A method for removing organic pollutants from pharmaceutical wastewater reverse osmosis concentrate

Abstract

The present application relates to a kind of methods for removing organic pollutants in pharmaceutical wastewater reverse osmosis concentrate.The method described in the present application is specifically as follows: providing pharmaceutical wastewater reverse osmosis concentrate, and placing it in electrolytic cell; adding PDS solution and mixing uniformly to obtain a mixture, adjusting the mixture to be acidic, and electrolyzing by passing electricity; ultrasonicizing the mixture at the end of electrolysis to achieve the removal of organic pollutants in pharmaceutical wastewater reverse osmosis concentrate.The present application uses PDS and hypochlorous acid to remove organic pollutants in pharmaceutical wastewater reverse osmosis concentrate under the conditions of electrolysis and ultrasonicization, aiming to achieve the efficient oxidation removal of organic pollutants in reverse osmosis concentrate, and to facilitate its subsequent resource utilization.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of water pollution control, in particular to a method for removing organic pollutants in reverse osmosis concentrated solution of pharmaceutical wastewater. BACKGROUND

[0002] In recent years, medicine as the main health resources, potential huge economic resources, plays an important role in China's economic and social development. With the acceleration of the aging process of the population, people's demand for medical services is more and more vigorous, and the scale of pharmaceutical industry is also expanding. At the same time, the discharge of pharmaceutical wastewater is also increasing. Pharmaceutical wastewater is mainly derived from the cleaning of medicinal materials and equipment, the extraction of medicinal ingredients, and the concentration of medicinal liquid according to its production process. Therefore, pharmaceutical wastewater usually contains a lot of valuable substances such as solvents and residual active substances, and the problem of how to realize the recycling of these substances should be considered. In this context, from the perspective of industrial development, resource utilization and ecological environment protection, pharmaceutical wastewater near zero emission is the inevitable choice of modern pharmaceutical industry under the guidance of resource development thought.

[0003] Pharmaceutical wastewater is one of the industrial wastewater that is difficult to treat because of its high pollutant content, poor biodegradability, and large changes in water quality and quantity. 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, and lignin; the SS content of wastewater is high, containing a lot of silt and drug residues, and also containing a large amount of floating matter; the COD concentration varies greatly, generally between 2000-6000mg / L, or even between 100-11000mg / L; the color 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 quality can meet the limit value of relevant discharge standards. However, the concentrated solution produced by reverse osmosis contains undegraded organic components and other toxic and harmful substances in the upstream water, and this concentrated solution is still a high-salt organic wastewater that is difficult to biodegrade. The common method for treating pharmaceutical reverse osmosis concentrated solution at present is to use evaporation crystallization process to resource the distilled water and crystalline salt obtained. However, the organic pollutants in the concentrated solution are easy to cause system scaling, and affect the purity of the crystalline salt product, which affects its resource utilization. Therefore, the pretreatment process has become a key step that affects the operation and treatment effect of the entire evaporation crystallization system.

[0004] To solve the above problems, the current common method is to use physical and chemical method combined with advanced oxidation technology to remove the refractory organic pollutants in the concentrated solution. The commonly used advanced oxidation process includes Fenton oxidation method, ozone oxidation method, photocatalytic method and the like to treat the concentrated solution. However, the current commonly used advanced oxidation technology has problems such as high cost, single oxidation active species, low treatment efficiency, easy to produce toxic and harmful by-products and the like when treating the membrane concentrated solution of pharmaceutical wastewater. For example, the Fenton method has strict requirements on the pH of the solution, and the solution must be acidic to function; the ozone oxidation is easy to react with bromide ions in the concentrated solution to generate bromate, which has strong carcinogenicity. At the same time, due to the high salinity of 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 weak oxidation. Therefore, the oxidation efficiency will be greatly reduced in the advanced oxidation system with only single active species. Therefore, it is an urgent problem to be solved in the prior art to provide a green and efficient method for treating the reverse osmosis concentrated solution of pharmaceutical wastewater. SUMMARY

[0005] To solve the above technical problems, the present application provides a method for removing organic pollutants in reverse osmosis concentrated solution of pharmaceutical wastewater. The present application uses strong oxidants (PDS, etc.) and hypochlorous acid to remove organic pollutants in reverse osmosis concentrated solution of pharmaceutical wastewater under electrolysis and ultrasonic conditions, aiming to realize efficient oxidation removal of organic pollutants in reverse osmosis concentrated solution, and to provide convenience for subsequent resource utilization. In the present application, under high temperature conditions, the background chloride ions are electrolyzed to generate hypochlorous acid, and the hypochlorous acid and strong oxidant (PDS) are reacted under ultrasonic to further generate chlorine radicals, hydroxyl radicals, sulfate radicals and singlet oxygen. The existence of multiple active components can improve the oxidation efficiency in concentrated brine. In addition, after oxidation, the active species will become chloride ions, sulfate ions, hydroxide ions and oxygen, without the generation of toxic and harmful by-products, and without affecting 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, realize high-concentration pollutant degradation, and is suitable for further treatment of reverse osmosis concentrated solution.

[0006] The present application aims to provide a method for removing organic pollutants in reverse osmosis concentrated solution of pharmaceutical wastewater, comprising the following steps:

[0007] Providing reverse osmosis concentrated solution of pharmaceutical wastewater and placing it in an electrolytic cell;

[0008] Adding an oxidant solution and mixing uniformly to obtain a mixed solution, adjusting the mixed solution to be acidic, and electrolyzing by passing electricity;

[0009] Ultrasonic treatment of the mixed solution after electrolysis to remove organic pollutants in the reverse osmosis concentrated solution of pharmaceutical wastewater.

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

[0011] In some embodiments of the present application, the oxidizing agent in the oxidizing agent solution is selected from peroxodisulfate; and the concentration of the oxidizing agent solution is 5.6-26.4 g / L.

[0012] In some embodiments of the present application, the mass ratio of the pharmaceutical wastewater reverse osmosis concentrate to the oxidizing agent solution is 1:1-1:3, for example, 1:1, 1:2 or 1:3, etc. When the proportion of the oxidizing agent solution is too low, the generation of sulfate radicals and hydroxyl radicals is inhibited; and when the proportion of the oxidizing agent 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 application, the organic pollutants include vitamins, benzene, chloroform, acetone.

[0014] In some embodiments of the present application, the acidic pH value of the mixed solution is 4.0-6.0, for example, 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 numerical values. Lower or higher pH value will reduce the activity of the oxidizing agent (PDS), thereby resulting in a decrease in the generation of strong oxidizing active species in the solution, ultimately leading to a decrease in the in-situ decomposition efficiency of hypochlorous acid, and a decrease in the removal efficiency of TOC, thereby affecting the treatment effect.

[0015] In some embodiments of the present application, the current density of the electrolysis is 0.5-3.0 A / dm 2 , for example, 0.5 A / dm 2 , 1.0 A / dm 2 , 1.5 A / dm 2 , 2.0 A / dm 2 , 2.5 A / dm 2 , 3.0 A / dm 2 , etc., or any interval value between any two numerical values. The chlorine gas generated on the anode surface will be partially attached to the electrode surface during the evolution process, thereby to some extent hindering the electrochemical reaction, and thereby reducing the generation efficiency of hypochlorous acid.

[0016] In some embodiments of the present application, the reaction temperature of the electrolysis is 25-45 DEG C, and exemplarily can be 25 DEG C, 30 DEG C, 35 DEG C, 40 DEG C, 45 DEG C, or any interval value between any two numerical values. The reaction time of the electrolysis is 10-30 min, and exemplarily can be 10 min, 11 min, 12 min, 13 min, 14 min, 15 min, 16 min, 17 min, 18 min, 19 min, 20 min, 21 min, 22 min, 23 min, 24 min, 25 min, 26 min, 27 min, 28 min, 29 min, 30 min, etc., or any interval value between any two numerical values. With the increase of the temperature, the adsorption and desorption efficiency of ions in the solution and the transfer efficiency of the generated product gradually increase, and the appropriate increase of the temperature helps the oxidation of the chloride ions; when the temperature is 35-45 DEG C, the increase of the temperature accelerates the overflow rate of the chlorine gas, which easily leads to the disproportionation reaction.

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

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

[0019] The principle of the present application is as follows: a large amount of chloride ions exist in the reverse osmosis concentrated solution of the pharmaceutical wastewater, which can generate hypochloric acid in situ under the electrolysis condition, under the conditions of the ultrasonic wave and the addition of PDS, the cavitation bubble generated by the ultrasonic wave at a higher temperature has a more stable property and a more intense explosion, combined with the oxidation and reduction of PDS, the hypochloric acid is easily decomposed to generate hydroxyl radicals, chlorine radicals, sulfate radicals and singlet oxygen, which are active components with strong oxidation, can effectively oxidize and degrade the organic pollutants in the reverse osmosis concentrated solution, improve the TOC removal efficiency in the pharmaceutical wastewater, and solve the problem of the difficult treatment of the reverse osmosis concentrated solution of the pharmaceutical wastewater.

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

[0021] (1) The present application is suitable for pharmaceutical wastewater reverse osmosis concentrate of different sources and different components, simple operation, low equipment requirement and low investment cost.

[0022] (2) The electrolysis method selected can make the chloride ions in the concentrated salt water directly undergo oxidation reaction to produce hypochlorous acid, and the mass transfer efficiency is extremely high.

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

[0024] The method for treating pharmaceutical wastewater in the process of PDS activated chloride ion reverse osmosis is simple and easy to operate, the reagents used are easy to obtain and low in price, and heating is an essential step in the reverse osmosis process, without increasing the energy input of the system, saving energy. DETAILED DESCRIPTION

[0025] The present application will be further described below in conjunction with specific examples, so that those skilled in the art can better understand the present application and implement it, but the examples are not limiting to the present application.

[0026] Example 1

[0027] The present example provides a method for removing organic pollutants in pharmaceutical wastewater reverse osmosis concentrate: under electrolysis conditions, hypochlorous acid is prepared in situ by using chloride ions in pharmaceutical wastewater reverse osmosis concentrate, and then PDS reagent is added and ultrasonic vibration is performed, so that hypochlorous acid is easy to decompose to produce strong oxidative active species such as hydroxyl radicals, chlorine radicals, sulfate radicals and singlet oxygen. The specific operation is as follows:

[0028] Pharmaceutical wastewater reverse osmosis concentrate (TOC: 8.0 g / L; chloride ion: 4 g / L) is taken from a pharmaceutical factory, placed in an electrolytic cell, and PDS solution (the concentration of PDS solution is 8 g / L) is added according to a mass ratio of 2:1, the solution is stirred to mix uniformly, the pH value of the mixed solution is set to 5.0, the current density of the electrolytic cell is set to 1.2 A / dm 2 , the reaction temperature is 35℃, and the reaction residence time is 20 min; the reaction liquid is taken out from the electrolytic cell and ultrasonic vibration is performed, the ultrasonic vibration frequency is set to 30 kHz, and finally the reverse osmosis concentrate treated by electrolysis, ultrasonic vibration and PDS is obtained, the TOC concentration in the system is determined by using a TOC analyzer, and the concentration of liquid chlorine in the system is determined by using DPD colorimetry. At the same time, the residual rate of hypochlorous acid in the system is calculated (residual rate of hypochlorous acid = (concentration of hypochlorous acid / concentration of chloride ions in reverse osmosis concentrate) x 100%), and the experimental results are shown in Table 1.

[0029] Example 2

[0030] The difference between this example and Example 1 is that the mass ratio of PDS solution and reverse osmosis concentrated liquid chlorine ion is 1:1. The residual rate of TOC and hypochlorous acid after treatment is shown in Table 1 below.

[0031] Example 3:

[0032] The difference between this example and Example 1 is that the mass ratio of PDS solution and reverse osmosis concentrated liquid chlorine ion is 3:1. The residual rate of TOC and hypochlorous acid after treatment is shown in Table 1 below.

[0033] Example 4:

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

[0035] Example 5:

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

[0037] Example 6:

[0038] The difference between this example and Example 1 is that the electrolytic cell current density is set to 0.5 A / dm 2 . The residual rate of TOC and hypochlorous acid after treatment is shown in Table 1 below.

[0039] Example 7:

[0040] The difference between this example and Example 1 is that the electrolytic cell current density is set to 2.0 A / dm 2 . The residual rate of TOC and hypochlorous acid after treatment is shown in Table 1 below.

[0041] Example 8:

[0042] The difference between this example and Example 1 is that the electrolytic cell current density is set to 3.0 A / dm 2 . The residual rate of TOC and hypochlorous acid after treatment is shown in Table 1 below.

[0043] Example 9:

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

[0045] Example 10:

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

[0047] Example 11

[0048] The difference between this example and Example 1 is that the electrolytic cell reaction residence time is 10 min. The TOC residual rate and the hypochlorous acid residual rate after treatment are shown in Table 1 below.

[0049] Example 12

[0050] The difference between this example and Example 1 is that the electrolytic cell reaction residence time is 30 min. The TOC residual rate and the hypochlorous acid residual rate after treatment are shown in Table 1 below.

[0051] Example 13

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

[0053] Example 14

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

[0055] Comparative Example 1

[0056] The difference between this example and Example 1 is that the electrolytic cell is not used, and the TOC residual rate and the hypochlorous acid residual rate after treatment are shown in Table 1 below.

[0057] Comparative Example 2

[0058] The difference between this example and Example 1 is that PDS is not added, and the TOC residual rate and the 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 PDS solution and reverse osmosis concentrated chlorine ions will affect the treatment effect of the method described in the present application. When the ratio of the two is 2:1, the treatment effect is better. When the ratio of PDS solution is too low, the generation of sulfate free radicals and hydroxyl radicals is inhibited; when the ratio of 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 is under acidic conditions, i.e. the pH is controlled at 4-6, and the treatment effect is better when the pH is 5. Lower or higher pH values will reduce the activity of PDS, resulting in a decrease in the generation of strong oxidizing active species in the solution, ultimately leading to a decrease in the in-situ decomposition efficiency of hypochlorous acid and a decrease in the removal efficiency of TOC, 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 affects the treatment effect of the method. As the current density increases, the mass concentration of available chlorine increases, but when the current density increases from 1.2 A / dm 2 to 3.0 A / dm 2 , the chlorine gas generated on the anode surface will partially adhere to the electrode surface during evolution, thereby hindering the electrochemical reaction to some extent and reducing the generation efficiency of hypochlorous acid.

[0065] From the results of Example 1 and Examples 9-10 in the above table, it can be seen that the reaction temperature of the mixed solution affects the treatment effect of the method. When the reaction temperature is 35°C, the mass concentration of available chlorine and the current efficiency are the highest, and the operating cost is the lowest. When the temperature is 25-35°C, as the temperature increases, the adsorption and desorption efficiency of ions in the solution and the transfer efficiency of generated products gradually increase, and appropriate temperature increase helps to oxidize chloride ions; when the temperature is 35-45°C, as the temperature increases, the overflow rate of chlorine gas increases, which easily leads to disproportionation reaction.

[0066] From the results of Example 1 and Examples 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 min, the treatment effect is the best. If the residence time is too short, the activity of PDS is low, and the generation efficiency of sulfate radicals is low; if the residence time is 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 utilization rate of hypochlorous acid 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. For the decomposition of hypochlorous acid, before reaching the optimal decomposition frequency, the decomposition effect increases with increasing frequency, but the effect of increasing frequency reduces the energy release in cavitation, which reduces the decomposition efficiency. Therefore, a best ultrasonic frequency is needed 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 affects the treatment effect. Without electrolysis, chloride ions in the solution are not easy to lose electrons to be oxidized to chlorine gas, and the rate of further combination of chlorine gas 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 the absence of PDS affects the treatment effect. The partial electrolysis generates hypochlorous acid, and the lack of PDS causes the generation of sulfate radicals, hydroxyl radicals, chlorine radicals and singlet oxygen to be blocked, thereby resulting in poor TOC removal effect.

[0070] Obviously, the above examples are merely illustrative examples for the sake of clarity, and are not limiting on the embodiments. Based on the above description, other different forms of changes or variations can also be made by those of ordinary skill in the art. Here, it is not necessary and also impossible to exhaust all the embodiments. The obvious changes or variations derived therefrom are still within the protection scope of the present application.

Claims

1. A method for removing organic pollutants from reverse osmosis concentrate of pharmaceutical wastewater, characterized in that, Includes the following steps: Provide reverse osmosis concentrate of pharmaceutical wastewater and place it in an electrolytic cell; Add an oxidizing agent solution and mix thoroughly to obtain a mixture. Adjust the mixture to acidity and then electrolyze it. The mixture after electrolysis is subjected to ultrasound to remove organic pollutants from the reverse osmosis concentrate of pharmaceutical wastewater. The oxidant in the oxidant solution is selected from persulfate; The concentration of the oxidant solution is 5.6 g / L to 26.4 g / L; The acidic pH value of the mixture is 4.0~6.0; The mass ratio of chloride ions to oxidant solution in the reverse osmosis concentrate of the pharmaceutical wastewater is 1:1 to 1:

3.

2. The method according to claim 1, characterized in that, The TOC concentration in the reverse osmosis concentrate 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 current density for electrolysis is 0.5~3.0 A / dm³. 2 .

4. The method according to claim 1, characterized in that, The electrolysis reaction temperature is 25~45℃, and the electrolysis time is 10~30min.

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

6. The method according to claim 1, characterized in that, The vibration frequency of the ultrasound is set to 20kHz~40kHz.

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