydrogenation catalyst. After detection, the wastewater contains 5.2 mg / L of ruthenium, 437.3 mg / L of zinc, the pH value of the wastewater is 13.2, and the color of the wastewater is light yellow). Adjust the pH value to 10.7 with sulfuric acid, and precipitation occurs. Stir for 10 min, add 0.2 g of a cationic polyacrylamide (cationicity is 12%) solution (mass fraction is 0.1%), stir for 1 h, let it stand for 2 h, suck out about 70 mL of the supernatant, filter the remaining liquid, mix the sucked supernatant and the filtrate. After detection, the ruthenium and zinc concentrations in the mixed liquid are both < 1.0 mg / L, and the mixed liquid is colorless.

[0042] Example 2

[0043] ​​​Take 100 g of ruthenium- and zinc-containing wastewater (wastewater generated during the preparation of a benzene selective hydrogenation catalyst. After detection, the wastewater contains 9.4 mg / L of ruthenium, 152.2 mg / L of zinc, the pH value of the wastewater is 12.9, and the color of the wastewater is yellow), add 0.5 g of a cationic polyacrylamide solution (cationicity is 20%) (mass fraction is 0.2%), adjust the pH value to 10.3 with hydrochloric acid, precipitate appears, stir for 1 h and then filter. After detection, the concentrations of ruthenium and zinc in the filtrate are both < 1.0 mg / L, and the filtrate is colorless.

[0044] Example 3

[0045] Take 100 g of ruthenium- and zinc-containing wastewater (wastewater generated during the preparation of a benzene selective hydrogenation catalyst. After detection, the wastewater contains 32.1 mg / L of ruthenium, 25.0 mg / L of zinc, the pH value of the wastewater is 12.2, and the color of the wastewater is yellow), adjust the pH value to 10.8 with hydrochloric acid, precipitate appears, stir for 10 min, add 0.8 g of a cationic polyacrylamide solution (cationicity is 25%) (mass fraction is 0.05%), stir for 1 h, let stand for 2 h, suck out about 70 mL of the supernatant, filter the remaining liquid, mix the sucked-out supernatant and the filtrate. After detection, the concentrations of ruthenium and zinc in the mixed liquid are both < 1.0 mg / L, and the mixed liquid is colorless.

[0046] Example 4

[0047] Take 100 g of ruthenium- and zinc-containing wastewater (wastewater generated during the preparation of a benzene selective hydrogenation catalyst. After detection, the wastewater contains 47.8 mg / L of ruthenium, 470.7 mg / L of zinc, the pH value of the wastewater is 13.5, and the color of the wastewater is brownish yellow), adjust the pH value to 10.5 with hydrochloric acid, precipitate appears, stir for 10 min, add 0.2 g of a cationic polyacrylamide solution (cationicity is 60%) (mass fraction is 0.3%), stir for 1 h, let stand for 2 h, suck out about 70 mL of the supernatant, filter the remaining liquid, mix the sucked-out supernatant and the filtrate. After detection, the ruthenium concentration in the mixed liquid is 1.8 mg / L and the zinc concentration is < 1.0 mg / L, and the mixed liquid is colorless.

[0048] Comparative Example 1

[0049] Take 100 g of ruthenium- and zinc-containing wastewater (wastewater generated during the preparation of a benzene selective hydrogenation catalyst. After detection, the wastewater contains 5.2 mg / L of ruthenium, 437.3 mg / L of zinc, the pH value of the wastewater is 13.2, and the color of the wastewater is light yellow), add 0.2 g of the cationic polyacrylamide solution in Example 1, stir for 1 h, no precipitate appears, and the wastewater remains light yellow.

[0050] Comparative Example 2

[0051] Take 100 g of ruthenium- and zinc-containing wastewater (wastewater generated during the preparation of a benzene selective hydrogenation catalyst. After detection, the wastewater contains 5.2 mg / L of ruthenium, 437.3 mg / L of zinc, the pH value of the wastewater is 13.2, and the color of the wastewater is light yellow). Adjust the pH value to 10.7 with sulfuric acid. Precipitation occurs. Stir for 1 h and filter. After detection, the ruthenium concentration in the filtrate is 5.2 mg / L, the zinc concentration is < 1.0 mg / L, and the color of the filtrate is still light yellow).

Claims

1. A method for simultaneously removing ruthenium and zinc from wastewater, comprising: adjusting the pH value of the wastewater to convert zinc into a precipitate; The ruthenium-containing groups in the wastewater are combined with the precipitate by a ruthenium binder; the precipitate is removed from the wastewater; the pH value of the wastewater is > 12, and ruthenium exists in an anionic group; in the wastewater, ruthenium exists in one or more forms of 3 - [RuCHO 2 H 3 SO 5 - [RuC 4 H 5 OCl 2 - and 3 H 4 O 4 Cl] - ; the ruthenium binder is cationic polyacrylamide; the wastewater is the wastewater generated during the preparation of a benzene selective hydrogenation catalyst.​​​ 2. The method according to claim 1, characterized in that the pH value of the wastewater is adjusted to 10-11.

3. The method according to claim 1, characterized in that a ruthenium binder is first added to the wastewater, then the pH value of the wastewater is adjusted, after precipitation appears, stirring is continued, and then the precipitate is separated and removed.

4. The method according to claim 1, characterized in that in the wastewater, calculated by the mass of ruthenium element, the ruthenium concentration is 5.0 mg / L to 50.0 mg / L.

5. The method according to claim 1, characterized in that in the wastewater, calculated by the mass of zinc element, the zinc concentration is 10.0 mg / L to 500.0 mg / L.

6. The method according to claim 1, characterized in that the ruthenium binder is quaternary ammonium cationic polyacrylamide.

7. The method according to claim 1, characterized in that The mass ratio of the ruthenium binder to the wastewater is (10 -6 ~10 -5 ):1.