A pretreatment method for palladium-containing wastewater

Abstract

The application discloses a pretreatment method of palladium-containing wastewater. First, the palladium-containing wastewater after equipment cleaning in a workshop is collected into a raw water tank through a collecting tank, then is pumped into a pipeline mixer, flocculants are added for mixing, then a vertical flow precipitator is used for reaction and precipitation, the precipitate is punched into a tubular centrifuge for sludge-water separation, the separated substance is recovered by drying, calcination and the like to recover metal palladium, the filtrate is concentrated and filtered through a ceramic membrane, the produced water is reused to the system, and the concentrated water is returned to the front end after being further concentrated to a certain multiple.

Description

Technical Field

[0001] This invention belongs to the field of palladium catalyst recycling, specifically relating to a method for treating palladium-containing wastewater. Background Technology

[0002] Palladium catalyst is a catalyst that uses metallic palladium as the main active component, supported on alumina, zeolite, or other supports using palladium black or palladium salts, and co-catalysts such as sodium, cadmium, and lead. It is a commonly used catalyst in chemical and chemical reaction processes, characterized by high catalytic activity, strong selectivity, convenient catalyst preparation, low dosage, and the ability to optimize performance by combining it with other metals or co-catalyst active components through changes and improvements in manufacturing methods.

[0003] Palladium catalyst is the main raw material for the catalyst carrier in hydrogen peroxide production. It is typically stored as solid granules, and because palladium is heavier than water, it naturally settles to the bottom. During each production process, a small amount of palladium dissolves in the water. If natural sedimentation is allowed directly, it is time-consuming and the palladium in the wastewater cannot be recovered. Directly discharging it as wastewater results in high production costs and increases wastewater treatment costs and complexity. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a treatment method for palladium-containing wastewater recovery, the specific steps of which are as follows:

[0005] (1) Because palladium-containing wastewater contains a large amount of particulate impurities, it needs to be pretreated by a vertical flow sedimentation tank. By adding flocculant in the pipeline mixer for thorough mixing and sedimentation, the palladium content in the palladium-containing wastewater can be reduced to below 8 ppm. The produced water is then sent to the produced water buffer tank for later use.

[0006] (2) The water-containing sludge in the sludge hopper of the sedimentation tank is separated into mud and water by a tubular centrifuge, and the separated palladium sludge is recycled.

[0007] (3) The filtrate produced by the tubular centrifuge is sent to the ceramic membrane for concentration and filtration, and then the ceramic membrane is circulated by a high-flow-rate circulating pump. The circulation flow rate is about 10-20 times the influent 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 scouring of the ceramic membrane surface and prevent scale from forming too quickly during the filtration process.

[0008] (4) The permeate (turbidity < 5 NTU) after being filtered through the ceramic membrane enters the permeate buffer tank for use. The concentrated water produced by filtration is returned to the concentration tank and concentrated to about 10-20 times before being discharged into the sedimentation tank.

[0009] The process parameters for the palladium-containing wastewater are as follows: temperature 20~30℃, influent flow rate 2-3m³ / d, palladium content 30-40 mg / L, pH value 6~9, and turbidity 20-30 NTU.

[0010] In step (1), the vertical flow sedimentation tank in the pipe mixer is lined with PO material. Although the water is slightly acidic and the temperature is normal, the flocculant has a certain viscosity and is easily adsorbed on the rough surface of the equipment. Therefore, using PO material as the lining material can ensure sufficient sedimentation. The flocculant is a mixture of fatty alcohol polyoxyethylene ether phosphate and ferrous sulfate.

[0011] In some embodiments, the vertical flow precipitator in step (b) is filled with anion exchange resin, which is a resin modified with 2,3-epoxypropyltrimethylammonium chloride onto polystyrene microspheres.

[0012] The anion exchange resin is obtained by epoxidizing the surface of polystyrene microspheres with epichlorohydrin, followed by ring-opening reaction of the epoxidized microspheres with 5%~15% sulfuric acid to obtain porous microspheres with hydroxylated surfaces; then, 2,3-epoxypropyltrimethylammonium chloride is added to the hydroxyl groups on the surface of the microspheres to obtain the anion exchange resin.

[0013] The tubular centrifuge has a separation cylinder made of polytetrafluoroethylene.

[0014] The ceramic membrane filtration described in step (3) is automatically controlled. The flow rate of ceramic membrane produced water entering the circulation tank is controlled to stabilize the liquid level in the ceramic membrane circulation tank.

[0015] The ceramic membrane filter described in step (3) is a ceramic membrane made of materials such as alumina and silicon dioxide, fired at 800-900℃. It has high mechanical strength, can withstand various environments, and has a high cost performance.

[0016] The ceramic membrane filtration described in step (3) adopts high-throughput circulation filtration, and its circulation flow rate is 10-20 times that of the feed rate. The main function of high-throughput circulation filtration is to increase the flow velocity of wastewater through the ceramic membrane, thereby greatly reducing the residence time of muddy water on the membrane surface, thus extending the fouling cycle and reducing the frequency of cleaning.

[0017] The technical solution of this invention involves storing impregnation wastewater from the catalyst workshop in a raw water tank, pumping it to a precipitator, adding flocculant, and allowing it to settle. The settled sludge is then discharged through a bottom valve to a tubular centrifuge for sludge-water separation. The palladium sludge is dried and calcined to remove impurities, and the palladium catalyst is recovered and reused. The product water is further filtered through a ceramic membrane and reused, while the concentrated water is returned to the upstream section for further treatment, thereby improving recovery efficiency and reducing the cost of using the palladium catalyst. The turbidity of the product water is reduced to below 0.2 NTU. Attached Figure Description

[0018] Figure 1 This is a process flow diagram of the present invention. The components include: a collection 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 Implementation

[0019] The present invention will be further illustrated below with reference to the embodiments, but the scope of protection of the present invention is not limited to the scope described in the embodiments.

[0020] Example 1

[0021] The pretreatment device for palladium-containing wastewater includes a collection tank 1 and a flocculation tank 3, which are connected to a vertical sedimentation tank 2 via pipelines. The bottom of the vertical sedimentation tank 2 is connected to a tubular centrifuge 4 via a pipeline.

[0022] The tubular centrifuge 4 is connected to the circulating pump 7 via a pipeline and then to the ceramic membrane filter 6. The ceramic membrane filter 6 is connected to the buffer tank 8 via a pipeline.

[0023] The tubular centrifuge 4 is connected to the ceramic membrane circulation tank 5 via a pipeline, and then to the circulation pump 7.

[0024] The upper part of the vertical sedimentation tank 2 is connected to the collection tank 1 via a pipe.

[0025] The ceramic membrane circulation tank 5 is connected to the side wall of the vertical sedimentation tank 2 via a pipe; the top of the ceramic membrane filter 6 is connected to the ceramic membrane circulation tank 5 via a pipe.

[0026] The bottom of the ceramic membrane filter 6 is connected to the collection tank 1 via a pipe.

[0027] Example 2

[0028] Step (1): Receive palladium-containing wastewater from the upstream production unit using a water tank. The water quality is palladium content 40 mg / L, pH value 6-9, turbidity 30 NTU, and temperature 28℃.

[0029] Step (2): A flow rate of 3 m³ / d is introduced into the vertical sedimentation tank for sedimentation. Flocculant (a mixture of fatty alcohol polyoxyethylene ether phosphate and ferrous sulfate at a mass ratio of 10:1) is added. The sedimentation time in the vertical sedimentation tank is 12 hours, and the surface loading is 0.4 m. 3 / m 2 •h, to reduce turbidity to 5 NTU, and reduce palladium content in palladium-containing wastewater to 5 ppm; the resulting permeate enters the collection tank for palladium-containing wastewater;

[0030] Step (3): The obtained precipitate (water-containing sludge) is dehydrated and separated by a tubular centrifuge, and then circulated through a ceramic membrane filter (alumina sintered material) (the ceramic membrane filter adopts a high-flow cross-flow filtration, and the circulation filtration flow rate is 24 m³ / d), reducing the turbidity of the produced water to 0.2 NTU and reducing the palladium content in the palladium-containing wastewater to 0.8 ppm;

[0031] Step (4): The clean water after step (3) is put into the production water buffer tank for later use as workshop cleaning water. The concentrated water is concentrated to about 10-20 times and then separated into mud and water by tubular centrifuge. The sludge is recovered, and the clean water continues to undergo the pre-sedimentation treatment.

[0032] Example 3

[0033] Step (1): Receive palladium-containing wastewater from the upstream production unit using a water tank. The water quality is palladium content 55 mg / L, pH value 7-9, turbidity 60 NTU, and temperature 26℃.

[0034] Step (2): A flow rate of 3 m³ / d is introduced into a vertical sedimentation tank for sedimentation. The vertical sedimentation tank is filled with anion exchange resin, and the sedimentation time is 5 hours with a surface loading of 0.3 m³ / d. 3 / m 2 •h, reducing turbidity to 3 NTU, and reducing palladium content in palladium-containing wastewater to 1 ppm; the resulting permeate enters the collection tank for palladium-containing wastewater;

[0035] Anion exchange resin: The preparation method of Example 1 of a high-temperature resistant strong base anion exchange resin (202311464121.7) is referred to.

[0036] Step (3): The obtained precipitate (water-containing sludge) is dehydrated and separated by a tubular centrifuge, and then circulated through a ceramic membrane filter (alumina sintered material) (the ceramic membrane filter adopts a high-flow cross-flow filtration method, and the circulation filtration flow rate is 24 m³ / d), reducing the turbidity of the produced water to 0.05 NTU and reducing the palladium content in the palladium-containing wastewater to 0.09 ppm;

[0037] Step (4): The clean water after step (3) is put into the production water buffer tank for later use as workshop cleaning water. The concentrated water is concentrated to about 10-20 times and then separated into mud and water by tubular centrifuge. The sludge is recovered, and the clean water continues to undergo the pre-sedimentation treatment.

Claims

1. A pretreatment method for palladium-containing wastewater, characterized in that, Wastewater is purified by sequentially employing a vertical flow sedimentation tank, a tubular centrifuge, and a ceramic membrane filter, including the following steps: (a) Collect palladium-containing wastewater from the workshop during production using a collection tank. The palladium content in the wastewater is 40-60 mg / L, pH value is 6-9, and turbidity is 25-40 NTU. (b) The palladium-containing wastewater is pumped into a vertical flow sedimentation tank for sedimentation, and the palladium-containing suspended solids are filtered out and collected; a flocculant is also added in step (b), which is a mixture of fatty alcohol polyoxyethylene ether phosphate and ferrous sulfate; The vertical flow precipitator is filled with anion exchange resin, which is a resin modified with 2,3-epoxypropyltrimethylammonium chloride onto polystyrene microspheres. The settling time in the vertical flow settler is 2-24 hours, and the surface load is <0.5m. 3 / m 2 ·h; (c) The precipitate from step (b) is dehydrated and separated by a tubular centrifuge; (d) The filtrate obtained from the dehydration separation in step (c) is transported to the ceramic membrane circulation tank, and then the ceramic membrane cross-flow filtration is performed by the circulation pump. The product water enters the product water buffer tank. The ceramic membrane filtration adopts high-flow cross-flow filtration, and the circulation flow rate is 10-20 times the influent flow rate. The ceramic membrane is made of alumina and silicon dioxide material and is fired at 800-900℃.

2. The pretreatment method for palladium-containing wastewater according to claim 1, characterized in that: The process parameters for palladium-containing wastewater are: temperature 20~30℃, influent flow rate 2-3m³. 3 / d.

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

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