A method for the synergistic treatment of sulfur dioxide-containing waste gas and sulfate ion-containing waste water

Abstract

The application discloses a kind of collaborative processing method of containing sulfur dioxide waste gas and containing sulphate ion waste water, comprising the following steps: (1) containing metal Ni nanoparticle catalyst is dispersed in sulphate ion containing waste water, and sulfur dioxide containing waste gas is imported, and pH is controlled between 2~5, and reaction is carried out;(2) calcium ion containing salt or alkali is added, and pH is adjusted to 9~10, and stirring reaction is generated calcium sulfite precipitate.The application directly treats sulfate salt waste water using SO2 waste gas, achieves waste collaborative processing, realizes "waste treatment with waste".

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of environmental pollution treatment or resource recovery, and particularly relates to a method for the synergistic treatment of waste gas containing sulfur dioxide and waste water containing sulfate ions. BACKGROUND

[0002] Industrial waste water (such as mine drainage, metallurgical waste water) contains high concentrations of sulfate, and traditional treatment methods include membrane processes, evaporation processes, etc. Membrane processes only transfer the sulfate ions in the water, and evaporation processes have high investment and operating costs. Existing sulfate reduction technologies (such as biological reduction) are low in efficiency and require external carbon sources.

[0003] Sulfur dioxide is a common industrial waste gas (such as coal-fired flue gas), which usually needs to be oxidized and desulfurized (such as generating sulfate), but is not effectively resourceized.

[0004] Existing technologies involve the oxidation of SO2 (such as the production of sulfuric acid) or the chemical reduction of sulfate (such as using H2S), but lack a synergistic method of directly utilizing SO2 gas to reduce SO4 2- . SUMMARY

[0005] The technical problem to be solved by the present application is to overcome the deficiencies and shortcomings mentioned in the above background technology, and to provide a method for the synergistic treatment of waste gas containing sulfur dioxide and waste water containing sulfate ions.

[0006] To solve the above technical problems, the technical solution proposed by the present application is as follows:

[0007] A method for the synergistic treatment of waste gas containing sulfur dioxide and waste water containing sulfate ions, comprising the following steps:

[0008] (1) dispersing a catalyst containing metal Ni nanoparticles in waste water containing sulfate ions, introducing waste gas containing sulfur dioxide, and controlling the pH to be between 2 and 5 to carry out the reaction;

[0009] (2) adding a salt or base containing calcium ions and adjusting the pH to between 9 and 10 to carry out the reaction, generating calcium sulfite precipitate.

[0010] As a further improvement, the preparation method of the catalyst containing metal Ni nanoparticles comprises:

[0011] (1') mixing a solution of metal salt containing Ni 2+ and La 3+ with pseudo-boehmite powder to form a paste, then standing and drying;

[0012] (2') calcining the dried product in air to form Ni 2+ and La 3+The pseudo-boehmite is converted into γ-Al2O3 to obtain a catalyst precursor;

[0013] (3') reducing the catalyst precursor under a reducing atmosphere to reduce the oxide of nickel into metallic nickel to obtain the catalyst containing metallic Ni nanoparticles.

[0014] As a further improvement, the catalyst containing metallic Ni nanoparticles has a mass fraction of Ni of 13-18% and a mass fraction of La2O3 of 2-4%.

[0015] As a further improvement, the metal salt solution is an aqueous solution prepared from Ni(NO3)2·6H2O and La(NO3)3·6H2O, and the mass ratio of Ni(NO3)2·6H2O to La(NO3)3·6H2O is (5-6):(0.6-1).

[0016] As a further improvement, the calcination comprises:

[0017] (a) heating to 110-130°C and keeping for 20-40 min;

[0018] (b) heating to 450-550°C and keeping for 2-4 hours;

[0019] (c) heating to 750-800°C and keeping for 3-5 hours.

[0020] As a further improvement, the temperature of the reduction is 350-450°C.

[0021] As a further improvement, the catalyst is added in an amount of 90-110 g / L, and the flow rate of the waste gas containing sulfur dioxide is 0.1-0.2 L / min.

[0022] As a further improvement, calcium hydroxide is added in step (1) to control the pH to be between 2 and 5.

[0023] As a further improvement, the salt or base containing calcium ions in step (2) is calcium hydroxide.

[0024] As a further improvement, the content of sulfate in the wastewater is reduced to <160 mg / L.

[0025] Compared with the prior art, the present application has the following beneficial effects:

[0026] Under the catalysis of the catalyst of the present application, in the presence of calcium ions, the sulfate ions in the solution are reduced into sulfite ions by the sulfur dioxide gas, and calcium sulfite precipitate is separated. The chemical equation is:

[0027] 2SO4 2- +2SO2+4Ca 2++4OH - →4CaSO3+O2+2H2O

[0028] The specific mechanism is that: under the acidic (pH=2~5) and catalytic conditions, SO2 and SO4 2- occur redox reaction to generate bisulfite ion (HSO3 - ), and E 0 (SO2 / HSO3 - )=-0.25V<E 0 (SO4 2- / HSO3 - )≈+0.17V, and the catalyst catalyzes reduction to accelerate electron transfer. Bisulfite ion becomes sulfite ion (SO3 2- ) under the condition of improving pH (pH=9~10), and the sulfite ion rapidly generates calcium sulfite precipitate with calcium ion, thereby reducing sulfate ion in the water body, and the reaction thermodynamics is spontaneous (ΔG<0).

[0029] The application directly treats sulfate wastewater by using SO2 waste gas, achieves waste collaborative treatment, and realizes "waste treatment by waste". The catalyst has high reduction efficiency and avoids byproduct generation. The application synchronously recycles sulfur and calcium, and reduces treatment cost. BRIEF DESCRIPTION OF DRAWINGS

[0030] In order to more clearly illustrate the technical solutions of the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiment or prior art description. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0031] Figure 1 is an X-ray photoelectron spectrum;

[0032] Figure 2 is an H2-temperature programmed reduction spectrum. DETAILED DESCRIPTION

[0033] In order to facilitate understanding of the present application, the following will combine the drawings of the specification and the preferred embodiments to make a more comprehensive and detailed description of the present application, but the protection scope of the present application is not limited to the following specific embodiments.

[0034] Unless otherwise defined, all professional terms used in the following have the same meaning as generally understood by those skilled in the art. The professional terms used in the present application are only for the purpose of describing the specific embodiments, and are not intended to limit the protection scope of the present application.

[0035] Unless otherwise specifically explained, various raw materials, reagents, instruments and equipment used in the present application can be purchased from the market or prepared by existing methods.

[0036] In some embodiments, the catalyst (nickel metal catalyst supported by pseudo-boehmite) used in the present application is prepared by the following steps:

[0037] (a) mixing a solution of a metal salt containing Ni 2+ and a carrier powder to form a paste, and then standing and drying.

[0038] In some embodiments, the carrier is pseudo-boehmite (AlOOH· n H2O).

[0039] In some embodiments, the solution of the metal salt further contains La 3+ .

[0040] In some embodiments, the solution of the metal salt is an aqueous solution prepared from Ni(NO3)2·6H2O and La(NO3)3·6H2O. The mass ratio of Ni(NO3)2·6H2O to La(NO3)3·6H2O is (5-6):(0.6-1). The mass ratio of Ni(NO3)2·6H2O to pseudo-boehmite is (5-6):(8-12).

[0041] In some embodiments, the standing is carried out at room temperature for 10-15 hours. This helps the metal ions to be more evenly distributed in the pores of the carrier.

[0042] In some embodiments, the drying is carried out at 110-130°C for 10-15 hours.

[0043] (b) calcining the dried product in air, so that Ni 2+ and La 3+ are converted into oxides, and the pseudo-boehmite is converted into γ-Al2O3, to obtain a catalyst precursor (denoted as NiO-La2O3 / γ-Al2O3).

[0044] In some embodiments, the calcining procedure is as follows:

[0045] (b1) heating to 110-130°C, and holding for 20-40 min to completely remove residual water;

[0046] (b2) heating to 450-550°C, and holding for 2-4 hours to decompose the metal nitrate, and to convert the pseudo-boehmite into γ-Al2O3 by dehydration and dehydroxylation;

[0047] (b3) heating to 750-800°C, and holding for 3-5 hours.

[0048] At 750-800℃, the specific surface area of γ-Al2O3 is still high, but has begun to transform to δ / θ phase with lower specific surface area, and the thermal stability is greatly enhanced. NiO at this temperature will interact with the carrier to some extent, and this strong interaction helps to prevent sintering and growth of metal particles in subsequent use. At this temperature, all impurity ions such as nitrate and ammonium in the precursor are completely decomposed and burned off.

[0049] In some embodiments, the heating rate is 2-5℃ / min. Slow heating prevents the destruction of the pore structure.

[0050] (c) reducing the catalyst precursor under a reducing atmosphere to reduce the oxide of nickel to metallic nickel, thereby obtaining the catalyst of the present application (denoted as Ni-La2O3 / γ-Al2O3).

[0051] In some embodiments, the reducing atmosphere is a hydrogen atmosphere.

[0052] In some embodiments, the reduction temperature is 350-450℃, and the reduction time is 1.5-2.5 hours.

[0053] In some embodiments, the NiO is reduced to metallic Ni nanoparticles with catalytic activity, the particle size of the Ni particles is mainly distributed in the range of 3-9nm, and the mass fraction of Ni in the catalyst is 13-18%, and the mass fraction of La2O3 is 2-4%.

[0054] In some specific embodiments, the method for the synergistic treatment of waste gas containing sulfur dioxide and waste water containing sulfate ions of the present application comprises the following steps:

[0055] (1) dispersing the catalyst of the present application in waste water containing sulfate ions, introducing waste gas containing sulfur dioxide, and controlling the pH to be between 2 and 5 to carry out the reaction.

[0056] In some embodiments, the amount of catalyst added is 90-110g / L. The flow rate of waste gas containing sulfur dioxide is 0.1-0.2L / min.

[0057] In some embodiments, an alkali (preferably calcium hydroxide) is added to adjust the pH to be between 2 and 5, so as to avoid the pH being reduced to below 2 due to the continuous introduction of sulfur dioxide.

[0058] In some embodiments, the reaction is carried out for 5-10min.

[0059] (2) adding a salt or alkali containing calcium ions and adjusting the pH to be between 9 and 10 to carry out the stirring reaction to generate calcium sulfite precipitate.

[0060] Preferably, calcium hydroxide is added. The amount of calcium ions should be excessive depending on the amount of sulfate and sulfur dioxide.

[0061] In some embodiments, the reaction is stirred for 10-20 minutes, then allowed to stand before being filtered to obtain a calcium sulfite precipitate (calcium sulfate content <0.5%) and a filtrate with a sulfate content <160 mg / L.

[0062] Example 1. Preparation of catalyst

[0063] (1) 5.84 g of Ni(NO3)2·6H2O and 0.80 g of La(NO3)3·6H2O were added to 8.8 mL of water and mixed to obtain a metal salt solution.

[0064] (2) The metal salt solution was slowly added to the support powder (10.93 g of industrial pseudoboehmite) while stirring to obtain a uniform paste, which was then allowed to stand at room temperature for 12 hours for aging.

[0065] (3) After aging, the sample was dried at 120°C for 12 hours and then calcined in air according to the following program: heating to 120°C at 2-5°C / min, holding for 30 min; continuing to heat to 500°C at the same rate, holding for 3 hours; and then heating to 750°C at the same rate, holding for 4 hours. The sample was naturally cooled to room temperature to obtain a catalyst precursor (denoted as NiO-La2O3 / γ-Al2O3).

[0066] (4) The catalyst precursor was reduced at 400°C under a 10% H2 / Ar atmosphere for 2 hours to obtain about 10.00 g of gray-black powder, which was the final catalyst (denoted as Ni-La2O3 / γ-Al2O3) with a Ni mass fraction of 15% and a La2O3 mass fraction of 3%.

[0067] The obtained catalyst precursor and final catalyst were characterized as follows:

[0068] (a) X-ray photoelectron spectroscopy (XPS) (Ni 2p region) as shown in Figure 1. Figure 1 For the reduced catalyst, a main peak was observed at a binding energy (BE) of about 852.8 eV, corresponding to the 2p3 / 2 level of metallic Ni 0 . This is direct evidence for the presence of active metal Ni.

[0069] Compared with pure Ni foil, the 2p3 / 2 binding energy of Ni 0 on the catalyst surface showed a positive shift of about 0.3 eV. This small change in binding energy indicates a slight decrease in the electron cloud density of the metallic Ni particles, which may be due to the electron-donating effect of La2O3 or residual interaction between Ni and the support γ-Al2O3, and this electron-donating effect helps to improve the catalytic activity.

[0070] (b) H2-temperature programmed reduction (H2-TPR) profile of the catalyst precursor (NiO-La2O3 / γ-Al2O3) is shown in Figure 1. Figure 2 The profile presents an asymmetric main reduction peak with a maximum hydrogen consumption peak temperature at 382°C, which is attributed to the reduction of free NiO species with weak interaction with the support. There is a tailing shoulder peak at the high temperature side (>600°C) of the main peak, which corresponds to the reduction of "hardly reducible" NiO species with strong interaction with the support, which can be embedded on the surface of the support or in close contact with La species.

[0071] Compared with the Ni / γ-Al2O3 catalyst without addition of La (the main reduction peak is usually at 400-450°C), the main reduction peak of the present catalyst is obviously shifted to lower temperature. This demonstrates that the addition of rare earth La significantly promotes the reduction of NiO, weakens the strong interaction between NiO and the γ-Al2O3 support, and enables the active metal Ni to be reduced under milder conditions.

[0072] Example 2 Synergistic treatment method of sulfur dioxide-containing waste gas and sulfate ion-containing waste water

[0073] (1) Take 500 ml of raw water (detection data as shown in Table 1), add 50 g of the catalyst prepared in Example 1, stir, and then directly introduce sulfur dioxide at a flow rate of 0.15 L / min.

[0074] Table 1

[0075]

[0076] (2) Until the pH value is between 2-3, by adding calcium hydroxide solution (5 wt%), the pH is always controlled between 2-5, and the introduction of sulfur dioxide is stopped for 5 min.

[0077] (3) Add calcium hydroxide solution (5 wt%) again to make the pH rise to 9-10, after stirring for 10 min, stand for 10 min, take the supernatant and filter, detect the indexes of the supernatant (i.e. the water quality of the effluent) as shown in Table 2.

[0078] Table 2

[0079]

[0080] (4) Filter the treated mixture to obtain precipitated sludge, and dry to a total weight of 14.9 g, of which calcium sulfite is 13.5 g (calcium sulfite detection method: oxidation-reduction titration method, GB / T15817-1995).

[0081] The above is only the preferred embodiment of the present application, and does not limit the present application in any form. Therefore, any simple modification, equivalent change and modification of the above embodiment according to the technical essence of the present application, without departing from the technical scheme of the present application, shall fall within the protection scope of the technical scheme of the present application.

Claims

1. A method for the synergistic treatment of sulfur dioxide-containing waste gas and sulfate-containing wastewater, characterized in that, Includes the following steps: (1) The catalyst containing Ni nanoparticles is dispersed in wastewater containing sulfate ions, and waste gas containing sulfur dioxide is introduced and the pH is controlled between 2 and 5 to carry out the reaction. (2) Add a salt or alkali containing calcium ions and adjust the pH to between 9 and 10. Stir the reaction to generate calcium sulfite precipitate. The method for preparing the catalyst containing Ni nanoparticles includes: (a) Ni-containing 2+ and La 3+ The metal salt solution was mixed with boehmite powder to form a paste, and then allowed to stand and dry. (b) The dried product is calcined in air, so that Ni 2+ and La 3+ It is converted into oxide, and pseudoboehmite is converted into γ-Al2O3 to obtain the catalyst precursor; (c) The catalyst precursor is reduced under a reducing atmosphere to reduce the nickel oxide to metallic nickel to obtain the catalyst containing metallic Ni nanoparticles.

2. The method for synergistic treatment of sulfur dioxide-containing waste gas and sulfate-containing wastewater according to claim 1, characterized in that, The catalyst containing Ni nanoparticles has a Ni mass fraction of 13-18% and a La2O3 mass fraction of 2-4%.

3. The method for synergistic treatment of sulfur dioxide-containing waste gas and sulfate-containing wastewater according to claim 1, characterized in that, The metal salt solution is an aqueous solution prepared from Ni(NO3)2·6H2O and La(NO3)3·6H2O, with a mass ratio of (5~6):(0.6~1).

4. The method for synergistic treatment of sulfur dioxide-containing waste gas and sulfate-containing wastewater according to claim 1, characterized in that, The roasting includes: (b1) Heat to 110~130℃ and hold for 20~40 minutes; (b2) Heat to 450~550℃ and keep warm for 2~4 hours; (b3) Heat to 750~800℃ and keep warm for 3~5 hours.

5. The method for synergistic treatment of sulfur dioxide-containing waste gas and sulfate-containing wastewater according to claim 1, characterized in that, The reduction temperature is 350~450℃.

6. The method for synergistic treatment of sulfur dioxide-containing waste gas and sulfate-containing wastewater according to any one of claims 1 to 5, characterized in that, The catalyst addition amount is 90~110g / L, and the flow rate of the sulfur dioxide-containing waste gas is 0.1~0.2L / min.

7. The method for synergistic treatment of sulfur dioxide-containing waste gas and sulfate-containing wastewater according to any one of claims 1 to 5, characterized in that, Step (1) Add calcium hydroxide to control the pH between 2 and 5.

8. The method for synergistic treatment of sulfur dioxide-containing waste gas and sulfate-containing wastewater according to any one of claims 1 to 5, characterized in that, The calcium-containing salt or alkali in step (2) is calcium hydroxide.

9. The method for synergistic treatment of sulfur dioxide-containing waste gas and sulfate-containing wastewater according to any one of claims 1 to 5, characterized in that, Reduce the sulfate content in the wastewater to <160mg / L.

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