A method for deep treatment of landfill leachate based on modified metal materials

Abstract

A method for deep treatment of landfill leachate based on modified metal materials, wherein halogen salt and transition metal are mixed at a mass ratio of 0.005 to 0.5:1, and then ball milled in an oxygen-free atmosphere to obtain modified metal materials. By using the modified transition metal with adjustable electron transfer rate to construct a reduction unit, rapid reduction and detoxification of electrophilic organic components and heavy metals in landfill leachate is achieved, and then coupling an oxidant to induce active species to form an oxidation unit, deep oxidation and mineralization of nucleophilic organic components is achieved, and finally a flocculant is introduced to adsorb and separate the residual small molecular carbon and nitrogen components, so as to achieve deep treatment of landfill leachate and enable landfill leachate to meet discharge standards.

Description

Technical Field

[0001] The invention belongs to the technical field of environmental protection, and particularly relates to a modified metal material and a preparation method thereof, as well as a landfill leachate deep treatment method based on the modified metal material. Background Art

[0002] Leachate is one of the harmful byproducts produced by solid waste in landfills through physical, chemical, and biological processes. It has the characteristics of complex composition and large fluctuations in water quality and quantity. With the rapid increase in the amount of domestic waste, how to effectively treat leachate has become one of the important research directions of waste treatment.

[0003] At present, the methods used in the treatment of landfill leachate mainly include biological method, chemical method and physical filtration method. Among them, the biological method is limited by the C / N of landfill leachate, and the presence of heavy metals and toxic and harmful elements also limits the degradation efficiency of the biological method; the physical filtration method has high requirements on the filtration efficiency and service life of the membrane component, and will produce a higher concentration of filtrate; the chemical method is mainly based on the Fenton method, which achieves efficient decomposition of organic pollutants through active oxygen species.

[0004] The types of pollutants in landfill leachate are complex, including organic matter that is easy to oxidize but difficult to reduce, and organic matter that is easy to reduce but difficult to oxidize, as well as dozens of heavy metals. It is difficult to achieve the simultaneous removal of these pollutants using a single treatment technology (such as physical adsorption, chemical oxidation, chemical reduction, etc.), which has led to a decline in effluent quality to a certain extent. Under this premise, the reduction-oxidation system came into being. Common reduction systems include electrochemical reduction, heterogeneous reduction, etc. Among them, transition metals have become a promising reducing material due to their high reduction activity, activation oxidation potential and low cost of use. Zero-valent iron in transition metals is widely popular due to its wide source, low toxicity and environmental friendliness. However, the oxide layer formed on the surface of zero-valent iron will greatly inhibit the efficiency of electron transfer, resulting in greatly inhibited reaction activity, and it is still impossible to remove organic matter and heavy metals in landfill leachate at the same time.

[0005] Therefore, there is an urgent need for a landfill leachate treatment method to achieve the simultaneous removal of multiple types of characteristic pollutants. Summary of the invention

[0006] 1. Purpose of the invention

[0007] The purpose of the present invention is to provide a method for deep treatment of landfill leachate based on modified metal materials. By adopting a modified transition metal with adjustable corrosion rate to construct a reduction unit, rapid reduction and detoxification of electrophilic organic components and heavy metals in the landfill leachate is achieved. Then, an oxidant is coupled to induce active species to form an oxidation unit to achieve deep oxidation and mineralization of aromatic organic components. Finally, a flocculant is introduced to adsorb and separate residual small molecular carbon and nitrogen components, thereby achieving deep treatment of the landfill leachate and allowing the landfill leachate to meet discharge standards.

[0008] (II) Technical solution

[0009] In order to achieve the above object, the present invention provides a method for preparing a modified metal material, comprising:

[0010] The halogen salt and the transition metal are mixed in a mass ratio of 0.005-0.5:1, and then ball-milled in an oxygen-free atmosphere to obtain a modified metal material.

[0011] Specifically, the halogen salt is selected from at least one of sodium fluoride, sodium chloride, potassium fluoride, potassium chloride, calcium fluoride, calcium chloride, sodium bromide, potassium bromide, and calcium bromide;

[0012] The transition metal is selected from at least one of iron, aluminum, copper and zinc.

[0013] Specifically, the specific conditions of the ball milling include:

[0014] The rotation speed is 300~900 rpm, and the ball milling time is 1~6 hours.

[0015] Another aspect of the present invention provides a modified metal material prepared by any of the above-mentioned methods for preparing a modified metal material.

[0016] In another aspect, the present invention provides a method for deep treatment of landfill leachate based on modified metal materials, comprising:

[0017] 1: mixing landfill leachate with a modified metal material, and performing a reduction reaction to obtain a mixed system 1, wherein the modified metal material is prepared by the aforementioned preparation method;

[0018] 2: adding an oxidant to the mixed system 1 and continuing stirring to carry out an oxidation mineralization reaction to obtain a mixed system 2;

[0019] 3: Add flocculant to the mixed system 2, stir for reaction, and then perform solid-liquid separation to obtain treated landfill leachate.

[0020] Among them, in step 1:

[0021] The dosage of modified metal materials in landfill leachate is 50 mg / L~5000 mg / L.

[0022] Wherein, the specific conditions of the reduction reaction include:

[0023] It is carried out under stirring conditions, with a stirring speed of 50~250 r / min;

[0024] Maintain pH between 3 and 5;

[0025] The reaction time is 0.5~3h.

[0026] Among them, in step 2:

[0027] The added oxidant is selected from hydrogen peroxide and / or persulfate;

[0028] The amount of the oxidant added is 1-100 mmol / L;

[0029] The specific conditions of the oxidation mineralization reaction include:

[0030] Add an oxidant to the mixed system 1 and continue stirring for 0.1 to 0.5 h to achieve an oxidation mineralization reaction.

[0031] Specifically, when the concentration of the reducible pollutants in the mixed system 1 is 10-50% of the concentration of the reducible pollutants in the landfill leachate added in step 1, the oxidant is added.

[0032] Among them, in step 3:

[0033] The flocculant is selected from at least one of calcium chloride, calcium oxide and aluminum chloride;

[0034] The amount of the flocculant added is 1000-5000 mg / L;

[0035] Add the flocculant to make the pH value of the mixed system 2 be 6-8;

[0036] The stirring reaction time is 3 to 10 minutes to allow the added flocculant to dissolve and disperse.

[0037] (III) Beneficial effects

[0038] The above technical solution of the present invention has the following beneficial technical effects:

[0039] The preparation method of the modified metal material provided by the embodiment of the present invention comprises the following steps: mixing a halogen salt and a transition metal in a required proportion, using mechanical ball milling to make the transition metal a core, and loading the halogen salt on the surface of the transition metal core and the surface layer of the transition metal core, thereby changing the oxygen partial pressure at the transition metal core interface, protecting the active sites on the surface of the transition metal core, and maintaining the stability and activity of the transition metal during long-term storage and transportation in a dry environment, while activating the active sites of the transition metal in a high humidity environment (such as in an aqueous solution), having extremely strong electron transmission efficiency, and improving the reduction ability and catalytic oxidation activity of the transition metal;

[0040] The preparation method provided by the embodiment of the present invention is simple in technology, low in cost, and has no secondary pollution source during the preparation process;

[0041] The halogen salt used in the preparation method provided in the embodiment of the present invention is green and pollution-free, has a wide range of sources, and has no pollution risk during use, which complies with the principle of green chemistry;

[0042] The method for deep treatment of landfill leachate based on modified metal materials provided in the embodiment of the present invention realizes rapid reduction and detoxification of electrophilic organic components and heavy metals in the landfill leachate by constructing a reduction unit using a modified transition metal with adjustable electron transfer rate, then couples an oxidant to activate the oxidant to produce free radicals and non-radical active substances, and induces the active species to form an oxidation unit, thereby realizing deep oxidation and mineralization of nucleophilic organic components, and finally introducing a flocculant to adsorb and separate the remaining small molecular carbon and nitrogen components, thereby realizing deep treatment of the landfill leachate and allowing the landfill leachate to meet discharge standards. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 The typical halogen (Cl) salt modified zero-valent iron (Cl_ZVI) of the present invention BM ) and ordinary zero-valent iron (ZVI BM ) characteristic element XPS spectrum (a) and Cl_ZVI BM Ar + Sputtering XPS spectrum (b);

[0044] Figure 2 Typical halogen (Cl) salt-modified zero-valent iron SEM-EDS spectrum of the present invention;

[0045] Figure 3 Typical halogen salt-modified zero-valent iron of the present invention and ordinary zero-valent iron electrochemical characteristics diagram (a) open circuit potential (OCPT); (b) Tafel curve; (c) electrochemical impedance spectroscopy (EIS);

[0046] Figure 4Typical halogen salt modified zero-valent iron and ordinary zero-valent iron of the present invention on the degradation effect diagram of the model pollutants, wherein a is the degradation effect diagram of SMT (easily oxidizable pollutants), b is the degradation effect diagram of CNB (easily reducible pollutants);

[0047] Figure 5 The graph shows the degradation effect of typical halogen salt-modified zero-valent iron of the present invention and ordinary zero-valent iron on model pollutants over time.

[0048] Figure 6 Schematic diagram of the reduction - oxidation - coagulation coupling process route used in Example Ⅱ;

[0049] Figure 7 The figures are diagrams showing the treatment effects of the process of the present invention on leachate and added model substances, wherein a is a three-dimensional fluorescence diagram of leachate influent, b is a three-dimensional fluorescence diagram of effluent leachate after reduction treatment, c is a three-dimensional fluorescence diagram of effluent leachate after oxidation treatment, d is a three-dimensional fluorescence diagram of effluent leachate after coagulation treatment, e is a diagram showing changes in COD content of leachate, f is a diagram showing changes in SMT content, g is a diagram showing changes in CNB content, and h is a diagram showing changes in Cr content. In the figures e, f, g, and h, "influent" represents the content of leachate before treatment, "reduction" represents the content after treatment in step 1, "oxidation" represents the content after treatment in step 2, and "effluent" represents the content after treatment in step 3. DETAILED DESCRIPTION

[0050] The embodiments of the present invention are described in detail below with reference to the accompanying drawings and examples.

[0051] An embodiment of the present invention provides a method for preparing a modified metal material, comprising:

[0052] The halogen salt and the transition metal are mixed in a mass ratio of 0.005-0.5:1, and then ball-milled in an oxygen-free atmosphere to obtain a modified metal material.

[0053] Specifically, the halogen salt is selected from at least one of sodium fluoride, sodium chloride, potassium fluoride, potassium chloride, calcium fluoride, calcium chloride, sodium bromide, potassium bromide, and calcium bromide;

[0054] The transition metal is selected from at least one of iron, aluminum, copper and zinc, preferably iron, and the iron is selected from at least one of micron zero-valent iron, nano zero-valent iron, magnetite, goethite and hematite;

[0055] The mass ratio of the halogen salt to the transition metal is preferably 0.01-0.16:1.

[0056] The preparation method of the modified metal material provided by the embodiment of the present invention comprises the following steps: mixing a halogen salt and a transition metal in a required proportion, using mechanical ball milling to make the transition metal a core, and loading the halogen salt on the surface of the transition metal core and the surface layer of the transition metal core, thereby changing the oxygen partial pressure at the interface of the transition metal core, protecting the active sites on the surface of the transition metal core, and maintaining the stability and activity of the transition metal core during long-term storage and transportation in a dry environment, while activating the active sites of the transition metal core in a high humidity environment (such as in an aqueous solution), having extremely strong electron transmission efficiency, and improving the reduction ability and catalytic oxidation activity of the transition metal;

[0057] The preparation method provided by the embodiment of the present invention is simple in technology, low in cost, and has no secondary pollution source during the preparation process;

[0058] The halogen salt used in the preparation method provided in the embodiment of the present invention is green and pollution-free, has a wide source, has no pollution risk during use, and complies with the principle of green chemistry.

[0059] Specifically, the specific conditions of the ball milling include:

[0060] The rotation speed is 300~900 rpm, and the ball milling time is 1~6 hours.

[0061] Ball milling under this condition can not only avoid energy loss and material overactivation caused by excessive energy input, but also ensure the high activity of the material, further improving the preparation efficiency of the material.

[0062] Another embodiment of the present invention provides a modified metal material prepared by any of the above-mentioned methods for preparing a modified metal material.

[0063] Please refer to the preparation method examples for specific descriptions and effects, which will not be repeated here.

[0064] Another embodiment of the present invention provides a method for deep treatment of landfill leachate based on modified metal materials, comprising:

[0065] Step 1: mixing landfill leachate with a modified metal material, and performing a reduction reaction to obtain a mixed system 1, wherein the modified metal material is prepared by any of the above-mentioned methods for preparing the modified metal material;

[0066] Step 2: adding an oxidant to the mixed system 1 and continuing stirring to perform an oxidation mineralization reaction to obtain a mixed system 2;

[0067] Step 3: Add flocculant to the mixed system 2, stir for reaction, and then perform solid-liquid separation to obtain treated landfill leachate.

[0068] The method for deep treatment of landfill leachate based on modified metal materials provided in an embodiment of the present invention adopts a modified transition metal with adjustable corrosion rate to construct a reduction unit, thereby realizing rapid reduction and detoxification of electrophilic organic components and heavy metals in the landfill leachate, and then couples an oxidant to induce active species to form an oxidation unit, thereby realizing deep oxidation and mineralization of aromatic organic components, and finally introducing a flocculant to adsorb and separate residual small molecular carbon and nitrogen components, thereby realizing deep treatment of the landfill leachate and allowing the landfill leachate to meet discharge standards.

[0069] Specifically, in step 1:

[0070] The dosage of the modified metal material in the landfill leachate is 50 mg / L to 5000 mg / L, preferably 100 to 1000 mg / L;

[0071] Under this condition, the high concentration of difficult-to-oxidize / difficult-to-reduce pollutants in the leachate can be removed synergistically and efficiently, while reducing the remediation cost.

[0072] The specific conditions of the reduction reaction include:

[0073] It is carried out under stirring conditions, with a stirring speed of 50~250 r / min;

[0074] Maintain pH between 3 and 5;

[0075] The reaction time is 0.5~3 h.

[0076] Under this condition, the material can not only effectively reduce pollutants, but also provide the influent of the oxidation process with an initial pH environment, free iron ions and pollutant types that meet the optimal oxidation conditions.

[0077] Specifically, in step 2:

[0078] The added oxidant is selected from hydrogen peroxide and / or persulfate, wherein the persulfate is selected from at least one of potassium peroxymonosulfate, sodium peroxymonosulfate, sodium peroxydisulfate, and potassium peroxydisulfate;

[0079] The amount of the oxidant added is 1 to 100 mmol / L, preferably 1 to 5 mmol / L;

[0080] Under this condition, the oxidant is fully activated to form a large amount of active oxygen. At the same time, an appropriate amount of oxidant dosage can reduce the competitive consumption of active oxygen. Furthermore, controlling the oxidant dosage under this condition can appropriately reduce the process cost.

[0081] The specific conditions of the oxidation mineralization reaction include:

[0082] Add an oxidant to the mixed system 1 and continue stirring for 0.1 to 0.5 h to achieve an oxidation mineralization reaction.

[0083] Specifically, when the concentration of the reducible pollutants in the mixed system 1 is 10-50% of the concentration of the reducible pollutants in the landfill leachate added in step 1 or the oxidant is added after the reaction for 2.5-3.5 hours.

[0084] Specifically, when the target pollutant (i.e., reducible pollutant) can be effectively removed to 10% to 50% of the original concentration within 2.5 to 3.5 hours in the reduction stage, the oxidant is added according to the time required for actual degradation; when the target pollutant (i.e., reducible pollutant) cannot be removed to 10% to 50% after 2.5 to 3.5 hours of reaction, the oxidant is added after 2.5 to 3.5 hours of reduction, preferably after 3 hours of reaction.

[0085] Under this condition, the pollutants in the leachate are degraded directly into non-toxic substances or into easily oxidized intermediate pollutants through reduction reactions. The timely addition of oxidants can activate the production of active oxygen, achieve deep oxidation and mineralization of the intermediate pollutants, and avoid the accumulation of some toxic intermediate pollutants after a single reduction treatment.

[0086] Specifically, in step 3:

[0087] The flocculant is selected from at least one of calcium chloride, calcium oxide and aluminum chloride;

[0088] The amount of the flocculant added is 1000-5000 mg / L;

[0089] After adding the flocculant, the pH value of the mixed system 2 is set to 6-8;

[0090] The stirring reaction time is 3 to 10 minutes to allow the added flocculant to be fully dissolved and dispersed.

[0091] Under this condition, the heavy metal ions in the leachate can be removed by adsorption, coagulation and co-precipitation, and the iron ions dissolved by the catalyst can also be precipitated to avoid excessive chromaticity of the effluent.

[0092] The following are specific embodiments of the present invention:

[0093] The raw materials used in each embodiment are all commercially available products, among which:

[0094] The commercial zero-valent iron is micron zero-valent iron purchased from Shanghai McLean Company, with a particle size of 100 mesh.

[0095] Example I-1

[0096] An appropriate amount of commercial zero-valent iron and sodium chloride were mixed in a mass ratio of 0.02:1, and ball-milled for 4 hours in an anaerobic environment at a ball-milling speed of 550 rpm. The modified material obtained by ball milling (denoted as: Cl_ZVI BM ).

[0097] Example I-2

[0098] An appropriate amount of commercial zero-valent iron and sodium chloride were mixed in a mass ratio of 0.06:1, and ball-milled for 4 hours in an anaerobic environment at a ball-milling speed of 550 rpm, and the modified material obtained by ball milling was collected.

[0099] Example I-3

[0100] An appropriate amount of commercial zero-valent iron and sodium chloride were mixed in a mass ratio of 0.16:1, and ball-milled for 4 hours in an anaerobic environment at a ball-milling speed of 550 rpm, and the modified material obtained by ball milling was collected.

[0101] Characterization and performance testing of the modified materials:

[0102] 1. Characterization and electrochemical analysis:

[0103] With Cl_ZVI provided in Example Ⅰ-1 BM Halogen salt modified zero-valent iron (X_ZVI BM ) is a typical representative of Figure 1 and 2 From the XPS spectrum and SEM-EDS, it can be seen that the halogen salt (sodium chloride) is uniformly loaded on the surface of the iron-based material through the mechanical co-milling method and corrodes into the core-shell layer. The modified materials obtained in other embodiments also have the same or similar properties.

[0104] See also Figure 3 Further electrochemical analysis showed that the interface electron transport performance was enhanced by halogen surface modification, which was manifested in the reduction of the impedance ring radius ( Figure 3 a), open circuit potential decreases ( Figure 3 b), self-corrosion potential decreases ( Figure 3 c). With the increase of halogen salt content, the self-corrosion potential of the modified material decreased from -0.78 V to -0.92 V, and the interfacial electron transport performance was regularly regulated.

[0105] 2. Reactivity test:

[0106] 100 mL of water (pH 4) contaminated with a simulated oxidizable pollutant (sulfadimethoxine, SMT) at a concentration of 10 mg / L was used as the remediation object, and 12 mg of Cl_ZVI prepared in Example Ⅰ-1 was added thereto. BM or unmodified ZVI BM(Control group), then add 2 mM hydrogen peroxide to start the reaction, set a constant speed (120 r / min) to stir the reaction for 14 min, regularly sample and filter, and analyze the SMT content in the upper liquid phase. BM As a control, the results Figure 4 As shown in a, after 14 minutes of reaction, Cl_ZVI BM The degradation rate of SMT reached 100% (the first-order reaction kinetic rate constant k obs = 0.95 min -1 ), under the same test conditions, the degradation rate of the modified materials prepared in Examples Ⅰ-2 and Ⅰ-3 to SMT reached 100% (k obs 0.86 min respectively -1 and 0.73 min -1 ), while the degradation rate of SMT in the control group was only about 60% (k obs = 0.08 min -1 ).

[0107] 100 mL of water (pH 4) contaminated with 10 mg / L of easily reducible pollutant (p-chloronitrobenzene, CNB) was used as the remediation object, and 12 mg of the Cl_ZVI prepared above was added to it. BM The reaction was stirred at a constant speed (120 r / min) for 2 h, and samples were taken regularly and filtered before analyzing the CNB content in the upper liquid phase.

[0108] The results are as follows Figure 4 As shown in b, after 2 h of reaction, Cl_ZVI BM The degradation rate of CNB is about 60%. Under the same test conditions, the degradation rates of CNB of the modified materials prepared in Examples Ⅰ-2 and Ⅰ-3 are 55% and 48%, respectively.

[0109] 3. Stability test:

[0110] The modified material Cl_ZVI obtained by ball milling in Example Ⅰ-1 BM , placed in a centrifuge tube and stored for 120 days.

[0111] 100 mL of simulated SMT-contaminated water (pH 4) with a concentration of 10 mg / L was used as the remediation object, and 12 mg of the Cl_ZVI prepared above was added to it. BM Then, 2 mM hydrogen peroxide was added to start the reaction. The reaction was stirred at a constant speed (120 r / min) for 14 minutes. Samples were taken regularly and filtered to analyze the SMT content in the upper liquid phase.

[0112] At the same time, zero-valent iron ZVI aged for 120 days was milled under the same conditions without sodium chloride modification.BM As a control, the results Figure 5 As shown, after 14 minutes of reaction, Cl_ZVI aged for 1 day BM and Cl_ZVI aged for 120 days BM The degradation rate of SMT reached 100%, while the degradation rate of SMT in the control group was only about 47%. It can be seen that the active sites of the iron-based material are effectively protected by the uniformly loaded halogen salt, so that it can still maintain its reaction activity under long-term air exposure conditions. Under the same test conditions, the modified materials prepared in Examples Ⅰ-2 and Ⅰ-3 can achieve complete degradation of SMT after 120 days.

[0113] Example II

[0114] Build as Figure 6 The three-level process system shown in the figure takes landfill leachate as an object and applies the constructed three-level process system to treat the leachate. In order to determine the key indicators and process effects, appropriate amounts of CNB, SMT, and Cr (VI) are added to the leachate as difficult-to-oxidize, difficult-to-reduce, and heavy metal model pollutants, respectively. The specific steps include:

[0115] Step 1: Add appropriate amount of CNB, SMT and Cr(VI) to 100 mL of leachate to make their concentrations 10 mg / L respectively. Maintain the pH at 4 and add 0.1 g of modified material Cl_ZVI BM , the reduction reaction was stirred at 120 r / min, and the CNB concentration was detected at appropriate time intervals;

[0116] Step 2: Based on step 1, determine whether the concentration of the target pollutant (CNB) is lower than 50% of the initial concentration. If it is higher, continue to reduce it until it is lower than 50% of the initial concentration. If it is lower, prepare to add oxidant H2O2. At the same time, sample and measure CNB, SMT, Cr(VI), COD and three-dimensional fluorescence spectrum.

[0117] Step 3: After the reduction reaction is completed, add an appropriate amount of H2O2 to make the system concentration 50 mmol / L, react for 15 minutes, and do not adjust the pH during the reaction. After the reaction is completed, sample and measure CNB, SMT, Cr(VI), COD and three-dimensional fluorescence spectrum.

[0118] Step 4: After the oxidation reaction is completed, 0.4 g of flocculant (CaCl2) is added to the system to make the pH value of the system 6-8, stirred for 4 minutes, and allowed to settle for 30 minutes. The supernatant is then collected to determine CNB, SMT, Cr(VI), COD and three-dimensional fluorescence spectrum.

[0119] The changes in COD before and after the reaction and the concentration of the added difficult-to-degrade pollutants and heavy metal internal standards are as follows: Figure 7. After the process treatment, the signal intensity of the humic acid fluorescence peak decreased significantly, and the COD degradation exceeded 82%, indicating that a large amount of humic acid substances in the influent were basically eliminated through the tertiary treatment process. The difficult oxidation model CNB, the difficult reduction model SMT and the heavy metal model Cr (VI) were added to the leachate at the same time. After the process treatment, the removal rate of the three types of pollutants reached 100%.

[0120] For those skilled in the art, based on the above principles, several changes and improvements can be made to the method of the present invention, and these changes and improvements should also be included in the protection scope of the present invention.

Claims

1. A method for deep treatment of landfill leachate based on modified metal materials, characterized in that: include: 1: mixing the landfill leachate with the modified metal material, and performing a reduction reaction to obtain a mixed system 1, wherein: the preparation method of the modified metal material comprises: mixing the halogen salt and the transition metal in a mass ratio of 0.005 to 0.5:1, and then ball milling in an oxygen-free atmosphere; The specific conditions of the ball milling include: The rotation speed is 300 to 900 rpm, and the ball milling time is 1 to 6 hours; The transition metal is iron; The reduction reaction maintains a pH value of 3 to 5; 2: adding an oxidant to the mixed system 1 and continuing stirring to carry out an oxidation mineralization reaction to obtain a mixed system 2; 3: Add flocculant to the mixed system 2, stir for reaction, and then perform solid-liquid separation to obtain treated landfill leachate.

2. The processing method according to claim 1, characterized in that: In step 1: The dosage of the modified metal material in the landfill leachate is 50 mg / L to 5000 mg / L.

3. The processing method according to claim 1 or 2, characterized in that: The specific conditions of the reduction reaction include: Carry out under stirring conditions, the stirring speed is 50~250r / min; The reaction time is 0.5 to 3 hours.

4. The processing method according to claim 1, characterized in that: In step 2: The added oxidant is selected from hydrogen peroxide and / or persulfate; The amount of the oxidant added is 1 to 100 mmol / L; The specific conditions of the oxidation mineralization reaction include: Add an oxidant to the mixed system 1 and continue stirring for 0.1 to 0.5 h to achieve oxidation mineralization reaction.

5. The processing method according to claim 1, characterized in that: When the concentration of the reducible pollutants in the mixed system 1 is 10-50% of the concentration of the reducible pollutants in the landfill leachate added in step 1 or the reaction time reaches 2.5-3.5 hours, the oxidant is added.

6. The processing method according to claim 1, characterized in that: In step 3: The flocculant is selected from at least one of calcium chloride, calcium oxide and aluminum chloride; The amount of the flocculant added is 1000-5000 mg / L; Adding the flocculant to make the pH value of the mixed system 2 be 6 to 8; The stirring reaction time is 3 to 10 minutes to allow the added flocculant to dissolve and disperse.

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