Thiocyanate radical removal method for enhancing electron transfer and transfer

Abstract

The invention discloses a thiocyanate radical removal method for enhancing electron transfer and transfer, and belongs to the field of industrial wastewater treatment. According to the method disclosed by the invention, the wastewater is pre-regulated, and then the selective regulation reagent is added for regulation treatment, so that the removal rate of more than 95% of thiocyanate ions in the wastewater is realized. The method disclosed by the invention is stable in reaction process, short in time consumption, easy in process condition regulation and control, suitable for treatment of various waste water containing thiocyanate radicals, and capable of effectively solving the problem that the pretreatment process is interfered by high-concentration thiocyanate radicals, organic matters and carnallite ions in actual industrial waste water; good industrial application prospects and remarkable economic and social values are realized.

Description

Technical Field

[0001] The invention belongs to the field of industrial wastewater treatment, and in particular relates to a thiocyanate removal method for strengthening electron transfer and transmission. Background Art

[0002] Thiocyanate is widely used in the pharmaceutical, textile, coking, metallurgical, printing and dyeing industries. These industries produce wastewater containing high concentrations of thiocyanate in the production process, and generally have water quality characteristics such as high concentrations of organic matter and complex salt ions. Thiocyanate is biologically toxic and will inhibit the biochemical treatment process of wastewater to a certain extent, resulting in poor treatment effects of traditional biochemical treatment for high-concentration thiocyanate wastewater. This type of wastewater has great environmental hazards, high difficulty in treatment, and high cost. Therefore, efficient and selective removal of thiocyanate in advance has become the key to efficient and low-cost biochemical treatment of this type of wastewater.

[0003] At present, there are mainly coagulation, ion exchange, adsorption, biodegradation, oxidation and other methods for the treatment of thiocyanate in industrial wastewater. Coagulation, ion exchange, adsorption and other methods have problems such as poor selectivity, low treatment efficiency and high treatment cost; biodegradation has problems such as slow reaction rate and sludge activity is easily affected by complex water quality. Chemical oxidation based on electron transfer and transfer can effectively destroy thiocyanate in water and convert it into harmless substances. It has the advantages of high reaction efficiency and simple reaction conditions. However, it is difficult for traditional oxidation methods to take into account reaction selectivity, pollutant removal effect and economic cost at the same time. On this basis, it is necessary to develop a treatment process for selectively removing thiocyanate from industrial wastewater by strengthening electron transfer and transfer, so as to achieve efficient and low-cost removal of thiocyanate.

[0004] In the prior art, a Chinese invention patent with publication number CN104045191A discloses a method for treating cyanide-containing wastewater. In this method, when treating cyanide-containing wastewater, the easily treatable cyanide is first removed by the Inco method, and the treated wastewater is coagulated and precipitated by adding a coagulant to remove heavy metal ions in the wastewater. Then, under the synergistic effect of ultraviolet light and ozone, the difficult-to-treat cyanide, thiocyanate and other organic pollutants remaining in the wastewater are removed. A Chinese invention patent with publication number CN104944695A discloses an emergency treatment method for accidental wastewater from a gold mine tailings pond. The method uses a grit chamber to remove sand and gravel from the accidental wastewater, a regulating tank to even out the water quality and quantity, and an intermittent vertical flow artificial wetland to first remove most of the suspended solids and part of the cyanide and thiocyanate. The treated accidental wastewater passes through vertical flow artificial wetlands and horizontal flow artificial wetlands to remove various pollutants such as cyanide, thiocyanate and heavy metals from the wastewater through dilution, filler adsorption, biological oxidation, plant absorption and other means. Finally, the treated wastewater is post-treated by the alkaline chlorination method, and the treated wastewater meets the first-level standard limit in the "Comprehensive Sewage Discharge Standard". Summary of the invention

[0005] The object of the present invention is to provide a method for removing thiocyanate radical by strengthening electron transfer and transmission.

[0006] The technical solution adopted by the present invention to achieve the above-mentioned purpose is: A method for removing thiocyanate by strengthening electron transfer and transmission comprises: pre-regulating wastewater, then adding a selective regulating agent for regulating treatment to obtain treated water; the selective regulating agent comprises an oxidant or an oxidative coupling system; In the pre-control, the pH of the wastewater is adjusted to 3-11, the conductivity of the wastewater is adjusted to 1-2 S / m, the flow Reynolds number of the wastewater is adjusted to >8000, and the dynamic viscosity of the wastewater is adjusted to 1-1000 mPa·s.

[0007] The present invention constructs an enhanced electron transfer and transfer flow field by changing the external conditions such as reaction temperature, pH, stirring, etc., reduces the competition of complex matrix in wastewater and the consumption caused by the self-quenching of the reaction reagent itself, and realizes the targeted reduction of thiocyanate in wastewater. At the same time, it promotes the release of free radicals by oxidants such as hydrogen peroxide, converts thiocyanate into substances such as sulfate ions and ammonium ions, thereby efficiently removing thiocyanate within a certain period of time and reducing the use of other agents.

[0008] Preferably, the oxidant comprises at least one of hydrogen peroxide, calcium peroxide, perchlorate, ferrate, persulfate, percarbonate, peracetic acid and vanadium trichloride.

[0009] Preferably, the oxidative coupling system comprises at least one of a Fenton reagent, a metal oxide-activated peroxide coupling system, an ultrasound-peroxide coupling system, and a bicarbonate-activated peroxide coupling system.

[0010] Preferably, the selective control reagent comprises a quaternary ammonium salt ligand, which is obtained by reacting N-(3-hydroxypyridine-2-yl) acetamide and halogenated hydrocarbon. Halogenated hydrocarbon at least comprises bromo-diethylene glycol-carboxylic acid. The nitrogen atom of N-(3-hydroxypyridine-2-yl) acetamide and the oxygen atom on the phenolic hydroxyl group can be combined with the carbon atom connected with the bromine atom in bromo-diethylene glycol-carboxylic acid to obtain a quaternary ammonium salt ligand. In the quaternary ammonium salt ligand, pyridine ring group, acetamide group and polyethylene glycol chain form a spatial configuration of multiple groups, thereby interacting with thiocyanate radical through the structure and spatial structure between the groups, improving the processing of thiocyanate radical in wastewater by the selective control reagent. Meanwhile, the quaternary ammonium salt ligand can reduce the influence of COD on the selective control reagent, and further improve the removal rate of thiocyanate radical under the synergistic effect of strengthening electron transfer and transfer flow field and promoting the release of free radicals.

[0011] Preferably, stirring is used in the regulation process; or, the temperature is adjusted to 10-100°C in the regulation process.

[0012] Preferably, stirring is used in the regulation process, and the stirring speed is 50-400 rpm.

[0013] Preferably, the oxidant and thiocyanate are used in a molar ratio of 0.3-10:1.

[0014] Preferably, the oxidative coupling system contains an oxidant, and the amount of the oxidative coupling system is calculated based on the oxidant, and the oxidant and thiocyanate are used in a molar ratio of 0.3-10:1.

[0015] Preferably, the metal oxide-activated peroxide coupling system comprises bismuth oxyiodide coupled to hydrogen peroxide or ferric oxychloride coupled to calcium peroxide.

[0016] Preferably, the wastewater comprises at least one of coking wastewater, electroplating wastewater, metal processing wastewater and pharmaceutical wastewater.

[0017] The invention discloses a thiocyanate removal method for strengthening electron transfer and transmission, which comprises the synthesis of a solid intermediate, the synthesis of a quaternary ammonium salt ligand, pre-regulation of wastewater, addition of a selective regulating agent and regulation treatment, and specifically comprises the following steps: Synthesis of solid intermediate: Add N-(3-hydroxypyridin-2-yl)acetamide and anhydrous potassium carbonate to acetonitrile, react at 80-100 °C for 1-3 h, then add halogenated hydrocarbon, continue to react for 8-18 h, then filter, rotary evaporate, use methanol and dichloromethane as eluents, separate by column chromatography, and rotary evaporate to obtain a solid intermediate.

[0018] Synthesis of quaternary ammonium salt ligand: add the solid intermediate to anhydrous ethanol, then add halogenated hydrocarbon, heat and reflux for 12-48 h, filter out the precipitated crystals, and dry at 50-80 °C to obtain the quaternary ammonium salt ligand.

[0019] Pre-control of wastewater: adjust the pH of wastewater to 3-11, adjust the conductivity of wastewater to 1-2 S / m, adjust the flow Reynolds number of wastewater to >8000, and adjust the dynamic viscosity of wastewater to 1-1000 mPa·s.

[0020] Dosing of selective regulating reagents and regulating treatment: Add selective regulating reagents to regulate the wastewater.

[0021] Preferably, in the synthesis of the solid intermediate, the ratio of N-(3-hydroxypyridin-2-yl)acetamide to acetonitrile is 12-18 mmol:15-45 mL, and the ratio of anhydrous potassium carbonate to acetonitrile is 30-38 mmol:15-45 mL.

[0022] Preferably, in the synthesis of the solid intermediate, the halogenated hydrocarbon at least includes bromo-diethylene glycol-carboxylic acid, and the amount ratio of bromo-diethylene glycol-carboxylic acid to acetonitrile is 15-20 mmol: 15-45 mL.

[0023] Preferably, in the synthesis of the solid intermediate, the volume ratio of methanol to dichloromethane is 3-5:50-80.

[0024] Preferably, in the synthesis of the quaternary ammonium salt ligand, the halogenated hydrocarbon includes at least brominated-diethylene glycol-carboxylic acid, the amount ratio of brominated-diethylene glycol-carboxylic acid to anhydrous ethanol is 25-75 mmol: 30-50 mL, and the synthesized quaternary ammonium salt ligand is named alcohol acid quaternary ammonium salt ligand.

[0025] Preferably, in the synthesis of the quaternary ammonium salt ligand, the usage ratio of the solid intermediate and anhydrous ethanol is 35-50 mmol:30-50 mL.

[0026] Preferably, in the pre-conditioning of wastewater, the wastewater comprises at least one of coking wastewater, electroplating wastewater, metal processing wastewater and pharmaceutical wastewater.

[0027] Preferably, in the pre-regulation of wastewater, adjusting the pH of the wastewater includes using sodium hydroxide and hydrochloric acid with a concentration of 0.1-1 mol / L, or waste acid water or waste alkaline water generated in other sections of the production enterprise. Adjusting the conductivity of the wastewater includes adding at least one ion exchanger such as zeolite, sulfonated coal and ion exchange resin. Adjusting the flow Reynolds number of the wastewater includes at least one of external stirring, ultrasound and oscillation. Adjusting the dynamic viscosity of the wastewater includes at least one of adjusting the wastewater temperature, dilution ratio and external stirring, the wastewater temperature is 30-70 ° C, and the dilution ratio is 0-10.

[0028] Preferably, in the addition and regulation process of the selective regulation reagent, the selective regulation reagent includes an oxidant or an oxidative coupling system.

[0029] Preferably, in the addition and regulation treatment of the selective regulation reagent, the oxidant includes at least one of hydrogen peroxide, calcium peroxide, perchlorate, ferrate, persulfate, percarbonate, peracetic acid and vanadium trichloride, and the molar ratio of the oxidant to the thiocyanate in the wastewater is 1-10:1, more preferably 3-5.5:1.

[0030] Preferably, in the addition and regulation process of the selective regulation reagent, the oxidative coupling system includes at least one of a Fenton reagent, a metal oxide-activated peroxide coupling system, an ultrasound-peroxide coupling system, and a bicarbonate-activated peroxide coupling system.

[0031] Preferably, in the addition and regulation of the selective regulating agent, the oxidative coupling system contains an oxidant, the amount of the oxidative coupling system is calculated based on the oxidant, and the oxidant and thiocyanate are used in a molar ratio of 0.3-10:1.

[0032] Preferably, in the addition and regulation process of the selective regulation reagent, the metal oxide-activated peroxide coupling system includes bismuth oxyiodide coupled with hydrogen peroxide or ferric oxychloride coupled with calcium peroxide.

[0033] More preferably, in the addition and regulation treatment of the selective regulation reagent, the selective regulation reagent includes a quaternary ammonium salt ligand, and the molar ratio of the quaternary ammonium salt ligand to the thiocyanate in the wastewater is 0.1-5:1.

[0034] Preferably, in the addition of the selective regulating agent and the regulating treatment, the regulating treatment includes mechanical stirring or magnetic stirring, the stirring speed in the regulating treatment is 50-400 rpm, more preferably 200-400 rpm; the stirring time in the regulating treatment is 5-480 min, more preferably 10-360 min; the temperature in the regulating treatment is 10-100 ° C, more preferably 30-70 ° C.

[0035] More preferably, in the synthesis of the solid intermediate, the halogenated hydrocarbon further includes 4-(bromomethyl)pyrimidine, and the usage ratio of 4-(bromomethyl)pyrimidine to acetonitrile is 15-20 mmol: 15-45 mL.

[0036] More preferably, in the synthesis of the quaternary ammonium salt ligand, the halogenated hydrocarbon also includes 4-(bromomethyl)pyrimidine, and the dosage ratio of 4-(bromomethyl)pyrimidine to anhydrous ethanol is 25-75 mmol: 30-50 mL. The synthesized quaternary ammonium salt ligand is named pyridyl quaternary ammonium salt ligand.

[0037] More preferably, in the addition and regulation of the selective regulating agent, the quaternary ammonium salt ligand includes an alcohol acid quaternary ammonium salt ligand and a pyridyl quaternary ammonium salt ligand, and the molar ratio of the alcohol acid quaternary ammonium salt ligand to the pyridyl quaternary ammonium salt ligand is 1-3: 1. The pyrimidine ring group introduced on 4-(bromomethyl)pyrimidine can react with N-(3-hydroxypyridin-2-yl)acetamide to form a quaternary ammonium salt ligand with a new structure, and in the presence of other quaternary ammonium salt ligands, under the joint action of the alcohol acid quaternary ammonium salt ligand and the pyridyl quaternary ammonium salt ligand, it has a better binding ability to the thiocyanate in the wastewater, improves the removal effect of the selective regulating agent on the thiocyanate, and at the same time, under the action of the alcohol acid quaternary ammonium salt ligand and the pyridyl quaternary ammonium salt ligand, avoids the influence of COD on the selective regulating agent, and then can achieve efficient removal of thiocyanate.

[0038] The present invention regulates the wastewater quality characteristics, and introduces a quaternary ammonium salt ligand when adding a selective regulating agent, significantly improves the binding ability and selectivity with thiocyanate in the wastewater through intermolecular interaction, prevents COD interference, and synergizes with strengthening electron transfer and transfer flow field and promoting the release of free radicals to accelerate the removal of thiocyanate, thereby having the following beneficial effects: high reaction efficiency, simple reaction conditions, strong selectivity for thiocyanate, and efficient destruction of thiocyanate in water. Therefore, the object of the present invention is to provide a thiocyanate removal method that strengthens electron transfer and transfer. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 The process flow chart of the thiocyanate removal method is shown in FIG.

[0040] Figure 2 This is the result graph of the calculation formula for thiocyanate concentration and absorbance.

[0041] Figure 3 This is a graph showing the results of measuring the thiocyanate removal rate in Example 1.

[0042] Figure 4 Schematic diagram of the principle of thiocyanate removal method. DETAILED DESCRIPTION

[0043] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0044] The following first describes the concepts involved in the present application in conjunction with the accompanying drawings. It should be noted that the following description of each concept is only to make the content of the present application easier to understand, and does not limit the scope of protection of the present application; at the same time, the embodiments and features in the embodiments of the present application can be combined with each other in the absence of conflict. The present application will be described in detail with reference to the accompanying drawings and in conjunction with the embodiments.

[0045] The process flow chart of the thiocyanate removal method for enhancing electron transfer and transfer of the present invention is as follows: Figure 1 As shown, firstly, the water quality characteristics of the wastewater are regulated, and selective regulating reagents are added to construct an electron transfer and transfer flow field to achieve efficient and selective removal of thiocyanate ions in the wastewater, thereby meeting the requirements of biological and biochemical treatment of influent thiocyanate ions.

[0046] Example 1: A method for removing thiocyanate by enhancing electron transfer and transport Thiocyanate wastewater is produced in the production process of a pharmaceutical industry. After inspection, the thiocyanate concentration is about 1800 mg / L, COD is about 66000 mg / L, sulfate ion is about 4000 mg / L, and suspended solids are 1000 mg / L. First, 10 L of wastewater is pre-regulated, the pH of the wastewater is adjusted to 5, the conductivity is 1.2 S / m, the flow Reynolds number is 8500 and the dynamic viscosity is 600 mPa·s to obtain treated water. Then the treated water is loaded into the reactor, hydrogen peroxide is added, and the reactor is sealed. Finally, the control treatment is carried out, the speed in the reactor is adjusted to 300 rpm, the temperature is 65 ℃, and stirring is carried out under this condition for 120 min. The pH of the wastewater is adjusted by using hydrochloric acid with a concentration of 1 mol / L, the conductivity of the wastewater is adjusted by adding zeolite, and the flow Reynolds number and dynamic viscosity of the wastewater are adjusted by external stirring. The molar ratio of hydrogen peroxide to thiocyanate in the wastewater is 4.5:1.

[0047] During the reaction process, as shown in Table 1, 5 mL of samples were taken at different reaction time intervals. Under strong acidic conditions, thiocyanate combined with trivalent iron to form a red complex and the change in thiocyanate concentration was measured by ultraviolet spectrophotometer, and the residual rate and removal rate of thiocyanate were calculated. The formula for calculating the residual rate of thiocyanate is: R=C1 / C0×100%, where C0 is the initial thiocyanate concentration in the wastewater, and C1 is the real-time concentration of thiocyanate measured at a specific sampling time, in mg / L. The formula for calculating the removal rate of thiocyanate is: r=(C0-C t )×100%, where C0 is the initial thiocyanate concentration in the wastewater, C t The concentration of thiocyanate in pharmaceutical wastewater after treatment for a specific period of time, in mg / L. The relationship between thiocyanate concentration and absorbance is shown in Table 1. The calculation formula for thiocyanate concentration and absorbance is as follows: Figure 2 The sampling time interval, thiocyanate concentration and removal rate are shown in Table 2, and the residual rate of thiocyanate is shown in Table 3. Figure 3 shown.

[0048] Table 1 Results of determination of the relationship between thiocyanate concentration and absorbance

[0049] Table 2 Sampling intervals and thiocyanate concentrations in pharmaceutical wastewater

[0050] It can be seen from Table 2 that with the increase of treatment time, the concentration of thiocyanate in pharmaceutical wastewater decreased from 1834 mg / L to 68 mg / L. Figure 2It can be seen that with the increase of treatment time, the residual rate of thiocyanate in the wastewater of the pharmaceutical industry gradually decreased, and finally reached 4% within 90 minutes, at which time the thiocyanate removal rate reached 96%. This treatment changed the external conditions such as reaction temperature, pH, stirring, etc., constructed an enhanced electron transfer and transfer flow field, promoted hydrogen peroxide to release hydroxyl radicals, and converted thiocyanate into sulfate ions, ammonium ions and other substances, thus achieving efficient removal of thiocyanate within a certain period of time. The specific principle diagram is shown in Figure 4 .

[0051] Example 2: A method for removing thiocyanate by enhancing electron transfer and transport Antibiotic waste mother liquor containing thiocyanate is produced in the production process of a pharmaceutical industry. After inspection, the concentration of thiocyanate is about 6000 mg / L, COD is about 50000 mg / L, sulfate ion is about 150 mg / L, and chloride ion is about 13000 mg / L. First, 10L of wastewater is pre-regulated, the pH of the wastewater is 6.0 and no regulation is performed. The conductivity of the wastewater is adjusted to 1.2 S / m, the flow Reynolds number is 8500, and the dynamic viscosity is 600 mPa·s to obtain treated water. Then the treated water is introduced into the ultrasonic treatment device, the ultrasonic power is adjusted to 400 W, and calcium peroxide is added. The temperature is adjusted to 40 ℃ and stirred for 60 min under this condition. The conductivity of the wastewater is adjusted by adding zeolite, and the flow Reynolds number and dynamic viscosity of the wastewater are adjusted by external stirring. The molar ratio of calcium peroxide to thiocyanate in the wastewater is 0.48:1.

[0052] The removal rate of thiocyanate in wastewater was 99% within 60 minutes under the ultrasound and calcium peroxide coupling system.

[0053] Example 3: A method for removing thiocyanate by enhancing electron transfer and transport A coking industry process produces coking wastewater containing thiocyanate. After inspection, the thiocyanate concentration is about 1500 mg / L, COD is about 3500 mg / L, ammonia nitrogen is 600 mg / L, and volatile phenol is 150 mg / L.

[0054] First, 10 L of wastewater was pre-regulated, and the pH of the wastewater was adjusted to 7, the conductivity was 1.2 S / m, the flow Reynolds number was 8500 and the dynamic viscosity was 600 mPa·s to obtain treated water. Then the treated water was introduced into the ozone contact reactor and regulated, the speed was adjusted to 300 rpm, the temperature was adjusted to 40 ℃, and stirred for 60 min under this condition. The pH of the wastewater was adjusted by using hydrochloric acid with a concentration of 1 mol / L, the conductivity of the wastewater was adjusted by adding zeolite, and the flow Reynolds number and dynamic viscosity of the wastewater were adjusted by external stirring. The molar ratio of ozone to thiocyanate in the wastewater was 5.6:1.

[0055] The thiocyanate in the wastewater was removed by 95% within 60 minutes.

[0056] Example 4: A method for removing thiocyanate by enhancing electron transfer and transport Synthesis of alcohol-based solid intermediate: N-(3-hydroxypyridin-2-yl)acetamide and anhydrous potassium carbonate were added to acetonitrile, reacted at 100 °C for 1 h, and then halogenated hydrocarbon was added, and the reaction was continued for 12 h, and then filtered and rotary evaporated. Methanol and dichloromethane were used as eluents, and column chromatography was used for separation and rotary evaporation to obtain an alcohol-based solid intermediate. The amount ratio of N-(3-hydroxypyridin-2-yl)acetamide to acetonitrile was 15.8 mmol:30 mL, and the amount ratio of anhydrous potassium carbonate to acetonitrile was 31.6 mmol:30 mL. The halogenated hydrocarbon was bromo-diethylene glycol-carboxylic acid, the amount ratio of bromo-diethylene glycol-carboxylic acid to acetonitrile was 15.8 mmol:30 mL, and the volume ratio of methanol to dichloromethane was 3:50.

[0057] Synthesis of alkyd quaternary ammonium salt ligand: Add alkyd solid intermediate to anhydrous ethanol, then add halogenated hydrocarbon, heat and reflux for 24 h, filter out crystals, and dry at 60 °C to obtain quaternary ammonium salt ligand. The halogenated hydrocarbon is brominated-diethylene glycol-carboxylic acid, and the ratio of brominated-diethylene glycol-carboxylic acid to anhydrous ethanol is 40 mmol:35 mL. The ratio of alkyd solid intermediate to anhydrous ethanol is 40 mmol:35 mL.

[0058] Thiocyanate wastewater is produced in the production process of a pharmaceutical industry. After inspection, the thiocyanate concentration is about 1800 mg / L, COD is about 66000 mg / L, sulfate ion is about 4000 mg / L, and suspended solids are 1000 mg / L. First, 10 L of wastewater is pre-regulated, the pH of the wastewater is adjusted to 5, the conductivity is 1.2 S / m, the flow Reynolds number is 8500 and the dynamic viscosity is 600 mPa·s to obtain treated water. Then the treated water is loaded into the reactor, and hydrogen peroxide and quaternary ammonium salt ligand are added, and the reactor is sealed. Finally, the control treatment is carried out, the speed in the reactor is adjusted to 300 rpm, the temperature is 65 ℃, and stirring is carried out under this condition for 120 min. The pH of the wastewater is adjusted by using hydrochloric acid with a concentration of 1 mol / L, the conductivity of the wastewater is adjusted by adding zeolite, and the flow Reynolds number and dynamic viscosity of the wastewater are adjusted by external stirring. The molar ratio of hydrogen peroxide to thiocyanate in the wastewater is 4.5:1, the quaternary ammonium salt ligand is an alkyd quaternary ammonium salt ligand, and the molar ratio of the alkyd quaternary ammonium salt ligand to thiocyanate in the wastewater is 1:1.

[0059] Example 5: A method for removing thiocyanate by enhancing electron transfer and transport The difference between this embodiment and embodiment 4 is that in the treatment of pharmaceutical wastewater, the quaternary ammonium salt ligand is an alkyd quaternary ammonium salt ligand, and the molar ratio of the alkyd quaternary ammonium salt ligand to the thiocyanate in the wastewater is 2:1. The rest is the same as embodiment 4.

[0060] Example 6: A method for removing thiocyanate by enhancing electron transfer and transport The difference between this embodiment and embodiment 4 is that pyridyl quaternary ammonium salt ligand is further added to the quaternary ammonium salt ligand, the molar ratio of the quaternary ammonium salt ligand to the thiocyanate in the wastewater is 1:1, and the molar ratio of the alcohol acid quaternary ammonium salt ligand to the pyridyl quaternary ammonium salt ligand in the quaternary ammonium salt ligand is 1:1.

[0061] Synthesis of pyridine solid intermediate: Add N-(3-hydroxypyridin-2-yl)acetamide and anhydrous potassium carbonate to acetonitrile, react at 100 °C for 1 h, then add halogenated hydrocarbon, continue to react for 12 h, then filter, rotary evaporate, use methanol and dichloromethane as eluents, separate by column chromatography, and rotary evaporate to obtain pyridine solid intermediate. The amount ratio of N-(3-hydroxypyridin-2-yl)acetamide to acetonitrile is 15.8 mmol:30 mL, and the amount ratio of anhydrous potassium carbonate to acetonitrile is 31.6 mmol:30 mL. The halogenated hydrocarbon is 4-(bromomethyl)pyrimidine, the amount ratio of 4-(bromomethyl)pyrimidine to acetonitrile is 15.8 mmol:30 mL, and the volume ratio of methanol to dichloromethane is 3:50.

[0062] Synthesis of pyridyl quaternary ammonium salt ligand: Add pyridyl solid intermediate to anhydrous ethanol, then add halogenated hydrocarbon, heat and reflux for 24 h, filter out crystals, and dry at 60 °C to obtain quaternary ammonium salt ligand. The halogenated hydrocarbon is 4-(bromomethyl)pyrimidine, and the ratio of 4-(bromomethyl)pyrimidine to anhydrous ethanol is 40 mmol:35 mL. The ratio of pyridyl solid intermediate to anhydrous ethanol is 40 mmol:35 mL. Others are the same as in Example 4.

[0063] Example 7: A method for removing thiocyanate by enhancing electron transfer and transport The difference between this embodiment and embodiment 6 is that in the treatment of pharmaceutical wastewater, the molar ratio of the quaternary ammonium salt ligand to the thiocyanate in the wastewater is 2:1, and the rest is the same as embodiment 6.

[0064] Comparative Example 1: A method for removing thiocyanate by enhancing electron transfer and transport Synthesis of alcohol-based solid intermediate: N-(3-hydroxypyridin-2-yl)acetamide and anhydrous potassium carbonate were added to acetonitrile, reacted at 100 °C for 1 h, and then halogenated hydrocarbon was added, and the reaction was continued for 12 h, and then filtered and rotary evaporated. Methanol and dichloromethane were used as eluents, and column chromatography was used for separation and rotary evaporation to obtain an alcohol-based solid intermediate. The amount ratio of N-(3-hydroxypyridin-2-yl)acetamide to acetonitrile was 15.8 mmol:30 mL, and the amount ratio of anhydrous potassium carbonate to acetonitrile was 31.6 mmol:30 mL. The halogenated hydrocarbon was bromo-diethylene glycol-carboxylic acid, the amount ratio of bromo-diethylene glycol-carboxylic acid to acetonitrile was 15.8 mmol:30 mL, and the volume ratio of methanol to dichloromethane was 3:50.

[0065] Thiocyanate wastewater is produced in the production process of a pharmaceutical industry. After inspection, the thiocyanate concentration is about 1800 mg / L, COD is about 66000 mg / L, sulfate ion is about 4000 mg / L, and suspended solids are 1000 mg / L. First, 10 L of wastewater is pre-regulated, the pH of the wastewater is adjusted to 5, the conductivity is 1.2 S / m, the flow Reynolds number is 8500 and the dynamic viscosity is 600 mPa·s to obtain treated water. Then the treated water is loaded into the reactor, and hydrogen peroxide and alkyd-based solid intermediates are added, and the reactor is sealed. Finally, the control treatment is carried out, the speed in the reactor is adjusted to 300 rpm, the temperature is 65 ℃, and stirring is carried out under this condition for 120 minutes. The pH of the wastewater is adjusted by using hydrochloric acid with a concentration of 1 mol / L, the conductivity of the wastewater is adjusted by adding zeolite, and the flow Reynolds number and dynamic viscosity of the wastewater are adjusted by external stirring. The molar ratio of hydrogen peroxide to thiocyanate in the wastewater is 4.5:1, and the molar ratio of the alkyd-based solid intermediate to thiocyanate in the wastewater is 1:1.

[0066] Comparative Example 2: A method for removing thiocyanate by enhancing electron transfer and transport Synthesis of alkyd quaternary ammonium salt ligand: Add N-(3-hydroxypyridin-2-yl)acetamide to anhydrous ethanol, then add halogenated hydrocarbon, heat and reflux for 24 h, filter out the crystals, and dry at 60 °C to obtain alkyd quaternary ammonium salt ligand. The halogenated hydrocarbon is bromo-diethylene glycol-carboxylic acid, and the ratio of bromo-diethylene glycol-carboxylic acid to anhydrous ethanol is 40 mmol:35 mL. The ratio of N-(3-hydroxypyridin-2-yl)acetamide to anhydrous ethanol is 40 mmol:35 mL.

[0067] Thiocyanate wastewater is produced in the production process of a pharmaceutical industry. After inspection, the thiocyanate concentration is about 1800 mg / L, COD is about 66000 mg / L, sulfate ion is about 4000 mg / L, and suspended solids are 1000 mg / L. First, 10 L of wastewater is pre-regulated, the pH of the wastewater is adjusted to 5, the conductivity is 1.2 S / m, the flow Reynolds number is 8500 and the dynamic viscosity is 600 mPa·s to obtain treated water. Then the treated water is loaded into the reactor, and hydrogen peroxide and alcohol acid quaternary ammonium salt ligand are added, and the reactor is sealed. Finally, the control treatment is carried out, the speed in the reactor is adjusted to 300 rpm, the temperature is 65 ℃, and stirring is carried out under this condition for 120 minutes. The pH of the wastewater is adjusted by using hydrochloric acid with a concentration of 1 mol / L, the conductivity of the wastewater is adjusted by adding zeolite, and the flow Reynolds number and dynamic viscosity of the wastewater are adjusted by external stirring. The molar ratio of hydrogen peroxide to thiocyanate in the wastewater is 4.5:1, and the molar ratio of the alcohol-based quaternary ammonium salt ligand to thiocyanate in the wastewater is 1:1.

[0068] Comparative Example 3: A method for removing thiocyanate by enhancing electron transfer and transport The difference between this comparative example and Example 6 is that in the synthesis of the quaternary ammonium salt ligand, no alkyd quaternary ammonium salt ligand is contained, and the rest is the same as Example 6.

[0069] Test example: Thiocyanate removal rate test 5 mL of the pharmaceutical wastewater treated in each example for 15 minutes was taken, and the change in thiocyanate concentration was measured by ultraviolet spectrophotometer, and the removal rate of thiocyanate in the pharmaceutical wastewater treated in each example for 15 minutes was calculated. The results of the thiocyanate removal rate measurement are shown in Table 3.

[0070] Table 3 Thiocyanate removal rate test

[0071] It can be seen from Table 3 that the thiocyanate removal rate of the wastewater in the embodiments after being treated for 15 min is relatively high, which indicates that by changing the external conditions such as reaction temperature, pH, stirring, etc., and constructing an enhanced electron transfer and transfer flow field, it is possible to promote hydrogen peroxide to release hydroxyl radicals, and convert thiocyanate into substances such as sulfate ions and ammonium ions, thereby achieving efficient removal of thiocyanate within a certain period of time; it can also be seen that the thiocyanate removal rate of the wastewater in Examples 4 and 5 after being treated for 15 min is higher than that in Example 1, which indicates that the introduction of quaternary ammonium salt ligands containing pyridine ring groups, acetamide groups and polyethylene glycol chains can improve the binding ability with thiocyanate through intermolecular interactions, and work together with the enhanced electron transfer and transfer flow field and the promotion of hydrogen peroxide to release free radicals to improve the thiocyanate removal rate; it can also be seen that the thiocyanate removal rate of the wastewater in Example 5 after being treated for 15 min is higher than that in Example 4, which indicates that the more the amount of quaternary ammonium salt ligands used, the higher the thiocyanate removal rate; it can also be seen that the thiocyanate removal rate of the wastewater in Example 6 and Example 7 after being treated for 15 min is higher than that of Example 4, which indicates that the more the amount of quaternary ammonium salt ligands used, the higher the thiocyanate removal rate; min after treatment, the thiocyanate removal rate of the wastewater is higher than that of Example 4, which indicates that when 4-(bromomethyl)pyrimidine reacts with N-(3-hydroxypyridin-2-yl)acetamide to form a new quaternary ammonium salt ligand, a pyrimidine ring group can be introduced, and on the basis of strengthening electron transfer and transfer flow field and promoting the release of free radicals by hydrogen peroxide, it works together with other quaternary ammonium salt ligands to improve the binding ability with thiocyanate in the wastewater, thereby improving the thiocyanate removal rate of the wastewater after treatment for 15 min; it can also be seen that the thiocyanate removal rate of the wastewater in Example 4 after treatment for 15 min is higher than that of Comparative Examples 1 and 2, which indicates that the quaternary ammonium salt ligand obtained by reacting N-(3-hydroxypyridin-2-yl)acetamide with two reaction sites of bromo-diethylene glycol-carboxylic acid in wastewater treatment has a higher thiocyanate removal rate than the quaternary ammonium salt ligand that reacts with only one reaction site of bromo-diethylene glycol-carboxylic acid; it can also be seen that Example 6 is treated for 15 min after treatment. min later, the thiocyanate removal rate of the wastewater was higher than that of Comparative Example 3, which indicates that the effect of introducing the quaternary ammonium salt ligand synthesized from 4-(bromomethyl)pyrimidine in wastewater treatment on improving the thiocyanate removal rate is lower than the effect of introducing the quaternary ammonium salt ligand synthesized from 4-(bromomethyl)pyrimidine and brominated-diethylene glycol-carboxylic acid respectively.

[0072] COD removal rate test The COD was determined by potassium dichromate method, and the COD removal rate was calculated as follows: P = (A0-A1) / A0×100%, where A0 is the original COD concentration in the pharmaceutical wastewater, and A1 is the COD concentration in the treated pharmaceutical wastewater. The test results are shown in Table 4.

[0073] Table 4 COD removal rate test results

[0074] It can be seen from Table 4 that the COD removal rate of the treated wastewater of the embodiment is low, which indicates that by changing the external conditions such as reaction temperature, pH, stirring, etc., and constructing an enhanced electron transfer and transfer flow field, the reaction of hydrogen peroxide and COD in the wastewater can be prevented; it can also be seen that the COD removal rate of the treated wastewater of Example 4 is lower than that of Example 1, which indicates that the introduction of quaternary ammonium salt ligands containing pyridine ring groups, acetamide groups and polyethylene glycol chains can prevent the reaction of hydrogen peroxide and COD through intermolecular interactions, thereby reducing the COD removal rate; it can also be seen that the COD removal rate of the treated wastewater of Example 6 is lower than that of Example 4, which indicates that when 4-(bromomethyl)pyrimidine reacts with N-(3-hydroxypyridin-2-yl)acetamide to form a new quaternary ammonium salt ligand, a pyrimidine ring group can be introduced to work together with other quaternary ammonium salt ligands to prevent Hydrogen peroxide reacts with COD, thereby reducing the removal rate of COD; it can also be seen that the COD removal rate of the treated wastewater in Example 4 is lower than that in Comparative Examples 1 and 2, which indicates that the quaternary ammonium salt ligand obtained by reacting two reaction sites of N-(3-hydroxypyridin-2-yl)acetamide with bromo-diethylene glycol-carboxylic acid in wastewater treatment has a COD removal rate lower than that of the quaternary ammonium salt ligand reacting with only one reaction site of bromo-diethylene glycol-carboxylic acid; it can also be seen that the COD removal rate of the treated wastewater in Example 6 is lower than that of Comparative Example 3, which indicates that the effect of reducing the COD removal rate by introducing the quaternary ammonium salt ligand synthesized from 4-(bromomethyl)pyrimidine in wastewater treatment is lower than the effect of introducing the quaternary ammonium salt ligand synthesized from 4-(bromomethyl)pyrimidine and bromo-diethylene glycol-carboxylic acid respectively.

[0075] The embodiments and / or implementation methods described above are only used to illustrate the preferred embodiments and / or implementation methods for realizing the technology of the present invention, and are not intended to limit the implementation methods of the technology of the present invention in any form. Any technical personnel in this field may make slight changes or modifications to other equivalent embodiments without departing from the scope of the technical means disclosed in the content of the present invention, but they should still be regarded as technologies or embodiments that are essentially the same as the present invention.

[0076] This article uses specific examples to illustrate the principles and implementation methods of this application. The description of the above embodiments is only used to help understand the method and its core ideas of this application. The above is only the preferred implementation method of this application. It should be pointed out that due to the limitations of textual expression and the objective existence of infinite specific structures, ordinary technicians in this technical field can make several improvements, modifications or changes without departing from the principles of this application, and can also combine the above technical features in an appropriate manner; these improvements, modifications, changes or combinations, or the direct application of the concept and technical solution of the invention to other occasions without improvement, should be regarded as the scope of protection of this application.

Claims

1. A method for removing thiocyanate by enhancing electron transfer and transport, comprising: Pre-regulating the wastewater, and then adding a selective regulating agent for regulation treatment to obtain treated water; Selective regulating agents include oxidants or oxidative coupling systems; In the pre-control, the pH of the wastewater is adjusted to 3-11, the conductivity of the wastewater is adjusted to 1-2 S / m, the flow Reynolds number of the wastewater is adjusted to >8000, and the dynamic viscosity of the wastewater is adjusted to 1-1000 mPa·s.

2. The method for removing thiocyanate by enhancing electron transfer and transport according to claim 1, characterized in that: The oxidant includes at least one of hydrogen peroxide, calcium peroxide, perchlorate, ferrate, persulfate, percarbonate, peracetic acid and vanadium trichloride.

3. The method for removing thiocyanate by enhancing electron transfer and transmission according to claim 1, characterized in that: The oxidative coupling system comprises at least one of a Fenton reagent, a metal oxide-activated peroxide coupling system, an ultrasound-peroxide coupling system, and a bicarbonate-activated peroxide coupling system.

4. The method for removing thiocyanate by enhancing electron transfer and transmission according to claim 1, characterized in that: The selective regulating agent comprises a quaternary ammonium salt ligand, and the quaternary ammonium salt ligand is obtained by reacting N-(3-hydroxypyridin-2-yl)acetamide and a halogenated hydrocarbon.

5. The method for removing thiocyanate by enhancing electron transfer and transmission according to claim 1, characterized in that: The regulating treatment adopts stirring treatment; or the temperature is adjusted to 10-100°C during the regulating treatment.

6. The method for removing thiocyanate by enhancing electron transfer and transport according to claim 1, characterized in that: The control process uses stirring, and the stirring speed is 50-400 rpm.

7. The method for removing thiocyanate by enhancing electron transfer and transmission according to claim 1, characterized in that: The oxidant and thiocyanate are used in a molar ratio of 0.3-10:

1.

8. The method for removing thiocyanate by enhancing electron transfer and transport according to claim 1, characterized in that: The oxidative coupling system contains an oxidant. The amount of the oxidative coupling system is calculated based on the oxidant. The oxidant and thiocyanate are used in a molar ratio of 0.3-10:

1.

9. The method for removing thiocyanate by enhancing electron transfer and transmission according to claim 3, characterized in that: The metal oxide-activated peroxide coupling system includes bismuth oxyiodide coupled with hydrogen peroxide or ferric oxychloride coupled with calcium peroxide.

10. The method for removing thiocyanate by enhancing electron transfer and transport according to claim 1, characterized in that: The wastewater comprises at least one of coking wastewater, electroplating wastewater, metal processing wastewater and pharmaceutical wastewater.

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