CN102923806A - Method for processing formaldehyde wastewater through modified nanometer material - Google Patents

Abstract

The invention relates to a method for treating formaldehyde wastewater by using a modified nanometer material. The method uses a modified layered clay nanocomposite adsorption material to treat the formaldehyde wastewater, and the treated formaldehyde wastewater can fully meet the biochemical treatment standard. The price of this method for processing formaldehyde wastewater is very cheap, and this method is very convenient for processing formaldehyde wastewater in real life. Generally, formaldehyde wastewater is acidic, and the acidity is very high. The method of the present invention is carried out under acidic conditions, but in Formaldehyde wastewater can also be treated under alkaline conditions. This method has lower requirements on the pH of wastewater. In formaldehyde wastewater, COD is generally high, and it also contains pollutants such as phosphorus and ammonia nitrogen. The modified layered clay nanometer used in this method Composite adsorption materials have a great effect on the removal of these pollutants, so this method is more environmentally friendly and has better economic value. Compared with other methods for removing formaldehyde, this method has a simpler and faster process, and the first environmental protection The secondary pollution is basically zero, and it also has a certain removal effect on viruses and bacteria.

Description

A method for treating formaldehyde wastewater by modifying nanomaterials

technical field

The invention relates to a method for treating formaldehyde wastewater by modifying nanomaterials.

Background technique

Formaldehyde (HCHO) is a colorless gas with a strong pungent odor that is easily soluble in water, alcohol and ether. It is an important organic raw material and is mainly used for artificial synthesis of binders. In addition to being directly used as a disinfection, sterilization and preservative, formaldehyde is mainly used in organic synthesis, synthetic materials, coatings, rubber, pesticides and other industries. Its derivative products are mainly polyformaldehyde, polyformaldehyde, phenolic resin, urea-formaldehyde resin, amino Resins, Uroto products and polyols, etc. Formaldehyde is widely used in synthetic resins, surfactants, plastics, rubber, leather, papermaking, dyes, pharmaceuticals, pesticides, photographic films, explosives, building materials, as well as in the processes of disinfection, fumigation and anticorrosion. Although it has a wide range of uses and low prices, its toxicity and harmfulness are also endangering the health of humans and organisms. The World Health Organization has pointed out that formaldehyde is carcinogenic in 2004. So now many people have studied the method of removing formaldehyde wastewater, but the method has many limitations and deficiencies.

There are many ways to deal with formaldehyde. Since formaldehyde has strong reducing properties, most of them use oxidation and subsequent treatment methods. There are many oxidation methods, such as Fenton method, photocatalytic oxidation method, wet oxidation method, chlorine dioxide oxidation method, ultrasonic/H ₂ O ₂ method and other oxidation methods to remove formaldehyde wastewater, either the investment cost is high and the operation cost is high, or the The effluent does not meet the national sewage discharge standards. There are also A/O (deficiency/oxygen), A-SBR (anaerobic SBR) and Carrousel oxidation ditch method, which are all traditional biochemical methods. The biggest disadvantage of biochemical methods is that the concentration of formaldehyde is very low and the treatment time is very long. Moreover, there are limits to on-site conditions, higher requirements on microorganisms, and higher costs. Another common treatment method is the lime method. In the presence of lime, formaldehyde will polymerize to form hexose. The key to lime treatment of formaldehyde wastewater is that the wastewater must be alkaline, and the greater the pH, the more thoroughly the formaldehyde in the wastewater can be treated. Formaldehyde, so it is often necessary to adjust the pH of the effluent with hydrochloric acid, and the lime method is easy to block the pipeline, and the removal time of formaldehyde is the shortest when the reaction temperature is around 90 degrees Celsius, so the reaction temperature has a limited value for the removal of formaldehyde. It is better to remove formaldehyde by heating device. Therefore, the removal of formaldehyde by the lime method has high requirements on the reaction conditions, and there is a possibility of clogging the equipment, so the effect of removing formaldehyde wastewater by lime is not good under general conditions. Often in the formaldehyde wastewater we treat, not only formaldehyde needs to be removed, but COD, ammonia nitrogen, total phosphorus, chroma, etc. are also treated in general wastewater, and these methods often cannot meet our wastewater treatment requirements. For the above treatment of formaldehyde wastewater We have developed a new method for treating formaldehyde wastewater, which is to use a new nanomaterial to treat formaldehyde wastewater.

Contents of the invention

The purpose of the present invention is to provide a method for treating formaldehyde wastewater through modified nano-materials which is convenient, fast, simple in process and low in treatment cost. The formaldehyde wastewater treated by the method has a good removal effect.

A new type of nanomaterial is used in this method. Nanomaterials refer to materials that have at least one dimension in the nanoscale range (1-100nm) in three-dimensional space or are made of them as basic units. This new type of nanomaterial is composed of nanoscale The clay mineral of particle (1-100nm) is made up of two silicon-oxygen tetrahedrons sandwiching a layer of aluminum-oxygen tetrahedron with a 2:1 type crystal structure, and what is used in the present invention is a modified layered clay nanocomposite Adsorption materials are used as raw materials, which are firstly modified at high temperature, then crushed into about 100 meshes, then soaked in water to make pulp, and the coarse residue is removed by sedimentation, then acidified with hydrochloric acid, washed with distilled water, and dried, and the modified layer can be produced Clay nanocomposite adsorption material, acid activation can increase the specific surface area and surface acid site concentration of the nanomaterial, remove impurities in the pores, and then improve its activity. The specific surface area of the material is large, up to 600-800 square meters per gram. The huge surface area produces huge surface energy, as well as its layered structure and the type and distribution of elements in the structure determine its strong adsorption. Performance, during the modification process, the interlayer metal cations of the layered clay nanocomposite adsorption material are dissolved in the acid, the interlayer bond energy is weakened, the interlayer distance becomes larger, and the surface activity increases. After the metal cations are replaced by hydrogen ions in the acid, a part of the hydrogen ions Replaced by aluminum ions in the solution, aluminum ions with stronger adsorption capacity can be formed, thereby greatly improving the adsorption performance of the modified layered clay nanocomposite adsorption material. The modified layered clay nanocomposite adsorption material mainly removes formaldehyde by adsorbing formaldehyde.

In order to treat formaldehyde waste water to the situation that can be discharged according to national discharge standards, the method proposed by the present invention for processing formaldehyde waste water by modified nanomaterials, the specific steps are as follows:

(1) Calcining the layered clay nanocomposite adsorption material at a temperature of 390-410°C to make it lose surface water and bound water in the hydration water structure skeleton, and reduce the adsorption resistance of the water film to formaldehyde, phosphorus and ammonia nitrogen; Then cool, grind and sieve, pulverize into 90-110 mesh, then modify it by acidification method, soak it in water to make pulp, remove the coarse residue by sedimentation, acidify it with hydrochloric acid, wash it with distilled water, and dry it to produce Modified layered clay nanocomposite adsorption material;

(2) Add the layered clay nanocomposite adsorption material obtained in step (1) to the wastewater, the reaction temperature is 10-80°C, the reaction time is 0.5-24 hours, the stirring speed is 115-125 revolutions per minute, and the stirring time is 8-15 hours. After 10 minutes, let it stand for 18-25 minutes, filter, add 3.8-4.2 grams of layered clay nanocomposite adsorption materials per milligram of formaldehyde, and discharge the treated formaldehyde wastewater. When discharging, control the pH value of the formaldehyde wastewater to 6-9. The formaldehyde wastewater treated by the method can reach the national first-class discharge standard. The concentration of formaldehyde in the formaldehyde wastewater we used in many experiments was 120.48 mg per liter.

In the present invention, the layered clay nanocomposite adsorption material described in the step (1) is any one of montmorillonite, zeolite or diatomaceous earth, etc., and is composed of 1-100nm nanoscale particles of clay minerals, which are composed of A 2:1 crystal structure consisting of two silicon-oxygen tetrahedrons sandwiching a layer of aluminum-oxygen tetrahedrons.

The main factors affecting the effect of the present invention on treating formaldehyde wastewater include: initial concentration of formaldehyde, reaction temperature, addition of modified layered clay nanocomposite adsorption material, pH value of wastewater, and the like. In general, the more the modified layered clay nanocomposite adsorption material is added, the more formaldehyde can be completely removed, and the treatment effect of formaldehyde is better, but when the formaldehyde concentration is about 50 micrograms per liter, continue to add modified layered clay Nanocomposite adsorbent materials are not effective.

The advantages of the present invention are as follows:

1. The price of this method to treat formaldehyde wastewater is very cheap. The modified layered clay nanocomposite adsorption material is very abundant in my country and widely distributed, so it has laid a material foundation for the treatment of formaldehyde wastewater in terms of resources;

Two, this method is very convenient in our real life to process formaldehyde waste water, and formaldehyde waste water is all acidic under normal circumstances, and acidity is very high, and the method of the present invention is exactly carried out under acidic conditions, but can be equally possible under alkaline conditions For the treatment of formaldehyde wastewater, this method has lower requirements on the pH of the wastewater, so the cost is lower;

Three, in formaldehyde waste water, COD is generally very high, also contains pollutants such as phosphorus and ammonia nitrogen, the layered clay nanocomposite adsorption material of hydrogen modification that this method uses all has very big effect to the removal of these pollutants, so This method is more environmentally friendly and has better economic value;

4. Compared with other methods for removing formaldehyde, this method has a simpler and faster process, and the second pollution to the environment is basically zero.

Description of drawings

Fig. 1 is a process flow diagram of the present invention.

Fig. 2 is the removal rate diagram of formaldehyde, ammonia nitrogen and total phosphorus in Example 1 of the present invention.

Figure 3 is a graph showing the removal rates of formaldehyde, ammonia nitrogen and total phosphorus measured at different pHs in Example 2 of the present invention.

Fig. 4 is a removal rate diagram of different dosages of Example 3 of the present invention.

Numbers in the figure: 1 is a dry dosing instrument, 2 is a mixer, 3 is a reaction tank, 4 is a sedimentation tank, and 5 is a filter tank.

Detailed ways

The present invention is further illustrated below by way of examples.

The present invention takes closed river sewage in a certain place as an example. There are a large number of chemical plants around the river water, which makes the river water contain a large amount of formaldehyde, phosphorus and ammonia nitrogen. This example further illustrates the treatment process and effect of formaldehyde wastewater.

The inventive method, concrete steps are as follows:

Step 1: Modification of layered clay nanocomposite adsorption materials by physical and chemical methods

First, the layered clay nanocomposite adsorption material is calcined at high temperature for a period of time, then cooled, ground and sieved, and the layered clay nanocomposite adsorption material is calcined at 400°C to lose surface water and hydration water in the structural skeleton. Combine water to reduce the adsorption resistance of water film to formaldehyde, phosphorus and ammonia nitrogen. The layered clay nanocomposite adsorption material modified by high temperature is then crushed into about 100 meshes, then modified by acidification method, soaked in water to make pulp, and the coarse residue is removed by sedimentation, then acidified with hydrochloric acid and washed with distilled water , and dried, the modified layered clay nanocomposite adsorption material can be manufactured.

Step 2: Dosing modified layered clay nanocomposite adsorption materials in wastewater

The results obtained after many experiments show that the more chemicals added to the wastewater is not the better, and the treatment of formaldehyde wastewater is the best under the condition of 3.8-4.2 grams of chemicals per mg of formaldehyde. The concentration of formaldehyde in the formaldehyde wastewater we used in many experiments was 120.48 mg per liter.

Step 3: Stir

The modified layered clay nanocomposite adsorption material is mixed with the formaldehyde wastewater according to a certain ratio, and stirred by a mixer to fully mix the modified layered clay nanocomposite adsorption material with the formaldehyde wastewater.

Step Four: Precipitation

After stirring for a certain period of time, because the layered clay nanocomposite adsorption material is insoluble in water, in the natural state, the modified layered clay nanocomposite adsorption material is allowed to settle naturally, and the sediment is removed through the mud discharge device.

Step Five: Filter

After the modified layered clay nanocomposite adsorption material is precipitated, there is still a part of suspended matter in the remaining formaldehyde wastewater, and the suspended matter is filtered out by a filter device.

Step 6: Adjust the PH value

In actual operation, formaldehyde wastewater is generally acidic, and the pH value (6-9) must be adjusted to discharge the treated formaldehyde wastewater.

Step Seven: Drain

According to relevant laws and regulations, the treated formaldehyde wastewater should be discharged or entered into the local sewage pipe network.

Example 1

The reaction temperature is 20°C, the mass ratio of the modified layered clay nanocomposite adsorption material to formaldehyde is 4g:1mg, and the formaldehyde wastewater solution with a concentration of 120.48mg.L ^-1 is taken, in which ammonia nitrogen is 15.6mg.L ^-1 and total phosphorus 3.1mg.L ^-1 was put into the container, and the removal rates of formaldehyde, ammonia nitrogen and total phosphorus measured in 30, 45, 60, 75 and 90 minutes were shown in Figure 2, and the removal of formaldehyde in 60 minutes It can almost reach 100% in time, and the removal effect on ammonia nitrogen is not good, and the removal rate is only 42% in 60 minutes. The removal effect on phosphorus is better than that of ammonia nitrogen, and the removal rate can reach 62%. Although the removal efficiencies of ammonia nitrogen and phosphorus reached 42% and 62%, but their initial amounts were very low, and the adsorption capacity of the material for ammonia nitrogen and phosphorus was not high. In short, the nanomaterials have a very good adsorption effect on formaldehyde, but the adsorption capacity on ammonia nitrogen and phosphorus is not high.

Example 2

The reaction temperature is 40°C, the mass ratio of the modified layered clay nanocomposite adsorption material to formaldehyde is 4g:1mg, and the formaldehyde wastewater solution with a concentration of 120.48mg.L ^-1 is taken, in which ammonia nitrogen is 15.6mg.L ^-1 and total phosphorus 3.1mg.L ^-1 was placed in the container, and the removal rates of formaldehyde, ammonia nitrogen and total phosphorus measured at different pH are shown in Figure 3. The treatment effect on formaldehyde is the best when the pH is 6. In other cases, the treatment effect is much worse, and can only reach about 85%. The treatment effect of ammonia nitrogen and phosphorus is similar to that of formaldehyde. It is best when PH=6, but the treatment of ammonia nitrogen and phosphorus is the best. The rate is only 43% and 64%. In short, the nanomaterial has a very good adsorption effect on formaldehyde, but the adsorption amount on ammonia nitrogen and phosphorus is not high.

Example 3

The reaction temperature is 20°C, the mass ratio of the modified layered clay nanocomposite adsorption material soil to formaldehyde is adjusted, and the formaldehyde wastewater solution with a concentration of 120.48 mg.L ^-1 is taken, wherein the ammonia nitrogen is 15.6 mg.L ^-1 and the total phosphorus is 3.1 mg.L ^-1 was put into the container, and 1g, 2g, 4g, 8g and 12g of adsorption materials were added respectively. After one hour of treatment, the measured formaldehyde concentration data was shown in Figure 4. The removal rates of formaldehyde, ammonia nitrogen and phosphorus were all It increases with the increase of dosage, but the removal rate does not increase to a certain extent.

It can be illustrated by the above examples that the treatment of formaldehyde wastewater by the present invention has a very good treatment effect. The final concentration of formaldehyde in the formaldehyde wastewater treated by this method is 0.52 mg.L ^-1 , ammonia nitrogen is 7.39 mg.L ^-1 and phosphorus is 0.85 mg.L ^-1 . According to the National Standards of the People's Republic of China on the pollutant discharge standards of urban sewage treatment plants (see Table 1 and Table 2), it can be seen that the sewage fully meets the first-level discharge A-level discharge standards, so this method is feasible and effective for the treatment of formaldehyde wastewater. .

Table 1:

Table 2:

Claims (2)

1. one kind is passed through the method that the modified Nano material processing is processed formaldehyde waste water, it is characterized in that concrete steps are as follows:

(1) first the laminated clay nanometer composite adsorbing material at 390-410 ℃ of temperature lower calcination, make its lose in surface water, the water of hydration structural framework in conjunction with water, the absorption resistance of minimizing moisture film PARA FORMALDEHYDE PRILLS(91,95), phosphorus and ammonia nitrogen; Then cool off and mill and sieve, pulverize the order into 90-110, acidified method is soaked slurrying to its modification again, removes thick slag by sedimentation, adds the hydrochloric acid acidifying again, uses distilled water wash, and oven dry just can be made the laminated clay nanometer composite adsorbing material of modification;

(2) in waste water, add step (1) gained laminated clay nanometer composite adsorbing material, temperature of reaction is 10～80 ℃, reaction times is 0.5～24 hour, stirring velocity is that per minute 115-125 turns, stir after 8-15 minute, time of repose 18-25 minute, filter, add 3.8-4.2 gram laminated clay nanometer composite adsorbing material in every milligram of formaldehyde, the formaldehyde waste water discharging of handling well, the pH value of control formaldehyde waste water is 6～9 during discharging, and treated formaldehyde waste water reaches national grade one discharge standard; The concentration of formaldehyde is 120.48 milligrams every liter in the formaldehyde waste water.

2. method according to claim 1, it is characterized in that laminated clay nanometer composite adsorbing material described in the described step (1) be in montmorillonite, zeolite or the diatomite any, clay mineral by the 1-100nm nano-scale particle forms presss from both sides the 2:1 type crystal structure that one deck aluminum-oxygen tetrahedrons form by two silicon-oxy tetrahedrons.

Images