A method for removing thiocyanate by enhancing electron transport and transfer

Abstract

The present invention discloses a method for removing thiocyanate by enhancing electron transfer and transmission, and belongs to the field of industrial wastewater treatment. The method of the present invention achieves a removal rate of more than 95% of thiocyanate ions in the wastewater by pre-regulating the wastewater and then adding a selective regulating agent for regulation treatment. The method of the present invention has a stable and time-saving reaction process, and the process conditions are easy to regulate. It is suitable for treating a variety of thiocyanate-containing wastewaters, and can effectively solve the problem of interference with the pretreatment process caused by high-concentration thiocyanate, organic matter, and miscellaneous salt ions in actual industrial wastewater. It has good industrial application prospects and significant economic and social value.

Description

Technical Field

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

[0002] Thiocyanate is widely used in the pharmaceutical, textile, coking, metallurgy, and printing and dyeing industries. These industries generate wastewater containing high concentrations of thiocyanate during their production processes, often characterized by high concentrations of organic matter and complex salt ions. Thiocyanate is biologically toxic and, to a certain extent, inhibits the biochemical treatment of wastewater, resulting in poor treatment effectiveness of traditional biochemical treatment for high-thiocyanate wastewater. This type of wastewater presents significant environmental hazards, difficulty in treatment, and high costs. Therefore, efficient and selective removal of thiocyanate in advance is key to the efficient and low-cost biochemical treatment of this type of wastewater.

[0003] Currently, the main methods for treating thiocyanate in industrial wastewater include coagulation, ion exchange, adsorption, biodegradation, and oxidation. Coagulation, ion exchange, adsorption, and other methods have problems such as poor selectivity, low treatment efficiency, and high treatment costs; 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 electron transfer can effectively destroy thiocyanate in water bodies and convert it into harmless substances. It has the advantages of high reaction efficiency and simple reaction conditions. However, traditional oxidation methods cannot simultaneously take into account reaction selectivity, pollutant removal effect, and economic cost. On this basis, it is necessary to develop a treatment process for the selective removal of thiocyanate in industrial wastewater that strengthens electron transfer and electron transfer 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, the cyanide-containing wastewater is first treated by the Inco process to remove the easily treatable cyanide. The treated wastewater is then coagulated and precipitated by adding a coagulant to remove heavy metal ions in the wastewater. Then, under the synergistic action of ultraviolet light and ozone, the residual difficult-to-treat cyanide, thiocyanate and other organic pollutants 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. This method uses a grit chamber to remove sand and gravel from the accidental wastewater, a regulating tank to even out the water quality and volume, and an intermittent vertical flow artificial wetland to first remove most of the suspended solids and some cyanide and thiocyanate. The treated accidental wastewater then passes through vertical and horizontal flow artificial wetlands to remove various pollutants such as cyanide, thiocyanate, and heavy metals through dilution, filler adsorption, biological oxidation, and plant absorption. Finally, through post-treatment with an alkaline chlorination method, the treated wastewater meets the first-level standard limit in the "Integrated Sewage Discharge Standard." Summary of the Invention

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

[0006] The technical solutions adopted by the present invention to achieve the above-mentioned purpose are:

[0007] A method for removing thiocyanate by enhancing 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;

[0008] During 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.

[0009] By modifying external conditions such as reaction temperature, pH, and stirring, the present invention creates an enhanced electron transfer and transport flow field, reducing competition with complex substrates in the wastewater and the consumption caused by self-quenching of the reaction reagents themselves, thereby achieving targeted reduction of thiocyanate in the wastewater. Simultaneously, the present invention promotes the release of free radicals from oxidants such as hydrogen peroxide, converting 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 reagents.

[0010] Preferably, the oxidizing agent comprises at least one of hydrogen peroxide, calcium peroxide, perchlorate, ferrate, persulfate, percarbonate, peracetic acid and vanadium oxychloride.

[0011] 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.

[0012] Preferably, the selective control reagent comprises a quaternary ammonium salt ligand, which is obtained by reacting N-(3-pyridinium-2-yl) acetamide and halogenated hydrocarbon. Halogenated hydrocarbon at least comprises bromo-diethylene glycol-carboxylic acid. The nitrogen-atoms of N-(3-pyridinium-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 the quaternary ammonium salt ligand. In the quaternary ammonium salt ligand, pyridine ring group, acetamide group and polyethylene glycol chain form a multi-group spatial configuration, thereby interacting with thiocyanate radical through the structure and spatial structure between the groups, improving the processing of the selective control reagent to the thiocyanate radical in the wastewater. Simultaneously, the quaternary ammonium salt ligand can reduce the impact of COD on the selective control reagent, and under the synergistic effect of strengthening electron transfer and transfer flow field and promoting the release of free radicals, further improves the removal rate of thiocyanate radical.

[0013] Preferably, stirring is used in the regulation and control process; or, the temperature is adjusted to 10-100°C in the regulation and control process.

[0014] Preferably, stirring is used in the regulation process, and the stirring speed is 50-400 rpm.

[0015] Preferably, the oxidant and thiocyanate are used in a molar ratio of 0.3-10:1.

[0016] Preferably, the oxidative coupling system contains an oxidant, and the amount of the oxidative coupling system used is calculated based on the oxidant, and the oxidant and thiocyanate are used in a molar ratio of 0.3-10:1.

[0017] Preferably, the metal oxide-activated peroxide coupling system comprises bismuth oxyiodide coupled with hydrogen peroxide or iron oxychloride coupled with calcium peroxide.

[0018] Preferably, the wastewater comprises at least one of coking wastewater, electroplating wastewater, metal processing wastewater and pharmaceutical wastewater.

[0019] The present invention discloses a method for removing thiocyanate by enhancing electron transfer and transmission, which comprises the synthesis of a solid intermediate, the synthesis of a quaternary ammonium salt ligand, pre-regulation of wastewater, the addition of a selective regulating agent and regulation treatment, and specifically comprises the following steps:

[0020] Synthesis of solid intermediate: Add N-(3-hydroxypyridin-2-yl)acetamide and anhydrous potassium carbonate to acetonitrile and react at 80-100°C for 1-3 hours. Then add halogenated hydrocarbon and continue the reaction for 8-18 hours. Then filter and rotary evaporate. Separate by column chromatography using methanol and dichloromethane as eluents and rotary evaporate to obtain a solid intermediate.

[0021] Synthesis of quaternary ammonium salt ligand: Add the solid intermediate to anhydrous ethanol, then add halogenated hydrocarbon, heat and reflux for 12-48 hours, filter and precipitate the crystals, and dry at 50-80 °C to obtain the quaternary ammonium salt ligand.

[0022] 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.

[0023] Dosing of selective regulating reagents and regulating treatment: Add selective regulating reagents to regulate the wastewater.

[0024] 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.

[0025] Preferably, in the synthesis of the solid intermediate, the halogenated hydrocarbon includes at least bromo-diethylene glycol-carboxylic acid, and the ratio of bromo-diethylene glycol-carboxylic acid to acetonitrile is 15-20 mmol: 15-45 mL.

[0026] Preferably, in the synthesis of the solid intermediate, the volume ratio of methanol to dichloromethane is 3-5:50-80.

[0027] Preferably, in the synthesis of the quaternary ammonium salt ligand, the halogenated hydrocarbon includes at least bromo-diethylene glycol-carboxylic acid, and the amount ratio of bromo-diethylene glycol-carboxylic acid to anhydrous ethanol is 25-75 mmol: 30-50 mL. The synthesized quaternary ammonium salt ligand is named alkyd quaternary ammonium salt ligand.

[0028] Preferably, in the synthesis of the quaternary ammonium salt ligand, the ratio of the solid intermediate to anhydrous ethanol is 35-50 mmol:30-50 mL.

[0029] Preferably, in the pre-regulation of wastewater, the wastewater comprises at least one of coking wastewater, electroplating wastewater, metal processing wastewater, and pharmaceutical wastewater.

[0030] 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 an 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, with the wastewater temperature being 30-70°C and the dilution ratio being 0-10.

[0031] Preferably, during the addition and regulation process of the selective regulation reagent, the selective regulation reagent comprises an oxidant or an oxidative coupling system.

[0032] 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.

[0033] 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.

[0034] Preferably, in the addition and regulation process of the selective regulation reagent, 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.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] More preferably, in the synthesis of the quaternary ammonium salt ligand, the halogenated hydrocarbon further comprises 4-(bromomethyl)pyrimidine, and the amount 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.

[0040] More preferably, during the addition and regulation of the selective regulating agent, the quaternary ammonium salt ligand comprises an alkyd quaternary ammonium salt ligand and a pyridyl quaternary ammonium salt ligand, and the molar ratio of the alkyd 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. In the presence of other quaternary ammonium salt ligands, under the combined action of the alkyd quaternary ammonium salt ligand and the pyridyl quaternary ammonium salt ligand, the quaternary ammonium salt ligand has a better binding ability to thiocyanate in wastewater, thereby improving the removal effect of the selective regulating agent on thiocyanate. At the same time, under the action of the alkyd quaternary ammonium salt ligand and the pyridyl quaternary ammonium salt ligand, the influence of COD on the selective regulating agent is avoided, thereby achieving efficient removal of thiocyanate.

[0041] The present invention regulates wastewater quality characteristics and introduces a quaternary ammonium salt ligand when adding a selective regulating agent. The quaternary ammonium salt ligand significantly improves the binding ability and selectivity of thiocyanate in the wastewater through intermolecular interaction, prevents COD interference, and synergistically accelerates thiocyanate removal by strengthening electron transfer and transfer flow fields and promoting the release of free radicals. The method has the following beneficial effects: high reaction efficiency, simple reaction conditions, strong selectivity for thiocyanate, and efficient destruction of thiocyanate in water. Therefore, the present invention aims to provide a thiocyanate removal method that strengthens electron transfer and transfer. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 This is a process flow chart of the thiocyanate removal method.

[0043] Figure 2 This is the result diagram of the calculation formula of thiocyanate concentration and absorbance.

[0044] Figure 3 This is a graph showing the results of measuring the thiocyanate removal rate in Example 1.

[0045] Figure 4 Schematic diagram of the principle of thiocyanate removal method. DETAILED DESCRIPTION

[0046] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. 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 making creative efforts are within the scope of protection of the present invention.

[0047] The following first describes the concepts involved in this application with reference to the accompanying drawings. It should be noted that the following description of each concept is intended only to make the content of this application easier to understand and does not limit the scope of protection of this application. At the same time, the embodiments and features in the embodiments of this application can be combined with each other unless there is a conflict. The following detailed description of this application will be made with reference to the accompanying drawings and in conjunction with the embodiments.

[0048] The process flow chart of the thiocyanate removal method for enhancing electron transport and transfer of the present invention is as follows: Figure 1 As shown, first, the wastewater quality characteristics 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.

[0049] Example 1: A method for removing thiocyanate by enhancing electron transport and transfer

[0050] A pharmaceutical production process generates thiocyanate wastewater. Testing revealed thiocyanate concentrations of approximately 1800 mg / L, COD of approximately 66,000 mg / L, sulfate ions of approximately 4000 mg / L, and suspended solids of 1000 mg / L. First, 10 L of wastewater was pre-conditioned to adjust the pH to 5, the conductivity to 1.2 S / m, the flow Reynolds number to 8500, and the dynamic viscosity to 600 mPa·s. This treated water was then placed in a reactor, hydrogen peroxide was added, and the reactor was sealed. Finally, the reactor was conditioned to a speed of 300 rpm and a temperature of 65°C, with stirring for 120 minutes. The wastewater pH was adjusted using 1 mol / L hydrochloric acid, the conductivity was adjusted by adding zeolite, and the flow Reynolds number and dynamic viscosity were adjusted by external stirring. The molar ratio of hydrogen peroxide to thiocyanate in the wastewater was 4.5:1.

[0051] 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 spectrophotometry, 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 time is expressed 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 2. Figure 3 shown.

[0052] Table 1 Results of the relationship between thiocyanate concentration and absorbance

[0053]

[0054] Table 2 Sampling intervals and thiocyanate concentration determination results of pharmaceutical industry wastewater

[0055]

[0056] As can be seen from Table 2, with the increase of treatment time, the concentration of thiocyanate in pharmaceutical industry 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 pharmaceutical industry wastewater gradually decreased and finally reached 4% within 90 minutes. At this 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, achieving efficient removal of thiocyanate within a certain period of time. The specific principle diagram is shown in Figure 4 .

[0057] Example 2: A method for removing thiocyanate by enhancing electron transport and transfer

[0058] A pharmaceutical production process produces antibiotic waste liquor containing thiocyanate. Testing revealed thiocyanate concentrations of approximately 6,000 mg / L, COD of approximately 50,000 mg / L, sulfate ions of approximately 150 mg / L, and chloride ions of approximately 13,000 mg / L. 10 L of wastewater was pre-conditioned to a pH of 6.0 without further adjustment. The treated water was then adjusted to a conductivity of 1.2 S / m, a flow Reynolds number of 8,500, and a dynamic viscosity of 600 mPa·s. The treated water was then introduced into an ultrasonic treatment apparatus. The ultrasonic power was adjusted to 400 W, calcium peroxide was added, and the temperature was maintained at 40°C. Stirring was continued for 60 minutes. The wastewater conductivity was adjusted by the addition of zeolite, and the flow Reynolds number and dynamic viscosity were adjusted by external stirring. The molar ratio of calcium peroxide to thiocyanate in the wastewater was 0.48:1.

[0059] The removal rate of thiocyanate in wastewater was 99% within 60 minutes under the ultrasound and calcium peroxide coupling system.

[0060] Example 3: A method for removing thiocyanate by enhancing electron transport and transfer

[0061] A coking industry process produces coking wastewater containing thiocyanate. After testing, 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.

[0062] First, 10 L of wastewater was pre-conditioned to a pH of 7, a conductivity of 1.2 S / m, a flow Reynolds number of 8500, and a dynamic viscosity of 600 mPa·s to obtain treated water. The treated water was then introduced into an ozone contact reactor and conditioned at a speed of 300 rpm and a temperature of 40°C, with stirring for 60 minutes. The pH of the wastewater was adjusted using 1 mol / L hydrochloric acid, the conductivity was adjusted by adding zeolite, and the flow Reynolds number and dynamic viscosity were adjusted by external stirring. The molar ratio of ozone to thiocyanate in the wastewater was 5.6:1.

[0063] The thiocyanate in the wastewater was removed by 95% within 60 minutes.

[0064] Example 4: A method for removing thiocyanate by enhancing electron transport and transfer

[0065] Synthesis of an alcohol-based solid intermediate: N-(3-hydroxypyridin-2-yl)acetamide and anhydrous potassium carbonate were added to acetonitrile and reacted at 100°C for 1 hour. A halogenated hydrocarbon was then added and the reaction continued for 12 hours. The product was then filtered and rotary evaporated. The product was separated by column chromatography using methanol and dichloromethane as eluents and rotary evaporated to obtain the alcohol-based solid intermediate. The ratio of N-(3-hydroxypyridin-2-yl)acetamide to acetonitrile was 15.8 mmol:30 mL, and the ratio of anhydrous potassium carbonate to acetonitrile was 31.6 mmol:30 mL. The halogenated hydrocarbon was bromo-diethylene glycol-carboxylic acid, and the ratio of bromo-diethylene glycol-carboxylic acid to acetonitrile was 15.8 mmol:30 mL. The volume ratio of methanol to dichloromethane was 3:50.

[0066] Synthesis of the alkyd-based quaternary ammonium salt ligand: The alkyd-based solid intermediate was added to anhydrous ethanol, followed by the addition of a halogenated hydrocarbon. The mixture was heated under reflux for 24 hours, filtered to precipitate the crystals, and dried at 60°C to obtain the quaternary ammonium salt ligand. The halogenated hydrocarbon was bromo-diethylene glycol-carboxylic acid, and the ratio of bromo-diethylene glycol-carboxylic acid to anhydrous ethanol was 40 mmol:35 mL. The ratio of the alkyd-based solid intermediate to anhydrous ethanol was also 40 mmol:35 mL.

[0067] A pharmaceutical industry production process generates thiocyanate wastewater. Testing revealed thiocyanate concentrations of approximately 1800 mg / L, COD of approximately 66,000 mg / L, sulfate ions of approximately 4000 mg / L, and suspended solids of 1000 mg / L. First, 10 L of wastewater was pre-conditioned to adjust the pH to 5, the conductivity to 1.2 S / m, the flow Reynolds number to 8500, and the dynamic viscosity to 600 mPa·s. This treated water was then placed in a reactor, where hydrogen peroxide and a quaternary ammonium salt ligand were added. The reactor was then sealed. Finally, the reactor was conditioned to a speed of 300 rpm and a temperature of 65°C, with stirring for 120 minutes. The wastewater pH was adjusted using 1 mol / L hydrochloric acid, the conductivity was adjusted by adding zeolite, and the flow Reynolds number and dynamic viscosity were 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.

[0068] Example 5: A method for removing thiocyanate by enhancing electron transport and transfer

[0069] 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. Others are the same as in embodiment 4.

[0070] Example 6: A method for removing thiocyanate by enhancing electron transport and transfer

[0071] The difference between this embodiment and embodiment 4 is that a 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-based quaternary ammonium salt ligand to the pyridyl quaternary ammonium salt ligand in the quaternary ammonium salt ligand is 1:1.

[0072] Synthesis of a pyridine-based solid intermediate: N-(3-hydroxypyridin-2-yl)acetamide and anhydrous potassium carbonate were added to acetonitrile and reacted at 100°C for 1 hour. A halogenated hydrocarbon was then added and the reaction continued for 12 hours. The product was then filtered and rotary evaporated. The product was separated by column chromatography using methanol and dichloromethane as eluents and rotary evaporated to obtain the pyridine-based solid intermediate. The ratio of N-(3-hydroxypyridin-2-yl)acetamide to acetonitrile was 15.8 mmol:30 mL, and the ratio of anhydrous potassium carbonate to acetonitrile was 31.6 mmol:30 mL. The halogenated hydrocarbon was 4-(bromomethyl)pyrimidine, and the ratio of 4-(bromomethyl)pyrimidine to acetonitrile was 15.8 mmol:30 mL. The volume ratio of methanol to dichloromethane was 3:50.

[0073] Synthesis of a pyridyl quaternary ammonium salt ligand: Add the pyridyl solid intermediate to anhydrous ethanol, then add a halogenated hydrocarbon. Heat under reflux for 24 hours, filter the precipitated crystals, and dry at 60°C to obtain the quaternary ammonium salt ligand. The halogenated hydrocarbon is 4-(bromomethyl)pyrimidine. The ratio of 4-(bromomethyl)pyrimidine to anhydrous ethanol is 40 mmol:35 mL. The ratio of the pyridyl solid intermediate to anhydrous ethanol is also 40 mmol:35 mL. Other conditions are the same as in Example 4.

[0074] Example 7: A method for removing thiocyanate by enhancing electron transport and transfer

[0075] 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.

[0076] Comparative Example 1: A method for removing thiocyanate by enhancing electron transport and transfer

[0077] Synthesis of an alcohol-based solid intermediate: N-(3-hydroxypyridin-2-yl)acetamide and anhydrous potassium carbonate were added to acetonitrile and reacted at 100°C for 1 hour. A halogenated hydrocarbon was then added and the reaction continued for 12 hours. The product was then filtered and rotary evaporated. The product was separated by column chromatography using methanol and dichloromethane as eluents and rotary evaporated to obtain the alcohol-based solid intermediate. The ratio of N-(3-hydroxypyridin-2-yl)acetamide to acetonitrile was 15.8 mmol:30 mL, and the ratio of anhydrous potassium carbonate to acetonitrile was 31.6 mmol:30 mL. The halogenated hydrocarbon was bromo-diethylene glycol-carboxylic acid, and the ratio of bromo-diethylene glycol-carboxylic acid to acetonitrile was 15.8 mmol:30 mL. The volume ratio of methanol to dichloromethane was 3:50.

[0078] A pharmaceutical industry production process generates thiocyanate wastewater. Testing revealed thiocyanate concentrations of approximately 1800 mg / L, COD of approximately 66,000 mg / L, sulfate ions of approximately 4,000 mg / L, and suspended solids of 1,000 mg / L. First, 10 L of wastewater was pre-conditioned to adjust the pH to 5, the conductivity to 1.2 S / m, the flow Reynolds number to 8,500, and the dynamic viscosity to 600 mPa·s. This treated water was then charged into a reactor, where hydrogen peroxide and an alkyd-based solid intermediate were added. The reactor was then sealed. Finally, the reactor was conditioned to a speed of 300 rpm and a temperature of 65°C, with stirring for 120 minutes. The wastewater pH was adjusted using 1 mol / L hydrochloric acid, the conductivity was adjusted by adding zeolite, and the flow Reynolds number and dynamic viscosity were 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.

[0079] Comparative Example 2: A method for removing thiocyanate by enhancing electron transport and transfer

[0080] Synthesis of the alkyd-based quaternary ammonium salt ligand: N-(3-hydroxypyridin-2-yl)acetamide was added to anhydrous ethanol, followed by a halogenated hydrocarbon. The mixture was heated under reflux for 24 hours, filtered to precipitate the crystals, and dried at 60°C to obtain the alkyd-based quaternary ammonium salt ligand. The halogenated hydrocarbon was bromo-diethylene glycol-carboxylic acid, and the ratio of bromo-diethylene glycol-carboxylic acid to anhydrous ethanol was 40 mmol:35 mL. The ratio of N-(3-hydroxypyridin-2-yl)acetamide to anhydrous ethanol was 40 mmol:35 mL.

[0081] A pharmaceutical industry production process generates thiocyanate wastewater. Testing revealed thiocyanate concentrations of approximately 1800 mg / L, COD of approximately 66,000 mg / L, sulfate ions of approximately 4000 mg / L, and suspended solids of 1000 mg / L. First, 10 L of wastewater was pre-conditioned to adjust the pH to 5, the conductivity to 1.2 S / m, the flow Reynolds number to 8500, and the dynamic viscosity to 600 mPa·s. This treated water was then charged into a reactor, where hydrogen peroxide and an alkyd-based quaternary ammonium salt ligand were added. The reactor was then sealed. Finally, the reactor was conditioned to a speed of 300 rpm and a temperature of 65°C, with stirring for 120 minutes. The wastewater pH was adjusted using 1 mol / L hydrochloric acid, the conductivity was adjusted by adding zeolite, and the flow Reynolds number and dynamic viscosity were 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 quaternary ammonium salt ligand to thiocyanate in the wastewater is 1:1.

[0082] Comparative Example 3: A method for removing thiocyanate by enhancing electron transport and transfer

[0083] 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.

[0084] Test example:

[0085] Thiocyanate removal rate test

[0086] 5 mL of pharmaceutical wastewater was collected after 15 minutes of treatment in each example. The change in thiocyanate concentration was measured using a UV spectrophotometer, and the thiocyanate removal rate was calculated for each example after 15 minutes of treatment. The results of the thiocyanate removal rate are shown in Table 3.

[0087] Table 3 Thiocyanate removal rate test

[0088]

[0089] It can be seen from Table 3 that the thiocyanate removal rate of the wastewater after treatment for 15 min in the embodiment is relatively high, which indicates that by changing the external conditions such as reaction temperature, pH, stirring, 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 after treatment for 15 min in Example 4 and Example 5 is higher than that in Example 1, which indicates that the introduction of a quaternary ammonium salt ligand containing a pyridine ring group, an acetamide group, and a polyethylene glycol chain 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 after treatment for 15 min in Example 5 is higher than that in Example 4, which indicates that the more the amount of quaternary ammonium salt ligand used, the higher the thiocyanate removal rate; it can also be seen that the thiocyanate removal rate of the wastewater after treatment for 15 min in Example 6 and Example 7 is higher than that in Example 4, which indicates that the more the amount of quaternary ammonium salt ligand 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, which, on the basis of strengthening electron transfer and transfer flow field and promoting the release of free radicals by hydrogen peroxide, acts 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. min after the thiocyanate removal rate of the wastewater is 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 bromo-diethylene glycol-carboxylic acid respectively.

[0090] COD removal rate test

[0091] COD was determined using the potassium dichromate method, and the COD removal rate was calculated using the formula: 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.

[0092] Table 4 COD removal rate test results

[0093]

[0094] It can be seen from Table 4 that the COD removal rate of the treated wastewater of the embodiment is lower, which illustrates that by changing the external conditions such as reaction temperature, pH, stirring, and constructing the 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 illustrates that the introduction of the quaternary ammonium salt ligand containing pyridine ring group, acetamide group and polyethylene glycol chain can prevent the reaction of hydrogen peroxide and COD by intermolecular interaction, 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 illustrates 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 act together with other quaternary ammonium salt ligands to prevent Hydrogen peroxide reacts with COD, thereby reducing the COD removal rate; 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 COD removal rate of 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 is lower than that of the quaternary ammonium salt ligand that reacts 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 introducing the quaternary ammonium salt ligand synthesized from 4-(bromomethyl)pyrimidine in wastewater treatment on reducing the COD removal rate is lower than the effect of introducing the quaternary ammonium salt ligand synthesized from 4-(bromomethyl)pyrimidine and bromo-diethylene glycol-carboxylic acid in combination.

[0095] 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 do not impose any form of limitation on the implementation methods of the technology of the present invention. Any person skilled in the art 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.

[0096] 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 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, there are objectively infinite specific structures. For ordinary technicians in this technical field, without departing from the principles of this application, they can also make several improvements, modifications or changes, and can also combine the above technical features in an appropriate manner; these improvements, modifications, changes or combinations, or the direct application of the inventive concept and technical solution 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 transport and transfer, 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; During 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; The oxidant comprises at least one of hydrogen peroxide, calcium peroxide, perchlorate, ferrate, persulfate, percarbonate, peracetic acid and vanadium trichloride; The selective regulating agent further comprises a quaternary ammonium salt ligand, which is obtained by reacting N-(3-hydroxypyridin-2-yl)acetamide and a halogenated hydrocarbon; the molar ratio of the quaternary ammonium salt ligand to the thiocyanate in the wastewater is 0.1-5:

1.

2. The method for removing thiocyanate by enhancing electron transfer and transport according to claim 1, wherein: 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.

3. The method for removing thiocyanate by enhancing electron transfer and transport according to claim 1, wherein: The control process adopts stirring process; or the temperature is adjusted to 10-100°C during the control process.

4. The method for removing thiocyanate by enhancing electron transfer and transport according to claim 1, wherein: The control process adopts stirring process, and the stirring speed is 50-400 rpm.

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

1.

6. The method for removing thiocyanate by enhancing electron transfer and transport according to claim 1, wherein: 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.

7. The method for removing thiocyanate by enhancing electron transfer and transport according to claim 2, wherein: The metal oxide-activated peroxide coupling system includes bismuth oxyiodide coupled with hydrogen peroxide or ferric oxychloride coupled with calcium peroxide.

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

Images