Method for removing organic pollutants in reverse osmosis concentrated solution of pharmaceutical wastewater

Abstract

The invention relates to a method for removing organic pollutants in a pharmaceutical wastewater reverse osmosis concentrated solution. The method specifically comprises the following steps: providing a pharmaceutical wastewater reverse osmosis concentrated solution, and placing the concentrated solution in an electrolytic bath; adding a PDS solution, uniformly mixing to obtain a mixed solution, adjusting the mixed solution to be acidic, and electrifying for electrolysis; and carrying out ultrasonic treatment on the electrolyzed mixed solution to remove the organic pollutants in the pharmaceutical wastewater reverse osmosis concentrated solution. According to the method for removing the organic pollutants in the reverse osmosis concentrated solution of the pharmaceutical wastewater by utilizing PDS and hypochlorous acid under electrolysis and ultrasonic conditions, efficient oxidation removal of the organic pollutants in the reverse osmosis concentrated solution is achieved, and convenience is provided for subsequent resource utilization of the reverse osmosis concentrated solution.

Description

Technical Field

[0001] The invention relates to the technical field of water pollution control, in particular to a method for removing organic pollutants in reverse osmosis concentrated liquid of pharmaceutical wastewater. Background Art

[0002] In recent years, medicine, as a major health resource and an economic resource with huge potential, has played an important role in my country's economic and social development. With the acceleration of the aging process of the population, people's demand for medical services is becoming more and more vigorous, and the scale of the pharmaceutical industry has also expanded accordingly. At the same time, the discharge of pharmaceutical wastewater is also increasing. According to its production process, pharmaceutical wastewater mainly comes from the cleaning of medicinal materials and equipment, the extraction of active ingredients, and the concentration of liquid medicine. Therefore, pharmaceutical wastewater usually contains more valuable substances, such as solvents, residual active substances, etc., and how to recycle and reuse these substances should be considered. In this context, from the perspectives of industrial development, resource utilization and ecological environmental protection, near-zero discharge of pharmaceutical wastewater is an inevitable choice for the modern pharmaceutical industry under the guidance of the idea of ​​resource-based development.

[0003] Pharmaceutical wastewater has a high content of pollutants, poor biodegradability, and large changes in water quality and quantity. It is one of the more difficult industrial wastewaters to treat. The water quality characteristics of pharmaceutical wastewater are that it contains a variety of organic matter such as sugars, glycosides, organic pigments, anthraquinones, tannins, alkaloids, cellulose, lignin, etc.; the wastewater has a high SS content, contains a lot of sediment and drug residues, and also contains a large amount of floating objects; the COD concentration varies greatly, generally between 2000-6000 mg / L, and even between 100-11000 mg / L; the chromaticity is high, about 500 times. At present, the combined process of biochemical treatment + reverse osmosis is widely used to treat pharmaceutical wastewater, and the effluent water quality can meet the limit values ​​specified in the relevant emission standards. However, the concentrate produced by reverse osmosis contains undegraded organic components and other toxic and harmful substances in the upstream water. The concentrate is still a high-salt organic wastewater that is difficult to biodegrade. The currently commonly used method for treating pharmaceutical reverse osmosis concentrate is to use the evaporation crystallization process to recycle the obtained distilled water and crystallized salt. The organic pollutants in the concentrate can easily cause scaling of the system and affect the purity of the crystallized salt product, thus affecting its resource utilization. Therefore, the pretreatment process has become a key step affecting the operation and treatment effect of the entire evaporation crystallization system.

[0004] In order to solve the above problems, currently, physicochemical methods combined with advanced oxidation technology are usually used to remove refractory organic pollutants in the concentrate. Among them, commonly used advanced oxidation processes include Fenton oxidation, ozone oxidation, photocatalysis, etc. to treat concentrated solutions. However, the commonly used advanced oxidation technology for treating membrane concentrated solutions of pharmaceutical wastewater has problems such as high cost, single oxidative active species, low treatment efficiency, and easy production of toxic and harmful by-products. For example, the Fenton method has strict requirements on the pH of the solution, and the pH of the solution must be acidic to work; ozone oxidation easily reacts with bromide ions in the concentrated solution to form bromate, which has strong carcinogenicity. At the same time, due to the high salinity in the concentrated solution, especially the high chloride ion content, the chloride ions will directly react with the generated hydroxyl radicals to form chlorine radicals with weaker oxidizing properties. Therefore, only a single active species is produced in the advanced oxidation system, and its oxidation efficiency will be greatly reduced. Therefore, providing a green and efficient method for treating reverse osmosis concentrated solutions of pharmaceutical wastewater is a problem that needs to be solved in the prior art. Summary of the invention

[0005] To solve the above technical problems, the present invention provides a method for removing organic pollutants from reverse osmosis concentrate of pharmaceutical wastewater. The present invention uses a strong oxidant (PDS, etc.) and hypochlorous acid to remove organic pollutants from reverse osmosis concentrate of pharmaceutical wastewater under electrolysis and ultrasonic conditions, aiming to achieve efficient oxidation and removal of organic pollutants in reverse osmosis concentrate, and provide convenience for its subsequent resource utilization. The present invention uses electrolytic oxidation of background chloride ions to generate hypochlorous acid under high temperature conditions, and hypochlorous acid and a strong oxidant (PDS) react under ultrasound to further produce chlorine free radicals, hydroxyl free radicals, sulfate free radicals, and singlet oxygen. The presence of multiple active components can improve the oxidation efficiency in concentrated brine. In addition, after the oxidation is completed, the active species will become chloride ions, sulfate ions, hydroxide ions, and oxygen, without toxic and harmful byproducts, and will not affect the purity of the final crystalline salt. At the same time, heating itself is a necessary step for crystallization and evaporation, so it will not significantly increase the energy input of the evaporation and crystallization process system, save energy, and can achieve high-concentration pollutant degradation, which is suitable for further treatment of reverse osmosis concentrate.

[0006] The object of the present invention is to provide a method for removing organic pollutants in reverse osmosis concentrate of pharmaceutical wastewater, comprising the following steps:

[0007] Provide reverse osmosis concentrate of pharmaceutical wastewater and place it in the electrolytic cell;

[0008] adding an oxidant solution and mixing uniformly to obtain a mixed solution, adjusting the mixed solution to be acidic, and applying electricity for electrolysis;

[0009] The mixed liquid after electrolysis is subjected to ultrasound to achieve the removal of organic pollutants in the reverse osmosis concentrate of pharmaceutical wastewater.

[0010] In some embodiments of the present invention, the TOC concentration in the reverse osmosis concentrate of pharmaceutical wastewater is 8.0 g / L to 10.0 g / L; the chloride ion concentration is 2.8 g / L to 13.2 g / L.

[0011] In some embodiments of the present invention, the oxidant in the oxidant solution is selected from peroxydisulfate; and the concentration of the oxidant solution is 5.6 g / L to 26.4 g / L.

[0012] In some embodiments of the present invention, the mass ratio of chloride ions in the pharmaceutical wastewater reverse osmosis concentrate to the oxidant solution is 1:1 to 1:3, and can be 1:1, 1:2 or 1:3, etc. When the ratio of the oxidant solution is too low, the generation of sulfate radicals and hydroxyl radicals is inhibited; when the ratio of the oxidant solution is too high, the reaction mass transfer efficiency of hypochlorous acid in the mixed solution is reduced.

[0013] In some embodiments of the present invention, the organic pollutants include vitamins, benzene, chloroform, and acetone.

[0014] In some embodiments of the present invention, the acidic pH value of the mixed solution is 4.0-6.0, and can be 4.0, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, 5.0, 5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7, 5.8, 5.9, 6.0, etc., or any interval value between any two values. A lower or higher pH value will reduce the activity of the oxidant (PDS), thereby reducing the generation of strong oxidizing active species in the solution, and ultimately reducing the in-situ decomposition efficiency of hypochlorous acid, and the removal efficiency of TOC will also decrease, thereby affecting the treatment effect.

[0015] In some embodiments of the present invention, the current density of the electrolysis is 0.5 to 3.0 A / dm 2 , for example, it can be 0.5A / dm 2 , 1.0A / dm 2 , 1.5A / dm 2 , 2.0A / dm 2 , 2.5A / dm 2 、3.0A / dm 2 The chlorine generated on the anode surface will partially adhere to the electrode surface during the precipitation process, which will hinder the electrochemical reaction to a certain extent, thereby reducing the generation efficiency of hypochlorous acid.

[0016] In some embodiments of the present invention, the reaction temperature of the electrolysis is 25-45°C, illustratively, it can be 25°C, 30°C, 35°C, 40°C, 45°C, or any interval value between any two values, and the reaction electrolysis time is 10-30min, illustratively, it can be 10min, 11min, 12min, 13min, 14min, 15min, 16min, 17min, 18min, 19min, 20min, 21min, 22min, 23min, 24min, 25min, 26min, 27min, 28min, 29min, 30min, etc., any interval value between any two values. With the increase of temperature, the adsorption and desorption efficiency of ions in the solution and the transfer efficiency of the generated products gradually increase, and appropriately increasing the temperature is conducive to the oxidation of chloride ions; at 35-45°C, with the increase of temperature, the overflow rate of chlorine is accelerated, which easily leads to the occurrence of disproportionation reaction.

[0017] In some embodiments of the present invention, the electrolysis time is 10 to 30 minutes. If the residence time is too short, the PDS activity is low and the sulfate radical generation efficiency is low; if the residence time is too long, the reaction between hypochlorous acid and PDS slows down, which is not conducive to the generation of multiple active components, the TOC removal efficiency is low, and the hypochlorous acid utilization rate is low.

[0018] In some embodiments of the present invention, the ultrasonic vibration frequency is set to 20kHz to 40kHz, and can be 20kHz, 25kHz, 30kHz, 35kHz, 40kHz, etc., or any interval value between any two values. The decomposition effect increases with increasing frequency, but the effect brought by the increase in frequency reduces the energy release in the cavitation effect, which reduces the decomposition efficiency. Therefore, an optimal ultrasonic frequency is required to achieve the best decomposition efficiency.

[0019] The principle of the invention is as follows: a large amount of chloride ions exist in the reverse osmosis concentrated liquid of pharmaceutical wastewater, and redox reactions can occur under electrolysis conditions to generate hypochlorous acid in situ. Under ultrasound and PDS addition conditions, the cavitation bubbles generated by ultrasound at a higher temperature are more stable and explode more strongly. Combined with PDS redox, hypochlorous acid is easily decomposed to generate hydroxyl free radicals, chlorine free radicals, sulfate free radicals, and singlet oxygen. Active components with strong oxidizing properties can effectively oxidize and degrade organic pollutants in the reverse osmosis concentrated liquid, thereby improving the removal efficiency of TOC in pharmaceutical wastewater and solving the problem that the reverse osmosis concentrated liquid of pharmaceutical wastewater is difficult to treat.

[0020] The above technical solution of the present invention has the following advantages compared with the prior art:

[0021] (1) The present invention is applicable to reverse osmosis concentrate of pharmaceutical wastewater from different sources and with different components, and has the advantages of simple operation, low equipment requirements and low investment cost.

[0022] (2) The electrolysis method used in the present invention can cause the chloride ions in the concentrated brine to directly undergo an oxidation reaction to produce hypochlorous acid, and the mass transfer efficiency is extremely high.

[0023] (3) Under the continuous action of ultrasound, hypochlorous acid easily generates active species such as chlorine-containing free radicals, hydroxyl free radicals, and singlet oxygen, thereby achieving efficient treatment of organic pollutants in pharmaceutical wastewater in reverse osmosis without producing toxic and harmful by-products, thus realizing resource utilization.

[0024] The method for treating pharmaceutical wastewater in a PDS-activated chloride ion reverse osmosis process is simple and easy to operate, and the used reagents are easily available and inexpensive. Moreover, heating is a necessary step in the reverse osmosis process, and the energy input of the system is not increased, thereby saving energy. DETAILED DESCRIPTION

[0025] The present invention is further described below in conjunction with specific embodiments so that those skilled in the art can better understand the present invention and implement it, but the embodiments are not intended to limit the present invention.

[0026] Embodiment 1:

[0027] This embodiment provides a method for removing organic pollutants from reverse osmosis concentrate of pharmaceutical wastewater: under electrolysis conditions, hypochlorous acid is prepared in situ using chloride ions in the reverse osmosis concentrate of pharmaceutical wastewater, and then hypochlorous acid is easily decomposed to produce strong oxidizing active species such as hydroxyl free radicals, chlorine free radicals, sulfate free radicals and singlet oxygen by adding PDS reagents and ultrasonic vibration. The specific operation is as follows:

[0028] The pharmaceutical wastewater reverse osmosis concentrate (TOC: 8.0 g / L; chloride ion: 4 g / L) was taken from the pharmaceutical factory and placed in an electrolytic cell. PDS solution (the concentration of PDS solution was 8 g / L) was added at a mass ratio of 2:1. The solution was stirred to mix evenly. The pH value of the mixed solution was set to 5.0 and the current density of the electrolytic cell was set to 1.2 A / dm 2 , the reaction temperature is 35°C, and the reaction residence time is 20min; the reaction liquid is taken out from the electrolytic cell and ultrasonicated, and the ultrasonic vibration frequency is set to 30kHz, and finally the reverse osmosis concentrated liquid after electrolysis, ultrasonication and PDS treatment is obtained, and the TOC concentration in the system is determined by TOC analyzer, and the concentration of liquid chlorine in the system is determined by DPD colorimetric method. At the same time, the residual rate of hypochlorous acid in the system is calculated (residual rate of hypochlorous acid = (hypochlorous acid concentration / chloride ion concentration in reverse osmosis concentrated liquid) × 100%), and the experimental results are shown in Table 1.

[0029] Embodiment 2:

[0030] Different from Example 1, the mass ratio of chloride ions in the PDS solution and the reverse osmosis concentrated solution in this example is 1: 1. The residual TOC rate and the residual hypochlorous acid rate after treatment are shown in Table 1 below.

[0031] Embodiment 3:

[0032] Different from Example 1, the mass ratio of chloride ions in the PDS solution and the reverse osmosis concentrated solution in this example is 3: 1. The residual TOC rate and the residual hypochlorous acid rate after treatment are shown in Table 1 below.

[0033] Embodiment 4:

[0034] Different from Example 1, the pH of the mixed solution in this example is controlled at 4.0. The residual TOC rate and the residual hypochlorous acid rate after treatment are shown in Table 1 below.

[0035] Embodiment 5:

[0036] Different from Example 1, the pH of the mixed solution in this example is controlled at 6.0. The TOC residual rate and hypochlorous acid residual rate after treatment are shown in Table 1 below.

[0037] Embodiment 6:

[0038] Different from Example 1, the current density of the electrolytic cell in this embodiment is set to 0.5A / dm 2 The TOC residual rate and hypochlorous acid residual rate after treatment are shown in Table 1 below.

[0039] Embodiment 7:

[0040] Different from Example 1, the current density of the electrolytic cell in this embodiment is set to 2.0 A / dm 2 The TOC residual rate and hypochlorous acid residual rate after treatment are shown in Table 1 below.

[0041] Embodiment 8:

[0042] Different from Example 1, the current density of the electrolytic cell in this embodiment is set to 3.0 A / dm 2 The TOC residual rate and hypochlorous acid residual rate after treatment are shown in Table 1 below.

[0043] Embodiment 9:

[0044] Different from Example 1, the reaction temperature of the electrolytic cell in this example is 25° C. The residual TOC rate and the residual hypochlorous acid rate after treatment are shown in Table 1 below.

[0045] Embodiment 10:

[0046] Different from Example 1, the reaction temperature of the electrolytic cell in this example is 45° C. The residual TOC rate and the residual hypochlorous acid rate after treatment are shown in Table 1 below.

[0047] Embodiment 11:

[0048] Different from Example 1, the electrolytic cell reaction residence time in this example is 10 minutes. The TOC residual rate and hypochlorous acid residual rate after treatment are shown in Table 1 below.

[0049] Embodiment 12:

[0050] Different from Example 1, the electrolytic cell reaction residence time in this example is 30 minutes. The TOC residual rate and hypochlorous acid residual rate after treatment are shown in Table 1 below.

[0051] Embodiment 13:

[0052] Different from Example 1, the ultrasonic vibration frequency in this example is set to 20 kHz. The TOC residual rate and hypochlorous acid residual rate after treatment are shown in Table 1 below.

[0053] Embodiment 14:

[0054] Different from Example 1, the ultrasonic vibration frequency in this example is set to 40 kHz. The TOC residual rate and hypochlorous acid residual rate after treatment are shown in Table 1 below.

[0055] Comparative Example 1:

[0056] Different from Example 1, this comparative example does not pass through an electrolytic cell. The TOC residual rate and hypochlorous acid residual rate after treatment are shown in Table 1 below.

[0057] Comparative Example 2:

[0058] Different from Example 1, PDS was not added in this comparative example. The TOC residual rate and hypochlorous acid residual rate after treatment are shown in Table 1 below.

[0059] Table 1

[0060]

[0061]

[0062] From the results of Examples 1-3 in the above table, it can be seen that the mass ratio of the PDS solution and the chloride ions in the reverse osmosis concentrate will affect the treatment effect of the method of the present invention. When the ratio of the two is 2:1, a better treatment effect is achieved. When the ratio of the PDS solution is too low, the generation of sulfate radicals and hydroxyl radicals is inhibited; when the ratio of the PDS solution is too high, the reaction mass transfer efficiency of hypochlorous acid in the mixed solution is reduced.

[0063] From the results of Example 1 and Examples 4-5 in the above table, it can be seen that the method has a better treatment effect under acidic conditions, that is, controlling the pH to be 4-6, and when the pH is 5. Lower or higher pH values ​​will reduce the activity of PDS, thereby reducing the generation of strong oxidizing active species in the solution, and ultimately reducing the in-situ decomposition efficiency of hypochlorous acid, and the removal efficiency of TOC also decreases, thereby affecting the treatment effect.

[0064] From the results of Example 1 and Examples 6-8 in the above table, it can be seen that the current density of the electrolytic cell will affect the treatment effect of the method of the present invention. As the current density increases, the mass concentration of effective chlorine increases continuously. However, when the current density increases from 1.2A / dm 2 Increased to 3.0A / dm 2 In the process, the chlorine gas generated on the anode surface will partially adhere to the electrode surface during the precipitation process, which will hinder the electrochemical reaction to a certain extent and reduce the generation efficiency of hypochlorous acid.

[0065] From the results of Example 1 and Example 9-10 in the above table, it can be seen that the reaction temperature of the mixed solution will affect the treatment effect of the method described in the present invention. When the reaction temperature is 35°C, the mass concentration and current efficiency of effective chlorine are the highest, and the operating cost is the lowest. At 25-35°C, as the temperature increases, the adsorption and desorption efficiency of ions in the solution and the transfer efficiency of the generated products gradually increase. Properly increasing the temperature is conducive to the oxidation of chloride ions; at 35-45°C, as the temperature increases, the overflow rate of chlorine is accelerated, which easily leads to the occurrence of disproportionation reaction.

[0066] From the results of Example 1 and Example 11-12 in the above table, it can be seen that the reaction residence time affects the treatment effect. When the reaction residence time is 20 minutes, the treatment effect is the best. When the residence time is too short, the PDS activity is low and the sulfate radical generation efficiency is low; when the residence time is long, the reaction of hypochlorous acid with PDS slows down, which is not conducive to the generation of multiple active components, the TOC removal efficiency is low, and the hypochlorous acid utilization rate is low.

[0067] From the results of Example 1 and Examples 13-14 in the above table, it can be seen that the ultrasonic frequency affects the treatment effect of the method of the present invention. For the decomposition of hypochlorous acid, before reaching the optimal decomposition frequency, the decomposition effect increases with the increase of frequency, but the effect brought about by the increase of frequency reduces the energy release in the cavitation effect, which reduces the decomposition efficiency. Therefore, an optimal ultrasonic frequency is required to achieve the best decomposition efficiency.

[0068] From the results of Example 1 and Comparative Example 1 in the above table, it can be seen that the lack of electrolysis will affect the treatment effect. Without electrolysis, the chloride ions in the solution are not easy to lose electrons and be oxidized into chlorine gas, and the rate at which chlorine gas further combines with water to generate hypochlorous acid is also greatly reduced.

[0069] From the results of Example 1 and Comparative Example 2 in the above table, it can be seen that not adding PDS will affect the treatment effect. Hypochlorous acid is produced by partial electrolysis, and the lack of PDS hinders the generation of sulfate radicals, hydroxyl radicals, chlorine radicals and singlet oxygen, resulting in poor TOC removal effect.

[0070] Obviously, the above embodiments are merely examples for clear explanation and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived from these are still within the protection scope of the invention.

Claims

1. A method for removing organic pollutants from reverse osmosis concentrate of pharmaceutical wastewater, characterized in that: The following steps are involved: Provide reverse osmosis concentrate of pharmaceutical wastewater and place it in the electrolytic cell; adding an oxidant solution and mixing uniformly to obtain a mixed solution, adjusting the mixed solution to be acidic, and applying electricity for electrolysis; The mixed liquid after electrolysis is subjected to ultrasound to achieve the removal of organic pollutants in the reverse osmosis concentrate of pharmaceutical wastewater.

2. The method according to claim 1, characterized in that The TOC concentration in the reverse osmosis concentrated liquid of the pharmaceutical wastewater is 8.0 g / L to 10.0 g / L; the chloride ion concentration is 2.8 g / L to 13.2 g / L.

3. The method according to claim 1, characterized in that The mass ratio of chloride ions to oxidant solution in the pharmaceutical wastewater reverse osmosis concentrated solution is 1:1 to 1:

3.

4. The method according to claim 1, characterized in that: The oxidant in the oxidant solution is selected from peroxodisulfate; The concentration of the oxidant solution is 5.6 g / L to 26.4 g / L.

5. The method according to claim 1, characterized in that The organic pollutants include vitamins, benzene, chloroform and acetone.

6. The method according to claim 1, characterized in that The acidic pH value of the mixed solution is 4.0-6.

0.

7. The method according to claim 1, characterized in that The current density of the electrolysis is 0.5 to 3.0 A / dm 2 .

8. The method according to claim 1, characterized in that The electrolysis reaction temperature is 25-45° C., and the electrolysis reaction time is 10-30 minutes.

9. The method according to claim 1, characterized in that: The electrolysis time is 10 to 30 minutes.

10. The method according to claim 1, characterized in that The ultrasonic vibration frequency is set to 20kHz to 40kHz.

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