A method for oxidative removal of phenanthrene and ofloxacin from coking wastewater and antibiotic wastewater using a gasification slag / sodium persulfate system.

Abstract

This invention relates to the field of wastewater treatment, particularly to coking wastewater and antibiotic wastewater. A method for removing phenanthrene from coking wastewater and ofloxacin from antibiotic wastewater using a gasification slag / sodium persulfate system is disclosed. The gasification slag is ground and passed through a 60-mesh sieve. The temperature of the wastewater to be treated is controlled at 20-30°C, and the pH of the wastewater is adjusted to 3 using sodium hydroxide or sulfuric acid. Gasification slag and sodium persulfate are added to the wastewater after the first step of treatment, and after a period of reaction, the mixture is filtered using a 0.22μm filter membrane. This patent achieves a removal rate of over 95% for phenanthrene (a recalcitrant polycyclic aromatic hydrocarbon) in coking wastewater and ofloxacin in antibiotic wastewater. While achieving highly efficient removal of phenanthrene and ofloxacin, it also promotes the recycling of solid waste gasification slag and overcomes the shortcomings of the activation method of persulfate advanced oxidation technology.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment, particularly to the field of coking wastewater treatment and antibiotic wastewater treatment. Background Technology

[0002] Coking wastewater accounts for approximately 5% of total industrial wastewater discharge in my country. This wastewater is characterized by complex pollutant composition, high concentration, and poor biodegradability, making it a typical type of toxic, recalcitrant, high-concentration industrial organic wastewater. The main organic pollutants include phenols, benzene compounds, heterocyclic compounds, and polycyclic aromatic hydrocarbons (PAHs), with PAHs accounting for 8-10% (up to 30 mg / L) in the raw water. Some PAHs fail to degrade effectively during the entire coking wastewater treatment process, which is one of the main factors contributing to the long treatment process and high costs.

[0003] Currently, the treatment of coking wastewater both domestically and internationally generally requires the combined use of multiple processes including pretreatment, biological treatment, and advanced treatment. While existing coking wastewater treatment technologies can ensure that the final effluent meets national standards (GB16171-2012 "Emission Standard of Pollutants for Coking Chemical Industry"), in actual production, over 90% of coking plant wastewater still fails to meet COD standards. One reason for this is that physicochemical pretreatment technologies used to improve the biodegradability of wastewater or advanced treatment technologies to ensure effluent quality, such as chemical oxidation, advanced oxidation, wet catalytic oxidation, MBR, and electrocatalytic oxidation-reverse osmosis, still have poor mineralization effects on some PAHs (polyphenolic compounds) and are costly to operate, making them unacceptable to enterprises. Therefore, seeking efficient, low-cost, pollution-free, and highly controllable new wastewater treatment technologies remains a major research direction for phenanthrene-containing wastewater.

[0004] Fluoroquinolone antibiotics (FQs) are an emerging class of environmental micropollutants. Due to the long-term irrational use of antibiotics and the low metabolic efficiency of most antibiotics in organisms, over 70% of FQs are not metabolized by the human body and enter the environment. Ofloxacin (OFL) is a typical second-generation fluoroquinolone antibiotic with a broad antibacterial spectrum and easy absorption. It is one of the most widely used antibiotics in the treatment of infectious diseases in humans and animals, and is also the most common antibiotic in natural water bodies and wastewater. OFL concentrations detected in surface water and wastewater range from ng / L to mg / L, and studies have shown that this substance has been detected in groundwater and drinking water. Residual OFL in natural water bodies not only pollutes the environment but also leads to increasing antibiotic resistance in aquatic bacteria, adversely affecting human health and ecosystems. Therefore, it is necessary to seek efficient methods for removing OFL from water, providing theoretical and technical support for the pollution control of OFL in water bodies.

[0005] Gasification slag is a solid waste generated during coal gasification, mainly composed of inorganic minerals such as SiO2, Al2O3, Fe2O3, and CaO, and some residual carbon. Statistics show that with the large-scale promotion of coal gasification technology, the annual production of gasification slag exceeds 33 million tons, but the comprehensive utilization rate of coal gasification slag in my country is less than 10% annually. Research reports indicate that gasification slag disposal not only increases transportation costs but, more seriously, causes environmental problems and safety hazards such as land encroachment, soil and water pollution, and dust pollution, resulting in significant environmental pressure. Among these, the iron-based substances contained in gasification slag have the potential to activate persulfates and can serve as catalysts for advanced oxidation processes. Therefore, the recycling and utilization of gasification slag can reduce its environmental pollution.

[0006] Advanced oxidation techniques (AOPs) for sodium persulfate have attracted significant attention due to their green, efficient, and powerful oxidizing properties. However, persulfates require activation to generate sulfate radicals in order to exert their high oxidizing activity. Activation methods for persulfates include thermal activation, transition metal activation, ultraviolet light activation, alkali activation, and ultrasonic activation. Among these, Fe... 2+ It can activate sodium persulfate to generate active free radicals (sulfate free radicals SO4). -. or hydroxyl radical HO . However, directly adding Fe 2+ Excessive use can easily lead to increased COD in the effluent, and its recovery is also a challenge. Summary of the Invention

[0007] The technical problem to be solved by this invention is: how to overcome the high cost of removing polycyclic aromatic hydrocarbons (PAHs) and other recalcitrant organic compounds from coking wastewater, the environmental impact of ofloxacin, and the defects of sodium persulfate activation methods in the technical background, and to achieve the goal of removing phenanthrene and ofloxacin from coking wastewater and antibiotic wastewater by combining the waste utilization of gasification slag with advanced persulfate oxidation technology.

[0008] The technical solution adopted in this invention is: a method for oxidative removal of phenanthrene from coking wastewater and ofloxacin from antibiotic wastewater using a gasification slag / sodium persulfate system, which is carried out according to the following steps:

[0009] Step 1: Grind the gasification slag until its particle diameter can pass through a 60-mesh sieve;

[0010] Step 2: Control the temperature of the wastewater to be treated to 20-30℃, adjust the pH of the wastewater to be treated to 3 using sodium hydroxide or sulfuric acid, and determine the initial concentration of pollutants;

[0011] Step 3: Add gasification slag and sodium persulfate to the wastewater treated in Step 2, wait for the reaction to proceed for a period of time, filter the wastewater using a 0.22μm filter membrane, and determine the residual concentration of pollutants.

[0012] For coking wastewater, in step three, the concentration of phenanthrene is 1 mg / L, the dosage of gasification slag is 0.7 g / L-0.9 g / L, the dosage of sodium persulfate is 0.6 mmol / L-1 mmol / L, and the reaction time is 60-80 min, which can achieve a phenanthrene removal rate of 84.23%-97.68%.

[0013] For antibiotic wastewater, in step three, the concentration of ofloxacin is 5 mg / L, the amount of gasification slag added is 0.7 g / L-0.9 g / L, the amount of sodium persulfate added is 0.6 mmol / L-1 mmol / L, and the reaction time is 60-80 min, which can achieve a removal rate of ofloxacin of 88.69%-98.56%.

[0014] As a preferred method: in step three, the phenanthrene concentration is 1 mg / L, the gasification slag content is 0.7 g / L, the sodium persulfate content is 1 mmol / L, and the reaction time is 60 min, which can achieve a phenanthrene removal rate of 97.68%.

[0015] As a preferred method: in step three, the concentration of ofloxacin is 5 mg / L, the content of gasification slag is 0.7 g / L, the content of sodium persulfate is 1 mmol / L, and the reaction time is 30 min, which can make the removal rate of ofloxacin 98.56%.

[0016] The beneficial effects of this invention are: This invention constructs a gasification slag / sodium persulfate system, innovatively utilizing gasification slag, a solid waste product of coal gasification, as an activator to activate persulfate. Through a series of chemical reactions occurring during the process, sulfate free radicals (SO4) are generated. -. ), hydroxyl radicals (HO) . It utilizes active free radicals such as phenanthrene and chlorine to regulate the low-consumption and high-efficiency removal of typical polycyclic aromatic hydrocarbons (tricyclic compounds) in coking wastewater (the removal principle is the same as that of ofloxacin). Simultaneously, the gasification slag possesses a certain degree of magnetism, facilitating solid-liquid separation. The reaction can proceed at ambient temperature and pressure, preventing secondary pollution and allowing for multiple reuses, thus achieving the dual goals of solid waste recycling and wastewater pollutant removal. Attached Figure Description

[0017] Figure 1 A schematic diagram illustrating the impact of different systems on the removal rate of phenanthrene.

[0018] Figure 2 SEM-EDS image of gasification slag.

[0019] Figure 3 A schematic diagram illustrating the effect of gasification slag dosage on phenanthrene removal rate.

[0020] Figure 4 A schematic diagram illustrating the effect of sodium persulfate dosage on phenanthrene removal rate.

[0021] Figure 5 Schematic diagram of the effect of initial solution pH on phenanthrene removal rate (PHE: concentration of PHE at reaction time t; PHE0: initial concentration of PHE).

[0022] Figure 6 A schematic diagram illustrating the effect of free radical quenchers on phenanthrene removal.

[0023] Figure 7 A schematic diagram illustrating the impact of the number of times gasification slag is used on the phenanthrene removal rate.

[0024] Figure 8 A schematic diagram of the removal of the antibiotic ofloxacin using a gasification slag / sodium persulfate system. Detailed Implementation

[0025] The method described in this invention enables the utilization of gasification slag as a waste and, in combination with persulfate advanced oxidation technology, the low-cost and high-efficiency removal of phenanthrene from coking wastewater and ofloxacin from antibiotic wastewater.

[0026] Example 1

[0027] A method for oxidative removal of phenanthrene from coking wastewater and ofloxacin from antibiotic wastewater using a gasification slag / sodium persulfate system, comprising the following steps:

[0028] Step 1: Grind the gasification slag until its particle diameter can pass through a 60-mesh sieve;

[0029] Step 2: Control the temperature of the wastewater to be treated to 20-30℃, adjust the pH of the wastewater to be treated to 3 using sodium hydroxide or sulfuric acid, and determine the initial concentration of pollutants;

[0030] Step 3: Add gasification slag and sodium persulfate to the wastewater treated in Step 2, wait for the reaction to proceed for a period of time, filter the wastewater through a 0.22μm filter membrane, and then measure the residual concentration of pollutants.

[0031] In step three, the concentration of phenanthrene is 1 mg / L, the concentration of gasification slag is 0.7 g / L, the concentration of sodium persulfate is 1 mmol / L, and the reaction time is 60 min. According to this dosage ratio, the removal rate of phenanthrene can reach 95.34%.

[0032] This method enables the utilization of gasification slag as a waste and, in combination with persulfate advanced oxidation technology, the low-cost and high-efficiency removal of phenanthrene from coking wastewater.

[0033] Example 2

[0034] Steps one and two are the same as in Example 1. The difference is that in step three, the concentration of ofloxacin is 5 mg / L, the concentration of gasification slag is 0.7 g / L, the concentration of sodium persulfate is 1 mmol / L, and the reaction time is 60 min. According to this dosage ratio, the removal rate of ofloxacin can reach 98.56%.

[0035] The following combination Figure 1 The effects of different systems on the removal rate of phenanthrene were investigated.

[0036] Take 2 mL of PHE stock solution (weigh 0.025 g PHE and dissolve it in 500 mL of acetonitrile solution, where the acetonitrile content is 2% by volume, and dilute to 100 mL with deionized water to obtain a 1 mg / L PHE solution). Place the obtained PHE solution (containing 1 mg PHE) into three 250 mL beakers respectively. After adjusting the pH of the water sample with sodium hydroxide or sulfuric acid, add 0.7 g / L of gasification slag, 1 mmol / L of sodium persulfate, 0.7 g / L of gasification slag, and 1 mmol / L of sodium persulfate respectively. After reacting for 60 min, filter through a 0.22 μm filter membrane and determine the PHE concentration.

[0037] Figure 1 This diagram illustrates the impact of different systems on phenanthrene removal rates. The diagram shows that when gasification slag (CGS) and persulfate (PS) are present individually, the phenanthrene removal rates are both low. In the CGS / PS system, the phenanthrene removal rate reaches 95.34% after 60 minutes of reaction.

[0038] Figure 2 This is a SEM-EDS image of the gasification slag. The image shows that the gasification slag powder is blocky, with a smooth but irregular surface, and a size range of 2-10 μm. It is mainly composed of elements such as C, O, Si, Fe, and Al.

[0039] Determination of the optimal reaction conditions for phenanthrene (PHE) removal in the gasification slag / sodium persulfate system.

[0040] Take 2 mL of PHE stock solution (0.025 g of PHE dissolved in 500 mL of acetonitrile solution, where the acetonitrile content is 2% by volume), and dilute to 100 mL with deionized water to obtain a 1 mg / L PHE solution. Place the obtained PHE solution (containing 1 mg of PHE) in a 250 mL beaker, adjust the pH of the water sample with sodium hydroxide or sulfuric acid, add a certain amount of gasification slag and sodium persulfate, react for 60 min, filter through a 0.22 μm filter membrane, and then determine the PHE concentration.

[0041] Figure 3 , 4Figures 5 and 6 respectively illustrate the effects of gasification slag dosage on phenanthrene removal rate, sodium persulfate dosage on phenanthrene removal rate, and initial solution pH on phenanthrene removal rate. The figures show that, within a certain range, the phenanthrene removal rate increases with increasing gasification slag dosage, increasing sodium persulfate dosage, and decreasing initial solution pH.

[0042] The following combination Figure 6 The effects of free radical quenchers ethanol, tert-butanol, and isopropanol on the removal efficiency of phenanthrene were investigated.

[0043] Take 2 mL of PHE stock solution (0.025 g of PHE dissolved in 500 mL of acetonitrile solution, where the acetonitrile content is 2% by volume), and dilute to 100 mL with deionized water to obtain a 1 mg / L PHE solution. Place the obtained PHE solution (containing 1 mg of PHE) in a 250 mL beaker, adjust the pH of the water sample with sodium hydroxide or sulfuric acid, and then prepare solutions of 100 mmol / L ethanol, tert-butanol, and isopropanol, respectively. Then add a certain amount of gasification slag and sodium persulfate, react for 60 min, filter through a 0.22 μm filter membrane, and determine the PHE concentration.

[0044] Figure 6 This is a schematic diagram illustrating the effect of free radical quenchers on phenanthrene removal. The diagram shows that the gasification slag / sodium persulfate system generates sulfate free radicals (SO4). -. or hydroxyl radical HO . sulfate radical SO4 -. It plays a major role in the removal process in the Philippines.

[0045] The following combination Figure 7 The impact of the number of times gasification residue is used on phenanthrene removal rate was investigated.

[0046] Take 2 mL of PHE stock solution (0.025 g of PHE dissolved in 500 mL of acetonitrile solution, where the acetonitrile content is 2% by volume), and dilute to 100 mL with deionized water to obtain a 1 mg / L PHE solution. Place the obtained PHE solution (containing 1 mg of PHE) in a 250 mL beaker, adjust the pH of the water sample with sodium hydroxide or sulfuric acid, add a certain amount of gasification slag and sodium persulfate, react for 60 min, filter through a 0.22 μm filter membrane, and determine the PHE concentration. After the first reaction, collect the gasification slag, wash with deionized water, and dry; the second and third reactions are the same as the first reaction.

[0047] Figure 7 This diagram illustrates the effect of the number of times the gasification slag is used on the phenanthrene removal rate. As can be seen from the diagram, with increasing usage frequency, the gasification slag's ability to activate sodium persulfate gradually weakens, and the phenanthrene removal rate also gradually decreases.

[0048] The following combination Figure 8 The removal of the antibiotic ofloxacin by the gasification slag / sodium persulfate system was investigated.

[0049] Take 5 mL of ofloxacin stock solution (weigh 0.1 g of ofloxacin dissolved in a 1000 mL volumetric flask), and dilute to 100 mL with deionized water to obtain a 5 mg / L ofloxacin solution. Place the obtained ofloxacin solution in a 250 mL beaker, adjust the pH of the water sample with sodium hydroxide or sulfuric acid, add a certain amount of gasification slag and sodium persulfate, react for 60 min, filter through a 0.22 μm filter membrane, and determine the ofloxacin concentration.

[0050] Figure 8 This is a schematic diagram of the removal of the antibiotic ofloxacin using a gasification slag / sodium persulfate system. As can be seen from the diagram, ofloxacin is gradually removed as the reaction proceeds, reaching a removal rate of 98.56% after 30 minutes.

Claims

1. A method for oxidative removal of phenanthrene from coking wastewater and ofloxacin from antibiotic wastewater using a gasification slag / sodium persulfate system, characterized in that, Follow these steps: Step 1: Grind the gasification slag until its particle diameter can pass through a 60-mesh sieve; Step 2: Control the temperature of the wastewater to be treated to 20-30℃, adjust the pH of the wastewater to be treated to 3 using sodium hydroxide or sulfuric acid, and determine the initial concentration of pollutants; Step 3: Add gasification slag and sodium persulfate to the wastewater after Step 2, wait for the reaction to proceed for a period of time, filter the wastewater through a 0.22μm filter membrane, and then measure the residual concentration of pollutants. For coking wastewater, in step three, the concentration of phenanthrene is 1 mg / L, the dosage of gasification slag is 0.7 g / L-0.9 g / L, the dosage of sodium persulfate is 0.6 mmol / L-1 mmol / L, and the reaction time is 60-80 min, which can achieve a phenanthrene removal rate of 84.23%-97.68%. For antibiotic wastewater, in step three, the concentration of ofloxacin is 5 mg / L, the dosage of gasification slag is 0.7 g / L-0.9 g / L, the dosage of sodium persulfate is 0.6 mmol / L-1 mmol / L, and the reaction time is 60-80 min, which can achieve a removal rate of ofloxacin of 88.69%-98.56%. In step three, the main reaction occurring in the gasification slag / sodium persulfate system is the reaction involving Fe in the solid waste gasification slag. 2+ After sodium persulfate is activated, active free radical SO4 is generated. -. and HO . This method further oxidizes and decomposes phenanthrene or ofloxacin; it enables the utilization of gasification slag and, combined with persulfate advanced oxidation technology, achieves low-cost and high-efficiency removal of phenanthrene from coking wastewater and ofloxacin from antibiotic wastewater.

2. The method for oxidative removal of phenanthrene from coking wastewater and ofloxacin from antibiotic wastewater using a gasification slag / sodium persulfate system according to claim 1, characterized in that: For coking wastewater, in step three, the concentrations of phenanthrene (1 mg / L), gasification slag (0.7 g / L), and sodium persulfate (1 mmol / L) are used. With this dosage ratio and a reaction time of 60 minutes, the removal rate of phenanthrene can reach 95.34%. For antibiotic wastewater, in step three, the concentrations of ofloxacin (5 mg / L), gasification slag (0.7 g / L), and sodium persulfate (1 mmol / L) are used. With this dosage ratio and a reaction time of 60 min, the removal rate of ofloxacin can reach 98.56%.

3. The method for oxidizing and removing phenanthrene and ofloxacin from coking wastewater and antibiotic wastewater using a gasification slag / sodium persulfate system according to claim 1 or 2, characterized in that: The removal rate of phenanthrene in coking wastewater was 95.34% in the first cycle of gasification residue recycling, 71.06% in the second cycle, and 46.18% in the third cycle.

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