A method for degrading sulfonamide antibiotics in wastewater by goethite composite Fe(II) salt

Abstract

The application discloses a method for degrading sulfonamide antibiotics in wastewater by using goethite and Fe(II) salt. The specific steps include: dissolving Fe(II) salt, adding goethite, and fully adsorbing Fe(II) to goethite to prepare a goethite and Fe(II) mixture; anaerobically pretreating wastewater containing sulfonamide antibiotics, adding the goethite and Fe(II) mixture to a sulfonamide antibiotic wastewater treatment unit, carrying out anaerobic reaction, separating and discharging water, and starting the next cycle of treatment; on-line monitoring the oxidation-reduction potential of each reaction stage, controlling the start and end of the reaction by the oxidation-reduction potential, and supplementing Fe(II) again to restore the degradation performance when the degradation efficiency of the sulfonamide antibiotic decreases and is controlled by the oxidation-reduction potential. The method is mild, the materials are cheap and easy to obtain, and the method is environment-friendly, and the sulfonamide antibiotic can be directionally degraded; Fe(II) can be recycled, and the purpose of efficiently treating sulfonamide antibiotic wastewater is achieved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of pollution control, and relates to a method for degrading sulfonamide antibiotic pollutants, in particular to a method for degrading sulfonamide antibiotics in wastewater by goethite combined with Fe(II) salt. BACKGROUND

[0002] In recent decades, pharmaceuticals and personal care products (PPCPs) have been widely used to treat and prevent human and animal diseases, and are often found in global water environments. Even at low concentration levels, long-term exposure to pharmaceutical compounds can change the microbial diversity in the environment. Antibiotics are important drugs in human medicine as well as in veterinary and agricultural medicine. However, most of the drugs are excreted in the form of original drugs or metabolites after administration, eventually entering surface water, groundwater or farmland, and the widespread use of antibiotics has raised concerns about the risk of spreading antibiotic-resistant bacterial genes and the negative impact on organisms in water ecosystems.

[0003] Sulfamethoxazole (SMX) is an important representative antibiotic that has been widely used to treat various bacterial infections (e.g., urinary, respiratory and intestinal infections) in human medicine and animal husbandry. It is reported that about 45-70% of SMX is excreted into the environment through urine, and the transformation products of human metabolism can also be easily re-transformed into SMX. Therefore, SMX is often one of the most commonly detected antibiotics in the environment, such as wastewater treatment plants, farmland systems, landfill leachate and sludge, with concentrations ranging from hundreds of ng / L to mg / L. Therefore, in view of the ecological safety problems caused by the discharge of sulfonamide antibiotics into the environment, efficient treatment methods are urgently needed.

[0004] In natural environments and engineering systems, the removal of antibiotics is generally divided into adsorption method, chemical oxidation method and biological degradation method. The adsorption method has the effect of quickly removing antibiotics, but the pollutants are only transferred from one medium to another. Chemical oxidation methods include Fenton oxidation, persulfate oxidation, photocatalytic oxidation, etc. These methods mainly utilize the hydroxyl radicals, sulfate radicals, etc. generated by chemical oxidation to degrade antibiotics. Chemical oxidation methods have the advantages of high efficiency and complete degradation of pollutants, however, the above measures still have the disadvantages of high cost and easy secondary pollution in practical application. Biological degradation method has the advantages of economic environmental protection and low cost, but the biological degradation process often has the disadvantages of incomplete mineralization and slow degradation rate. Therefore, finding a green and efficient method for degrading antibiotic pollutants has become a hot topic.

[0005] Goethite is a common mineral with high activity in soil, and researchers have found that goethite has good adsorption capacity. In addition, researchers have also found that in the microbial process of anaerobic dissimilatory reduction of Fe(III) and sulfate, many organic and inorganic compounds can be abiotically degraded. However, the reduction efficiency of antibiotics under the combined conditions of different valence Fe salts and goethite under anaerobic conditions is not clear. Under anaerobic non-energy conditions, efficient and rapid degradation of antibiotics without secondary pollution is a technical problem in the treatment of antibiotic environmental pollution.

[0006] The present application attempts to find a method of using cheap and readily available goethite and Fe(II) salt to achieve the degradation of antibiotics in an environmentally friendly way under efficient and low-cost conditions. Traditional advanced oxidation often uses high-cost catalytic materials, metals or oxidants, which has high operating costs and certain operation risks. If cheap and readily available soil goethite and cheap Fe(II) salt are used for the treatment of wastewater containing antibiotics, the technical problems of such wastewater treatment can be solved, the treatment cost and the generation of secondary pollutants can be significantly reduced, and efficient degradation of refractory pollutants such as sulfonamides can be achieved.

[0007] Therefore, the key of the present application is to find a new method with low cost, simple process and environmental friendliness for rapid and efficient degradation of sulfonamide antibiotic pollutants. SUMMARY

[0008] The present application aims to solve the problem of wastewater containing antibiotics by using cheap and readily available goethite and cheap and environmentally friendly Fe(II) salt, and provides a method for treating wastewater containing sulfonamide antibiotics to achieve efficient and low-cost degradation of pollutants.

[0009] The present application provides a method for degrading sulfonamide antibiotics in wastewater by goethite combined with Fe(II) salt, comprising the following steps:

[0010] (1) In a closed unit, dissolve Fe(II) salt solid into water or anaerobic water, then put goethite into the Fe(II) salt solution and do deoxidation treatment, then oscillate for 0.5-1h to make Fe(II) fully adsorbed to goethite, to prepare a goethite combined with Fe(II) mixture, for standby;

[0011] (2) Anaerobic pretreatment unit is used to pretreat wastewater containing sulfonamide antibiotics to consume most of the dissolved oxygen in the wastewater, then the goethite combined with Fe(II) mixture is added to the reaction treatment unit containing the wastewater containing sulfonamide antibiotics, the anaerobic environment is maintained, and the reaction is carried out for 8-12h, then the treated wastewater is discharged and the next treatment cycle is started.

[0012] Further, when the conversion efficiency of the sulfonamide antibiotic begins to decrease, the supernatant of the reaction treatment unit is emptied, the anaerobic environment is maintained, and Fe(II) salt is added to the residue at the bottom of the reaction treatment unit after being emptied, and the mixture of goethite and Fe(II) is dissolved and oscillated for 0.5-1 h, so that the degradation performance of the mixture is restored.

[0013] Preferably, the ratio of the molar amount of goethite to the molar amount of Fe(II) salt in step (1) is greater than 70.

[0014] Further, the redox potential is monitored in each stage of the anaerobic pretreatment, the reaction treatment unit, and the precipitation unit, and a control system is arranged in the precipitation unit to control the starting point and the ending point of the reaction according to the redox potential, and the addition of Fe(II) salt can be controlled when the degradation efficiency of the sulfonamide antibiotic decreases and the redox potential indicates that the degradation efficiency decreases.

[0015] The basic principle of the degradation of the sulfonamide antibiotic by the mixture of goethite and cheap Fe(II) salt is as follows: the goethite has a strong adsorption capacity for metal ions Fe(II) salt, Fe(II) is adsorbed to the goethite and undergoes a water complexation reaction, the adsorption of Fe(II) to the surface hydroxyl group reduces the standard reduction potential of the Fe(III) / Fe(II) redox pair. Meanwhile, more Lewis groups donate electrons to replace the H2O molecules coordinated to Fe(II), and the electron density of the Fe(II) reaction center is increased, so that the Fe(II) becomes a strong reducing agent, which further reduces the sulfonamide antibiotic and other organic matters. In addition, in addition to the surface effect, the absorption of Fe(II) by the Fe(III) hydroxide mineral also has an interface electron transfer effect.

[0016] The present application has the following beneficial effects:

[0017] 1. Compared with other advanced oxidation methods such as the ozone oxidation method and the Fenton oxidation method, the goethite is a common mineral with a high content in soil, and the Fe(II) salt is a common chemical agent that is cheap and easy to obtain, the chemical reaction of the two substances is more moderate, and the materials are more cheap, easy to obtain, non-toxic, and more environmentally friendly, so that the problems of expensive and complicated material preparation, safety hazards, and secondary pollution are solved.

[0018] 2. The reaction is carried out under anaerobic conditions, and aeration treatment is not required, which is beneficial to saving the energy consumption in the wastewater treatment process.

[0019] 3. The mixture of goethite and Fe(II) can directionally degrade the sulfonamide antibiotic, the process is more targeted, the redox potential is coupled to control the reaction, the role of Fe(II) can be fully played, the addition amount of Fe(II) is low, and the utilization efficiency is higher. Meanwhile, when the Fe(II) is consumed, it can be directly supplemented, and the goethite has a high adsorption capacity, so that the goethite can be recycled. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 Flow chart of the present invention.

[0021] Figure 2 Effect of different goethite amount on degradation of sulfamethoxazole in the presence of Fe(II) mixture. DETAILED DESCRIPTION

[0022] The present invention will be further described in conjunction with the following examples, which do not limit the scope of the present invention. Various modifications or variations can be made to the technical solutions of the present invention without creative labor, and still fall within the scope of the present invention.

[0023] Example

[0024] Reference Figure 1 As a specific example of the present invention suitable for the treatment method of sulfonamide antibiotic wastewater, the following steps are included:

[0025] 1. Take FeSO4 to prepare a 0.5 mM FeSO4 solution, weigh goethite and put it into the FeSO4 solution, so that the final concentration of goethite is 2 g / L, shake for 1 h to make Fe(II) fully adsorbed into goethite, and after 1 h, the Fe(II) concentration in the supernatant of the goethite-Fe(II) mixture is measured to be 0.25 mM, indicating that 50% of Fe(II) is adsorbed into goethite.

[0026] 2. Take sulfonamide antibiotic wastewater containing sulfamethoxazole at a concentration of 10 mg / L, which has been pretreated by anaerobic treatment, and the dissolved oxygen concentration is less than 0.2 mg / L. Put the wastewater into the SBR reactor, which includes the processes of water inlet, stirring, sedimentation, water discharge, idling, nitrogen blowing and dosing. Add the goethite-Fe(II) mixture to the SBR reactor and start the SBR operation mode.

[0027] 3. During the SBR reaction process, the mixed liquor in the reactor is intermittently taken to measure the concentrations of sulfamethoxazole and Fe(II). The concentrations of sulfamethoxazole at 10 min, 1 h, 4 h, 8 h and 12 h of the reaction are measured to be 10.666, 7.971, 2.693, 0.372 and 0 mg / L, respectively, and the concentrations of Fe(II) are measured to be 0.27, 0.25, 0.21, 0.19 and 0.18 mM, respectively. After 8 h of reaction, sulfamethoxazole is basically completely degraded, and the consumption of Fe(II) during this process is only about 60 mg / L. Then, sedimentation is carried out for 1 h, water is discharged, and the next cycle of treatment is started, and the removal rate remains stable.

[0028] 4. After the sixth cycle, the ORP increased from -30 mV to -12 mV, and the degradation efficiency of sulfamethoxazole decreased. After the SBR was idle for a period, the dosing pump was turned on and 0.5 mM FeSO₄ solution was added again. Stirring was resumed for 1 hour. After that, the SBR operation mode was resumed, and the degradation rate of sulfamethoxazole returned to over 90% within 8 hours.

[0029] 5. Compared with the blank reactor, the degradation effect of wastewater containing sulfonamide antibiotics was basically zero when adding only goethite, only Fe(II), and a mixture of goethite and Fe(II) under aerobic conditions.

[0030] 6. As the amount of goethite increases, Fe(II) gradually increases, and the treatment effect of sulfamethoxazole wastewater also increases significantly (e.g. Figure 2 ).

Claims

1. A method for degradation of sulfonamide antibiotics in wastewater by goethite composite Fe(II) salt, characterized in that, The method comprises the following steps: (1) dissolving Fe(II) salt solid into water in a closed unit, then putting goethite into the Fe(II) salt solution and doing deoxidation treatment, and then oscillating for 0.5-1 h to make Fe(II) fully adsorbed into goethite, thereby preparing a goethite composite Fe(II) mixture for standby; (2) anaerobically pretreating the wastewater containing sulfonamide antibiotics in an anaerobic pretreatment unit, then adding the goethite composite Fe(II) mixture into a reaction treatment unit of the wastewater containing sulfonamide antibiotics, keeping an anaerobic environment, and reacting for 8-12 h, and then entering a sedimentation unit for sedimentation, discharging the treated wastewater, and starting a next treatment cycle; when the sulfonamide antibiotic conversion efficiency decreases, emptying the supernatant of the reaction treatment unit, keeping the anaerobic environment, and adding Fe(II) salt into the residue at the bottom of the emptied reaction treatment unit, dissolving and oscillating for 0.5-1 h to restore the degradation performance of the goethite composite Fe(II) mixture; the stages of the anaerobic pretreatment unit, the reaction treatment unit and the sedimentation unit are all provided with redox potential monitoring, and a control system is arranged in the sedimentation unit to control the start and end points of the reaction according to the redox potential; when the sulfonamide antibiotic degradation efficiency decreases and is indicated by the redox potential, the addition of Fe(II) salt can be controlled.

2. The method of degrading sulfonamide antibiotics from wastewater by goethite complexed Fe(II) salt according to claim 1, characterized in that, In step (1), the molar ratio of goethite to Fe(II) salt is greater than 70.

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