CN108275753B - A method for treating landfill leachate membrane filtration concentrate and its special device - Google Patents

Abstract

The invention provides a method for treating membrane filtration concentrated solution of landfill leachate and a special device thereof, wherein an anode electro-catalysis electrode and a cathode electro-Fenton electrode are applied to the same electrochemical system, and the membrane filtration concentrated solution of landfill leachate is effectively treated by means of electrocatalysis and electro-Fenton, so that the technical problems that the degradation contribution of a cathode to high-concentration organic matters in a single electrocatalysis system is small and the removal effect of the electrocatalysis system is limited are solved. Iron oxide is loaded in active carbon by an impregnation method to prepare a heterogeneous Fenton catalyst, and the iron-loaded carbon-based titanium mesh composite electrode prepared by using the catalyst as a main material can effectively inhibit the dissolution of iron ions, reduce iron oxide precipitates generated after reaction and improve the Fe content of a system²⁺And H₂O₂The utilization ratio of the electro-Fenton treatment device and the electro-Fenton treatment effect are further enhanced. The device effectively combines anode electro-catalysis and cathode electro-Fenton, improves the electric energy utilization rate, further enhances the treatment effect on high-concentration organic matters, and has good application prospect.

Description

A method for treating landfill leachate membrane filtration concentrate and its special device

technical field

The invention relates to the technical field of sewage treatment, in particular to a method and a special device for treating the membrane concentrate produced by "pretreatment + biological treatment + advanced treatment" for landfill leachate.

Background technique

Landfill leachate is one of the main causes of secondary pollution in the process of landfill. If it is not properly controlled, it will seriously pollute groundwater, surface water, soil and the surrounding environment, resulting in serious waste of water resources, and a large amount of organic pollutants in the leachate. After entering the food chain, it will directly threaten human health, and even cause the outbreak of epidemic diseases in serious cases. At present, the commonly used landfill leachate treatment method in China is pretreatment + biological treatment + advanced treatment. The conventional process route for landfill leachate treatment recommended by the Technical Specifications (CJJ150-2010). The advantages of this set of combined processes are that the impact resistance is strong, the treatment effect is good, and the effluent quality directly meets the discharge standard. However, the concentrated solution produced by membrane filtration technology has become a difficult problem in the current landfill leachate treatment due to its high pollutant concentration, poor biochemical properties, high salt content and high chromaticity.

At present, the main methods for the treatment of landfill leachate membrane filtration concentrate at home and abroad are the recharge method and the evaporation method, but these two methods have certain shortcomings and limitations. The recharge method includes the recharge of the landfill body and the backflow adjustment tank. The recharged concentrate flows through the landfill layer or the backflow tank again, and uses a large number of original microorganisms to biodegrade, adsorb, and filter the organic matter in the concentrate. , so as to achieve the purpose of degrading the landfill leachate membrane filtration concentrate. However, the treatment cycle of the recharge method is long, and the pollutants continue to accumulate over time, resulting in poor biochemical properties of landfill leachate, increased salt content, and increased treatment difficulty. In turn, the membrane filtration treatment is affected, the membrane water production rate is continuously reduced, fouling is more likely to occur, and the maintenance cost is increased. Evaporation refers to the process of separating relatively volatile components from a mixed liquid at a certain temperature and pressure. The evaporation process can concentrate the liquid to be treated to less than 2% to 10% of the volume of the original liquid. However, there are also some problems with the evaporation method. During the evaporation process, some pollutants such as volatile hydrocarbons, volatile organic acids and ammonia will enter the vapor and eventually exist in the condensate, which must be treated and discharged before reaching the standard. The evaporated concentrate needs to be further dried, and the treatment cost is relatively high, and the evaporation equipment is expensive, easily corroded and scaled, and the maintenance cost is high. Therefore, how to effectively treat the landfill leachate membrane filtration concentrate while considering the treatment cost has become an urgent problem to be solved in various landfills at present.

Electrocatalytic technology is to degrade macromolecular organic pollutants through hydroxyl radicals ( OH) and ClO ^- generated in the electrochemical oxidation system. The most commonly used electrocatalytic electrode in domestic and foreign research is DSA (dimensionally stable anode), DSA has the characteristics of good conductivity, low density, high mechanical strength, stable chemical properties, and is not easy to be oxidized, which can effectively improve the current utilization efficiency. Moreover, the rare metal oxide on the surface has a high oxygen evolution potential, which is the anode with the best performance in electrocatalytic applications. Because the landfill leachate membrane filtration concentrate has high electrical conductivity, good electrical conductivity, and the Cl ^- content is very high, and it is easy to generate ClO ^- , electrocatalysis has great development potential in the treatment of membrane filtration concentrate, but there are few related studies at home and abroad. And a single electrocatalytic treatment membrane filtration concentrate is difficult to achieve the ideal treatment effect.

_{The Fenton} method is an advanced oxidation technology that is most widely used in the treatment of various refractory ^organics . Refractory wastewater such as chemicals, pesticides, printing and dyeing, coking and landfill leachate, etc., but the cost of chemicals is high. Electro-Fenton method is a new technology developed on the basis of Fenton in recent years. Among them, the cathodic electro-Fenton method utilizes electrochemistry to generate H ₂ O ₂ and Fe ²⁺ , without adding H ₂ O ₂ , which reduces the cost of adding chemicals, and the organic matter is degraded completely, and it is not easy to produce intermediate toxic and harmful substances, and has many advantages. However, the development of its technology has also encountered certain obstacles. The most prominent problem at present is that it is mainly limited by the cathode material and the mass transfer of O ₂ in the solution, so that the reaction rate of the reduction of oxygen to H ₂ O ₂ on the cathode surface is affected by It is extremely limited, and the total efficiency of H ₂ O ₂ and Fe ²⁺ is also very low. Due to these limitations, the application of the electro-Fenton method in practice is not very ideal.

SUMMARY OF THE INVENTION

In order to solve the problems described in the background art, the present invention provides a method for treating landfill leachate membrane filtration concentrated solution and a special device thereof, wherein the anode electrocatalytic electrode and the cathode electrocatalytic Fenton electrode are applied in the same electrochemical system, Catalytic synergy with electro-Fenton effectively treats landfill leachate membrane filtration concentrate, overcoming the technical difficulties that the cathode in a single electro-catalytic system contributes little to the degradation of high-concentration organic matter and the removal effect of the electro-catalytic system is limited. In view of the problems that Fe ²⁺ in the cathode electro-Fenton needs to be externally injected, the utilization rate is low, the amount of iron sludge produced is large, the production efficiency of cathode H ₂ O ₂ is low, the pH of the reaction effluent needs to be adjusted to neutral, and the cost of adding chemicals is high. In the invention, the iron oxide is supported in the activated carbon by the impregnation method to prepare the heterogeneous Fenton catalyst, and the iron-carrying carbon-based titanium mesh composite electrode made of the catalyst as the main material can effectively inhibit the dissolution of iron ions and reduce the The precipitation of iron oxides formed after the reaction improves the utilization rate of Fe ²⁺ and H ₂ O ₂ in the system, thereby enhancing the effect of electro-Fenton treatment. The treatment device effectively combines anode electrocatalysis and cathode electro-Fenton, improves the utilization rate of electric energy and further enhances the treatment effect of high-concentration organic matter, and has a good application prospect.

In order to achieve the above object, the present invention adopts the following technical solutions to realize:

A method for treating landfill leachate membrane filtration concentrate, which uses anode electrocatalytic electrode and cathode electro-Fenton electrode in the same electrochemical system, and effectively treats landfill leachate membrane filtration concentrate by means of electrocatalysis and electro-Fenton.

The anode electrocatalytic electrode adopts DSA anode.

The cathode electrode of the cathode electro-Fenton electrode adopts a high-efficiency iron-carrying carbon-based titanium mesh composite electrode, and the manufacturing method of the high-efficiency iron-carrying carbon-based titanium mesh composite electrode includes the following steps:

Step 1. Select a suitable type of activated carbon, put the activated carbon in 2mol/L NaOH solution for dipping, the dipping time is 24h, then wash with deionized water until it is neutral, and then impregnate it with concentrated HNO ₃ for the dipping time 24h, then use deionized water to wash it to neutrality, and finally dry it at 105 °C for later use;

Step 2: Prepare an appropriate amount of iron oxide solution, load the iron oxide on the activated carbon by impregnation method, completely dry the loaded activated carbon, then select a certain temperature to calcine the activated carbon, and cool the calcined activated carbon to room temperature for preparation of electrodes;

Step 3: Put the Fe-loaded activated carbon container in the ultrasonic reactor, add an appropriate amount of ethanol for ultrasonic vibration for 5 minutes, then add an appropriate amount of conductive agent and binder for ultrasonic vibration for 15 minutes, take out the container after ultrasonic vibration and place it on the heater, The temperature is controlled at 80°C, and the mixture is uniformly heated by mechanical stirring, and the anhydrous ethanol is gradually evaporated from it, and the mixture gradually sticks into a mass to form a paste;

Step 4: Roll out the steamed to semi-dry paste mixture into a regular-shaped membrane structure, then place it on a double-roller press and press repeatedly to make the activated carbon composite material form a fibrous electrode film, and cut the electrode film into an appropriate size , Using the pretreated titanium mesh as the electrode skeleton, the electrode film and the titanium mesh are placed on the tablet machine and pressed into an electrode with a certain pressure.

A special device for the treatment of landfill leachate membrane filtration concentrate, comprising a reaction tank, an electrode fixing tank, an electrode slideway, an anode electrode, a cathode electrode, an aeration device, a blower, and a power supply, and the electrode fixing tank is vertically installed in the reaction tank, The electrode slideway is laterally installed in the reaction tank, the anode electrode and the cathode electrode are respectively inserted into the electrode fixing groove, the electrode fixing groove moves through the electrode slideway, and the anode electrode and the cathode electrode are connected to the power source through wires.

The reaction tank is provided with a scale, and the distance between electrodes is determined by the scale of the reaction groove.

An aeration device is installed near the bottom of the cathode electrode, and a sufficient amount of oxygen is directly supplied to the cathode through a blower, and sufficient stirring is ensured in the entire reaction.

The anode electrode is designed as a mesh hollow structure, which is convenient for the flow of the liquid in the reaction tank.

Compared with the prior art, the beneficial effects of the present invention are:

1. The cathode electrode independently developed by the present invention has high H ₂ O ₂ generation efficiency and current utilization rate, and Fe ^{2+ does} not need external investment, the amount of iron sludge generated is extremely small, and the cathode electro-Fenton reaction requires a wide range of pH values. , which greatly saves the cost of adding chemicals for the reaction. The invention effectively combines anode electrocatalysis and cathode electro-Fenton, improves the electrical energy utilization rate of the electrochemical system, enhances the treatment effect of the landfill leachate membrane filtration concentrate, and can effectively reduce the landfill leachate membrane filtration concentrate COD, TOC and chromaticity, and significantly improve the biodegradability of water, with good application prospects.

2. The present invention provides a method for treating landfill leachate membrane filtration concentrate and its special device, which can effectively improve the treatment effect of the membrane filtration concentrate and greatly reduce the concentration of landfill leachate membrane filtration while taking into account the processing cost. The concentration of organic pollutants in the liquid, effectively remove the color and significantly improve the biodegradability.

Description of drawings

FIG. 1 is a schematic structural diagram of a special device for processing a landfill leachate membrane filtration concentrate according to the present invention.

Among them: 1-reaction tank, 2-electrode fixing tank, 3-slideway, 4-reaction tank scale, 5-aeration device, 6-blower, 7-power supply, 8-cathode, 9-anode.

Detailed ways

The specific embodiments provided by the present invention will be described in detail below with reference to the accompanying drawings.

A method for treating landfill leachate membrane filtration concentrate. An anode electrocatalytic electrode and a cathode electro-Fenton electrode are applied in the same electrochemical system, and the landfill leachate membrane filtration concentrate is effectively treated by means of electrocatalysis and electro-Fenton.

The anode electrocatalytic electrode adopts DSA anode.

The cathode electrode of the cathode electro-Fenton electrode adopts a high-efficiency iron-carrying carbon-based titanium mesh composite electrode, and the manufacturing method of the high-efficiency iron-carrying carbon-based titanium mesh composite electrode includes the following steps:

Step 1. Select a suitable type of activated carbon, put the activated carbon in 2mol/L NaOH solution for dipping, the dipping time is 24h, then wash with deionized water until it is neutral, and then impregnate it with concentrated HNO ₃ for the dipping time 24h, then use deionized water to wash it to neutrality, and finally dry it at 105 °C for later use;

Step 2: Prepare an appropriate amount of iron oxide solution, load the iron oxide on the activated carbon by impregnation method, completely dry the loaded activated carbon, then select a certain temperature to calcine the activated carbon, and cool the calcined activated carbon to room temperature for preparation of electrodes;

Step 3: Put the Fe-loaded activated carbon container in the ultrasonic reactor, add an appropriate amount of ethanol for ultrasonic vibration for 5 minutes, then add an appropriate amount of conductive agent and binder for ultrasonic vibration for 15 minutes, take out the container after ultrasonic vibration and place it on the heater, The temperature is controlled at 80°C, and the mixture is uniformly heated by mechanical stirring, and the anhydrous ethanol is gradually evaporated from it, and the mixture gradually sticks into a mass to form a paste;

Step 4: Roll out the steamed to semi-dry paste mixture into a regular-shaped membrane structure, then place it on a double-roller press and press repeatedly to make the activated carbon composite material form a fibrous electrode film, and cut the electrode film into an appropriate size , Using the pretreated titanium mesh as the electrode skeleton, the electrode film and the titanium mesh are placed on the tablet machine and pressed into an electrode with a certain pressure.

As shown in Figure 1, a special device for the treatment of landfill leachate membrane filtration concentrate includes a reaction tank 1, an electrode fixing tank 2, an electrode slideway 3, an anode electrode 8, a cathode electrode 9, an aeration device 5, and a blower 6. 7, the power supply 7, the electrode fixing groove 2 is vertically installed in the reaction tank 1, the electrode slideway is installed in the reaction tank 1 horizontally, the anode electrode 8 and the cathode electrode 9 are respectively inserted into the electrode fixing groove 2, and the electrode fixing groove 2 passes through the electrode The slideway 3 moves, and the anode electrode 8 and the cathode electrode 9 are connected to the power source 7 through wires.

The reaction tank 1 is provided with a scale 4, and the distance between electrodes is determined by the scale 4 of the reaction groove.

The aeration device 5 is installed near the bottom of the cathode electrode 8, and a sufficient amount of oxygen is directly supplied to the cathode 8 through the blower 6 to ensure sufficient stirring inside the entire reaction.

The anode electrode 9 is designed as a net-shaped hollow structure, which is convenient for the flow of the liquid in the reaction tank.

When the special device for treating the landfill leachate membrane filtration concentrate of the present invention is used, the pH of the water sample needs to be adjusted before the concentrate enters the reaction tank for reaction. Variety.

The pH value of the effluent treated by the special device for treating the landfill leachate membrane filtration concentrate can directly reach neutrality or weak alkalinity, and the pH value does not need to be adjusted again.

Specific embodiment 1:

The method and the special device of the invention are used to treat the reverse osmosis concentrate of the landfill leachate. The water sample comes from a landfill plant in Wuhan, the COD of the water sample is 191.0 mg·L ^-1 and the chromaticity is 80 times.

When the distance between the plates = 3cm, the applied voltage = 9V, the initial solution pH = 3.0, and the reaction time is 280min, the concentration of CODcr in the effluent decreases from 191.0mg/L to 22.4mg/L, the removal rate reaches 88.3%, and the chromaticity increases from 80 times. To colorless, the removal rate reaches 100%.

Specific embodiment 2:

The method and the special device of the present invention are used to treat the landfill leachate nanofiltration concentrate. The water sample comes from a landfill plant in Wuhan. The COD of the water sample is 3102.4 mg·L ^-1 , the TOC is 1203 mg·L ^-1 , and the BOD ₅ /CODcr is 0.093, and the chromaticity is 2048 times.

When the distance between the plates = 2cm, the applied voltage = 10V, the initial solution pH = 3.0, and the reaction time is 280min, the concentration of CODcr in the effluent decreases from 3102.4mg/L to 975.0mg/L, the removal rate reaches 68.6%, and the chromaticity increases from 2048 times. It was reduced to 4 times, the removal rate was as high as 99.8%, the TOC concentration decreased from 1203mg/L to 471mg/L, the removal rate reached 60.8%, and the BOD ₅ /CODcr increased from 0.093 to 0.37.

Specific embodiment 3:

The method and the special device of the present invention are used to treat the landfill leachate nanofiltration concentrate. The water sample comes from a landfill plant in Anshan. The COD of the water sample is 1512.3 mg·L ^-1 , the BOD ₅ /CODcr is 0.03, and the chromaticity is 980 times. .

When the distance between the plates = 1cm, the applied voltage = 10V, the initial solution pH = 7.0, and the reaction time is 280min, the concentration of CODcr in the effluent decreases from 1512.3mg/L to 44.5mg/L, the removal rate reaches 97.1%, and the chromaticity is removed after 40min treatment. rate reaches 100%.

The above embodiments are implemented on the premise of the technical solutions of the present invention, and provide detailed embodiments and specific operation processes, but the protection scope of the present invention is not limited to the above-mentioned embodiments. The methods used in the above embodiments are conventional methods unless otherwise specified.

Claims (1)

1. A method for processing membrane filtration concentrated solution of landfill leachate is characterized in that an anode electro-catalysis electrode and a cathode electro-Fenton electrode are applied to the same electrochemical system, and the membrane filtration concentrated solution of the landfill leachate is effectively processed by means of electrocatalysis and electro-Fenton;

the anode electrocatalytic electrode adopts a DSA anode;

the cathode electrode of the cathode electro-Fenton adopts a high-efficiency iron-carrying carbon-based titanium mesh composite electrode, and the manufacturing method of the high-efficiency iron-carrying carbon-based titanium mesh composite electrode comprises the following steps:

step one, selecting proper activated carbon types, soaking the activated carbon in 2mol/L NaOH solution for 24 hours, washing with deionized water until the activated carbon is neutral, and then washing with concentrated HNO₃Dipping for 24h, then washing the product to be neutral by using deionized water, and finally drying the product for later use at 105 ℃;

preparing a proper amount of iron oxide solution, loading iron oxide on the activated carbon by an impregnation method, completely drying the loaded activated carbon, then selecting a certain temperature to calcine the activated carbon, and cooling the calcined activated carbon to room temperature for preparing for manufacturing an electrode;

placing a container filled with the Fe-loaded activated carbon into an ultrasonic reactor, adding a proper amount of ethanol, performing ultrasonic oscillation for 5min, then adding a proper amount of conductive agent and binder, performing ultrasonic oscillation for 15min, taking out the container after the ultrasonic oscillation, placing the container on a heater, controlling the temperature to be 80 ℃, uniformly heating the mixture through mechanical stirring, gradually evaporating anhydrous ethanol from the mixture, and gradually sticking the mixture into a mass to form a paste;

and step four, rolling the paste mixture steamed to be semi-dry into a membrane structure with a regular shape, then placing the membrane structure on a double-roller press, repeatedly pressing to enable the activated carbon composite material to form a fibrous electrode membrane, cutting the electrode membrane into a proper size, taking the pretreated titanium mesh as an electrode framework, placing the electrode membrane and the titanium mesh on a tablet press, and pressing into an electrode with a certain pressure.

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