Pretreatment method of palladium-containing wastewater

Abstract

The invention discloses a pretreatment method of palladium-containing wastewater. The method comprises the following steps: feeding palladium-containing wastewater generated after equipment cleaning after workshop production into a raw water tank through a collecting tank, pumping into a pipeline mixer by a pump, adding a flocculating agent for mixing, carrying out reaction precipitation by adopting a vertical flow precipitator, pumping the precipitate into a tubular centrifuge for mud-water separation, and recovering metal palladium from the separated substance in manners of drying, roasting and the like. Filtrate is concentrated and filtered through a ceramic membrane, produced water is recycled to a system, and concentrated water is further concentrated to a certain multiple and then is returned to the front end.

Description

Technical Field

[0001] The invention belongs to the field of palladium catalyst recycling, and specifically relates to a treatment method for recycling palladium-containing wastewater. Background Art

[0002] Palladium catalyst is a catalyst with metallic palladium as the main active component, using palladium black or palladium salts loaded on carriers such as alumina and zeolite, with sodium, cadmium, lead and other salts as co-catalysts. It is a catalyst frequently used in chemical and chemical reaction processes, with high catalytic activity, strong selectivity, easy catalyst preparation, small usage, and can be optimized by changing and improving the manufacturing method and compounding with other metals or co-catalyst active components.

[0003] Palladium catalyst is the main raw material of catalyst carrier in hydrogen peroxide production. It is generally stored in the form of solid particles. Since palladium catalyst is heavier than water, it will naturally settle to the bottom. In each production process of palladium catalyst, a small amount of palladium will dissolve in water. If natural precipitation is used directly, it will take a long time and the palladium in the wastewater cannot be recycled. Direct discharge as sewage will cause high production consumption, increase sewage treatment costs, and increase the difficulty of sewage treatment. Summary of the invention

[0004] In view of the above technical problems, the present invention provides a treatment method for recycling palladium-containing wastewater, and the specific steps are as follows: (1) Because palladium-containing wastewater contains a large amount of particulate impurities, it needs to be pre-treated in a vertical flow sedimentator. By adding flocculants in the pipeline mixer for sufficient mixing and sedimentation, the palladium content in the palladium-containing wastewater can be reduced to below 8 ppm, and the produced water is sent to the water production buffer tank for standby use.

[0005] (2) The water-containing sludge in the sedimentation tank hopper is separated into mud and water by a tubular centrifuge, and the separated palladium sludge is recovered.

[0006] (3) The filtrate produced by the tubular centrifuge is sent to the ceramic membrane for concentration filtration, and then the ceramic membrane filtration circulation pump is used for high-throughput circulation filtration. The circulation flow rate is about 10-20 times the inlet flow rate. The ceramic membrane is cleaned once every 1-3 months. When the pressure difference of the ceramic membrane increases significantly, backwashing is performed to increase the flushing of the ceramic membrane surface to prevent scaling too quickly during the filtration process.

[0007] (4) The produced water (turbidity <5NTU) after being filtered by the ceramic membrane enters the produced water buffer tank for standby use, and the concentrated water produced by filtration returns to the concentration tank again, and after being concentrated to about 10-20 times, it is discharged into the sedimentation tank.

[0008] The process indicators of the palladium-containing wastewater are as follows: temperature 20~30℃, water inlet 2-3m³ / d, palladium content 30-40 mg / L, pH value 6~9, and turbidity 20-30 NTU.

[0009] The vertical flow sedimentation vessel in the pipeline mixer in step (1) is lined with PO material. Although the water quality is slightly acidic and the temperature is room temperature, the flocculant has a certain viscosity and is easily adsorbed on the rough surface of the equipment, so the PO material can be fully settled. The flocculant is a mixture of fatty alcohol polyoxyethylene ether phosphate and ferrous sulfate.

[0010] In some embodiments, the vertical flow sedimentation vessel in step (b) is filled with an anion exchange resin, and the anion exchange resin is a resin modified with 2,3-epoxypropyltrimethylammonium chloride onto polystyrene microspheres.

[0011] The anion exchange resin is a polystyrene microsphere whose surface is epoxidized with epichlorohydrin, and then the epoxidized microsphere is subjected to a ring-opening reaction with 5% to 15% sulfuric acid to obtain a surface hydroxylated porous microsphere; and then 2,3-epoxypropyltrimethylammonium chloride is modified on the hydroxyl group on the surface of the microsphere to obtain an anion exchange resin.

[0012] The tubular centrifuge is a separation cylinder made of polytetrafluoroethylene.

[0013] The ceramic membrane filtration described in step (3) is automatically controlled by controlling the flow rate of ceramic membrane produced water entering the circulation tank to stabilize the liquid level of the ceramic membrane circulation tank.

[0014] The ceramic membrane filter in step (3) is a ceramic membrane made of materials such as aluminum oxide and silicon dioxide and fired at 800-900° C. It has high mechanical strength, can withstand a variety of environments, and is cost-effective.

[0015] The ceramic membrane filtration described in step (3) adopts large-flux circulation filtration, and its circulation flow rate is 10-20 times the feed amount; the use of large-flux circulation filtration mainly increases the membrane surface flow rate of wastewater passing through the ceramic membrane, thereby greatly reducing the residence time of muddy water on the membrane surface, thereby extending the fouling cycle and reducing the cleaning frequency.

[0016] According to the technical solution of the present invention, the impregnation wastewater from the catalyst workshop enters the raw water tank for storage, is pumped to the precipitator, and is precipitated in the precipitator by adding a flocculant. The muddy water after precipitation is discharged to the tubular centrifuge through the bottom valve for mud-water separation, the palladium mud is dried and roasted to remove impurities, the palladium catalyst is recycled, the produced water is further filtered through a ceramic membrane and reused, and the concentrated water is returned to the front stage for further treatment, thereby improving the recovery efficiency and reducing the use cost of the palladium catalyst. The turbidity of the produced water is reduced to within 0.2 NTU. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 The process flow chart of the present invention includes a collecting tank 1, a vertical sedimentation tank 2, a flocculation tank 3, a tubular centrifuge 4, a ceramic membrane circulation tank 5, a ceramic membrane filter 6, a circulation pump 7, and a buffer tank 8. DETAILED DESCRIPTION

[0018] The present invention is further described below with reference to embodiments, but the scope of protection claimed by the present invention is not limited to the scope described in the embodiments.

[0019] Example 1 A pretreatment device for palladium-containing wastewater, wherein the collecting tank 1 and the flocculation tank 3 are respectively connected to the vertical sedimentation tank 2 via pipelines, and the bottom of the vertical sedimentation tank 2 is connected to the tubular centrifuge 4 via pipelines; The tubular centrifuge 4 is connected to the circulation pump 7 via a pipeline and then connected to the ceramic membrane filter 6, and the ceramic membrane filter 6 is connected to the buffer tank 8 via a pipeline.

[0020] The tubular centrifuge 4 is connected to the ceramic membrane circulation tank 5 through a pipeline and then connected to the circulation pump 7.

[0021] The upper part of the vertical sedimentation tank 2 is connected to the collection tank 1 through a pipeline.

[0022] The ceramic membrane circulation tank 5 is connected to the side wall of the vertical precipitator 2 via a pipeline; the top of the ceramic membrane filter 6 is connected to the ceramic membrane circulation tank 5 via a pipeline.

[0023] The bottom of the ceramic membrane filter 6 is connected to the collection tank 1 via a pipeline.

[0024] Example 2 Step (1): using a water tank to receive palladium-containing wastewater provided by an upstream production unit, the water quality of which is a palladium content of 40 mg / L, a pH value of 6-9, a turbidity of 30 NTU, and a temperature of 28°C; Step (2): 3 m³ / d of water is fed into a vertical sedimentation vessel for sedimentation, and a flocculant is added (the flocculant is a mixture of fatty alcohol polyoxyethylene ether phosphate and ferrous sulfate in a mass ratio of 10:1). The vertical flow sedimentation vessel sedimentation time is 12 h, and the surface load is 0.4 m 3 / m 2 h, the turbidity is reduced to 5 NTU, and the palladium content in the palladium-containing wastewater is reduced to 5 ppm; the produced water is discharged into the palladium-containing wastewater in the collection tank; Step (3): The obtained precipitate (water-containing sludge) is dehydrated and separated by a tubular centrifuge, and then circulated and filtered through a ceramic membrane filter (a fired material of aluminum oxide) (the ceramic membrane filtration adopts a large flux cross-flow filtration, and the flow rate of the circulating filtration is 24m³ / d), and the turbidity of the produced water is reduced to 0.2 NTU, and the palladium content in the palladium-containing wastewater is reduced to 0.8ppm; Step (4): The clean water treated in step (3) enters the water production buffer tank for standby use and is subsequently used as workshop cleaning water. The concentrated water is concentrated to about 10-20 times and then separated into mud and water by a tubular centrifuge. The sludge is recovered and the clean water continues to be subjected to the previous sedimentation treatment.

[0025] Example 3 Step (1): using a water tank to receive palladium-containing wastewater provided by an upstream production unit, the water quality of which is a palladium content of 55 mg / L, a pH value of 7-9, a turbidity of 60 NTU, and a temperature of 26°C; Step (2): 3 m³ / d of water is fed into a vertical sedimentation vessel for sedimentation. The vertical sedimentation vessel is filled with anion exchange resin. The sedimentation time of the vertical sedimentation vessel is 5 h and the surface load is 0.3 m 3 / m 2 h, the turbidity is reduced to 3 NTU, and the palladium content in the palladium-containing wastewater is reduced to 1 ppm; the produced water is discharged into the palladium-containing wastewater in the collection tank; Anion exchange resin: refer to the preparation method of Example 1 of a preparation method of a high temperature resistant strong alkaline anion exchange resin (202311464121.7).

[0026] Step (3): The obtained precipitate (water-containing sludge) is dehydrated and separated by a tubular centrifuge, and then circulated and filtered through a ceramic membrane filter (a fired material of aluminum oxide) (the ceramic membrane filtration adopts large-flux cross-flow filtration, and the flow rate of the circulating filtration is 24m³ / d), and the turbidity of the produced water is reduced to 0.05 NTU, and the palladium content in the palladium-containing wastewater is reduced to 0.09ppm; Step (4): The clean water treated in step (3) enters the water production buffer tank for standby use and is subsequently used as workshop cleaning water. The concentrated water is concentrated to about 10-20 times and then separated into mud and water by a tubular centrifuge. The sludge is recovered and the clean water continues to be subjected to the previous sedimentation treatment.

Claims

1. A method for pretreating palladium-containing wastewater, characterized in that: The wastewater is purified by using a vertical flow sedimentator, a tubular centrifuge, and a ceramic membrane filter in sequence, including the following steps: (a) Using a collection pool to collect palladium-containing wastewater from workshop production; (b) pumping the palladium-containing wastewater into a vertical flow sedimentation tank for preliminary filtration, filtering and collecting the palladium-containing suspended matter; (c) dehydrating and separating the precipitate from step (b) by using a tubular centrifuge; (d) The filtrate obtained by dehydration and separation in step (c) is transported to a ceramic membrane circulation tank, and then a circulation pump is used to perform ceramic membrane cross-flow filtration, and the produced water enters a water production buffer tank.

2. The pretreatment method for palladium-containing wastewater according to claim 1, wherein: The process indicators of palladium-containing wastewater are temperature 20~30℃, palladium content 40-60 mg / L, pH value 6~9, turbidity 25-40 NTU, and water inlet 2-3m³ / d.

3. The pretreatment method for palladium-containing wastewater according to claim 1, characterized in that: The sedimentation time of the vertical flow sedimentation tank is 2-24h, and the surface load is <0.5m 3 / m 2 ·h.

4. The pretreatment method for palladium-containing wastewater according to claim 1, wherein: In the step (b), a flocculant is also added, and the flocculant is a mixture of fatty alcohol polyoxyethylene ether phosphate and ferrous sulfate.

5. The pretreatment method for palladium-containing wastewater according to claim 1, characterized in that: The vertical flow precipitator in step (b) is filled with an anion exchange resin, which is a resin modified with 2,3-epoxypropyltrimethylammonium chloride to form polystyrene microspheres.

6. The pretreatment method for palladium-containing wastewater according to claim 1, characterized in that, The ceramic membrane filtration adopts large-flux cross-flow filtration, and the circulation flow rate is 10-20 times the inlet water flow rate.

7. The pretreatment method for palladium-containing wastewater according to claim 1, characterized in that, The ceramic membrane is made of aluminum oxide and silicon dioxide and fired at 800-900°C.

8. The pretreatment method for palladium-containing wastewater according to claim 1, characterized in that, The tubular centrifuge has a separation cylinder made of polytetrafluoroethylene.

Images