An adsorption fast sedimentation tank for regeneration and recycling of activated carbon

Abstract

The present invention relates to an adsorption fast settling tank for activated carbon regeneration and recycling, including a sewage treatment system, a cyclone separator, a backwash filter, and an activated carbon regeneration system; the activated carbon regeneration system includes an ultrasonic cleaner, a pickling immersion tank, a first modification treatment tank, a second modification treatment tank, and an activated carbon regeneration furnace connected in sequence; the pickling immersion tank includes 2-5wt% nitric acid; the first modification treatment tank includes 0.2-0.5M Cu(II) ions; the second modification treatment tank includes 0.1-0.2M polyols, and 0.05-0.1M polyamines; the cyclone separator, the backwash filter, and the activated carbon regeneration system are provided with a pipeline for returning the activated carbon to the adsorption tank. In the process of the present invention, the activated carbon is recycled by the cyclone separator, the backwash filter, and the activated carbon regeneration system. The process of the present invention has high activated carbon utilization and good treatment effect on organic sewage.

Description

Technical Field

[0001] The invention belongs to the field of industrial wastewater treatment, and in particular relates to an adsorption fast settling tank for regenerating and recycling activated carbon. Background Art

[0002] After nearly half a century of rapid economic development, my country has become the world's main production base for various chemicals. The annual total discharge of wastewater has gradually increased, of which industrial wastewater accounts for more than 32% of the total wastewater discharge. The water environment situation is severe, especially for wastewater from the pharmaceutical, chemical, coking, leather, biological and other industries, which has the characteristics of high pollutant concentration, difficult biological degradation and great harm. The efficient and low-consumption treatment of this type of wastewater has become a global problem.

[0003] The biodegradable hydrophobic organic matter in industrial wastewater includes the persistent organic pollutants that are currently receiving much attention. Due to their high resistance to biodegradation, chemical decomposition, photolysis, etc., traditional biochemical treatment processes can only slightly degrade them or cannot degrade them at all. Even if the basic indicators such as COD and BOD in the wastewater after secondary or even tertiary treatment can meet the requirements, the difficult-to-degrade organic pollutants still exist. After being discharged into natural water bodies, they will remain in water bodies, soil, sediment and other media for a long time. At the same time, due to their low water solubility and high fat solubility, they will produce bioaccumulative toxicity when entering the body, which seriously limits the compliance of industrial wastewater discharge and resource reuse.

[0004] At present, common advanced oxidation technologies such as ozone oxidation and Fenton oxidation are usually used to deeply treat the bio-refractory hydrophobic organic matter in the effluent of biochemical treatment. However, in actual engineering applications, ozone oxidation and Fenton oxidation technologies often have problems such as high cost and high energy consumption.

[0005] The adsorption method uses porous, adsorbent materials to adsorb substances in water bodies on the surface, separate and enrich pollutants in water bodies, mainly including physical adsorption, chemical adsorption, and exchange adsorption. The physical adsorption method uses adsorption materials with large porous specific surface areas, such as activated carbon, macroporous resin, activated clay, diatomaceous earth, etc., to adsorb pollutants in wastewater into the pores of the material. It is often used for the treatment of difficult-to-degrade organic wastewater. However, due to the limitations of the specific surface area, porosity, and adsorption capacity of the adsorption material, the traditional activated carbon adsorption method has low adsorption efficiency. In high humidity or wastewater environments, it is very easy to adsorb a large amount of water, resulting in a decrease in adsorption capacity.

[0006] In addition, when the concentration of organic pollutants is high, activated carbon loses its ability to adsorb organic pollutants after reaching saturated adsorption. In the prior art, the activated carbon that has reached saturated adsorption is recycled and reused. However, the processes of activated carbon adsorption and activated carbon regeneration are generally separate. If activated carbon adsorption and regeneration can be integrated into a system, activated carbon can be recycled, reducing process flow and transportation costs, and achieving resource recycling, which is a feasible method. However, the current activated carbon regeneration process cannot meet the requirements of organic wastewater treatment.

[0007] CN202021124929.2 discloses an activated carbon regeneration and wastewater system treatment device, but its activated carbon is used for gas adsorption and is not suitable for the activated carbon regeneration process of industrial wastewater. Summary of the invention

[0008] Based on the bio-refractory hydrophobic organic matter present in the effluent of biochemical treatment of industrial wastewater, the present invention provides a composite activated carbon adsorption fast sedimentation tank to replace the secondary sedimentation tank and conventional advanced oxidation processes such as ozone oxidation and Fenton oxidation; with matching activated carbon regeneration equipment and process, the activated carbon can be regenerated and recycled, the process is simple, and is suitable for use in processes that continuously generate organic wastewater, such as chemical wastewater, pharmaceutical wastewater, printing and dyeing wastewater, coking wastewater, leather wastewater and other high-COD wastewater that has been initially treated.

[0009] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0010] An adsorption fast settling tank for activated carbon regeneration and recycling, comprising a sewage treatment system, a cyclone separator, a backwash filter tank, and an activated carbon regeneration system connected in sequence;

[0011] Wherein, the sewage treatment system comprises a material dosing device, and a mixed adsorption tank, a coagulation tank, a flocculation tank and a sedimentation tank connected in sequence; the material dosing device comprises an activated carbon dosing device, a coagulant dosing device and a flocculant dosing device; the activated carbon dosing device is connected to the mixed adsorption tank, the coagulant dosing device is connected to the mixed adsorption tank and the coagulation tank, and the flocculant dosing device is connected to the flocculation tank;

[0012] The activated carbon regeneration system comprises an ultrasonic cleaner, an acid pickling and immersion tank, a first modification treatment tank, a second modification treatment tank, and an activated carbon regeneration furnace which are connected in sequence; the acid pickling and immersion tank comprises 2-5wt% nitric acid; the first modification treatment tank comprises 0.2-0.5M Cu(II) ions; the second modification treatment tank comprises 0.1-0.2M polyol and 0.05-0.1M polyamine;

[0013] The cyclone separator, backwash filter tank and activated carbon regeneration system are provided with pipelines for returning the activated carbon to the mixed adsorption tank.

[0014] Furthermore, the coagulant is at least one of polyaluminium chloride (PAC), polyaluminium sulfate (PAS), polyferric chloride (PFC) and polyferric sulfate (PFS), and the flocculant is polyacrylamide (PAM), preferably cationic polyacrylamide (CPAM). The activated carbon is granular with a particle size of 2-5 mm, preferably 3-4 mm.

[0015] The dosage of activated carbon, coagulant and flocculant is adjusted according to the wastewater index to be treated, such as COD and other parameters. In a specific technical solution of the present invention, for example, for organic wastewater with COD of 1000-2000 mg / L, in the mixed adsorption tank, the dosage of activated carbon is 500-1000 g / ton of wastewater; the dosage of coagulant is 30-50 g / ton of wastewater; in the coagulation tank, the dosage of coagulant is 150-200 g / ton of wastewater; in the flocculation tank, the dosage of flocculant is 5-10 g / ton of wastewater.

[0016] In the mixed adsorption tank, activated carbon particles and coagulants are added at the same time. The activated carbon adsorbs the hydrophobic organic matter that is difficult to biodegrade in the biochemical effluent, reducing the concentration of organic matter. The impurity particles in the wastewater after the suspended matter and colloidal particles are destabilized by the coagulant use the activated carbon particles as crystal nuclei. Through the adsorption of activated carbon and the capture of sedimentation nets, alum flowers with high density are quickly generated, thereby greatly shortening the sedimentation time and improving the treatment capacity and speed of the sewage treatment system. After the wastewater is adsorbed and mixed by activated carbon and coagulants, the effluent is coagulated and flocculated in turn. The flocculated effluent enters the sedimentation tank, and the effluent of the sedimentation tank enters the subsequent treatment system.

[0017] Furthermore, the sedimentation tank is provided with a drain pipe and a mud discharge pipe, the mud discharge pipe is connected to the inlet of the cyclone separator through the first gas stripper; the bottom outlet of the cyclone separator is connected to the feed port of the backwash filter through the second gas stripper, the air inlet pipe of the first gas stripper and the air inlet pipe of the second gas stripper are connected to the aeration fan; the discharge port of the backwash filter is connected to the activated carbon regeneration system; further, the backwash filter is provided with an air inlet pipe, and the air inlet pipe is connected to the aeration fan.

[0018] The sludge at the bottom of the sedimentation tank and the activated carbon particles wrapped in the sludge are lifted to the cyclone separator through the air lifter to separate the activated carbon and sludge, discharge the sludge, and return the activated carbon particles to the mixed adsorption tank for recycling; or the activated carbon particles enter the backwash filter. The principle of the cyclone separator is to use the density difference between the activated carbon particles and the sludge to separate the sludge with lower density from the top and deposit the activated carbon particles with higher density to the bottom of the cyclone separator. The parameters of the cyclone separator are well known in the art and are not particularly limited, as long as the separation of sludge and activated carbon can be completed. In a specific embodiment of the present invention, the parameters of the cyclone separator are: inlet flow rate 20-30m 3 / h, inlet pressure difference 0.15-0.25MPa, split ratio 0.10-0.15.

[0019] Backwashing filter uses air and water to backwash activated carbon to clean the sludge and other substances that clog the activated carbon pores. The activated carbon pores are easily clogged by small-sized impurities. After clogging, the adsorption capacity of activated carbon decreases significantly, so the clogged activated carbon needs to be cleaned. The operating parameters of the backwashing filter are well known in the art and are not particularly limited, as long as the activated carbon blockage can be fully cleaned. In a specific embodiment of the present invention, the operating parameters of the backwashing filter are: filtration rate 10-14m / h, gas flow rate 10-20L / m 2 ·s, water flow 3-5L / m 2 ·s, flushing time 10-15min.

[0020] The principle of the activated carbon recycling of the present invention is: judging whether the activated carbon after cyclone separation in the cyclone separator is blocked, and when the activated carbon is not blocked, it is refluxed back to the mixed adsorption tank; when the activated carbon is blocked, the activated carbon after cyclone separation enters the backwash filter tank, and the sludge blocking the surface and inside of the activated carbon is washed away by air-water backwashing; judging whether the activated carbon after air-water backwashing in the backwash filter tank has sufficient organic adsorption capacity, and when the activated carbon has sufficient organic adsorption capacity, it is refluxed back to the mixed adsorption tank; when the activated carbon does not have sufficient organic adsorption capacity, it enters the activated carbon regeneration system for regeneration.

[0021] Furthermore, to determine whether the activated carbon after cyclone separation is blocked, it is to test whether the density of the activated carbon separated and dried by cyclone is more than 140% of the fresh activated carbon (density ≥ 140% of the fresh activated carbon indicates that the activated carbon has been blocked, and density < 140% of the fresh activated carbon indicates that the activated carbon is not blocked and can flow back to the front end); to determine whether the activated carbon after air-water backwashing in the backwash filter tank has sufficient organic adsorption capacity, it is to test whether the organic adsorption amount of the activated carbon after air-water backwashing reaches more than 30% of the organic adsorption amount of the fresh activated carbon (saturated adsorption capacity ≤ 50% of the fresh activated carbon adsorption capacity indicates that the activated carbon has insufficient organic adsorption capacity and needs to be regenerated; saturated adsorption capacity > 50% of the fresh activated carbon adsorption capacity indicates that the activated carbon still has sufficient organic adsorption capacity and can flow back to the front end).

[0022] Further, in the activated carbon regeneration system, the activated carbon is regenerated by a method comprising the following steps:

[0023] (S1) pretreatment: adding waste activated carbon material and water into an ultrasonic cleaner, performing ultrasonic cleaning, filtering, and drying;

[0024] (S2) pickling: immersing the activated carbon pretreated in step (S1) in a pickling tank under ultrasonic conditions, wherein the pickling tank contains a mixed acid solution including nitric acid, sulfuric acid, and perchloric acid; filtering after immersion, washing with water, and drying;

[0025] (S3) modification treatment: the activated carbon acid-washed in step (S2) is sequentially immersed in a first modification treatment tank and a second modification treatment tank II, wherein the solution in the first modification treatment tank contains Cu(II) ions, and the solution in the second modification treatment tank contains polyols and polyamines; after immersion, the activated carbon is filtered and dried;

[0026] (S4) High temperature activation treatment: The activated carbon modified in step (S3) is subjected to programmed heating and programmed annealing in an activated carbon regeneration furnace, and then naturally cooled to room temperature.

[0027] Preferably, in step (S1), ultrasonic cleaning can preliminarily remove impurities in the pores of the activated carbon and dredge the pores of the activated carbon. The ultrasonic cleaning power is 300-500W, the ultrasonic frequency is 80-120KHz, and the ultrasonic cleaning time is 8-12h; the amount of water used is 10-15 times the mass of the activated carbon. In step (S2), the ultrasonic conditions are 300-500W of ultrasonic instrument power and 80-120kHz of ultrasonic power.

[0028] Preferably, in step (S2), the mixed acid comprises 2-5wt% nitric acid, 1.5-3wt% perchloric acid, and 3-6wt% sulfuric acid, and the immersion time is 10-30 min.

[0029] After pickling, the organic impurities inside the activated carbon can be basically removed, but the number of acidic oxygen-containing groups on the surface of the activated carbon increases after pickling, which is not conducive to the adsorption of low-polarity organic matter, and the hydrophilicity of the activated carbon increases. In wastewater treatment and in humid air, it will absorb a large amount of water. The competitive adsorption of water molecules will reduce the adsorption capacity of the activated carbon for organic matter. Therefore, in the pickling process of the present invention, the concentration of the acid cannot be too high and the immersion time cannot be too long. The present invention pickles under ultrasonic conditions, and a lower concentration of acid and a lower pickling time can be used to complete the pickling process. While removing organic impurities in the activated carbon, the hydrophilicity of the activated carbon will not be increased too much.

[0030] Preferably, in step (S3), the Cu(II) ions are soluble salts of Cu(II), including at least one of copper nitrate, copper sulfate, copper chloride, copper acetate, and copper oxalate; the polyol is selected from at least one of sucrose, glucose, and mannitol; the polyamine includes at least one of ethylenediamine, diethylenetriamine, and triethylenetetramine; the Cu(II) ion concentration in the first modification treatment tank is 0.2-0.5M; the polyol concentration in the second modification tank is 0.1-0.2M, the polyamine concentration is 0.05-0.1M, and the solvent in the second modification tank is 40-60% alcohol aqueous solution, and the alcohol is selected from at least one of methanol, ethanol, and isopropanol.

[0031] The inventor unexpectedly found that after the modification treatment of step (S3), the regeneration of activated carbon can be effectively completed. The activated carbon restores the adsorption capacity of organic pollutants in wastewater, and even enhances the adsorption capacity of some organic matter. After the activated carbon is acid-washed, the content of surface acidic oxygen increases, and the adsorption capacity of metal ions increases. After that, it is immersed in an aqueous solution containing Cu (II), and after adsorbing copper ions, it is immersed in a solution containing polyols and polyamines. The presence of copper ions is conducive to the anchoring effect of polyols and polyamines on copper ions. After that, after subsequent pyrolysis, the regeneration and modification of the activated carbon are completed.

[0032] Preferably, in step (S4), the programmed temperature is heated at 500°C-600°C for 15-20h, 600°C-700°C for 20-30h, and 800°C-900°C for 10-15h; the heating rate during the heating is 40-70°C / h, and the programmed annealing is annealed at 210-240°C for 1-2h, then cooled to 160-180°C for annealing for 3-5h, and the cooling rate is 20-30°C / h.

[0033] The programmed temperature converts the disordered carbon in the activated carbon into a layered structure, greatly improving the order of carbon atoms on the surface of the activated carbon, and reducing the content of oxygen-containing functional groups by 70%. At the same time, the substances in the pores of the discarded activated carbon are thermally desorbed. After the above-mentioned programmed temperature increase, the disorder of the activated carbon can be fully and effectively adjusted to achieve uniform and stable graphitization. The inventors found that after a suitable annealing procedure, the regenerated activated carbon has a larger adsorption capacity and a faster adsorption rate, and can be more effectively used as an adsorbent for wastewater treatment.

[0034] If the modification treatment of step (S3) is not performed, the quality of the regenerated activated carbon is poor. The inventor speculates that the reason is that, on the one hand, the activated carbon after acid washing has good hydrophilicity, and the competitive adsorption of water reduces the adsorption capacity of activated carbon for organic matter. The modification containing polyamines enhances the hydrophobicity of activated carbon, and nitrogen doping also helps the adsorption capacity of activated carbon; on the other hand, the presence of copper ions as a catalyst is conducive to the oxidative degradation of organic matter during the subsequent high-temperature calcination activation process. The inventor speculates that the following reactions may have occurred: first, copper salts produce copper oxide during high-temperature calcination, and copper oxide and carbon are reduced to copper at high temperature; then copper reacts with bound water to generate carbon dioxide and copper oxide.

[0035] CuO+C=Cu+CO

[0036] Cu+H2O=CuO+H2

[0037] CuO+CO=Cu+CO2

[0038] Copper acts as a catalyst in the catalytic regeneration reaction.

[0039] The present invention also provides a method for treating organic wastewater using the above-mentioned activated carbon regeneration and recycling adsorption fast settling tank, comprising the following steps:

[0040] (T1) The organic wastewater passes through the mixed adsorption tank, coagulation tank, and flocculation tank of the sewage treatment system in sequence, and activated carbon and coagulant are added to the mixed adsorption tank, coagulant is added to the coagulation tank, and flocculant is added to the flocculation tank; the treated wastewater is precipitated in the sedimentation tank, and the effluent meets the discharge standards. The sludge and activated carbon at the bottom of the sedimentation tank enter the cyclone separator;

[0041] (T2) The sludge and activated carbon are separated in the cyclone separator. When the separated activated carbon is not blocked, the activated carbon is refluxed back to the mixed adsorption tank; when the separated activated carbon is blocked, the activated carbon enters the backwash filter tank to perform step (T3);

[0042] (T3) The clogged activated carbon is in the backwash filter tank. When the activated carbon after the air-water backwash still has the ability to adsorb organic pollutants, the activated carbon is refluxed back to the mixed adsorption tank; when the activated carbon after the air-water backwash does not have the ability to adsorb organic pollutants, the activated carbon enters the activated carbon regeneration system to perform step (T4);

[0043] (T4) The activated carbon is regenerated in the activated carbon regeneration system, and the regenerated activated carbon is refluxed back to the mixed adsorption tank.

[0044] The COD of the organic wastewater is 500-2000 mg / L.

[0045] Compared with the prior art, the present invention has achieved the following beneficial effects:

[0046] 1. Through the compound use of activated carbon and coagulant, the bio-difficult-to-degrade hydrophobic organic matter in the biochemical effluent can be quickly adsorbed. With the activated carbon as the crystal nucleus, the coagulant destabilizes the suspended matter and colloidal particles in the wastewater, and quickly generates alum flocs with a high density, which can accelerate the "growth" and precipitation of flocs, with a high precipitation rate and precipitation efficiency, thereby greatly shortening the sedimentation time, improving the treatment capacity and treatment speed of the sewage treatment system, solving the problem of removing hydrophobic organic matter in the biochemical effluent, and reducing sewage pollutants. After subsequent coagulation, flocculation, and sedimentation, the drainage meets the discharge standards.

[0047] Second, the adsorption fast sedimentation tank for activated carbon regeneration and recycling of the present invention replaces the conventional secondary sedimentation tank and advanced oxidation processes such as Fenton oxidation and ozone oxidation.

[0048] 3. In the process of the present invention, the activated carbon is recycled through a cyclone separator, a backwash filter, and an activated carbon regeneration system. By judging the deactivation capacity of the activated carbon, it is flexibly selected whether the activated carbon is refluxed for recycling or subjected to subsequent activated carbon treatment.

[0049] Fourth, the activated carbon regenerated by the activated carbon regeneration system of the present invention has restored its organic matter adsorption capacity and even improved it. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 Schematic diagram of an adsorption fast settling tank for regeneration and recycling of activated carbon according to the present invention.

[0051] In the figure: 1-water inlet pipe, 2-mixing adsorption tank, 3-coagulation tank, 4-flocculation tank, 5-sedimentation tank, 6-cyclone separator, 7-backwash filter, 8-activated carbon regeneration system, 9-high hydrophobic activated carbon dosing device, 10-coagulant dosing device, 11-flocculant dosing device, 12-water outlet pipe, 13-sludge discharge port, 14-aeration fan, 15-air stripping device. DETAILED DESCRIPTION

[0052] To make the purpose, technical scheme and advantages of the present invention clearer, the technical scheme of the present invention will be described in detail below. The following examples are convenient for better understanding of the present invention, but are not intended to limit the present invention. The experimental methods in the following examples are conventional methods unless otherwise specified.

[0053] The activated carbon used in the present invention was purchased from Shijiazhuang Hongsen Activated Carbon Co., Ltd. and was in granular form with a particle size of about 3 mm and a density of 0.52 g / cm 3At 25°C, the saturated adsorption capacity for phenol is 136.2 mg / g, the saturated adsorption capacity for methylene blue is 427.4 mg / g, and the saturated adsorption capacity for bisphenol A is 92.1 mg / g. Waste activated carbon is the activated carbon that has reached saturated adsorption on a certain raw material pharmaceutical wastewater (COD is 1000-1300 mg / g) after pretreatment.

[0054] Polyaluminium chloride (PAC) was purchased from Suzhou Blue Ocean Chemical Technology Co., Ltd. It was a light yellow powder with an Al2O3 content of 26 wt %. The pH of its 1 wt % aqueous solution was 3.0.

[0055] Cationic polyacrylamide was purchased from Jiangyin Haomei Chemical Co., Ltd. with a molecular weight of 8 million and a cationic concentration of 8.6%.

[0056] Example 1 Condition screening for activated carbon regeneration

[0057] Example 1-1

[0058] (S1) Pretreatment: The waste activated carbon material is put into 15 times the mass of clean water, ultrasonically cleaned at 300 W ultrasonic power and 120 KHz ultrasonic frequency for 10 h, filtered, and dried;

[0059] (S2) acid washing: immersing the activated carbon pretreated in step (S1) in a mixed acid aqueous solution containing 3 wt% nitric acid, 2 wt% perchloric acid, and 4 wt% sulfuric acid, at 300 W ultrasonic power and 120 KHz ultrasonic frequency, for 30 min, washing with water until the pH value of the washing liquid is 6.3-6.6; filtering, and drying;

[0060] (S3) modification treatment: the activated carbon acid-washed in step (S2) is immersed in a 0.2M copper nitrate solution for 10 hours, and then immersed in a 50% ethanol aqueous solution containing 0.1M mannitol and 0.05M triethylenetetramine for 2 hours, filtered, and dried;

[0061] (S4) High temperature activation treatment: The activated carbon modified in step (S3) is heated at 600°C for 15 h, 700°C for 20 h, and 900°C for 10 h, with a heating rate of 40°C / h; then cooled to 220°C at a cooling rate of 20°C / h, annealed for 1 h, then cooled to 160°C and annealed for 3 h, and finally naturally cooled to room temperature to obtain regenerated activated carbon.

[0062] Example 1-2

[0063] The other conditions and steps are the same as those in Example 1-1, except that step (S3) is changed to: the activated carbon acid-washed in step (S2) is immersed in a 0.3M copper acetate solution for 8 hours, then immersed in a 50% ethanol aqueous solution containing 0.2M sucrose and 0.1M ethylenediamine for 2 hours, filtered, and dried.

[0064] Examples 1-3

[0065] The other conditions and steps are the same as those in Example 1-1, except that step (S4) is changed to: the activated carbon modified in step (S3) is heated at 700°C for 20h and 900°C for 15h, with a heating rate of 40°C / h; then cooled to 200°C at a cooling rate of 20°C / h, annealed for 1h, then cooled to 160°C and annealed for 3h, and finally cooled to room temperature to obtain regenerated activated carbon.

[0066] Examples 1-4

[0067] The other conditions and steps are the same as those in Example 1-1, except that step (S4) is changed to: the activated carbon modified in step (S3) is heated at 600°C for 15h, 700°C for 20h, and 900°C for 10h, with a heating rate of 40°C / h; then cooled to 200°C at a cooling rate of 20°C / h, annealed for 3h, and finally naturally cooled to room temperature to obtain regenerated activated carbon.

[0068] Comparative Example 1-1

[0069] The other conditions and steps are the same as those in Example 1-1, except that step (S3) is changed to: the activated carbon acid-washed in step (S2) is immersed in a 50% ethanol aqueous solution containing 0.1M mannitol and 0.05M triethylenetetramine for 2h, filtered, and dried; that is, the step of immersing in copper nitrate solution is cancelled.

[0070] Comparative Example 1-2

[0071] The other conditions and steps are the same as those in Example 1-1, except that step (S3) is changed to immersing the activated carbon acid-washed in step (S2) in a 0.2M copper nitrate solution for 10 hours, and then immersing it in a 50% ethanol aqueous solution containing 0.1M mannitol for 2 hours, filtering, and drying; that is, the step of immersing in triethylenetetramine solution is cancelled.

[0072] Comparative Examples 1-3

[0073] The other conditions and steps are the same as those in Example 1-1, except that step (S3) is changed to: the activated carbon acid-washed in step (S2) is immersed in a 0.2M copper nitrate solution for 10 hours, then immersed in a 50% ethanol aqueous solution containing 0.05M triethylenetetramine for 2 hours, filtered, and dried; that is, the step of immersing in mannitol solution is cancelled.

[0074] Comparative Examples 1-4

[0075] The other conditions and steps are the same as those in Example 1-1, except that step (S4) is changed to: the activated carbon modified in step (S3) is heated at 600°C for 15h, 700°C for 20h, and 900°C for 10h, with a heating rate of 40°C / h; and then naturally cooled to room temperature. That is, the annealing step is eliminated.

[0076] The activated carbon regenerated in the above examples and comparative examples was tested for the following properties, and the results are shown in Table 1 below:

[0077] 1. Regeneration rate:

[0078] Three representative pollutants were selected for testing of the activated carbon regeneration rate, namely phenol, methylene blue and bisphenol A. The saturated adsorption capacity of activated carbon was tested at 25 °C.

[0079] 2. Recovery rate:

[0080] Table 1 Activated carbon regeneration performance test

[0081]

[0082]

[0083] It can be seen from the data in Table 1 that the activated carbon after regeneration of the present invention has restored its adsorption capacity for organic matter and even improved it. This is due to the process of impregnating the activated carbon with Cu(II) ion solution and polyol, polyamine solution modification, and the subsequent program heating and program annealing process. In addition, the activated carbon regeneration process of the present invention has a high activated carbon recovery rate, and more than 95% of the activated carbon can be recycled.

[0084] Example 2

[0085] The water volume of a certain API pharmaceutical wastewater is 1150m 3 / d, including low-concentration water from the API production workshop, high-concentration water from the API production workshop, circulating water drainage, water consumption, and domestic sewage. The main pollutants are dichloromethane, acetone, methanol, ethanol, triethylamine, ammonia, sulfuric acid, acetonitrile, ethyl acetate, dimethyl carbonate, tetrahydrofuran, tetramethylguanidine, and benzothiazole after opening. The COD of the influent is as high as 24000 mg / L. After pretreatment of wastewater grid filtration, coagulation sedimentation, electroflocculation, and biological treatment, the COD of the pretreated effluent is 1209 mg / L. The pretreated effluent is deeply treated using the adsorption fast sedimentation tank for activated carbon regeneration and recycling of the present invention, and the steps are as follows:

[0086] (T1) The pretreated organic wastewater enters the water inlet pipe 1 and passes through the mixed adsorption tank 2, the coagulation tank 3, and the flocculation tank 4 of the sewage treatment system in sequence. In the mixed adsorption tank 2, activated carbon (800g / ton) is added through the highly hydrophobic activated carbon dosing device 9, and the coagulant PAC (30g / ton·day) is added through the coagulant dosing device 10. In the coagulation tank 3, the coagulant PAC (150g / ton·day) is also added through the coagulant dosing device 10. In the flocculation tank 4, the flocculant CPAM (10g / ton·day) is added through the flocculant dosing device 11; the treated sewage is precipitated in the sedimentation tank 5, the effluent COD is less than 100mg / L, and the COD removal rate is more than 90%. It is discharged through the outlet pipe 12 to meet the discharge standards. The sludge and activated carbon at the bottom of the sedimentation tank 5 enter the cyclone separator 6 through the air stripper 15-1;

[0087] (T2) Sludge and activated carbon are separated in the cyclone separator 6. The parameters of the cyclone separator are: inlet flow rate 20m 3 / h, inlet pressure difference 0.15MPa, split ratio 0.10; when the separated activated carbon is not blocked (the density of the separated and dried activated carbon is less than 0.73g / cm 3 ), the activated carbon refluxes back to the mixed adsorption tank 2; when the separated activated carbon is blocked (the density of the separated and dried activated carbon is ≥0.73g / cm 3 ), the activated carbon enters the backwash filter tank 7 through the stripper 15-2 to perform step (T3); the sludge is discharged through the sludge discharge port 13;

[0088] (T3) The blocked activated carbon is in the backwash filter 7, the filtration rate is 10m / h, and the gas flow rate is 15L / m 2 ·s, water flow 4.5L / m 2·s, flushing time 10min; when the activated carbon after air-water backwashing still has sufficient organic pollutant adsorption capacity (the saturated adsorption capacity of activated carbon for phenol>68.1mg / L), the activated carbon is refluxed back to the mixed adsorption tank 2; when the organic pollutant adsorption capacity of the activated carbon after air-water backwashing is insufficient (the saturated adsorption capacity of activated carbon for phenol≤68.1mg / L), the activated carbon enters the activated carbon regeneration system 8 to perform step (T4);

[0089] (T4) The activated carbon is regenerated in the activated carbon regeneration system 8. The regeneration process is performed according to the operation of Example 1-1. The regenerated activated carbon is refluxed back to the mixed adsorption tank.

[0090] The air strippers 15 - 1 and 15 - 2 and the backwash filter 7 are all supplied with air by the aeration fan 14 .

[0091] The activated carbon regeneration system comprises an ultrasonic cleaner, a pickling and dipping tank, a first modification treatment tank, a second modification treatment tank, and an activated carbon regeneration furnace which are connected in sequence.

[0092] According to the above sewage treatment process, it can be operated stably for more than 18 days without adding activated carbon, and the effluent water quality is basically not affected. It shows that the adsorption fast sedimentation tank with activated carbon regeneration and recycling of the present invention can effectively treat organic wastewater with high COD, and the activated carbon is fully recycled in the whole process, reducing the operating cost of sewage treatment.

Claims

1. An adsorption fast settling tank for activated carbon regeneration and recycling, characterized in that: It includes a sewage treatment system, a cyclone separator, a backwash filter, and an activated carbon regeneration system connected in sequence; Wherein, the sewage treatment system comprises a material dosing device, and a mixed adsorption tank, a coagulation tank, a flocculation tank and a sedimentation tank connected in sequence; the material dosing device comprises an activated carbon dosing device, a coagulant dosing device and a flocculant dosing device; the activated carbon dosing device is connected to the mixed adsorption tank, the coagulant dosing device is connected to the mixed adsorption tank and the coagulation tank, and the flocculant dosing device is connected to the flocculation tank; The activated carbon regeneration system comprises an ultrasonic cleaner, an acid pickling and dipping tank, a first modification treatment tank, a second modification treatment tank, and an activated carbon regeneration furnace which are connected in sequence; The activated carbon is regenerated by a process comprising the following steps: (S1) pretreatment: adding waste activated carbon material and water into an ultrasonic cleaner, performing ultrasonic cleaning, filtering, and drying; (S2) pickling: immersing the activated carbon pretreated in step (S1) in a pickling tank under ultrasonic conditions, wherein the pickling tank contains a mixed acid solution including nitric acid, sulfuric acid and perchloric acid; filtering, washing and drying after immersion; the mixed acid includes 2-5wt% nitric acid, 1.5-3wt% perchloric acid and 3-6wt% sulfuric acid, and the immersion time is 10-30min; (S3) modification treatment: the activated carbon acid-washed in step (S2) is sequentially immersed in a first modification treatment tank and a second modification treatment tank II, wherein the solution in the first modification treatment tank contains Cu(II) ions, and the solution in the second modification treatment tank contains polyols and polyamines; after immersion, the mixture is filtered and dried; the Cu(II) ions are soluble salts of Cu(II), selected from at least one of copper nitrate, copper sulfate, copper chloride, copper acetate, and copper oxalate; the polyol is selected from at least one of sucrose, glucose, and mannitol; the polyamine includes at least one of ethylenediamine, diethylenetriamine, and triethylenetetramine; the Cu(II) ion concentration in the first modification treatment tank is 0.2-0.5M; the polyol concentration in the second modification tank is 0.1-0.2M, and the polyamine concentration is 0.05-0.1M; (S4) high temperature activation treatment: the activated carbon modified in step (S3) is subjected to programmed heating and programmed annealing in an activated carbon regeneration furnace, and then naturally cooled to room temperature; The cyclone separator, backwash filter tank and activated carbon regeneration system are provided with pipelines for returning the activated carbon to the mixed adsorption tank.

2. The adsorption fast settling tank according to claim 1, characterized in that: The coagulant is at least one of polyaluminium chloride, polyaluminium sulfate, polyferric chloride and polyferric sulfate; and the flocculant is polyacrylamide.

3. The adsorption fast settling tank according to claim 1, characterized in that: In the mixed adsorption tank, the dosage of activated carbon is 500-1000 g / ton of wastewater; the dosage of coagulant is 30-50 g / ton of wastewater; in the coagulation tank, the dosage of coagulant is 150-200 g / ton of wastewater; in the flocculation tank, the dosage of flocculant is 5-10 g / ton of wastewater.

4. The adsorption fast settling tank according to claim 1, characterized in that: The sedimentation tank is provided with a drainage pipe and a mud discharge pipe, the mud discharge pipe is connected to the cyclone separator inlet through the first gas stripper; the bottom outlet of the cyclone separator is connected to the backwash filter feed port through the second gas stripper, the first gas stripper air inlet pipe and the second gas stripper air inlet pipe are connected to the aeration fan; the backwash filter outlet is connected to the activated carbon regeneration system.

5. The adsorption fast settling tank according to claim 4, characterized in that: The backwash filter is provided with an air inlet pipe, which is connected to the aeration fan.

6. The adsorption fast settling tank according to claim 1, characterized in that: Determine whether the activated carbon after cyclone separation is blocked. If it is not blocked, it will flow back to the mixed adsorption tank. If it is blocked, the activated carbon after cyclone separation will enter the backwash filter tank, and the sludge on the surface and inside of the activated carbon will be washed away by air-water backwashing. Determine whether the activated carbon after backwashing with air and water in the backwash filter has sufficient organic adsorption capacity. If the activated carbon has sufficient organic adsorption capacity, it will be refluxed back to the mixed adsorption tank; When the activated carbon does not have sufficient organic matter adsorption capacity, it enters the activated carbon regeneration system for regeneration.

7. The adsorption fast settling tank according to claim 6, characterized in that: To determine whether the activated carbon after cyclone separation is blocked, it is necessary to test whether the density of the activated carbon separated by cyclone and dried reaches more than 140% of the fresh activated carbon; to determine whether the activated carbon after air-water backwashing in the backwash filter tank has the ability to adsorb organic matter, it is necessary to test whether the amount of organic matter adsorbed by the activated carbon after air-water backwashing reaches more than 50% of the amount of fresh activated carbon.

8. The adsorption fast settling tank according to claim 1, characterized in that: In step (S4), the programmed temperature is heated at 500°C-600°C for 15-20h, 600°C-700°C for 20-30h, and 800°C-900°C for 10-15h; the heating rate during the heating is 40-70°C / h, and the programmed annealing is annealed at 210-240°C for 1-2h, then cooled to 160-180°C for annealing for 3-5h, and the cooling rate is 20-30°C / h.

9. A method for treating organic wastewater using an adsorption fast settling tank for regeneration and recycling of activated carbon according to any one of claims 1 to 8, characterized in that: The following steps are involved: (T1) Organic wastewater passes through the mixed adsorption tank, coagulation tank, and flocculation tank of the sewage treatment system in sequence; activated carbon and coagulant are added to the mixed adsorption tank, coagulant is added to the coagulation tank, and flocculant is added to the flocculation tank; the treated wastewater is precipitated in the sedimentation tank, and the effluent meets the discharge standards. The sludge and activated carbon at the bottom of the sedimentation tank enter the cyclone separator; (T2) The sludge and activated carbon are separated in the cyclone separator. When the separated activated carbon is not blocked, the activated carbon is refluxed back to the mixed adsorption tank; When the separated activated carbon is clogged, the activated carbon enters the backwash filter tank for step (T3); (T3) The clogged activated carbon is in the backwash filter tank. When the activated carbon after the air-water backwash has sufficient organic pollutant adsorption capacity, the activated carbon is refluxed back to the mixed adsorption tank; when the activated carbon after the air-water backwash does not have sufficient organic pollutant adsorption capacity, the activated carbon enters the activated carbon regeneration system to perform step (T4); (T4) The activated carbon is regenerated in the activated carbon regeneration system, and the regenerated activated carbon is refluxed back to the mixed adsorption tank.

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