Process for ammonia and sulphide recovery from ammonia-containing sulphide-containing wastewater

Abstract

The application provides an ammonia-sulfur recovery process for ammonia-containing and sulfide-containing wastewater, which comprises the following steps: adsorbing and separating sulfides in ammonia-containing and sulfide-containing wastewater by using iron-carbon composite material to obtain iron-carbon composite material with adsorbed sulfides and ammonia-containing wastewater; and separating and recovering ammonia in the ammonia-containing wastewater by using a gaseous membrane device. The ammonia-sulfur recovery process for ammonia-containing and sulfide-containing wastewater can efficiently recover ammonia and sulfur, has the advantages of low energy consumption and cost, high recovery rate and avoidance of ammonia escape compared with a traditional stripping and stripping method, has the advantages of low comprehensive cost, high recovery efficiency and realization of ammonia and sulfur resource reuse compared with a chemical precipitation method and a biological method. Further, the iron-carbon composite material in the ammonia-sulfur recovery process for ammonia-containing and sulfide-containing wastewater can be recycled, further reducing the cost of consumables.

Description

Technical Field

[0001] This invention belongs to the field of ammonia and sulfur recovery technology in wastewater, specifically relating to an ammonia and sulfur recovery process for ammonia-containing and sulfur-containing wastewater. Background Technology

[0002] High concentrations of ammonia and sulfides in wastewater from industries such as refining and coking, if discharged directly without treatment, can cause eutrophication, foul odors, and toxic pollution, posing a significant threat to the environment. Current mainstream treatment methods for ammonia- and sulfide-containing wastewater include traditional steam stripping, chemical precipitation, and biological methods, each with the following limitations: Traditional steam stripping uses steam or flue gas to convert ammonia and sulfides in wastewater into ammonia and hydrogen sulfide, requiring a large amount of steam (temperature >100℃), with energy consumption accounting for over 60% of the treatment cost. It also requires more acid and alkali reagents (to adjust the pH to alkaline), resulting in high treatment costs, and ammonia escape can easily cause secondary pollution. Chemical precipitation (such as iron salt precipitation of sulfides) requires continuous addition of chemical agents, producing large amounts of sludge, and cannot simultaneously recover ammonia. Biological methods have long treatment cycles (several days to several weeks), poor tolerance to high-concentration wastewater, and sulfides have toxic inhibitory effects on microorganisms. Furthermore, in chemical precipitation and biological methods, sulfides are mostly discarded as sludge, failing to achieve resource utilization. Summary of the Invention

[0003] The purpose of this invention is to provide an ammonia-sulfur recovery process for ammonia-containing and sulfur-containing wastewater with high ammonia-sulfur recovery rate and lower cost.

[0004] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0005] This invention provides an ammonia-sulfur recovery process for ammonia-containing and sulfide-containing wastewater. The process involves using an iron-carbon composite material to adsorb and separate sulfides from the wastewater, resulting in an iron-carbon composite material adsorbed with sulfides and the ammonia-containing wastewater. The iron-carbon composite material adsorbed with sulfides is then reacted with hydrogen peroxide under stirring. Elemental sulfur and the iron-carbon composite material are separated from the reactants. Ammonia is then recovered from the ammonia-containing wastewater using a gaseous membrane device. The porous structure consists of micropores and / or mesopores with a pore size range of 1-5 nm and macropores with a pore size range of 100 nm-10 μm, or consists of mesopores with an average pore size of 2-4 nm and macropores with a pore size range of 100 nm-10 μm. The specific surface area of ​​the iron-carbon composite material is 200 m². 2 / g-300m 2 / g, the iron element exists in the forms of FeO, Fe2O3, Fe3O4, Fe3C and Fe2C.

[0006] In some embodiments of the present invention, the porous structure of the iron-carbon composite material of the present invention consists of a microporous structure with a pore size range of 1-2 nm, mesoporous structures with a pore size range of 2-5 nm, and macroporous structures with a pore size range of 100 nm-10 μm, wherein some of the microporous structures and mesoporous structures form a micro / mesoporous composite structure.

[0007] Preferably, the porous structure includes a microporous structure with a pore size range of 1-1.5 nm, a micro / mesoporous composite structure with a pore size range of 1.6-2.8 nm, and a macroporous structure with a pore size range of 200 nm-5 μm.

[0008] In some specific embodiments, the porous structure includes mesoporous structures with an average pore size of 2-3 nm and macroporous structures with an average pore size of 200 nm-5 μm.

[0009] In some specific embodiments, the specific surface area of ​​the iron-carbon composite material is 220 m². 2 / g-260m 2 / g, further preferably 230m 2 / g-260m 2 / g, further preferably 240m 2 / g-260m 2 / g, more preferably 250m 2 / g-260m 2 / g.

[0010] In an embodiment of the present invention, the ammonia-containing wastewater and the sulfuric acid aqueous solution are simultaneously introduced into a gaseous membrane device, and the ammonia in the ammonia-containing wastewater flows out from the gaseous membrane device in the form of an ammonium sulfate aqueous solution.

[0011] According to some specific embodiments of the present invention, the iron-carbon composite material is added to the ammonia- and sulfur-containing wastewater, stirred and mixed at 20-30°C, and then separated after standing to obtain the iron-carbon composite material adsorbed with sulfides and the ammonia-containing wastewater.

[0012] Furthermore, the dosage of the iron-carbon composite material is 1-5 g / L, for example, 1 g / L, 2 g / L, 3 g / L, 4 g / L, or 5 g / L.

[0013] Furthermore, the stirring speed of the mixing process is 40-80 r / min, for example, 40 r / min, 50 r / min, 60 r / min, 70 r / min, or 80 r / min.

[0014] Furthermore, the mixing time is 10-30 minutes, for example, 10 minutes, 15 minutes, 20 minutes, 25 minutes, or 30 minutes.

[0015] According to other specific embodiments of the present invention, at 20-30°C, the ammonia-containing and sulfur-containing wastewater is introduced into a reactor equipped with a fixed bed. After passing through the fixed bed, the ammonia-containing and sulfur-containing wastewater flows out from the outlet of the reactor, and the outflowing liquid is the ammonia-containing wastewater. The material of the fixed bed is the iron-carbon composite material.

[0016] Furthermore, the ammonia- and sulfur-containing wastewater is introduced into the reactor at a constant flow rate.

[0017] Furthermore, the ammonia- and sulfide-containing wastewater passes through the fixed bed at a flow rate of 4-6 L / h.

[0018] Furthermore, the volume of ammonia- and sulfur-containing wastewater that can be treated by a unit of catalytic material in the fixed bed is 0.2-1 L / g, for example, 0.2 L / g, 0.3 L / g, 0.4 L / g, 0.5 L / g, 0.6 L / g, 0.7 L / g, 0.8 L / g, 0.9 L / g, or 1 L / g.

[0019] In embodiments of the present invention, the hydrogen peroxide has a mass fraction of 10%-20%, for example 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, or 20%.

[0020] In an embodiment of the present invention, each g of the iron-carbon composite material adsorbed with sulfides corresponds to 50-100 mL of the hydrogen peroxide, for example, each g of the iron-carbon composite material adsorbed with sulfides corresponds to 50 mL, 55 mL, 60 mL, 65 mL, 70 mL, 75 mL, 80 mL, 85 mL, 90 mL, 95 mL or 100 mL of the hydrogen peroxide.

[0021] In an embodiment of the present invention, the stirring speed of the stirring reaction is 40-80 r / min, for example 40 r / min, 50 r / min, 60 r / min, 70 r / min, or 80 r / min.

[0022] In an embodiment of the present invention, the stirring reaction time is 4-10 min, for example 4 min, 5 min, 6 min, 7 min, 8 min, 9 min, or 10 min.

[0023] In embodiments of the present invention, the mass concentration of the sulfuric acid aqueous solution is 1%-10%, for example 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, or 10%.

[0024] In an embodiment of the present invention, the ammonia-containing wastewater is discharged at a rate of 1 L / (h·m³). 2 )-5L / (h·m 2A constant flow rate is introduced into the gaseous membrane device, for example, 1 L / (h·m). 2 ), 1.5L / (h·m 2 ), 2L / (h·m 2 ), 2.5L / (h·m 2 ), 3L / (h·m 2 ), 3.5L / (h·m 2 ), 4L / (h·m 2 ), 4.5L / (h·m 2 ), 5L / (h·m 2 ).

[0025] In an embodiment of the present invention, the sulfuric acid aqueous solution is prepared at a concentration of 150 L / (h·m). 2 )-250L / (h·m 2 A constant flow rate is introduced into the gaseous membrane device, for example, 150 L / (h·m). 2 ), 160L / (h·m 2 ), 170L / (h·m 2 ), 180L / (h·m 2 ), 190L / (h·m 2 ), 200L / (h·m 2 ), 210L / (h·m 2 ), 220L / (h·m 2 ), 230L / (h·m 2 ), 240L / (h·m 2 ), 250L / (h·m 2 ).

[0026] In this invention, the pH value of the ammonia- and sulfide-containing wastewater is 8.5-10, and the NH4+ content is... + -N content is 400-600 mg / L, S 2- The content is 200-400 mg / L.

[0027] According to a specific embodiment of the present invention, the preparation method of the iron-carbon composite material includes:

[0028] (1) Porous cedar charcoal was obtained by calcining KOH-adsorbed cedar powder at 400-600℃ in a CO2 atmosphere.

[0029] (2) Porous cypress charcoal adsorbed with K2FeO4 was prepared using the aforementioned porous cypress charcoal and K2FeO4;

[0030] (3) The porous fir charcoal adsorbed with K2FeO4 is first calcined at 450-550℃ in a CO2 atmosphere, and then calcined at 650-750℃ to obtain the iron-carbon composite material.

[0031] In an embodiment of the present invention, the mass ratio of KOH to cedar powder in the KOH-adsorbed cedar powder is 1:(0.8-1.2).

[0032] In an embodiment of the present invention, the mass ratio of the porous fir charcoal to K2FeO4 is 1:(0.5-1), more preferably 1:(0.7-0.9).

[0033] In an embodiment of the present invention, in step (1), the KOH-adsorbed fir powder is heated to 400-600°C in a CO2 atmosphere at a heating rate of 1-10°C / min and held at 400-600°C for 1-3 hours to obtain the porous fir charcoal.

[0034] More preferably, the temperature is increased to 400-600°C at a heating rate of 4-8°C / min, and then further increased to 400-600°C at a heating rate of 4-6°C / min.

[0035] In an embodiment of the present invention, in step (2), the porous fir charcoal and K2FeO4 are first stirred and evaporated in water at 75-85°C until the water content is reduced by 85%-90%, and then dried at 75-85°C to obtain the porous fir charcoal adsorbed with K2FeO4.

[0036] In an embodiment of the present invention, in step (3), the temperature is first raised to 450-550°C at a heating rate of 1-10°C / min and held at 450-550°C for 0.5-1.5h, and then raised to 650-750°C at a heating rate of 1-10°C / min and held at 650-750°C for 1-3h to obtain the iron-carbon composite material.

[0037] Furthermore, in step (3), the heating rate is 4-8℃ / min, and more preferably 4-6℃ / min.

[0038] In an embodiment of the present invention, step (3) further includes post-processing, which is as follows: the porous fir charcoal obtained by calcination is cooled to room temperature, washed with 0.05-0.15M HCl, then washed with deionized water until the eluent is neutral, and then vacuum dried and ground at 75-85℃.

[0039] In this invention, the iron-carbon composite material combines chemical adsorption and physical adsorption, enabling rapid and efficient chemical adsorption and ion exchange of sulfides in wastewater. Hydrogen peroxide is used to oxidize the sulfides adsorbed on the iron-carbon composite material into elemental sulfur, while simultaneously regenerating the composite material. The iron-carbon composite material can be recycled; verification shows it can be recycled more than 50 times, and even after 20 cycles, the sulfide adsorption rate is still greater than 90%. Ammonia-containing wastewater passes through one side of a gaseous membrane, while sulfuric acid-containing wastewater is on the other side. Through acidic traction, ammonia in the ammonia-containing wastewater, in the form of gaseous free ammonia, passes through the gaseous membrane to the other side, dissolving in sulfuric acid to form an ammonium sulfate solution. The recovered ammonium sulfate solution is then concentrated in an RO membrane to form a high-concentration sulfate solution, or it can be evaporated at low temperature to form sulfate crystals.

[0040] Compared with the prior art, the present invention has the following advantages:

[0041] The ammonia-sulfur recovery process for ammonia-containing and sulfide-containing wastewater of this invention can efficiently recover ammonia and sulfur. Compared with the traditional stripping method, this invention has the advantages of low energy consumption and cost, high recovery rate, and prevention of ammonia escape. Compared with chemical precipitation and biological methods, this invention has the advantages of low overall cost, high recovery efficiency, and the ability to reuse ammonia and sulfur resources. Furthermore, the iron-carbon composite material in the ammonia-sulfur recovery process for ammonia-containing and sulfide-containing wastewater of this invention can be recycled, further reducing consumable costs. Attached Figure Description

[0042] Figure 1 The microstructure diagrams of the iron-carbon composite material of Example 1 at different magnifications are shown.

[0043] Figure 2 The image shows the pore size distribution of the iron-carbon composite material in Example 1 (large pores are not shown).

[0044] Figure 3 This is a nitrogen adsorption curve of the iron-carbon composite material in Example 1;

[0045] Figure 4 This is the XPS full spectrum result of the iron-carbon composite material in Example 1;

[0046] Figure 5 The image shows the infrared test results of the iron-carbon composite material in Example 1.

[0047] Figure 6 The image shows the XRD results of the iron-carbon composite material in Example 1.

[0048] Figure 7 This is the XPS result of the Fe2p peak separation of the iron-carbon composite material in Example 1;

[0049] Figure 8The image shows the microstructure of the iron-carbon composite material in Example 2.

[0050] Figure 9 This is a schematic diagram of the ammonia-sulfur recovery process for ammonia-containing and sulfide-containing wastewater. Detailed Implementation

[0051] The present invention will be further described below with reference to embodiments. However, the present invention is not limited to the following embodiments. The implementation conditions used in the embodiments can be further adjusted according to different requirements of specific use, and the implementation conditions not specified are conventional conditions in this industry. The technical features involved in the various embodiments of the present invention can be combined with each other as long as they do not conflict with each other. The implementation conditions used in the embodiments can be further adjusted according to specific requirements, and the implementation conditions not specified are usually conditions in conventional experiments.

[0052] It should be noted that in this invention, "room temperature" refers to 25±5℃.

[0053] It should be noted that, unless otherwise specified, all raw materials used in this invention are commercially available products, and the instruments and equipment are those conventionally used in the art. The gaseous membrane device is made of PP material, and the gaseous membrane itself is hydrophobic, with a porosity >70% and a membrane area loading of 0.5-1.5m². 3 / (m 2 Hollow fiber membrane (h).

[0054] The iron-carbon composite material used in this invention is self-made. Before being used in the ammonia-sulfur recovery process, the iron-carbon composite material was optimized and screened. The following are some of the iron-carbon composite materials tested in this invention, and their preparation methods are as follows:

[0055] Preparation of cedar wood powder: 30g of dried cedar wood was placed in a pulverizer and pulverized for 30 minutes. Afterwards, it was washed with ultrapure water and dried in an 80℃ forced-air drying oven to obtain cedar wood powder for later use. Ultrapure water (>18.2MΩ) was produced using a Milli-Q pure water system (Bedford, MA, USA).

[0056] Iron-carbon composite material A:

[0057] 1. Weigh 5g of cedar powder and 5g of KOH into 100mL of ultrapure water, and stir at 200r / min for 12h at room temperature to allow the cedar raw material to fully and uniformly adsorb KOH. After the mixture is allowed to stand and centrifuged, the resulting solid is placed in an 80℃ forced-air drying oven to dry, thus obtaining cedar powder with adsorbed KOH.

[0058] 2. Place the KOH-adsorbed cedar powder in an alumina ceramic boat, transfer it to a tube furnace, purge with high-purity CO2 gas for 30 min to remove air interference in the tube, continue purging with high-purity CO2 gas, heat to 500℃ at a heating rate of 5℃ / min and hold for 2 h, cool to room temperature, wash the obtained material three times with ultrapure water to remove excess potassium salt, and obtain porous cedar charcoal.

[0059] 3. Weigh out K2FeO4 according to a mass ratio of porous fir charcoal to K2FeO4 of 1:0.8. Place the porous fir charcoal and K2FeO4 in ultrapure water, with the amount of water being 22 times the sum of the masses of the porous fir charcoal and K2FeO4. Stir the mixture at 120 r / min at 80℃ until the water content in the beaker decreases by about 85%. Place the remaining material in the beaker in an 80℃ drying oven to dry, thus obtaining porous fir charcoal adsorbed with K2FeO4.

[0060] 4. The porous fir charcoal adsorbed with K2FeO4 was placed in an alumina ceramic boat and transferred to a tube furnace. High-purity CO2 gas was passed through the tube furnace to purge the air. High-purity CO2 gas was continued to be passed through the furnace, and the furnace was heated to 500℃ at a heating rate of 5℃ / min and held at 500℃ for 1 hour. Then, the furnace was heated to 700℃ at a heating rate of 5℃ / min and held at 700℃ for 2 hours. After cooling to room temperature, the furnace was washed with 0.1mol / L HCl and then washed with deionized water until the eluent was neutral to remove ash, uncrystallized material and unloaded metal salts. The washed material was dried and ground in an 80℃ vacuum oven (a small amount of agglomerates were present in the dried product, which were crushed by grinding) to obtain the iron-carbon composite material.

[0061] Iron-carbon composite material A has a rich pore structure, consisting of microporous structures with a pore size range of 1.09-1.35 nm, micro / mesoporous composite structures with a pore size range of 1.71-2.73 nm, and macroporous structures with a pore size range of 200 nm-5 μm. Figure 1 , Figure 2 ), with a specific surface area of ​​254 m². 2 / g(according to) Figure 3 The nitrogen adsorption curve shown is obtained through BET model calculation, mainly including Fe, C, and O. Figure 4 The surface contains oxygen-containing functional groups such as -OH, -COOH, -C=O, -COC-, and -Fe-O. Figure 5 Iron exists in the forms of FeO, Fe2O3, Fe3O4, Fe3C, and Fe2C. Figure 6 Fe is present. 2+ Fe 3+ Mixed valence state ( Figure 7 ), in amorphous particulate form, loaded on the surface, channels, and under the carbon layer of biochar ( Figure 1 ).

[0062] Iron-carbon composite material B:

[0063] The preparation method of iron-carbon composite material B is basically the same as that of iron-carbon composite material A, except that step 3 is slightly different. Except for changing the mass ratio of porous fir charcoal to K2FeO4 in step 3 to 1:0.9, the rest of the operations are the same as those for iron-carbon composite material A. The resulting iron-carbon composite material B has a rich pore structure. Figure 8 It consists of a mesoporous structure with an average pore size of 2.51 nm and a macroporous structure with a pore size range of 200 nm to 5 μm, and has a specific surface area of ​​227 m². 2 / g, iron exists in the forms of FeO, Fe2O3, Fe3O4, Fe3C, and Fe2C, and Fe is present. 2+ Fe 3+ Mixed valence states, in amorphous particulate form, are loaded on the surface, channels, and under the carbon layer of biochar.

[0064] Iron-carbon composite material C:

[0065] The preparation method of iron-carbon composite material C is basically the same as that of iron-carbon composite material A, except that step 4 is slightly different. Except for shortening the holding time at 700℃ for 2 hours to 1 hour in step 4, the rest of the operation is the same as that of iron-carbon composite material A. The obtained iron-carbon composite material C has a rich pore structure, consisting of mesoporous structures with an average pore size of approximately 2.09 nm and macroporous structures with a pore size range of 200 nm to 5 μm, and a specific surface area of ​​241 m². 2 / g, iron exists in the forms of FeO, Fe2O3, Fe3O4, Fe3C, and Fe2C, and Fe is present. 2+ Fe 3+ Mixed valence states, in amorphous particulate form, are loaded on the surface, channels, and under the carbon layer of biochar.

[0066] Iron-carbon composite material D:

[0067] The preparation method of iron-carbon composite material D is basically the same as that of iron-carbon composite material A, except that the high-purity CO2 gas in steps 1 and 3 is replaced with high-purity N2 gas. All other operations are the same as those of iron-carbon composite material A.

[0068] Iron-carbon composite material E:

[0069] The preparation method of iron-carbon composite material E is basically the same as that of iron-carbon composite material A. The only difference is that the operation of heating to 500°C at a heating rate of 5°C / min and holding at 500°C for 1 hour, and then continuing to heat to 700°C at a heating rate of 5°C / min and holding at 700°C for 2 hours in step 4 is replaced by heating to 500°C at a heating rate of 5°C / min and holding at 500°C for 3 hours. All other operations are the same as those of iron-carbon composite material A.

[0070] Iron-carbon composite material F:

[0071] The preparation method of iron-carbon composite material F is basically the same as that of iron-carbon composite material A. The only difference is that the operation of heating to 500℃ at a heating rate of 5℃ / min and holding at 500℃ for 1h, and then continuing to heat to 700℃ at a heating rate of 5℃ / min and holding at 700℃ for 2h, is replaced by heating to 900℃ at a heating rate of 5℃ / min and holding for 2h. All other operations are the same as those of iron-carbon composite material A.

[0072] Comparison of the adsorption effects of iron-carbon composite material AF on sulfides in water:

[0073] A sulfide solution was prepared using Na2S·9H2O to simulate sulfur-containing wastewater. Sulfide adsorption experiments were conducted using the aforementioned iron-carbon composite material AF, as follows:

[0074] 1. Weigh 100 mg of Na2S·9H2O solid and mix it with 100 mL of water to prepare a sulfide solution. Use a syringe to draw 0.05 mL of the sulfide solution to test the sulfide content in the solution before treatment.

[0075] 2. Weigh 0.05g of iron-carbon composite material and add it to a stoppered conical flask containing the above sulfide solution. Adjust the pH of the solution to 7.13 with concentrated hydrochloric acid. Then place the conical flask in a constant temperature shaker (shaking rate of 150r / min) and shake at 37℃ for 3h. After standing, use a syringe to draw 0.05mL of the supernatant to test the sulfide content in the treated solution.

[0076] The sulfide content in the solution before and after the reaction was determined by methylene blue spectrophotometry (GB / T 16489-1996) at a detection wavelength of 665 nm. Based on the sulfide content in the solution before and after treatment, the adsorption capacity of a unit of iron-carbon composite material for sulfides in water was calculated. The adsorption capacity of iron-carbon composite material A for sulfides in water was 584.7 mg / g, that of iron-carbon composite material B was 479.0 mg / g, that of iron-carbon composite material C was 407.0 mg / g, that of iron-carbon composite material D was 318.0 mg / g, that of iron-carbon composite material E was 367.2 mg / g, and that of iron-carbon composite material F was 198.6 mg / g.

[0077] Iron-carbon composite material A, which has the best adsorption effect, was selected for the ammonia-sulfur recovery process of ammonia-containing and sulfide-containing wastewater.

[0078] The technical solutions and effects of the present invention are further illustrated below through application examples.

[0079] In this application example, the raw water to be treated is refinery wastewater: NH4 + -N 500mg / L, S 2- 300 mg / L, pH 9.2, temperature 25℃.

[0080] Application Example 1

[0081] This embodiment 1 provides an ammonia-sulfur recovery process for ammonia-containing and sulfur-containing wastewater, such as... Figure 1 As shown, the wastewater containing ammonia and sulfides is first adsorbed and separated by iron-carbon composite material A to recover sulfides, and then the wastewater containing ammonia is separated and recovered by gaseous membrane separation. The specific operation is as follows:

[0082] 1. At room temperature, iron-carbon composite material A is added to ammonia-containing and sulfide-containing wastewater at a dosage of 2 g / L. The mixture is stirred at 50 r / min for 2 h, allowed to stand and settle for 10 min, and the precipitate is separated and recovered. The resulting water is ammonia-containing wastewater.

[0083] 2. The ammonia-containing wastewater after precipitate recovery and dilute sulfuric acid are simultaneously passed into the gas membrane device, with the ammonia-containing wastewater flowing at a rate of 3 L / (h·m). 2 The gaseous membrane device is fed with a flow rate of 6% dilute sulfuric acid at a rate of 200 L / (h·m). 2 The flow rate of the ammonia-containing wastewater is fed into the gaseous membrane device, and the operating temperature is controlled at 25℃. The residence time of the ammonia-containing wastewater in the gaseous membrane device is 60 minutes. The treated wastewater is discharged from one side of the ammonia-containing wastewater, and the ammonium sulfate solution is discharged from the other side. The ammonium sulfate solution is concentrated by the RO membrane to form a high-concentration sulfate solution (about 10g / L), and then sulfate crystals are formed by low-temperature evaporation (28-30℃).

[0084] 3. Add the recovered precipitate to 15% hydrogen peroxide solution to achieve a precipitate concentration of 500 g / L. Stir at 50 rpm for 5 minutes at room temperature. The hydrogen peroxide oxidizes the sulfides adsorbed on the adsorbent into elemental sulfur. The reactants are filtered to obtain a solid. The solid is then centrifuged at 6000 rpm to separate elemental sulfur from iron-carbon materials. The elemental sulfur, being lighter, is located in the upper layer, while the regenerated iron-carbon materials in the lower layer can be used for a new round of ammonia- and sulfur-containing wastewater treatment.

[0085] Tests showed that, compared to the raw water, the treated wastewater achieved a 98.5% sulfide removal rate, a 200g / ton sulfur recovery rate, an 88% ammonia recovery rate, a 96% ammonium sulfate crystal purity, and an adsorption efficiency of >90% after 20 cycles of the iron-carbon composite material. The overall treatment cost was approximately 0.8 yuan / ton of wastewater, representing a cost reduction of at least 50% compared to the traditional stripping and descaling process.

[0086] Application Example 2

[0087] This embodiment provides an ammonia-sulfur recovery process for ammonia-containing and sulfide-containing wastewater, which is basically the same as in Embodiment 1. The difference is that the ammonia-containing and sulfide-containing wastewater is passed through a fixed bed adsorption separation and recovery of sulfides formed by iron-carbon composite material A. The specific operation is as follows:

[0088] 1. At room temperature, ammonia-containing and sulfide-containing wastewater is fed into a reactor equipped with a fixed bed at a flow rate of 5L / h. When the ammonia-containing and sulfide-containing wastewater flows through the fixed bed at a flow rate of 5L / h, the sulfides in it are adsorbed onto the fixed bed. In this application example, the fixed bed contains 20g of iron-carbon composite material A, and the continuous feeding time is 4h.

[0089] 2. Ammonia-containing wastewater and dilute sulfuric acid flowing out of the reactor are simultaneously introduced into a gaseous membrane device, with the ammonia-containing wastewater flowing at a rate of 4 L / (h·m). 2 The gaseous membrane device is fed with a flow rate of 250 L / (h·m). The concentration of the dilute sulfuric acid is 8%. 2 The flow rate of the gaseous membrane device is fed into the device, and the operating temperature is controlled at 25℃. The treated wastewater is discharged from one side of the ammonia-containing wastewater and the ammonium sulfate solution is discharged from the other side. The ammonium sulfate solution is concentrated by the RO membrane to form a high-concentration sulfate solution (about 10g / L), and then sulfate crystals are formed by low-temperature evaporation (25-30℃).

[0090] 3. Remove the adsorbed iron-carbon composite material A from the reactor and place it in hydrogen peroxide solution with a mass fraction of 15%, so that the content of iron-carbon composite material A in hydrogen peroxide solution is 500 g / L. Stir the reaction at 50 r / min for 5 min at room temperature. Use hydrogen peroxide to oxidize the sulfides adsorbed on the adsorbent to elemental sulfur. The reactants are filtered to obtain solids. The obtained solids are centrifuged at a speed of 6000 r / min to separate elemental sulfur and iron-carbon materials. Elemental sulfur is lighter and is located in the upper layer. The regenerated iron-carbon materials in the lower layer can be used for a new round of ammonia and sulfur-containing wastewater treatment.

[0091] Tests showed that, compared to the original water, the treated wastewater had a 90% sulfide removal rate, a sulfur recovery rate of 180g / ton of wastewater, an ammonia recovery rate of 85%, and an ammonium sulfate crystal purity of 96%.

[0092] The present invention has been described in detail above, with the aim of enabling those skilled in the art to understand and implement the invention. However, this description should not be construed as limiting the scope of protection of the invention. All equivalent changes or modifications made in accordance with the spirit and essence of the invention should be included within the scope of protection of the invention.

Claims

1. An ammonia-sulfur recovery process for ammonia-containing and sulfide-containing wastewater, characterized in that, A method for separating sulfides from ammonia- and sulfur-containing wastewater using an iron-carbon composite material is employed. This yields an iron-carbon composite material adsorbed with sulfides and the ammonia-containing wastewater. The sulfide-adsorbed iron-carbon composite material is then reacted with hydrogen peroxide under stirring. Elemental sulfur and the iron-carbon composite material are separated from the reactants. Ammonia in the ammonia-containing wastewater is then separated and recovered using a gaseous membrane device. The iron-carbon composite material has a porous structure, consisting of micropores with a pore size range of 1-2 nm, mesopores with a pore size range of 2-5 nm, and macropores with a pore size range of 100 nm-10 μm. Some of the micropores and mesopores form a micro / mesopore composite structure. The specific surface area of ​​the iron-carbon composite material is 200 m². 2 / g-300m 2 / g, iron exists in the forms of FeO, Fe2O3, Fe3O4, Fe3C, and Fe2C. The preparation method of the iron-carbon composite material includes: (1) Porous cedar charcoal was obtained by calcining KOH-adsorbed cedar powder at 400-600℃ in a CO2 atmosphere; (2) Porous cypress charcoal adsorbed with K2FeO4 was prepared using the aforementioned porous cypress charcoal and K2FeO4; (3) The porous fir charcoal adsorbed with K2FeO4 is first calcined at 450-550℃ in a CO2 atmosphere, and then calcined at 650-750℃ to obtain the iron-carbon composite material.

2. The ammonia-sulfur recovery process for ammonia-containing and sulfide-containing wastewater according to claim 1, characterized in that, The ammonia- and sulfur-containing wastewater is stirred and mixed with the iron-carbon composite material at 20-30°C, and after settling and separation, the iron-carbon composite material adsorbed with sulfides and the ammonia-containing wastewater are obtained.

3. The ammonia-sulfur recovery process for ammonia-containing and sulfide-containing wastewater according to claim 2, characterized in that, The dosage of the iron-carbon composite material is 1-5 g / L; and / or the stirring speed is 40-80 r / min; and / or the stirring time is 10-30 min.

4. The ammonia-sulfur recovery process for ammonia-containing and sulfide-containing wastewater according to claim 1, characterized in that, At 20-30℃, the ammonia-containing and sulfide-containing wastewater is fed into a reactor equipped with a fixed bed. After passing through the fixed bed, the ammonia-containing and sulfide-containing wastewater flows out from the outlet of the reactor. The outflowing liquid is the ammonia-containing wastewater. The catalytic material in the fixed bed is the iron-carbon composite material.

5. The ammonia-sulfur recovery process for ammonia-containing and sulfide-containing wastewater according to claim 4, characterized in that, The ammonia- and sulfur-containing wastewater passes through the fixed bed at a flow rate of 4-6 L / h, and / or the volume of the ammonia- and sulfur-containing wastewater that can be treated by a unit of catalyst material in the fixed bed is 0.2-1 L / g.

6. The ammonia-sulfur recovery process for ammonia-containing and sulfide-containing wastewater according to claim 1, characterized in that, The ammonia-containing wastewater and sulfuric acid aqueous solution are simultaneously introduced into the gaseous membrane device, and the ammonia in the ammonia-containing wastewater flows out from the gaseous membrane device in the form of ammonium sulfate aqueous solution.

7. The ammonia-sulfur recovery process for ammonia-containing and sulfide-containing wastewater according to claim 6, characterized in that, The ammonia-containing wastewater is discharged at a rate of 1 L / (h·m 2 )-5L / (h·m 2 A flow rate of ) is introduced into the gaseous membrane device, and the residence time in the gaseous membrane device is 1-2 hours; And / or, the sulfuric acid aqueous solution has a mass concentration of 6%-10%, and the sulfuric acid aqueous solution is prepared at a flow rate of 150 L / (h·m³). 2 )-250L / (h·m 2 The flow rate of the gaseous membrane device is introduced into the gaseous membrane device.

8. The ammonia-sulfur recovery process for ammonia-containing and sulfide-containing wastewater according to claim 1, characterized in that, The hydrogen peroxide has a mass fraction of 10%-20%; and / or, 50-100 mL of the hydrogen peroxide is used per gram of the iron-carbon composite material adsorbed with sulfides; and / or, the stirring speed of the stirring reaction is 40-80 r / min; and / or, the stirring reaction time is 4-10 min.

9. The ammonia-sulfur recovery process for ammonia-containing and sulfide-containing wastewater according to claim 1, characterized in that, The pH value of the ammonia- and sulfide-containing wastewater is 8.5-10, and the NH4+ content is... + -N content is 400-600 mg / L, S 2- The content is 200-400 mg / L.

10. The ammonia-sulfur recovery process for ammonia-containing and sulfide-containing wastewater according to claim 1, characterized in that, The mass ratio of KOH to cedar powder in the KOH-adsorbed cedar powder is 1:(0.8-1.2). And / or, the mass ratio of the porous fir charcoal to K2FeO4 is 1:(0.5-1); And / or, in step (1), the KOH-adsorbed fir powder is heated to 400-600℃ in a CO2 atmosphere at a heating rate of 1-10℃ / min and held at 400-600℃ for 1-3h to obtain the porous fir charcoal; And / or, in step (2), the porous fir charcoal and K2FeO4 are placed in water, first evaporated at 75-85℃ until the water content is reduced by 80%-90%, and then dried at 75-85℃ to obtain the porous fir charcoal adsorbed with K2FeO4. And / or, in step (3), the temperature is first raised to 450-550℃ at a heating rate of 1-10℃ / min and held at 450-550℃ for 0.5-1.5h, and then raised to 650-750℃ at a heating rate of 1-10℃ / min and held at 650-750℃ for 1-3h to obtain the iron-carbon composite material; And / or, step (3) further includes post-processing, which is: cooling the porous fir charcoal obtained by roasting to room temperature, washing it first with 0.05-0.15M HCl, then washing it with deionized water until the eluent is neutral, and then drying it under vacuum at 75-85℃ and grinding it.

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