A nano-zero-valent iron-aquatic earthworm complex for removing halogenated antibiotics from wastewater and its application

Abstract

This invention discloses a nano-zero-valent iron-aquatic earthworm composite for removing halogenated antibiotics from wastewater and its application, relating to the field of water pollution remediation technology. Based on screening nano-zero-valent iron materials, this invention constructs a nano-zero-valent iron-aquatic earthworm interaction system with a specific ratio. This system activates the nano-zero-valent iron through nano-biological interface interaction, significantly improving the material's reduction performance for halogenated antibiotics in wastewater. Ultimately, 100nm zero-valent iron was selected as the remediation material, and the optimal remediation combination was determined: 1g / L nano-zero-valent iron and 3×10⁻⁶ earthworms. 3 The degradation products generated are all less toxic than the halogenated antibiotics in the wastewater, achieving the removal of halogenated antibiotics from wastewater while ensuring ecological safety.

Description

Technical Field

[0001] This invention relates to the field of water pollution remediation technology, specifically to a nano-zero-valent iron-water earthworm composite for removing halogenated antibiotics from wastewater and its application. Background Technology

[0002] Halogenated antibiotic pollution is one of the emerging environmental problems facing the world. Low bioavailability means that most halogenated antibiotics enter the environment in the form of both the active ingredient and metabolites through feces and urine, posing a dual risk of biotoxicity and antibiotic resistance. For example, chloramphenicol antibiotics (CAPs) are inexpensive and have a broad antibacterial spectrum, leading to their massive use in animal husbandry, making intensive farms heavily polluted areas. Traditional antibiotic treatment technologies include sedimentation and filtration, chlorination, ozone oxidation, Fenton or photo-Fenton treatment, and bioremediation. However, because halogenated antibiotics are not only structurally stable but also have strong inhibitory effects on microorganisms, these traditional wastewater treatment processes are difficult to achieve efficient removal. Therefore, developing efficient removal technologies for halogenated antibiotics is crucial for controlling antibiotic pollution at its source and is a technological necessity related to the sustainable development of my country's animal husbandry industry and public health.

[0003] Given that halogenated antibiotics contain halogen groups such as -Cl and -F, developing reducing materials and technologies is an important approach to controlling halogenated antibiotic pollution. Nano-zero-valent iron (NZFe) is a classic reducing material that can efficiently degrade halogenated pollutants through adsorption and hydrogenation dehalogenation. However, in practical applications, the high reactivity of NZFe makes it prone to reaction with water and oxygen, forming a passivation layer after oxidation and losing its activity. For example, Xu et al. (2020) showed that passivated NZFe is difficult to effectively degrade fluoromethylphenidate (FF). Therefore, it is necessary to seek suitable methods to activate NZFe in practical environmental applications. Nanomaterial-biosynergistic remediation technology is a new concept that aims to enhance the degradation effect of nanomaterials on pollutants through the physiological and biochemical responses of organisms, or to stimulate the degradation capacity of organisms through nanomaterials, forming a low-cost, high-efficiency co-remediation technology. Hou et al. (2021) also found that *Caenorhabditis elegans* in soil can enhance the removal performance of pentachlorophenol by nano-zero-valent iron by secreting reducing molecules such as glutathione and cysteine. Therefore, constructing a nanomaterial-biological interaction system is a feasible approach to achieve efficient removal of halogenated antibiotics.

[0004] Tubificidae, belonging to the class Oligochaeta within the phylum Annelida, is an important group of freshwater benthic animals and a dominant species in many polluted water bodies, including aquaculture wastewater. Studies have shown that they can stably survive in the biological treatment tanks of wastewater treatment systems, exhibiting strong tolerance to many organic pollutants, and have been used for sludge reduction and decontamination. Although surface-passivated nano-zero-valent iron has poor degradation performance against halogenated antibiotics, its interaction with Tubificidae may stimulate the production of large-molecule proteins and small-molecule metabolites such as organic acids, adhering the nano-zero-valent iron to its body surface. The organic acids may then corrode the passivation layer on the nano-zero-valent iron surface, potentially activating the nano-zero-valent iron and improving its reductive degradation performance against halogenated antibiotics. Therefore, constructing a nano-zero-valent iron-Tubificidae interaction system holds promise for overcoming bottlenecks in nanoremediation technology such as "difficult mass transfer" and "oxidative inactivation," providing technical support for the control of halogenated antibiotic pollution.

[0005] References:

[0006] [1]Xu, J.et al.Sulfur loading and speciation control thehydrophobicity, electron transfer, reactivity, and selectivity of sulfidizednanoscale zerovalent iron.Adv.Mater.32, 1906910(2020).

[0007] [2] Hou, J. et al. Nano-zoo interfacial interaction as a design principle for hybrid soil remediation technology. ACS Nano 15, 14954-14964 (2021). Summary of the Invention

[0008] This invention provides a nano-zero-valent iron-aquatic earthworm composite for removing halogenated antibiotics from wastewater and its applications. Compared with traditional technologies, the composite of this invention is simple to operate and can simultaneously remove multiple halogenated antibiotics. It overcomes the technical bottlenecks of single nano-zero-valent iron remediation technology, such as "difficult mass transfer" and "oxidative inactivation," and combines the advantages of high efficiency of nano-remediation technology with the environmental friendliness of bioremediation technology. It is expected to be used for the efficient in-situ removal of halogenated antibiotics from water.

[0009] The specific technical solution is as follows:

[0010] This invention provides a nano-zero-valent iron-water tubifex complex for removing halogenated antibiotics from wastewater, wherein the nano-zero-valent iron-water tubifex complex comprises nano-zero-valent iron and tubifex worms.

[0011] The concentration of nano-zero-valent iron in the nano-earthworm composite is 0.3–3 g / L, and the concentration of earthworms is 10 g / L. 3 ~10 4 Item / L.

[0012] In an unexpected discovery during the embodiments of this invention, tubifex worms were able to adsorb and activate nano-zero-valent iron through their epidermal interface, thereby enhancing the removal of halogenated antibiotics. The reason for this phenomenon may be that a passivation layer exists on the surface of the nano-zero-valent iron, hindering electron transfer between it and the halogenated antibiotics. Tubifex worms can adsorb nano-zero-valent iron through their epidermal proteins and, in response to exposure to halogenated antibiotics, secrete organic acids and other molecules to dissolve the passivation layer. Through conjugation, this promotes electron transfer on the material surface, enhancing the degradation of halogenated antibiotics by the nano-zero-valent iron.

[0013] The nano-zero-valent iron is nano-zero-valent iron with different particle sizes and surface modifications.

[0014] Preferably, the particle size of the nano-zero valent iron is 50-3000 nm. More preferably, the particle size of the nano-zero valent iron is 100 nm.

[0015] Preferably, the concentration of nano-zero valent iron in the nano-earthworm composite is 1 g / L, and the concentration of earthworms is 3 × 10³ worms / L.

[0016] Preferably, the halogenated antibiotics in the wastewater are chloramphenicol antibiotics.

[0017] More preferably, the chloramphenicol antibiotic is chloramphenicol, thiamphenicol, or fluorothiamphenicol.

[0018] This invention also provides the application of the aforementioned nano-zero-valent iron-water earthworm composite in the removal of halogenated antibiotics from wastewater.

[0019] The present invention also provides a method for removing halogenated antibiotics from wastewater, wherein the nano-zero-valent iron-water earthworm complex is added to wastewater containing halogenated antibiotics.

[0020] This invention relates to a method for constructing a nano-zero-valent iron-water earthworm interaction system for removing halogenated antibiotics from wastewater, comprising the following steps:

[0021] (1) Preferred nano-zero-valent iron materials:

[0022] We collected actual aquaculture wastewater to construct a micro-universe, and set up different treatment groups for exposure experiments. We added a certain amount of tubifex worms, nano-zero-valent iron with different particle sizes and surface modifications, and a composite system of the two to evaluate the survival rate of tubifex worms under different conditions to ensure technical feasibility. We compared the degradation effects of nano-zero-valent iron with different particle sizes and surface modifications on halogenated antibiotics in wastewater with and without tubifex worms. We selected a nano-zero-valent iron material with good degradation performance of halogenated antibiotics to construct a material-biotechnology interaction system.

[0023] (2) Construction of a nano-zero-valent iron-water earthworm interaction system:

[0024] A water-medium simulation experiment was conducted, mixing different doses of nano-zero-valent iron with tubifex worms of varying biomass. Nano-armored tubifex worms were prepared by utilizing the adsorption of nano-zero-valent iron on the tubifex worm epidermis. The synergistic removal effect on typical halogenated antibiotics under different ratios was measured, and the optimal ratio was selected to construct a nano-zero-valent iron-tubifex worm interaction system. The types and toxicities of the transformation products were analyzed to ensure the ecological safety of the technology.

[0025] According to the above plan,

[0026] Furthermore, in step (1), the aquaculture wastewater originates from an aquaculture farm, and the main halogenated antibiotics in the wastewater are chloramphenicol (CAP), thiamphenicol (TAP), and FF, etc., and the constructed micro-universe is 1L;

[0027] Further, in step (1), the amount of tubifex worms added is 10. 4 The concentration of nano-zero valent iron with different particle sizes and surface modifications was 1 g / L, and the exposure period was 7 days. The survival rate of tubifex worms was 100%.

[0028] Furthermore, in step (1), the preferred nano-zero valent iron particle size is 100 nm;

[0029] Furthermore, in step (2), the water medium simulation experiment is carried out in a 6-well plate with a volume of 10 mL per well;

[0030] Further, in step (2), the typical halogenated antibiotic is FF, and the concentration is 1 mg / L;

[0031] Furthermore, in step (2), the amount of 100nm zero-valent iron used in the simulation study was 0, 0.3, 1, and 3 g / L, and the amount of tubifex worms used was 0, 10, and 10 g / L. 3 3×10 3 10 4 Items / L, with an exposure period of 7 days;

[0032] Further, in step (2), the conversion products are the dechlorination product (FF-Cl) and the dechlorination product (FF-2Cl) of FF.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] Based on the screening of nano-zero-valent iron materials, this invention constructs a nano-zero-valent iron-aquatic earthworm interaction system with a specific ratio. This system activates the nano-zero-valent iron through nano-biological interface interactions, significantly improving the material's reduction performance for halogenated antibiotics in wastewater. Ultimately, 100nm zero-valent iron was selected as the remediation material, and the optimal remediation combination was determined: 1 g / L of nano-zero-valent iron and 3 × 10⁻⁶ earthworms. 3 The degradation products generated are all less toxic than the halogenated antibiotics in the wastewater, achieving the removal of halogenated antibiotics from wastewater while ensuring ecological safety. Attached Figure Description

[0035] Figure 1 This invention demonstrates the removal effect of nano-zero valent iron with different particle sizes and surface modifications on halogenated antibiotics in wastewater in the presence or absence of aquatic earthworms, as shown in Example 1 of this invention.

[0036] Figure 2 This is a schematic diagram of the nano-zero-valent iron-water earthworm interaction system constructed in Example 1 of the present invention;

[0037] Figure 3 This illustrates the synergistic removal effect of different doses of 100nm nano-zero valent iron and tubifex worms on FF in water in Example 1 of the present invention.

[0038] Figure 4 The removal effect of nano-zero valent iron, tubifex worms and their interaction system on FF in water and the concentration of conversion products are shown in Example 1 of this invention. Detailed Implementation

[0039] The present invention will be further described below with reference to specific embodiments. The following are only specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto.

[0040] Example 1

[0041] The specific steps of the method of this invention are as follows:

[0042] (1) Preferred nano-zero-valent iron materials:

[0043] Wastewater samples were collected from an aquaculture farm. An investigation revealed that the farm primarily used CAPs (aquatic organic compounds). Basic water quality parameters were measured (pH 7.2, total organic carbon 5.1 mg / L, total organic carbon 56.0 mg / L Na). + 15.2 mg / L Mg 2+ 16.1 mg / LK+ 58.6 mg / L Ca 2+ 46.7 mg / L - 109.1 mg / L SO4 2- A micro-universe with a wastewater volume of 1L was constructed in a 1.5L circulating water tank. The original wastewater was used as a control group. A single water worm treatment group, a single nano zero-valent iron treatment group, and a composite treatment group were set up, with an exposure period of 7 days.

[0044] Purchase healthy tubifex worms with bright colors (identified as *Brucellus tremula*) and temporarily raise them for 2 weeks; the amount of tubifex worms added to the treatment group was 10. 4 The treatment group consisted of nano-zero-valent iron particles (50 nm, 100 nm), 3 μm flake-like zero-valent iron, and carboxymethyl cellulose (CMC) surface-modified nano-zero-valent iron, each dissolved in 10 mL of ultrapure water. After vortexing for 10 seconds and sonicating for 30 minutes, the solutions were added uniformly to the microsphere. During the 7-day exposure period, the water lost through evaporation was replenished periodically, and the survival of the tubifex worms was observed. No significant mortality was observed in the tubifex worms.

[0045] After exposure, a 1 mL water sample was collected, filtered through a 0.22 μm filter membrane, and the filtrate was stored in a 2 mL injection bottle. The solution was diluted 10-fold with a methanol:water mixture (1:9 v / v) before CAPs were determined using liquid chromatography-mass spectrometry (LC-MS / MS). The chromatographic column was a Waters ACQUITY BEH C18 column (1.7 μm, 2.1 mm × 100 mm), the column temperature was 313 K, the flow rate was 0.2 mL / min, and the injection volume was 4 μL. Mobile phase A was ultrapure water, and mobile phase B was methanol. The mass spectrometry parameters are as follows: ion source temperature (TEM) 350℃, curtain gas (CUR) 30psi, nebulizer voltage (IS) -4000V, nebulizer gas (GS1) 65psi, auxiliary gas (GS2) 45psi, declustering voltage (DP) -30V, injection voltage (EP) -10V, collision energy (CE) -40V, collision chamber exit voltage (CXP) -16V. Quantification was performed in MRM mode. CAP, TAP, and FF were determined in anion mode using external standard method. The detection limits were all 0.1 μg / L, and the calibration range was 1–100 μg / L. The correlation coefficient R0 was [not specified in the original text]. 2 Greater than 0.99.

[0046] The initial concentrations of CAP, TAP, and FF in the wastewater were measured to be 0.56±0.01, 0.09±0.00, and 0.17±0.00 μmol / L, respectively. The results showed ( Figure 1In the absence of aquatic earthworms, the removal performance of nano-zero-valent iron with different particle sizes and surface modifications for CAPs in wastewater was poor. For example, 1 g / L of 100 nm zero-valent iron could only reduce the concentrations of CAP, TAP, and FF to 0.50±0.01, 0.07±0.01, and 0.16±0.00 μmol / L after 7 days, with a total CAP removal rate of only 12%. However, in the presence of aquatic earthworms, the removal effect of 100 nm nano-zero-valent iron was better, reducing the concentrations of CAP, TAP, and FF to 0.27±0.04, 0.00±0.00, and 0.07±0.01 μmol / L after 7 days, with a total CAP removal rate of 58%. Therefore, in this case, 100 nm nano-zero-valent iron was selected as the preferred remediation material for the subsequent construction of the material-bio-interaction system.

[0047] (2) Construction of a nano-zero-valent iron-water earthworm interaction system:

[0048] This case study uses FF as a representative CAP and conducts an aqueous medium simulation experiment in a 6-well plate based on factorial experimental design. The specific steps are as follows: 2 mg / L FF aqueous solution and 0.6, 2, and 6 g / L 100 nm zero-valent iron nanoparticle solutions are prepared and added to the same well in 5 mL increments, with three replicates. In each composite treatment group, 10 μL of FF solution is placed in each well. 3 3×10 3 10 4 1 / L of tubifex worms, utilizing the adsorption of nano-zero valent iron on the tubifex worm's epidermis to form nano-armored tubifex worms ( Figure 2 After 7 days of exposure, the concentration of FF in the solution samples was determined by sampling and LC-MS / MS as described in step (1). The results showed that 1 g / L 100 nm zero-valent iron nanoparticles and 3 × 10 3 One / L tubifex worm can completely degrade FF within 7 days. Figure 3 Furthermore, the survival rate of tubifex worms was 100%. Therefore, this case study preferred the above ratio for constructing a nano-zero-valent iron-tubifex worm interaction system.

[0049] To further confirm the eco-safety of the degradation products, 1 g / L 100 nm nano-zero valent iron and 10 3 FF degradation experiments were conducted in six-well plates using tubifex worms per L and a composite system of the two (considering that the FF removal rate was 87% after 7 days in this system, there may be relatively abundant conversion products). The results showed that ( Figure 4After 7 days of exposure, the concentrations of FF and degradation products in the solution samples were measured. FF-Cl and FF-2Cl were measured in anion mode, while florfenicol (FFA) was measured in cationic mode. External standard method was used for quantification. The detection limits for FF-Cl, FF-2Cl, and FFA were 0.5, 0.1, and 0.1 μg / L, respectively. The results showed that the main products of the co-degradation were FF-Cl and FF-2Cl. The microbial toxicity of this transformation product was significantly lower than that of FF, indicating that the degradation and removal of FF using the nano-zero-valent iron-water earthworm interaction system has good ecological safety.

[0050] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Those skilled in the art can modify or make equivalent substitutions to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention. All such modifications and substitutions should be covered within the scope of the claims of the present invention and are within the scope of protection of the present invention.

Claims

1. A nano-zero-valent iron-water earthworm composite for removing halogenated antibiotics from wastewater, characterized in that, The nano-zero-valent iron-water earthworm complex comprises nano-zero-valent iron and water earthworms. The concentration of nano-zero-valent iron in the nano-Bugella worm composite is 0.3~3 g / L, and the concentration of Garuda worms is 10 g / L. 3 ~10 4 Item / L; The particle size of the nano-zero valent iron is 50-100 nm; The halogenated antibiotics in the wastewater are chloramphenicol antibiotics. The chloramphenicol antibiotics mentioned are chloramphenicol, thiamphenicol, or fluorothiamphenicol.

2. The nano-zero-valent iron-water earthworm composite as described in claim 1, characterized in that, The particle size of the nano-zero valent iron is 100 nm.

3. The nano-zero-valent iron-water earthworm composite as described in claim 1, characterized in that, The concentration of nano-zero-valent iron in the nano-Turtwig composite is 1 g / L, and the concentration of Turtwig is 3 × 10⁻⁶ g / L. 3 Item / L.

4. A method for removing halogenated antibiotics from wastewater, characterized in that, The nano-zero-valent iron-water earthworm complex according to any one of claims 1-3 is added to wastewater containing halogenated antibiotics.

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