CN115519638B

CN115519638B - Method for enhancing in-situ digestion of VOCs by cooperation of surfactant and ultrasound

Info

Publication number: CN115519638B
Application number: CN202211338324.7A
Authority: CN
Inventors: 张世锋; 沈玉林; 李玉男; 黄安民
Original assignee: Tianjin Xiqing District Airui Environmental Monitoring Center; Beijing Forestry University
Current assignee: Tianjin Xiqing District Airui Environmental Monitoring Center; Beijing Forestry University
Priority date: 2022-10-28
Filing date: 2022-10-28
Publication date: 2023-09-12
Anticipated expiration: 2042-10-28
Also published as: CN115519638A

Abstract

The invention relates to a method for enhancing in-situ digestion of VOCs by synergistic ultrasonic mediation of a surfactant, and belongs to the technical field of wood modification. The method comprises the following steps: air-drying the wood to be treated by temperature and humidity adjustment to ensure that the water content reaches 25-30%; preparing a surfactant-persulfate mixed solution; soaking the air-dried wood in mixed solution of surfactant and persulfate with a certain concentration for a period of time, performing ultrasonic treatment at 40-80 ℃, and drying; taking out the treated wood after the oxidation treatment, repeating the steps 2-3 for treatment, and circulating for 2-3 times; and then drying. According to the invention, the surfactant is adopted to assist the ultrasonic wave to strengthen the extraction and enrichment of the VOCs, meanwhile, the ultrasonic wave is adopted to activate persulfate to generate sulfate radical in-situ to digest the VOCs in the wood, and the surfactant is cooperated with the multiple functions of the ultrasonic wave to further enhance the in-situ oxidative decomposition of the free radical on the VOCs.

Description

Method for enhancing in-situ digestion of VOCs by cooperation of surfactant and ultrasound

Technical Field

The invention relates to the technical field of wood modification, and particularly provides a method for enhancing in-situ digestion of VOCs by synergistic ultrasonic mediation of a surfactant.

Background

Compared with other materials, the wood has the natural advantages of mild touch feeling, unique affinity, good visual effect and the like, so that the wood is widely applied to interior decoration and furniture manufacturing. However, most wood products can release VOCs (including natural compounds such as terpenes and alcohols) and unpleasant odors such as pungent taste of fir core, pungent taste of cedar, putty taste of basswood and the like during processing and utilization due to the fact that extracts/volatile oil are contained in the wood parenchyma cells and the resin channels. When the wood is gathered to reach a certain concentration, the wood has a certain influence on human health or emotion, and a series of environmental pollution problems are brought to influence the relationship between the wood environment and the human health. And at the same time limit the suitability of wood for applications such as packaging of tea and food. In order to improve the relationship between the wood environment and the human health, and meet the spirit pursuit of human beings on living environment, the boosting wood processing industry realizes green production, the furniture manufacturing industry realizes environment protection upgrading, and a corresponding treatment method is necessary to remove VOCs in the wood.

The existing treatment technology of VOCs at home and abroad mainly comprises a combustion method, a condensation method, an absorption method, an adsorption method, a catalysis method and a biodegradation method. Although the treatment technology has a certain effect, the problems of low efficiency, incomplete treatment, secondary pollution and the like exist. The chemical agent method such as acid-base treatment has high extraction efficiency, but has the problems of great loss of three elements of wood, strong equipment corrosion, serious environmental pollution and the like. The solvent extraction method is a method for generally removing the extract in a laboratory, but has the advantages of complex operation, long period and high toxicity, and has certain desirable effect when the method is applied to industrial production, but has the problems of high cost, low safety, difficult reagent recovery and treatment, high equipment investment and the like. Physical methods such as high-temperature drying, vacuum drying and the like have the problems of poor treatment effect, long period, high energy consumption and the like.

The treatment method in the prior art has complex process, is easy to form secondary pollution and has certain harm to human bodies and environment, so that a green and efficient method is needed to eradicate the release sources of the wood VOCs, namely the wood extract and the volatile oil, so as to achieve the purpose of thoroughly controlling the release of the wood VOCs.

Disclosure of Invention

In order to solve the problems in the prior art, the invention provides a method for enhancing in-situ digestion of VOCs by cooperating with a surfactant and ultrasonic mediation. According to the invention, the surface active agent is adopted to assist the ultrasonic wave to strengthen the extraction and enrichment of the VOCs in the wood, and meanwhile, the ultrasonic wave is used for activating persulfate to generate sulfate radical to in-situ digest the VOCs in the wood.

In order to solve the technical problems, the invention provides the following technical scheme:

in one aspect, the invention provides a method for enhancing in-situ digestion of VOCs by surfactant synergistic ultrasound mediation, which comprises the following steps:

step 1: pretreatment: air-drying the wood to be treated by temperature and humidity adjustment to ensure that the water content reaches 25-30%;

step 2: preparing a surfactant-persulfate mixed solution: and adding a surfactant into deionized water at 20-25 ℃, stirring at a low speed until the surfactant is completely dissolved, adding persulfate in batches after defoaming, and stirring at a low speed for dissolving. After defoaming, the mixture is sealed and stored at a low temperature for standby.

Step 3: and (3) oxidation treatment: completely soaking the air-dried wood in a mixed solution of surfactant with a certain concentration and persulfate for a period of time, and then carrying out ultrasonic treatment at 40-60 ℃; and then drying.

Step 4: circularly treating; taking out the treated wood after the oxidation treatment, repeating the step 2 for treatment, and circulating for 2-3 times; and then drying.

Further, in the step 2, the concentration of the surfactant is 1-3%, the concentration of the persulfate is 0.05-0.2mol/L, the pH value is 3-5, and the soaking time is 6-8 hours.

Preferably, the surfactant is an ionic surfactant (sodium dodecyl sulfate (SDS), sodium dodecyl diphenyl ether disulfonate (C12-MADS)) with good compatibility and stability with an oxidant. The persulfate is potassium persulfate, sodium persulfate or ammonium persulfate.

Further, the ultrasonic power of the ultrasonic treatment is 210-270W, and the treatment time is 3-4 hours.

Preferably, in the step 2, when the wood is chipped or wood powder, the solid-liquid ratio of the chipped or wood powder is 1:101:15, and the soaking time is 0.5-1 hour. Or in the step 2, when the wood is a wood board or log, the mixed solution of the surfactant and the persulfate is soaked for 6-8 hours after 1-2cm of the wood.

The invention is thatThe main action mechanism is that the surfactant can obviously reduce the interfacial tension of aqueous solution and has the characteristic of amphiphilic structure, the hydrophobic wood extract and volatile oil are dissolved, and the extract and volatile oil are extracted and enriched from the interior of wood to the aqueous phase environment through the ultrasonic mechanical oscillation action. Simultaneously, under the cavitation of ultrasonic wave, persulfate is decomposed at high temperature and high pressure in the moment of a micro area to generate sulfate radical with strong oxidability, extract and volatile oil are oxidized in situ, and mineralized into CO ₂ And H ₂ O, thereby achieving the purpose of controlling the release of VOCs and odor of wood.

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

compared with the existing method, the Fenton reaction system has sulfate radical with longer half-life and higher oxidation potential, and has strong oxidative decomposition effect on organic matters. Compared with an ultrasonic activated persulfate system, the introduction of the surfactant assists the ultrasonic to forcedly extract and enrich the VOCs in the wood, and the construction of the water/solid biphasic oxidation system overcomes the problems of difficult inward diffusion of free radicals, large oxidation target volume and the like, and improves the effective utilization rate of the free radicals. The method has the advantages of simple treatment process, high removal rate, green and environment-friendly property, and is little influenced by the compact structure of the wood. The treatment process only involves ultrasound, persulfate and surfactant, and the pollution to the environment can be effectively reduced while removing VOCs and unpleasant odor in the wood by only controlling the concentration of the surfactant, the concentration of the persulfate, the pH value and the ultrasound power.

The invention can effectively remove the extractives in the wood, reduce the generation and volatilization of VOCs in the processing and using processes of the wood, and avoid generating unpleasant odor. Through the actions of surfactant enhanced extraction, ultrasonic mediated enhancement, free radical efficient mineralization and the like, not only can the extractives in the wood be removed, but also the number of cell lines and the aperture can be increased. Therefore, as the wood drying pretreatment, not only can the emission of VOCs be reduced and the pollution to the environment and the harm to the human body of workers be avoided, but also the water diffusion in the drying process can be facilitated, the drying period can be shortened, and the energy consumption can be saved. The method can effectively remove the extractives and improve the permeability of the wood, so the method can be used as a pretreatment means for the functional modification treatment of the wood.

Drawings

FIG. 1 is a TIC chart of an untreated wood block of an embodiment of the present invention as measured by GC-MS;

FIG. 2 is a TIC chart of the treated wood blocks of example 1 (S-US/PS), comparative example 1 (US), comparative example 2 (S-US), comparative example 3 (US/PS) of the present invention as detected by GC-MS;

FIG. 3 is a TIC chart obtained by GC-MS detection of the treated wood blocks of example 2, comparative example 6 and comparative example 7 according to the present invention.

Detailed Description

In order to make the technical problems, technical solutions and advantages to be solved by the present invention more apparent, the following detailed description will be made with reference to specific embodiments.

The reagents and materials used in the examples and comparative examples of the present invention were commercially available unless otherwise specified. The wood to be treated is selected from artificial fir heartwood with more pungent smell and extract.

The invention provides a method for enhancing in-situ digestion of VOCs by synergistic ultrasonic mediation of a surfactant, and specific embodiments are as follows.

Example 1

A method for enhancing in situ digestion of VOCs by surfactant synergistic ultrasound mediated enhancement, comprising:

step 1: pretreatment: the wood to be treated is artificial fir wood, the specification is wood blocks with the length of 20 multiplied by 20mm (length multiplied by width multiplied by thickness), the initial water content is about 70%, and the wood powder to be treated is subjected to air drying treatment to ensure that the water content reaches 20%;

step 2: preparing a surfactant-persulfate mixed solution: a beaker containing 1000mL of deionized water was placed in a 25℃water bath and 15g of surfactant SDS (sodium dodecyl sulfate) was added in portions with low-speed stirring until complete dissolution. After defoaming, sodium persulfate was added in portions with low-speed stirring until completely dissolved, and the pH was adjusted to 4.2 with sodium hydroxide. A stable and uniform mixture of 1.5% surfactant SDS and 0.1mol/L sodium persulfate was prepared.

Step 3: and (3) oxidation treatment: taking 20 wood blocks with set specifications, placing the wood blocks into a beaker, adding a prepared surfactant-sodium persulfate mixed solution, and soaking the wood blocks for 6 hours under the condition that the liquid level is 2 cm; the mixture is put into an ultrasonic cleaner for ultrasonic treatment, the ultrasonic power is 210W, the temperature is set to 60 ℃, and the ultrasonic time is 3 hours.

Step 4: and (3) cyclic treatment: after the oxidation treatment is finished, taking out the treated timber, drying at 60 ℃, and repeating the steps 2-3 for treatment for 2 times; and then drying at 60 ℃.

Example 2

A method for enhancing in situ digestion of VOCs using surfactant synergistic ultrasound mediated enhancement, comprising:

step 1: pretreatment: same as in example 1

Step 2: preparing a surfactant-persulfate mixed solution: a beaker containing 1000mL of deionized water was placed in a 25℃water bath and 15g of surfactant C12-MADS was added in portions with low speed stirring until complete dissolution. After defoaming, sodium persulfate was added in portions with low-speed stirring until completely dissolved, and the pH was adjusted to 4.2 with sodium hydroxide. The stable and uniform mixed solution of the surfactant C12-MADS with the concentration of 1.5 percent and 0.1mol/L sodium persulfate is prepared.

Step 3: and (3) oxidation treatment: taking 20 wood blocks with set specifications, placing the wood blocks into a beaker, adding a prepared surfactant-sodium persulfate mixed solution, and soaking the wood blocks for 8 hours under the condition that the liquid level is 2 cm; the mixture is put into an ultrasonic cleaner for ultrasonic treatment, the ultrasonic power is 210W, the temperature is set to 60 ℃, and the ultrasonic time is 4 hours.

Example 3

step 1: pretreatment: same as in example 1

Step 2: preparing a surfactant-persulfate mixed solution: a beaker containing 1000mL of deionized water was placed in a 25℃water bath and 15g of surfactant SDS was added in portions with low speed stirring until complete dissolution. After defoaming, potassium persulfate is added in batches under low-speed stirring until the potassium persulfate is completely dissolved, and the pH value of the sulfuric acid is 3. A stable and uniform mixture of 1.0% surfactant SDS and 0.2mol/L potassium persulfate was prepared.

Step 3: and (3) oxidation treatment: taking 20 wood blocks with set specifications, placing the wood blocks into a beaker, adding a prepared surfactant-potassium persulfate mixed solution, and soaking the wood blocks for 8 hours under the condition that the liquid level is 2 cm; the mixture is put into an ultrasonic cleaner for ultrasonic treatment, the ultrasonic power is 270W, the temperature is set to 40 ℃, and the ultrasonic time is 4 hours.

Example 4

step 1: pretreatment: same as in example 1

Step 2: preparing a surfactant-persulfate mixed solution: a beaker containing 1000mL of deionized water was placed in a 25℃water bath and 30g of surfactant SDS was added in portions with low speed stirring until complete dissolution. After defoaming, ammonium persulfate was added in portions with low-speed stirring until complete dissolution, and the pH was adjusted to 5 with sodium hydroxide. A stable and uniform mixed solution of 3.0% surfactant SDS and 0.05mol/L ammonium persulfate was prepared.

Step 3: and (3) oxidation treatment: taking 20 wood blocks with set specifications, placing the wood blocks into a beaker, adding a prepared surfactant-ammonium persulfate mixed solution, and soaking the wood blocks for 7 hours under the condition that the liquid level is 2 cm; the mixture is put into an ultrasonic cleaner for ultrasonic treatment, the ultrasonic power is 210W, the temperature is set at 80 ℃, and the ultrasonic time is 3 hours.

To further highlight the beneficial effects of the present invention, the following comparative examples were constructed, for example.

Comparative example 1

In this comparative example, deionized water was used instead of the surfactant-sodium persulfate mixture, and the other conditions were the same as in example 1.

Comparative example 2

The comparative example step 2 is: the beaker containing 1000mL of deionized water is placed in a water bath at 25 ℃, the surfactant is added in batches under low-speed stirring until the surfactant is completely dissolved, and the pH value of the sulfuric acid is 3. Preparing a 1.5% surfactant solution;

the step 3 is as follows: taking 20 wood blocks with set specifications, placing the wood blocks into a beaker, adding a prepared surfactant solution, enabling the wood blocks to be under the 2cm liquid level, and soaking for 6 hours; the mixture is put into an ultrasonic cleaner for ultrasonic treatment, the ultrasonic power is 210W, the temperature is set to 60 ℃, and the ultrasonic time is 3 hours. The remaining steps were the same as in example 1.

Comparative example 3

The comparative example step 2 is: placing a beaker containing 1000mL of deionized water in a water bath at 25 ℃, stirring at a low speed, adding sodium persulfate in batches until the sodium persulfate is completely dissolved, and regulating the pH value to be 3 by utilizing sulfuric acid; preparing 0.2mol/L sodium persulfate solution;

the step 3 is as follows: taking 20 wood blocks with set specifications, placing the wood blocks into a beaker, adding the prepared sodium persulfate solution, enabling the wood blocks to be under the 2cm liquid level, and soaking for 6 hours; the mixture is put into an ultrasonic cleaner for ultrasonic treatment, the ultrasonic power is 210W, the temperature is set to 60 ℃, and the ultrasonic time is 3 hours. The remaining steps were the same as in example 1.

Comparative example 4

Step 3 of this comparative example: taking 20 wood blocks with set specifications, placing the wood blocks into a beaker, adding the prepared surfactant-sodium persulfate mixed solution, and soaking the wood blocks at room temperature for 10 hours under the condition that the liquid level is 2 cm. The remaining steps were the same as in example 1.

Comparative example 5

Step 3 of this comparative example: taking 20 wood blocks with set specifications, placing the wood blocks into a beaker, adding a prepared surfactant-sodium persulfate mixed solution, and soaking the wood blocks for 6 hours under the condition that the liquid level is 2 cm; then put it into water bath, the temperature is set at 60 ℃, and soaked for 3 hours. The remaining steps were the same as in example 1.

Comparative example 6

In this comparative example, the nonionic surfactant polyethylene glycol octylphenyl ether Triton X-100 was used in place of the surfactant C12-MADS, with the remainder being the same as in example 2.

Comparative example 7

This comparative example replaces the surfactant C12-MADS with the cationic surfactant cetyltrimethylammonium bromide CTAB, with the remainder of the same conditions as in example 2.

The wood and the original materials treated by the above examples and comparative examples are detected by a headspace solid-phase microextraction and gas phase mass spectrometer (HS/SPME/GC MS) combined technology detection method: the wood is frozen and crushed into 40-mesh wood powder, and the main components and the content of VOCs in the wood under a certain temperature condition are measured. The main components of the original wood are shown in table 1, and the total ion flow chromatogram is shown in fig. 1.

The TIC patterns obtained by GC-MS detection of the treated wood blocks of example 1, comparative example 2 and comparative example 3 of the present invention are shown in FIG. 2, and the main components of the VOCs are shown in Table 2.

The TIC patterns obtained by GC-MS detection of the treated wood blocks of example 2, comparative example 6 and comparative example 7 of the present invention are shown in FIG. 3, and the main components of the VOCs are shown in Table 3.

The main ingredients of the wood block VOCs treated in examples 3-4 of the present invention are shown in Table 4.

TABLE 1

As can be seen from table 1 and fig. 1, the primary component of the original wood, which is released by VOCs, is relatively large and not easy to remove.

TABLE 2

Sequence number	Terpenes%	Alcohols%	Esters%	Total degradation rate%
					Example 1	73.41	86.81	75.23	78.48
Comparative example 1	26.81	36.54	23.39	28.91
					Comparative example 2	42.09	45.23	34.51	40.61
Comparative example 3	50.22	52.34	43.45	48.67
					Comparative example 4	21.03	18.57	19.47	19.69
Comparative example 5	71.3	63.55	51.48	62.11

As can be seen from Table 2 and FIG. 2, the method for enhancing in-situ digestion of VOCs by synergistic ultrasonic mediation of the surfactant provided by the invention has a certain efficiency on removal of VOCs from wood raw materials, and the total degradation rate can reach 78.48%. Compared with single ultrasonic treatment (comparative example 1), the technology of the invention improves the total degradation rate by 171.48 percent and obviously improves the removal rate of various VOCs.

Compared with the surfactant combined ultrasonic treatment (comparative example 2), the method of the invention has the advantages that the total degradation rate is improved by 93.25%, which shows that the addition of the surfactant plays a positive role in removing the VOCs of the wood material and strengthens the extraction of the VOCs.

Compared with an ultrasonic activation persulfate system (comparative example 3), the method of the invention has the advantages that the total degradation rate is increased by 61.24 percent, and the limitation of the free radical oxidation blocky wood material generated by ultrasonic activation persulfate under the condition of no surfactant addition, such as poor permeability of the wood material, inward diffusion of free radicals, short free radical service life and the like, can be seen.

Compared with the method without ultrasonic mediation (comparative example 4), the method has the advantages that the total degradation rate is improved by 298.57%, which shows that the ultrasonic mediation plays a key role in the technology of the invention, and mainly has cavitation effect to activate persulfate to generate free radicals, mechanical oscillation desorption effect and enhance mass transfer.

Compared with the method without ultrasonic mediation, the method has the advantages that the total degradation rate is improved to a certain extent by the cooperation of the surfactant and the heat-activated persulfate (comparative example 5), and the key effect of ultrasonic mediation is further proved.

TABLE 3 Table 3

Sequence number	Terpenes%	Alcohols%	Esters%	Total degradation rate%
					Example 2	64.60	81.68	76.53	74.27
Comparative example 6	-5.67	38.82	31.97	21.7
					Comparative example 7	13.72	11.95	9.61	11.76

As can be seen from table 3 and fig. 3, the selection of the surfactant is critical, and the surfactant having good compatibility with the oxidizing agent and strong stability should be selected when preparing the surfactant-persulfate mixture. The method of the invention selects anionic surfactant (example 2) compared with nonionic surfactant (comparative example 6) and cationic surfactant (comparative example 7), and the total degradation rate is obviously improved.

TABLE 4 Table 4

Sequence number	Terpenes%	Alcohols%	Esters%	Total degradation rate%
					Example 3	61.13	71.23	76.35	69.57
Example 4	72.04	76.22	52.44	66.90

As can be seen from Table 4, the method of the present invention can effectively remove various extractives contained in wood and reduce volatilization of VOCs in the wood processing process.

In conclusion, the invention effectively enhances the free radical oxidation effect under the synergistic ultrasonic mediation of the surfactant, can effectively remove the extractives in the wood, reduces the generation and volatilization of VOCs in the processing and using processes of the wood, and avoids generating unpleasant odor.

While the foregoing is directed to the preferred embodiments of the present invention, it will be appreciated by those skilled in the art that various modifications and adaptations can be made without departing from the principles of the present invention, and such modifications and adaptations are intended to be comprehended within the scope of the present invention.

Claims

1. A method for enhancing in situ digestion of VOCs by surfactant synergistic ultrasound mediated enhancement, comprising:

step 1: pretreatment: air-drying the wood to be treated by temperature and humidity adjustment to ensure that the water content is 25-30%; the wood is a wood block;

step 2: preparing a surfactant-persulfate mixed solution: adding surfactant into deionized water at 20-25deg.C, stirring at low speed until completely dissolving, adding persulfate in batches after defoaming, and stirring at low speed for dissolving; sealing and preserving at low temperature for standby after defoaming;

the surfactant is sodium dodecyl sulfate or sodium dodecyl diphenyl ether disulfonate, and the concentration is 1-3wt%; the persulfate is potassium persulfate, sodium persulfate or ammonium persulfate, and the concentration is 0.05-0.2 mol/L; the pH value of the surfactant-persulfate mixed solution is 3-5;

step 3: and (3) oxidation treatment: completely soaking the air-dried wood in the surfactant-persulfate mixed solution obtained in the step 2, wherein the wood is 1-2cm in length and soaked for 6-8 hours; then carrying out ultrasonic treatment at 40-80 ℃, and drying;

step 4: circularly treating; taking out the treated wood after oxidation treatment, repeating the steps 2-3, and circulating for 2-3 times; and then drying.

2. The method for enhancing in-situ digestion of VOCs by co-ultrasonic mediation with a surfactant according to claim 1, wherein in step 3, the ultrasonic power of the ultrasonic process is 210-270W and the ultrasonic time is 3-4 hours.