CN110075802B - Iron oxide loaded activated carbon and synthesis method and application thereof - Google Patents

Abstract

The invention belongs to the field of water treatment, and discloses iron oxide loaded activated carbon and a synthesis method and application thereof. The synthesis method comprises the following steps: and (3) dipping the activated carbon in an aqueous solution of an iron source, carrying out ultrasonic treatment, then evaporating to dryness and roasting to obtain the iron oxide loaded activated carbon. The synthesis method brings Fe load, Fe-O-C bond generation and fiber filamentous structure formation in the pore channel; the active carbon has large specific surface area, organic pollutants are more fully adsorbed in the pore canal of the active carbon, the extracellular electron transfer rate of the attached and growing microorganism is accelerated, and the formation of a biological film is promoted. The invention not only reduces the disinfection by-products and pathogenic microorganisms in the factory water, but also has the function of inhibiting the generation of the disinfection by-products and the regrowth of the pathogenic microorganisms in the subsequent tap water pipe network.

Description

A kind of iron oxide supported activated carbon and its synthesis method and application

technical field

The invention belongs to the field of water treatment, and particularly relates to an iron oxide-supported activated carbon and a synthesis method and application thereof.

Background technique

In recent years, the microbial problem of drinking water pipeline network has gradually attracted social attention. Generally speaking, compared with the outgoing water of the waterworks, the water quality of the tap water of residential users deteriorates significantly due to the regrowth of microorganisms in the pipe network. To reduce this hazard, chlorine disinfectants were introduced in the 20th century because of their low cost and continuous sterilization by maintaining a certain residual chlorine concentration throughout the pipe network. However, chlorine disinfectants can react with natural organic matter in water to produce a series of harmful disinfection by-products such as trihalomethanes and haloacetic acids, which are carcinogenic to humans.

Recently, opportunistic pathogens such as Mycobacterium avium, Legionella pneumophila and Hartmanella vermiformis that are abundant in drinking water networks have become a new focus of public attention. Unlike gut microbes that are easily killed by chlorine disinfectants, opportunistic pathogens can survive well in pipe networks, multiply and multiply even at very high concentrations of disinfectants because of a range of advantages including It is easy to form biofilm, produce a large number of extracellular polymers, and resist oligotrophy.

In order to improve drinking water quality, ozone-biological activated carbon combined process is widely used as an advanced treatment method in drinking water plants. Ozone has been proven to oxidize the precursors of disinfection by-products, remove odorants, inactivate pathogenic microorganisms, and improve the biodegradability of organic matter, while promoting the microbial metabolic activity of subsequent bio-activated carbons. Biological activated carbon can significantly remove organic pollutants and disinfection by-product precursors, while retaining most of the pathogenic bacteria.

However, the combined ozone-biological activated carbon technology also has certain defects, such as the formation of new precursors of disinfection by-products in the process of ozone oxidation of organic matter. While biological activated carbon efficiently removes organic pollutants, the shed biofilm and soluble microbial metabolites can also be used as precursors of disinfection by-products, and the latter can cause harm to the human body. In addition, the shed biofilm contains a large number of pathogenic microorganisms, and the relatively mature biofilm structure plays a protective role for the microorganisms. After entering the pipe network, it is difficult to be inactivated by chlorine disinfectants and can grow again. Although most of the microorganisms in the tap water factory water have been inactivated after chlorination disinfection, the pathogenic microorganisms in the tap water have not been effectively controlled after being transported through the pipe network, and disinfection by-products will continue to be generated. If the transition metal oxides can be loaded on the surface of activated carbon for modification, metal-oxygen bonds can be formed to enhance the complexation of organic matter and the rate of extracellular electron transfer of microorganisms, and the biofilm structure on the surface of activated carbon can be better. Membrane morphology and microbial community structure, thereby ensuring the water quality stability in the subsequent pipe network, can simultaneously solve the problems of disinfection by-products and pathogenic microorganisms in tap water.

SUMMARY OF THE INVENTION

In order to overcome the above-mentioned shortcomings and deficiencies of the prior art, the primary purpose of the present invention is to provide a method for synthesizing an iron oxide-supported activated carbon. The method uses ordinary activated carbon as a matrix, and synthesizes the target new activated carbon through three steps of impregnation into iron source, evaporation to dryness and calcination.

Another object of the present invention is to provide an iron oxide-supported activated carbon prepared by the above-mentioned method, and the above-mentioned synthesis method brings about the loading of Fe, the generation of Fe-O-C bonds and the formation of fibrous filamentous structures in the pores; the activated carbon has a large specific gravity. Surface area, organic pollutants are more fully adsorbed in the activated carbon pores, the extracellular electron transfer rate of the attached and growing microorganisms is accelerated, and the formation of biofilms is promoted.

Another object of the present invention is to provide the application of the above-mentioned iron oxide-supported activated carbon in inhibiting disinfection by-products and pathogenic microorganisms in the effluent of the tap water pipe network, which ordinary activated carbon does not possess.

The object of the present invention is realized through the following scheme:

A method for synthesizing activated carbon supported by iron oxides, comprising the following steps: immersing the activated carbon in an aqueous solution of an iron source, ultrasonically treating, then evaporating to dryness and roasting to obtain the activated carbon supported by iron oxides.

The activated carbon is one of coconut shell activated carbon, coal activated carbon, wood activated carbon and bamboo activated carbon, preferably coconut shell activated carbon;

The diameter of the activated carbon is 0.5 to 3 mm, preferably 1.2 mm;

Described iron source is a kind of in ferric chloride hexahydrate (FeCl ₃ .6H ₂ O) and ferric nitrate nonahydrate (FeNO ₃ .9H ₂ O), preferably ferric chloride hexahydrate (FeCl ₃ .6H _{2 )} . O);

The concentration of the iron source aqueous solution is 15-25 g/L, preferably 20 g/L.

The dosages of the activated carbon and the iron source aqueous solution meet the following requirements: every 1 g of activated carbon is immersed in (2-4) mL of an iron source aqueous solution, preferably every 1 g of activated carbon is immersed in 3 mL of an iron source aqueous solution;

The ultrasonic treatment refers to ultrasonic treatment at a power of 300W for 0.5 to 1.5 hours, preferably ultrasonic treatment at a power of 300W for 1 hour. Ultrasonic treatment mainly promotes the dispersion of iron salts in the developed pores of activated carbon, which is conducive to the formation of fibrous filamentous structure iron oxides in the pores. External electron transfer rate.

Described evaporation to dryness refers to evaporation to dryness at 75-95°C;

The heating rate of the roasting is less than 20°C/min, preferably 5°C/min; the roasting temperature is 200-400°C, preferably 300°C; the roasting time is 0.5-2h, preferably 1h;

The activated carbon also includes a pretreatment step before being impregnated into the aqueous solution of the iron source. The pretreatment has two purposes, one is to remove impurities, and the other is to activate the surface groups of the activated carbon, which is more conducive to the surface carbon material and the synthesis process. The formation of Fe-O-C bonds is essential for the formation of iron oxide bonds. The pretreatment step specifically includes the following steps: sequentially immersing the activated carbon in an alkaline aqueous solution and an acidic aqueous solution, then washing with water, and drying for subsequent use;

The alkaline aqueous solution is preferably a sodium hydroxide aqueous solution of 50-150 g/L, preferably a sodium hydroxide aqueous solution of 100 g/L; the immersion time in the alkaline aqueous solution is 0.5-2 h; After soaking, it is preferred to wash with water and then soak in an acidic aqueous solution.

The acidic aqueous solution is preferably an HNO ₃ aqueous solution with a concentration of 5% to 15% (v/v), preferably a 10% (v/v) HNO ₃ aqueous solution; the soaking time in the acidic aqueous solution is 0.5 ~2h;

The drying is preferably drying at 100-200°C, preferably at 160°C.

An iron oxide-supported activated carbon prepared by the above method. The iron oxide-supported activated carbon prepared by the above method is still black solid particles, and its appearance is no different from that of ordinary activated carbon; its microstructure is that the fibrous iron oxide structure is formed in the well-developed pores of the activated carbon. Iron enters into the structural framework of the activated carbon surface to form Fe-O-C bonds. The iron oxide-supported activated carbon has a larger specific surface area, organic pollutants are more fully adsorbed in the activated carbon pores, and the extracellular electron transfer rate of the attached and growing microorganisms is accelerated.

The application of the above-mentioned iron oxide-loaded activated carbon in inhibiting disinfection by-products and pathogenic microorganisms in drinking water and tap water pipe network effluent.

The disinfection by-products may include trihalomethanes and haloacetic acids; the pathogenic microorganisms include Legionella pneumophila, Mycobacterium avium, Neglia flexneri and the like.

Compared with the prior art, the present invention has the following advantages and beneficial effects:

(1) The iron oxide-supported activated carbon of the present invention has a higher removal rate for disinfection by-product precursors.

(2) The activated carbon of the present invention has a better pore structure, a large specific surface area, and a fibrous filamentous structure is formed in the pores, and its active components are greatly exposed on the surface of the activated carbon, which greatly increases the adsorption site of organic matter.

(3) The present invention will not produce heavy metal pollution during use.

(4) The microbial metabolic activity on the surface of the activated carbon of the present invention is higher, and the biofilm structure is more developed.

(5) The activated carbon of the present invention releases less microorganisms in the process of biodegrading organic pollutants and has a smaller scale of biofilm.

(6) The effluent of activated carbon loaded with iron oxides has less organic matter and precursors of disinfection by-products, and the suspended biofilm in the effluent water body is smaller in size and easier to be inactivated by disinfectants. Such water bodies are chlorinated and disinfected into After the pipeline network, the generation of disinfection byproducts and the regrowth of pathogenic microorganisms are continuously inhibited due to the lack of organic matter and precursors of disinfection byproducts and the limitation of the size of biofilms. Therefore, the present invention not only reduces the disinfection by-products and pathogenic microorganisms in the factory water, but also has the effect of inhibiting the generation of disinfection by-products and the regrowth of pathogenic microorganisms in the subsequent tap water pipe network.

Description of drawings

FIG. 1 is a SEM image of Fe/CAC prepared in Example 1 and raw material CAC.

Figure ₂ shows the N adsorption and desorption isotherms of Fe/CAC prepared in Example 1 and raw material CAC.

FIG. 3 is the XRD patterns of Fe/CAC prepared in Example 1 and raw material CAC.

FIG. 4 is an infrared spectrogram of Fe/CAC prepared in Example 1 and raw material CAC.

5 is the O1s XPS spectrum of Fe/CAC prepared in Example 1 and the raw material CAC.

Figure 6 is a graph showing the generation of trihalomethanes and haloacetic acids in the effluent of the simulated pipe network under the conditions of Fe/CAC prepared in Example 1 and a control activated carbon carrier (common CAC).

Figure 7 is a graph showing the condition of conditional pathogenic bacteria in simulated pipe network effluent under the conditions of Fe/CAC prepared in Example 1 and a control activated carbon carrier (common CAC).

Detailed ways

The present invention will be described in further detail below with reference to the embodiments and accompanying drawings, but the embodiments of the present invention are not limited thereto.

The reagents used in the examples can be routinely purchased from the market unless otherwise specified.

Example 1

The synthetic method of the coconut shell activated carbon Fe/CAC of the iron oxide load of the present invention, comprises the following steps:

(1) immerse coconut shell activated carbon (CAC) with an average particle size of 1.2 mm in 100 g/L sodium hydroxide solution (NaOH) for 1 hour;

(2) take out above-mentioned coconut shell activated carbon and wash with deionized water, then immerse in the nitric acid aqueous solution (HNO ₃ ) of 10% volume concentration for 1 hour;

(3) Take out the above-mentioned coconut shell activated carbon and repeatedly wash it with deionized water for 5 times, and dry it in an oven at 160° C. for subsequent use.

(4) dissolving ferric chloride hexahydrate (FeCl ₃ ·6H ₂ O) into deionized water to form a solution A with a concentration of 20 g/L;

(5) Mix solution A with the pretreated coconut shell activated carbon at a ratio of 3mL:1.0g, 300W power ultrasonic treatment for 1 hour, 85 ° C of water bath heating, until the liquid is evaporated to dryness;

(6) calcining the coconut shell activated carbon after being evaporated to dryness in the above-mentioned water bath at 300° C. for 1 hour in a muffle furnace, and obtaining the final iron oxide-supported new coconut shell activated carbon Fe/CAC after natural cooling.

FIG. 1 is a SEM image of Fe/CAC prepared in Example 1 and raw material CAC. It can be seen from the figure that Fe/CAC itself has a particle size of about 1-2 mm, and has a relatively developed pore structure, forming a fibrous structure in the pores.

Fig. 2 is the N ₂ adsorption and desorption isotherms of Fe/CAC prepared in Example 1 and raw material CAC. By BET measurement, the specific surface area of raw material CAC is 641.09 m ² g ^-1 , and Fe/CAC has a larger specific surface area , about 680m ² g ^-1 . By EDS analysis, the surface Fe content of Fe/CAC was 3.33 wt%, while its bulk iron content was about 1.25 wt%, indicating that a large number of Fe sites were exposed on the activated carbon surface.

3 is the XRD pattern of Fe/CAC prepared in Example 1 and the raw material CAC. It can be seen from the figure that the iron oxides supported on the surface of Fe/CAC mainly exist in the crystal form of Fe ₂ O ₃ , and the carbon substances mainly exist in the form of graphitized carbon.

Fig. 4 is the infrared spectrogram of Fe/CAC prepared in Example 1 and the raw material CAC. When iron is loaded on the surface of coconut shell activated carbon, two new peaks of 544 cm ^-1 and 474 cm ^-1 appear, which are the peaks in Fe ₂ O ₃ . The characteristic peaks of Fe-O bonds are consistent with the above XRD results. In addition, a new characteristic peak at 1701cm ^-1 appeared, representing the CO bond in the carboxylic acid and ketone structures. The peak intensities at 2924 cm ^-1 and 2860 cm- ¹ , which represent the asymmetric and symmetric stretching vibrations of _CH2 , decrease, indicating that the COH bonds on the activated carbon surface have increased. The hydroxyl group at 3480 cm ^-1 moved to 3425 cm ^-1 , indicating that Fe-OH was introduced by iron loading in addition to COH, thus causing the shift of the hydroxyl peak.

5 is the O1s XPS spectrum of Fe/CAC prepared in Example 1 and the raw material CAC. It can be seen from the figure that the iron species on the Fe/CAC surface is bound to the activated carbon surface by Fe-O-C bonds, and further confirms the existence of Fe-O-Fe and Fe-O-H.

Application Example

The effluent from the sand filter was obtained from a waterworks, first subjected to ozone treatment, and then entered into a fixed bed loaded with activated carbon with a residence time of 30 minutes. After the water body is treated with iron oxide-loaded activated carbon, it is chlorinated and disinfected. The disinfectant is sodium hypochlorite, and then it enters the chlorine reaction pool with a residence time of 4 hours. The effluent from the chlorine reaction tank immediately enters the simulated tap water pipe network. (The process conditions of ozone treatment and activated carbon treatment are commonly used parameters in actual water plants. The dosage of ozone is 1.0 mg/L, and the residence time and filtration rate of activated carbon are 30 minutes and 10 meters per hour, respectively.)

Figure 6 is a graph of the generation of trihalomethanes and haloacetic acids in the simulated pipe network effluent (the test methods are all US EPA standard methods) under the conditions of Fe/CAC prepared in Example 1 and the control activated carbon carrier (common CAC). As shown in Figure 6, under the use of CAC and Fe/CAC, the concentrations of trihalomethanes in the effluent of the simulated pipe network were 8.46ug/L and 2.15ug/L, and the concentrations of haloacetic acids were 28.45ug/L and 10.55ug/L, respectively. L. Obviously, by using the iron oxide-supported activated carbon prepared by the invention, the trihalomethanes and haloacetic acids in the effluent of the pipe network are obviously suppressed, and the risk of disinfection by-products in the tap water is reduced.

Figure 7 is a graph showing the condition of conditional pathogenic bacteria in simulated pipe network effluent under the conditions of Fe/CAC prepared in Example 1 and a control activated carbon carrier (common CAC). As shown in Figure 7, in the case of using Fe/CAC prepared in Example 1, at the genus level, the gene copy numbers of Legionella, Mycobacterium and Negriamoebae per milliliter of water were reduced to 1.18, 0.97 and 0 log. And from the level of confirmed pathogenic species, Legionella pneumophila, Mycobacterium avium and Neglia flexneri were all inactivated. In addition, in the whole reaction, Fe/CAC iron was released very little, less than 0.1 mg L ^-1 and iron itself was non-toxic and harmless. Therefore, Fe/CAC effectively inhibits the disinfection by-products and pathogenic microorganisms in the pipe network, and ensures the water quality safety of the tap water.

The above-mentioned embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited by the above-mentioned embodiments, and any other changes, modifications, substitutions, combinations, The simplification should be equivalent replacement manners, which are all included in the protection scope of the present invention.

Claims (8)

1. The application of the iron oxide loaded activated carbon in inhibiting disinfection byproducts and pathogenic microorganisms in drinking water and tap water pipe network outlet water is characterized in that the iron oxide loaded activated carbon is prepared by the following steps: and (3) dipping the activated carbon in an aqueous solution of an iron source, carrying out ultrasonic treatment, then evaporating to dryness and roasting to obtain the iron oxide loaded activated carbon.

2. The use of the iron oxide-loaded activated carbon of claim 1 for inhibiting disinfection by-products and pathogenic microorganisms in drinking water and tap water pipe network effluent, wherein:

the active carbon is one of coconut shell active carbon, coal active carbon, wood active carbon and bamboo active carbon;

the iron source is one of ferric chloride hexahydrate and ferric nitrate nonahydrate.

3. The use of the iron oxide-loaded activated carbon of claim 1 for inhibiting disinfection by-products and pathogenic microorganisms in drinking water and tap water pipe network effluent, wherein:

the active carbon is coconut shell active carbon;

the iron source is ferric chloride hexahydrate.

4. The use of the iron oxide-loaded activated carbon of claim 1 or 2 for inhibiting disinfection by-products and pathogenic microorganisms in drinking water and tap water pipe network effluent, characterized in that:

the concentration of the iron source water solution is 15-25 g/L;

the dosage of the active carbon and the iron source water solution meets the following requirements: every 1g of activated carbon is correspondingly soaked in (2-4) mL of iron source water solution.

5. The use of the iron oxide-loaded activated carbon of claim 1 or 2 for inhibiting disinfection by-products and pathogenic microorganisms in drinking water and tap water pipe network effluent, characterized in that:

the concentration of the iron source water solution is 20 g/L;

the dosage of the active carbon and the iron source water solution meets the following requirements: each 1g of the activated carbon was soaked in 3mL of an aqueous iron source solution.

6. The use of the iron oxide-loaded activated carbon of claim 1 or 2 for inhibiting disinfection by-products and pathogenic microorganisms in drinking water and tap water pipe network effluent, characterized in that:

the ultrasonic treatment is ultrasonic treatment at 300W power for 0.5-1.5 hours;

the drying by distillation refers to drying by distillation at 75-95 ℃;

the temperature rise rate of the roasting is less than 20 ℃/min; the roasting temperature is 200-400 ℃; the roasting time is 0.5-2 h.

7. The use of the iron oxide-loaded activated carbon of claim 1 for inhibiting disinfection by-products and pathogenic microorganisms in drinking water and tap water pipe network effluent, wherein:

before the activated carbon is immersed in the aqueous solution of the iron source, the activated carbon further comprises a pretreatment step, and the pretreatment step specifically comprises the following steps: sequentially dipping the activated carbon in an alkaline aqueous solution and an acidic aqueous solution, washing with water, and drying for later use;

the alkaline aqueous solution is 50-150 g/L sodium hydroxide aqueous solution, and the time for soaking in the alkaline aqueous solution is 0.5-2 h;

the acidic aqueous solution is HNO with the volume concentration of 5-15 percent₃The water solution is soaked in the acidic water solution for 0.5-2 hours;

the drying is drying at 100-200 ℃.

8. The use of the iron oxide-loaded activated carbon of claim 1 for inhibiting disinfection by-products and pathogenic microorganisms in drinking water and tap water pipe network effluent, wherein:

the disinfection by-products comprise trihalomethane and haloacetic acid; the pathogenic microorganism comprises legionella pneumophila, mycobacterium avium and formica furiosa.

Images