KR20220140967A - Fiberboard filters fabricated with wood bark-produced active carbon for the reduction of particulate matter, volatile organic compounds and heavy metals - Google Patents

Abstract

The present invention relates to an activated carbon-added fiberboard filter made of wood bark for absorption/adsorption of pollutants such as fine dust, VOC, and heavy metals in the air and a manufacturing technology thereof. Provided is a fiberboard filter containing wood bark activated carbon for absorption and adsorption of fine dust, volatile organic compounds and heavy metals, which is formed in a three-layer structure of upper, middle, and lower layers, and includes only wood fibers in the upper and lower layers and a mixture in which wood fibers and activated carbon are randomly mixed in the middle layer.

Description

Fiberboard filters fabricated with wood bark-produced active carbon for the reduction of particulate matter, volatile organic compounds and heavy metals

The present invention relates to a fiberboard filter containing activated carbon from wood bark for the absorption and absorption of fine dust, volatile organic compounds, and heavy metals, and a method for manufacturing the same.

In a situation where the deterioration of indoor and outdoor air quality due to the inflow and occurrence of fine dust causes a decrease in people's life satisfaction and health anxiety, it is urgent to prepare measures to effectively reduce fine dust in various indoor and outdoor spaces. In particular, since the subway-related spaces such as platforms, underground tunnels, and inside trains are enclosed spaces, it is difficult for subway operation and discharge of fine dust and harmful substances from various pollutants or entering the outdoors, and natural ventilation is impossible. and directly or indirectly adversely affect the health of subway workers. However, since strict control of pollutant emission sources is impossible, the application of emission source management measures to solve this problem is limited so far. There is a need to come up with a solution.

As a technology commercialized for the reduction of fine dust so far, the method of controlling various sized pollutants by using a membrane having micropores as a filtration filter is mainly used. Scrubbers, etc. are being applied alone or jointly (Female, 2016). However, the above technologies cannot handle the high flow rate, so they cannot be applied to large facilities, or have disadvantages such as low fine dust removal efficiency, short filter lifespan, and high filter replacement cost burden (Lee, 2019). On the other hand, the dry filtration filter is an air purifying technology that mainly reduces only fine dust, so it reduces only limited amounts of volatile organic compounds and heavy metals that are harmful to humans in indoor and outdoor spaces. In addition, filtration filters used in air purifiers and fine dust reduction devices are made of synthetic fiber non-woven fabrics such as polypropylene (PP) and polyethylene terephthalate (PET). of waste, and incineration generates a large amount of carbon dioxide, a major cause of global warming (Bok, 2018; Marketsandmarkets, 2020). Therefore, it is necessary to develop a high-efficiency, low-cost, new collection and filtration technology using regenerated fibers that can replace non-woven fabrics as a raw material for filtration filters.

Looking at the technological trends being developed at home and abroad in relation to fine dust reduction, overall, technologies for performance such as fine dust treatment materials, process development technology, and ICT-based air pollutant management fields are mainly secured (Ha & Lee). , 2018). In particular, in the case of Korea, we are focusing on identifying the cause of the removal reaction for each material, developing material source technology and material/process key technology, and also focusing on the removal of precursors for primary emission (dust collection) and secondary generation (denitrification/desulfurization). this is aligned In addition, rather than the development of emission reduction technology, technology development for a dust collector that can dramatically reduce fine dust emission while minimizing the installation space at the source of fine dust is in progress. However, since the target to be reduced is moving from TSP (total suspended particles) of 50 μm or less to PM 2.5 of 2.5 μm or less, it is required to secure technology for improvement of existing facilities and performance improvement of dust collection technology. Overseas, the highest level of fine dust reduction technology is developing various facilities related to post-exhaust treatment systems for industrial facilities in Germany and Sweden, mainly in the United States and Japan, where ultrafine dust regulations are strengthened, but indoor and outdoor ultrafine dust reduction The development of the technology is still insufficient (Lee & Baek, 2018).

Therefore, the development of dust collection and filtration technology using existing facilities is required to effectively reduce various pollutants, including ultrafine dust, in terms of practical use and cost.

The present invention is a fiberboard filter containing activated carbon from wood bark, which is formed of a three-layer structure of an upper layer, a middle layer and a lower layer, the upper and lower layers contain only wood fibers, and the middle layer contains a mixture in which wood fibers and activated carbon are randomly mixed. A fiberboard filter is provided. Without limitation, a fiberboard filter according to the present invention is provided with a plurality of vents passing through the upper, middle and lower layers. The weight ratio of activated carbon in the filter according to the present invention is 20 wt% to 40 wt% based on the filter, and the density of the fiberboard filter is preferably designed to be 150kg/m ³ to 250kg/m ³ . According to the present invention, the mixture constituting the middle layer of the filter is prepared by spraying wood fiber and activated carbon using a natural adhesive containing a hydrolyzate of natural raw materials selected from human hair, pig hair and pig blood and a hot water extract of larch bark.

The filtration filter according to the present invention effectively reduces volatile organic compounds (VOC) and heavy metals, including fine dust, present in indoor and outdoor spaces. In addition, it is possible to respond to the climate change agreement by reducing greenhouse gas by converting waste filtration filters into solid biofuels, in addition to realizing recycling of living/slaughtering/industrial wastes and creating a foundation for commercialization through waste reduction.

1 is a schematic diagram of a spiked caul plate for making fiberboard.
2 is a photograph of various fiberboard filters according to the present invention.

The present invention relates to an activated carbon-added biomass fiber-based fiberboard type filtration filter and a manufacturing method for replacing synthetic fiber-based non-woven fabric for absorption/adsorption of fine dust, VOC, and heavy metals.

It is necessary to develop a technology to replace the raw material of the filtration filter, which is currently mainly made of non-woven fabric, which is a synthetic fiber, with renewable vegetable fibers. Among vegetable fibers, wood fiber is judged to be the most suitable as a raw material for filtration filters based on the domestic supply amount and price. This method is uneconomical in terms of manufacturing cost because it requires a multi-step process. Therefore, the present invention focused on a method of manufacturing wood fibers in the form of low-density fiberboards and using them as a filtration filter. However, filtration filters manufactured using only wood fibers are expected to have limitations in filtration of contaminants such as volatile organic compounds (VOC) and heavy metals present in various indoor and outdoor spaces. A method for producing a fiberboard form by adding excellent activated carbon as a medium is devised. In consideration of the economic feasibility and recycling of waste, the activated carbon used in the manufacture of filtration filters has been proposed to use unutilized wood by-products as raw materials. A filter made of wood fiber and wood-based activated carbon must have a certain level of strength because it is in the form of a fiberboard, and for this purpose, an adhesive is required. Since the fiber raw material used to manufacture the filter filter is a carbon-neutral wood-based resource, the used/collected filter can be used as a solid biofuel. A way to do this has been suggested. When a filter made of natural adhesive is used as a solid fuel, it is possible to minimize the amount of toxic gas and carbon dioxide generated during combustion. In addition, if household/slaughter/industrial wastes are used as raw materials for adhesives, it is judged that the production of filtration filters will be possible at very low cost in addition to the efficient recycling of waste resources and added value along with the reduction of the amount of waste generated. As a raw material that satisfies these conditions, it has been proposed to use human hair, pig hair, pig blood, and wood bark, which are generated in large quantities as waste at home and abroad, as raw materials for adhesives.

Hereinafter, the present invention will be described with reference to specific examples, but is not limited thereto.

Materials and Methods

1.1 Disclosure material

Wood fiber (moisture content: 10 ± 1%) and emulsion wax (solid content: 43 ± 1%) used to manufacture fiberboard-type filtration filters were supplied free of charge from UNID (Jeonbuk, Gunsan) and used.

Human hair (HH) used as an adhesive raw material was obtained free of charge from a beauty salon near the Jeonju campus of Chonbuk National University, and then cut to a size of about 1 cm with ordinary scissors and used for adhesive preparation without pretreatment. Pig hair (PH) and pig blood (PB) were used free of charge from Mokwoo Village in Gimje-si, Jeollabuk-do. The collected PH was dried naturally for at least one week to adjust the moisture content to 9 ± 1%, and it was cut into a size of about 1 cm with ordinary scissors in the same way as human hair and used as an adhesive raw material. In the case of PB, it was used as an adhesive raw material without additional processing. In order to improve the strength of the adhesive, which is mostly composed of protein, hot water extract of larch bark, which was supplied free of charge from the Dongbu Wood Distribution Center (Gangwon, Donghae) of the Korea Forestry Cooperative Federation, was added.

Sodium hydroxide used for hydrolysis of HH, PH, PB, oxalic acid and sodium borate added for preservative purposes were purchased from Lab Story Science (Chungbuk, Cheongju) and used as reagents for chemical experiments. Phosphoric acid-based flame retardant added to the adhesive to impart flame-retardant performance to the fiberboard filter was supplied from Happy Home Wood Tech (Jeonnam, Muan) and used. On the other hand, phenol formaldehyde (hereinafter PF) used as a control to compare the adhesive properties with the prepared protein-based natural adhesive had a solids content of 50% and a viscosity of 200 m Pa s. Anyang).

Activated carbon added to adsorb VOC and heavy metals in the fiberboard filter was manufactured using the bark of larch and cypress, which are domestic unused wood by-products. was supplied with In addition, good charcoal (Seoul, Songpa), which manufactures oyster oak charcoal for grilling meat, partially contains bark, so charcoal (cork oak active-carbon, COA), which is not sold, was supplied free of charge and used as activated carbon. To compare the adsorption capacity of larch bark (LBA), cypress bark active-carbon (CBA), and COA on VOC and heavy metals, coconut shell active-carbon (CSA) and Activated carbon embedded in the integrated filter for S company's air purifier was purchased from Eco Household & Health Care (Daegu, Nam-gu) and S company's internet shopping mall, respectively, and used as a control.

1.2 Preparation of Adhesive Components

Liquefaction is required to use HH and PH as raw materials for adhesive. For this purpose, 200 g of HH and PH were slowly added to a 5% concentration of NaOH (AK) aqueous solution (350 ml), respectively, at 95 ± 2.5 ℃ 240 Minute hydrolysis was performed (Yang & Ahn, 2017; Park et al., 2017). In order to remove the foam generated during the hydrolysis reaction, 15 drops of an antifoaming agent (Defoamer-NW) manufactured by Ilshin Chemical (Gyeongbuk, Goryeong) was added using a plastic dropper with a capacity of 3 ml. The solids content of human hair (HH-AK) and pig hair alkali hydrolyzate (PH-AK) obtained by the hydrolysis reaction was 35 - 40%, pH was about 12.8, and the viscosity was measured in the range of 500 m Pa s at 25 ° C. , and insufficiently hydrolyzed human hair and pig hair were removed through the screening process, so there was no problem such as clogging of the nozzle during spraying.

Unlike HH and PH, PB was sufficiently stirred because it was in a liquid phase, and then directly hydrolyzed. Since the pH of HH-AK and PH-AK was 12 or higher, the necessity of adding a curing agent to lower the pH was raised to shorten the curing reaction, and as a result, an acid hydrolyzate of PB was used as a curing agent. Acid hydrolyzate (PB-AC) of PB is a non-organic acid containing chlorine, sulfur, and nitrogen to provide as a solid biofuel for thermal power plants after use and collection of a fiberboard filter manufactured using a natural protein-based adhesive It was reacted with an organic acid, oxalic acid (HOOCCOOH). The hydrolysis reaction was performed by adding 5% oxalic acid based on the PB solid content to sufficiently stirred PB, and then reacting at 90 ± 5 ° C. for 0.5 hours to obtain a hydrolyzate (PB-AC) (Yang et al., 2017; Yang et al., 2017; Yang & Ahn, 2017). The solid content of PB-AC was measured to be 19.3%, and the pH was measured to be 2.1, and it was impossible to measure the viscosity because it became mud-like upon completion of the reaction.

When an adhesive composed of only protein-based components is used to manufacture fiberboard, phenolic compounds such as tannins were extracted from the bark and added to the adhesive because of concerns about a decrease in strength. For this, larch bark crushed to a certain size was first reacted in hot water at 95 ± 2 °C for 4 hours, and then concentrated hydrolyzate (LB-HE) was obtained through evaporation. The LB-HE thus obtained had a solid content of about 38%, a viscosity of 1,000 m·Pa·s or more, and a pH of 5.4. This extraction process takes a long time and the amount that can be secured is small, so as a solution to this, a large amount of LB-HE was obtained by requesting a health center. The specific method is as follows. After putting about 7 kg of larch bark in a boiling water heater (50 liter) with sufficient water, it was reacted at 120° C. for 1 hour, and maintained overnight in that state. In addition to the liquid extract, the hot water extracted bark was placed in a press to additionally secure the liquid extract. After removing large-sized residues from this liquid extract three times with a sorter, it was packaged in a pouch. The solid content of LB-HE stored in the pouch was about 5%, and it was concentrated to around 38% through an evaporation process prior to adhesive preparation and used for adhesive preparation. LB-HE obtained by extraction in the laboratory deteriorated in a short period of time when stored at room temperature, but LB-HE prepared in large quantities at the Health Center was packaged in a pouch and could be stored at room temperature for more than 6 months without spoilage.

1.3 Adhesive preparation

The adhesive for the manufacture of a fiberboard filter was prepared by reacting HH-AK, PH-AK, PB-AC and/or LB-HE. According to the results of previous studies, HH-AK/PH-AK/PB-AC/LB-HE based on the solid content of 40/40/10/10, 40/40/20/0, 35/35/10/20, 35/ The adhesive was prepared by adjusting 35/20/10 (wt%/wt%/wt%/wt%) (Yang et al., 2014; Park et al., 2017; Yang & Ahn 2017; Yang et al., 2017; Yang et al., 2018). On the other hand, since the main component of the adhesive is protein, there is a possibility of spoilage. After preparing an aqueous solution of sodium borate having a concentration of 20%, 15 drops were added to the adhesive prior to application. In the case of the European Union, the use of borates as a food preservative is currently prohibited, but in many other regions and countries, it is added as a preservative material for various uses, so it was used because it was considered harmless to the human body (Thevenon et al., 2010). ). In order to impart flame-retardant performance to the fiberboard filter to be manufactured, a phosphoric acid-based flame-retardant solution was provided from Happy Home Wood Tech, and 15 drops were added to the adhesive.

1.4 Preparation of Activated Carbon and Elemental Analysis

A 200-liter capacity steel drum was used to secure large amounts of LBA and CBA, and the process is as follows. After cutting the upper and lower parts of the drum, 4 firewoods with a height of 2.5 cm were erected on the inner corners as pedestals. An open 75 liter drum was placed on the firewood and a grill was used as a partition to control the amount of raw material used for carbonization. After bending the drum as much as possible using a tool so that the upper part of the drum faces outward, the skirt drum was hung, and an iron pipe with a diameter of 60 mm was installed on the upper part of the drum to discharge the vaporized material and used as an exhaust port. The carbonization furnace was buried in the lower part of the two-thirds of the drum, and the contents consisting of 1 part of slaked lime, 2 parts of briquettes, and 1 part of loess were filled around it. Various types of LBA and CBA were obtained by slowly carbonizing and cooling using briquettes or lignite over 48 hours (Figure 1). On the other hand, the COA, which was provided free of charge, was currently on sale, so it was not possible to secure the specific manufacturing process from the provider, but it was confirmed that it was mass-produced with the application of high carbonization temperature and long carbonization time in a charcoal kiln.

For elemental analysis of each activated carbon, the sample was burned at a temperature of 1,014 ° C. and passed through the copper layer of the quartz tube, and converted into gas molecules (CO ₂ , N ₂ , H ₂ O) that are easy to analyze for each constituent element. After passing this mixed gas through a gas chromatography column, each was separated, and then quantitatively converted into an electrical signal by a Thermal Conductivity Detector. Finally, after creating a calibration curve using a standard sample, the carbon, hydrogen, and nitrogen contents of each sample were measured, and the result of elemental analysis was expressed as an average value of three repetitions.

1.5 Heavy Metals and Volatile Organic Compounds in Activated Carbon adsorption capacity Assessment Methods

Prior to evaluation of adsorption capacity, 50 g of activated carbon stored overnight in an oven at 95 ± 2.5 °C was placed in a non-woven bag, and then sealed and stored in a zipper bag. After exposing them to various indoor and outdoor spaces (smoking rooms, metal processing companies, building corridors near subway stations, sawmills, underground parking lots) for more than a week, they are recovered, and lead, copper, iron, aluminum, chrome, The amount of zinc was measured. That is, after removing all components except ash from the activated carbon after exposure has been completed using a 65% nitric acid solution (HNO ₃ ), a solution diluted with distilled water is inductively coupled plasma (ICP) emission according to the detection wavelength of each element irradiated. It was performed using a spectrometer (Perkin-Elmer Optima 4300 DV). For example, the copper content was obtained by irradiating the amount detected at a wavelength of 324.8 nm.

In order to measure the amount of VOC adsorbed on the activated carbon, the activated carbon sample used for measuring the heavy metal adsorption capacity is placed in a microchamber made of stainless steel and purged with high-purity nitrogen at a flow rate of 120 mL/min while maintaining the temperature at 50, 100, and 150 ℃. The generated gas was collected with a Tenax TA adsorption tube for 10 minutes at a flow rate of 100 mL/min, and the VOC was quantitatively analyzed by applying the thermal desorption-gas chromatography-MS method. For the VOCs adsorption performance test method of activated carbon, an activated carbon sample that has not been exposed to the external environment is placed in a fixed frame, liquid VOCs (benzene, toluene, ethylbenzene, xylene, styrene) standard material is vaporized at 200 °C, and then the flow rate is 100 mL/min. The activated carbon sample was passed through a fixed frame installed. In this way, gas samples before and after passing through the activated carbon were collected with a Tenax TA adsorption tube and quantitatively analyzed using thermal desorption GC/MS.

As a method for quantitative evaluation of VOCs, the Indoor Air Quality Process Test Standard (2020) Measuring method of volatile organic compounds emitted from indoor and building materials - Solid adsorption tube and gas chromatography - MS, FID method (ES 02602.1c) was used.

1.6 Manufacture of Fibreboard Filters

In order to determine the target density of the fiberboard filter, 6, 10 or 12 minutes of hot pressing time at various loading rates (4, 8, 10, 14%), and the temperature and pressure of the thermopresser were fixed at 180 ℃ and 24 kg/cm ² , respectively. After adjusting the amount of activated carbon in the fiberboard to ³⁰ wt%, 40 wt%, or 50 wt% in the state of A thick fiberboard (25 cm x 25 cm) was prepared using a closed thermopresser. Based on the strength and air permeability results of the fiberboard thus prepared, the target density of the fiberboard filter was determined to be 200 kg/m ³ or more. However, the air permeability of the fiberboard manufactured in this way was low. produced. Using this, a fiberboard filter was manufactured in the following manner.

According to the specified dimensions and target density, a certain amount of wood fiber is put into a 60 liter plastic barrel, and 2% of wax emulsion is sprayed based on the total dry weight of the wood fiber using a high-viscosity paint sprayer. was sprayed. To explain the molding process, first, 25% of the total weight of wood fibers sprayed with adhesive is uniformly dispersed in a hot-pressing mold on which a spiked caul plate is placed, and then a mixture of 50% of the total weight of wood fibers and activated carbon is sequentially molded thereon. and finally, the remaining 25% of the weight of wood fiber was molded thereon. After placing the flat caul plate on the finished wood fiber and activated carbon mat, hot pressing was performed for 12 minutes at a thermopresser temperature of 180 °C and a pressure of 24 kg/cm ² . On the other hand, the PF resin used as a control was hot-pressed for 7 minutes with a 5% coverage ratio under the same thermopresser temperature and pressure to prepare a fiberboard. Two to three fiberboard filters were prepared for each condition, and after being left in a constant temperature and humidity room for more than 24 hours, they were placed in a zipper bag and stored until the performance test.

1.7 Comparison of strength of fiberboard filters and measurement of pollutant emissions

The strength of the manufactured fiberboard filter was compared by type by measuring the flexural strength while applying a load to the surface of the test piece at an average speed of 10 min/mm according to the "Standards and Quality Standards for Wood Products" announced by the National Institute of Forest Science (National Institute of Forestry and Science) , 2015). The amount of pollutant emission was measured according to the test method for certification of eco-friendly building materials. It was measured according to the Indoor Air Quality Process Test Standard (No. 2020-19) announced by the National Academy of Environmental Sciences (No. 2020-19), the test method for volatile organic compounds and formaldehyde in building materials - the small chamber method (ES 02131.1d). The release test was conducted after exposing the fiberboard for 7 days at the temperature (25 ± 1.0) ℃ relative humidity (50 ± 5) % in a small release test chamber, and the total volatile organic compounds (TVOC, molecular weight between C ₆ and C ₁₆ ) total), benzene, toluene, ethylbenzene, xylene, styrene, formaldehyde and acetaldehyde emissions were measured.

1.8 Fine dust from fiberboard filters absorbency evaluation

According to the National Institute of Environmental Sciences Notice (No. 2020-30) Air Pollution Process Test Criteria, the dust measurement method in the environment-high-capacity air sampling method (ES 01604.1) was performed.

The weights of fiberboard, Korean paper, and quartz filter for dust measurement were measured at (20 ± 5) ℃, (20 ± 5) % for 7 days or more. On the day the fine dust advisory was issued, dust was collected from the outside on the 2nd floor of Seoul National University Building 201, Sillim-dong, Gwanak-gu, Seoul at a flow rate of 500 L/min for 8 hours, and then subjected to constant temperature and humidity treatment again. was investigated.

Results and Discussion

1.1 Heavy Metals in Activated Carbon adsorption capacity

As a result of measuring the heavy metal adsorption capacity of activated carbon exposed to various indoor and outdoor spaces, in the case of coconut shell activated carbon (CSA), compared to non-exposed CSA, all samples except for the low aluminum content in the samples exposed to smoking rooms and underground parking lots adsorbed a lot of heavy metals. appeared to be In particular, it was measured that 10 times more iron and aluminum than unexposed CSA were adsorbed in the passageway connected to the open window of the building about 30 m away from the outdoor subway station and in the CSA exposed at the sawmill. is expected to exist.

1.2 Volatile Organic Compounds in Activated Carbon adsorption capacity

VOCs adsorbed on activated carbon exposed to indoor and outdoor spaces were not detected in exposed-activated carbon vaporized at 50°C and 100°C. This is presumed to be the result of insufficient VOC physically and chemically bound to the activated carbon. On the other hand, TVOC and some 5VOC were detected in exposed activated carbon vaporized at 150 °C.

In order to accurately measure the VOC adsorbed on the activated carbon, before measuring the VOC adsorption capacity of the activated carbon, the vaporized VOC was forcibly passed through the sample thoroughly purified by putting it in an oven to measure the amount of VOC before and after passing. Looking at the results, it was measured that CSA, COA, and SAA adsorbed more than 99% of 5VOC. However, the adsorption amount of 5VOC of LBA and CBA was 76.0% and 35.2%, respectively, which was very low compared to other activated carbons. In addition, the TVOC adsorption capacity of COA was highest at 98.5%, followed by CSA (97.2%) and SAA (93.0%). The TVOC adsorption capacity of LBA and CBA was similar to that of 5VOC. Therefore, when manufacturing a fiberboard filter using COA, it is thought that VOC present in the atmosphere will be reduced. On the other hand, the low VOC adsorption capacity of LBA and CBA was judged to be the result of insufficient carbonization due to the use of briquettes with a low calorific value, and was carbonized using lignite with a high calorific value. As a result of measuring the VOC adsorption capacity of LBA-L and CBA-L prepared in this way, the adsorption capacity of TVOCs was 92.0% and 95.5%, respectively, which was significantly increased than that of LBA and CBA, and was measured to be higher than that of SAA. In addition, the adsorption capacity of TVOC and 5VOC was exhibited with no difference or higher than that of CSA or COA. Based on these results, it was concluded that carbonization using lignite is necessary to use larch and cypress bark as raw materials for activated carbon.

1.3 Elemental Analysis of Activated Carbon

Carbon, hydrogen, and nitrogen analysis was performed on each activated carbon to confirm the conclusion that the activated carbon carbonized with lignite had better adsorption capacity for heavy metals and VOC than briquettes. Compared with LBA and CBA carbonized with briquettes, carbonization using lignite (LBA-L and CBA-L) increased the carbon content and decreased the hydrogen content. In particular, the carbon content of LBA-L and CBA-L was lower than that of CSA, but higher than that of SSA and COA. Therefore, as mentioned in the results of many studies, it was confirmed that the VOC and heavy metal adsorption capacity of activated carbon is proportional to the carbon content.

1.4 Adhesive properties

Since the adhesive used in the manufacture of the fiberboard filter is composed of 70 wt% or more of highly alkaline HH-AK and PH-AK, 10 wt% or 20 wt% of highly acidic PB-AC and neutral LB-HE, the pH is 11 or more was measured as In the case of solid content, the main components were prepared with HH-AK and PH-AK of 37 wt% or more, PB-AC of about 20 wt% or more, and LB-HE of 38 wt% or more, and approximately 35% of the total was investigated. As a result of measuring the viscosity of the adhesive prepared under these conditions using a viscoelasticity meter (ARES, TA Instruments, USA), it showed a viscosity similar to that of urea-formaldehyde, a thermosetting adhesive for manufacturing wood composite materials.

Looking at the curing behavior measured while raising the temperature from room temperature to 200 °C at a rate of 2 °C/min using the above viscoelasticity measuring instrument (ARES, TA Instruments, USA), there was no change in storage modulus in the temperature range of 40 - 90 °C. , in the 90 - 100 ℃ range, the effect of water evaporation began to appear. After 100 ℃, the storage modulus increases as the temperature rises, confirming the viscoelastic properties shown in most thermosetting adhesives, and the maximum value at 170 ℃ shows that a higher thermo-pressing temperature is required for complete curing of the adhesive.

1.5 Selection of manufacturing conditions according to the results of bending strength and air permeability of fiberboard filters

First, although the flexural strength of the fiberboard manufactured at a density of 200 kg/m ³ was excellent, there was a problem in air permeability. In the case of the fiberboard manufactured by lowering the density to 100 and 125 kg/m ³ , although the air permeability was improved, the strength was very low, indicating that it was not suitable for the target density. Although the flexural strength of the fiberboard manufactured with the target density of 150 and 180 kg/m ³ was increased by increasing the target density, it was judged that it was necessary to improve the air permeability along with partial destruction during the manufacturing and transportation process. Next, the flexural strength of fiberboards prepared with a target density of 200 kg/m ³ fixed at 200 kg/m 3 and 4%, 8%, 10%, and 14% coverage showed a tendency to increase with the increase of the coverage ratio. Through the results of previous studies for determining the target density and coverage ratio, the target density and coverage ratio of the fiberboard filter were determined to be 200 kg/m ³ or more and 8% or 10%, respectively.

When fiberboard was prepared by adding 30 wt%, 40 wt%, or 50 wt% of activated carbon based on the total dry weight of the fiberboard filter under the above conditions, the effect on strength was not significant at 30 wt% and 40 wt%, but 50 wt% The % addition amount had a negative effect on the strength. Therefore, the amount of added activated carbon was determined to be a maximum of 40 wt%. On the other hand, as a result of visually checking the strength due to the distribution of activated carbon in the fiberboard, it did not significantly affect the strength when randomly added. excluded from Next, it was prepared by adding activated carbon as a single layer (1 layer) to the middle layer in the thickness direction of the fiberboard, but an adhesive was not applied to the activated carbon. Based on these results, it was decided to use only wood fibers for the fiberboard surface layer (upper and lower layers), and randomly mix wood fibers and activated carbon for the deep layer (middle layer) to produce a three-layer fiberboard. Meanwhile, as a result of confirming the effect of the particle size of the activated carbon on the strength of the fiberboard filter, 50 wt% of powdered activated carbon (< 4 mesh) relative to the total dry weight of the fiberboard was added as a single layer to the middle layer in the thickness direction. Separation from the central layer occurred during cutting for specimen production. However, in the case of a fiberboard made of particulate activated carbon (>2 mesh) under the same conditions, no separation caused by cutting occurred. Therefore, in terms of strength, it was decided to manufacture a fiberboard by applying particulate activated carbon rather than powder.

Based on the conditions determined above, in the case of a three-layer fiberboard prepared by adding 40 wt% of particulate activated carbon to the deep layer together with wood fibers at a target density of 200 kg/m ³ , the high density and low air permeability are low in order to compensate for this problem. It was drilled using an electric drill so as to have vents of the same diameter. Through this, the breathability was improved, but it was judged that there would be a lot of fine dust and VOC/heavy metal that passed without being absorbed or adsorbed. It was decided to use a fiberboard filter set composed of On the other hand, due to the low density of the fiberboard (200 kg/m ³ ), there was a problem in the appearance of the fibers swelling around the vents during the drilling process ^. It was decided to investigate how to make fiberboard with ventilation holes by bonding them.

1.6 coconut Selection of manufacturing conditions based on activated carbon-added fiberboard filter strength

1.6.1 Target density and amount of activated carbon added

First, in order to determine the hot-pressing time, the fiberboard prepared with a target density of 200 kg/m ³ , an activated carbon content of 40 wt%, and a content of 10% with a hot-pressing time of 6 minutes had low strength, and was easily broken. occurred (Fig. 2, A). The strength of the manufactured fiberboard was improved by extending the hot-pressing time to 12 minutes, but a phenomenon in which the edge portion was broken in the process of handling the manufactured product occurred in some cases (Fig. 2, B). Therefore, the strength of the fiberboard manufactured by raising the target density to 300 kg/m ³ under the same conditions was significantly improved compared to that prepared at 200 kg/m ³ , and overall handling was very easy ( FIG. 2 , C ). Next, it was found that the fiberboard prepared by adjusting the target density to 250 kg/m ³ had sufficient strength to handle it (FIG. 2, D).

Next target with 40 wt% activated carbon using HH-AK/PH-AK/PB-AC/LB-HE = 40 wt%/40 wt%/10 wt%/10 wt% as adhesive for making fiberboard The flexural strengths of the fiberboard prepared by hot pressing at 180 °C for 12 minutes with the density adjusted to 200 kg/m ³ and 250 kg/m ³ were measured to be 0.27 and 0.39 kgf/cm ² , respectively, but there was no statistical difference ( p = 0.13). Based on the above results, the target density of the fiberboard filter and the amount of activated carbon added were determined to be 200 kg/m ³ , 30 wt%, and 250 kg/m ³ , 40 wt%, respectively.

1.6.2 Coverage rate

Using the same adhesive as described above, the content was adjusted to 8%, 10%, and 12% together with 40 wt% of activated carbon to a target density of 200 kg/m ³ , 180 ° C., and a hot pressure temperature and time of 12 minutes. Flexural strength of fiberboard was 0.43, 0.23 and 0.32 kgf/cm ² , which was the highest at 8% coverage (8%/10%: p = 0.04; 8%/12%: p = 0.33), and 10% and 12%. It was analyzed that there was no difference in knowledge rate (p = 0.27). Since the fiberboard filter to be collected after future use is to be used as a solid biofuel, it was decided to fix the loading ratio to 8% to minimize nitrogen and sulfur emissions present in the protein-based adhesive during combustion.

1.6.3 Types of Adhesives

Based on the above results, after fixing at a target density of 250 kg/m ³ , an activated carbon content of 40 wt %, a loading rate of 8%, and a hot pressing temperature and time of 180 ° C. and 12 minutes, various types of adhesives were applied to prepare a fiberboard to measure the flexural strength, except for 35 wt% HH-AK/35 wt% PH-AK/20 wt% PB-AC/10 wt% LB-HE (p = 0.02), The flexural strength was not statistically different from the flexural strength of the fiberboard made of the control, phenolic resin. On the other hand, in the case of 40 wt% HH-AK/40 wt% PH-AK/20 wt% PB-AC adhesive, the nozzle of the sprayer was often clogged during application, which caused HH-AK or PH contained in the adhesive before spraying. -AK and PB-AC in an increased amount up to 20 wt% were combined and it was assumed that the molecular weight was increased, so it was excluded from the fiberboard adhesive. Next, in the case of 40 wt% HH-AK/40 wt% PH-AK/10 wt% PB-AC/10 wt% LB-HE, the raw material cost and manufacturing cost of HH-AK and PH-AK are higher than that of LB-HE. It was judged that the cost of the adhesive would increase, so it was excluded from the adhesive for manufacturing fiberboard. As a result, the adhesive for manufacturing fiberboard was determined to be 35 wt% HH-AK/35 wt% PH-AK/10 wt% PB-AC/20 wt% LB-HE.

1.6 Contaminant emissions from fiberboard filters

Looking at the types of pollutants emitted from the fiberboard manufactured with the adhesive, total volatile organic compounds (TVOC), which is the sum of substances between C6 - C16, and 5VOC, which is the sum of benzene, toluene, ethylbenzene, xylene, and styrene, formaldehyde, acetone With aldehyde, the results are shown in Table 5. Emitted 5VOC was not present at all, TVOC was significantly lower than the highest grade standard in the HB eco-friendly building material grade standard, and aldehydes were also found to be significantly lower than the standard value. As a result, it was confirmed that the fiberboard filter proposed in the present invention satisfies the environment-friendly board grade and the highest grade standard of the HB mark.

1.7 Fibreboard filter VOC low ability

Looking at the results of measuring the VOC reduction ability of the fiberboard filter manufactured by adding CSA and COA as activated carbon, all the activated carbon-added fiberboard filters manufactured in the present invention, including the filter manufactured only with wood fiber, were compared to the S company air purifier non-woven fabric filter. Comparatively, it was confirmed that it had a high VOC reduction ability, which is judged to be the result of measuring the VOC reduction ability of the S company's non-woven filter without a deodorizing filter composed of activated carbon. However, looking at the results of measuring the VOC reduction ability for activated carbon alone, the VOC reduction ability of the S company's filter is expected to be lower than the activated carbon-added fiberboard filter manufactured in the present invention from the low VOC adsorption capacity of the S company's activated carbon. Next, the VOC reduction ability of the fiberboard filter manufactured without activated carbon was lower than that of the fiberboard filter manufactured with activated carbon, and through this result, it was confirmed that activated carbon plays an important role for VOC adsorption and filtration in the fiberboard filter.

The TVOC and 5VOC reduction ability of the fiberboard filter prepared by adjusting the CSA activated carbon addition amount to 30 wt% and 40 wt% with the target densities fixed at 200 and 250 kg/m ³ , respectively, was investigated. There was no difference with the increase, but at 40 wt%, it decreased with the increase of the Mokpo density. This is thought to be the result of the low air permeability of the high-density fiberboard filter itself, excluding the ventilation hole. Based on these results, the target density of the fiberboard - the amount of activated carbon added was set at 250 kg/m ³ -40 wt%, 200 kg/m ³ -30 wt%, 200 kg/m ³ -20 wt%, 150 kg/m ³ -20 wt%. It was decided to prepare by adjusting the %.

On the other hand, looking at the measurement results of the VOC reduction capacity of the fiberboard filters manufactured using CSA and COA, respectively, the TVOCs and 5VOC reduction ability of the COA-added fiberboard filter was higher than that of the CSA-added fiberboard filter under the same manufacturing conditions. However, although the difference between the VOC adsorption capacity of COA and CSA itself is not large, the reason for the difference in the VOC reduction capacity of the fiberboard filter is presumed to be due to some interaction between the COA and the wood fiber within the fiberboard filter.

Looking at the results of the VOC reduction capacity of the COA-added fiberboard filter, the TVOCs were the highest in the specimens prepared under the condition of 200 kg/m ³ -30 wt%, 250 kg/m ³ -40 wt%, 200 kg/m ³ -20 wt%, 150 kg/m ³ -20 wt% was measured in that order. In the case of 5VOC, 200 kg/m ³ -30 wt% and 250 kg/m ³ -40 wt% were the highest with the same reduction capacity, followed by 200 kg/m ³ -20 wt% and 150 kg/m ³ It was measured in the order of -20 wt%. From this result, it was concluded that at least 30 wt% of activated carbon is required in the fiberboard filter, and the target density needs to be adjusted in order to maintain the strength for easy handling at this added amount.

Finally, in order to reduce the manufacturing cost of the filter filter, a filter was manufactured by replacing the wood fiber with a low-cost regenerated fiber. To this end, it was manufactured under various conditions using sludge (SW) generated in the corrugated cardboard production process, which is easy to secure ^. was necessary to control. The TVOCs and 5VOC reduction ability of this filter was very low compared to the filter made of wood fiber, which was due to the reduced air permeability due to the high target density of the filter, the use of cypress bark activated carbon (CBA) with low VOC adsorption capacity as activated carbon, and the low amount of CBA added appears to be a result of

1.8 Fine dust from fiberboard filters low ability

As a result of measuring the fine dust reduction ability of the fiberboard filter manufactured in the present invention, the fine dust reduction ability of most of the activated carbon-added fiberboard and/or filter papers manufactured in the present invention was higher than that of the quartz filter. In particular, the fine dust reduction ability of the fiberboard filter prepared at 200 kg/m ³ by adding 20 wt% of COA and 40 wt% of CSA was measured to be very good. Even the activated carbon-free fiberboard filter set showed high fine dust reduction ability. Therefore, it was possible to confirm the fine dust reduction ability of the fiberboard filter, but unlike the quartz filter, the fiberboard and filter paper are mostly composed of hydrophilic natural fibers. Thus, the weight change rate of the fiberboard filter according to the humidity was investigated. As the humidity increased from 20% to 50%, the weight of the fiberboard also increased by 2 - 4%, but as the humidity was lowered back to 20%, it was measured that the weight increased by less than 0.5% from the initial weight. With these results, in order to measure the fine dust reduction ability of the fiberboard and filter paper, after storing it for 24 hours in a constant temperature and humidity room at 25 ℃ and 20% humidity, the weight was measured. The impact is thought to be extremely limited.

On the other hand, according to the results of comparing the fine dust reduction ability of each fiberboard filter set, it was possible to confirm the high fine dust reduction ability under the manufacturing conditions of all the fiberboards investigated by the present inventors, especially 30 wt%-200 kg/m ³ and 40 wt%-250 kg/m ³ COA-added fiberboard showed very good TVOCs and 5VOC reduction ability. Therefore, it is judged that the filter set composed of fiberboard and filter paper proposed in the present invention can be used as a filter for indoor and outdoor fine dust filtration.

The present invention relates to an activated carbon-added fiberboard filter made of wood bark for the absorption/adsorption of fine dust, VOC, and heavy metals, which are pollutants present in the atmosphere, and a manufacturing technology thereof. In the case of activated carbon exposed to various indoor and outdoor spaces, significant amounts of metal components were detected in COA, LBA-L, and CBA-L as well as control CSA and SAA, so ventilation is difficult, including indoor spaces such as subway trains and platforms. It is expected that many metal components will also be present. In addition, since a large amount of TVOCs and 5VOCs are detected in this activated carbon, when used as a raw material for filter manufacturing, it is thought that it will play a sufficient role in reducing VOCs existing in a certain space. Through the carbon content analysis, it was possible to confirm the ability of the activated carbon to adsorb heavy metals and VOCs. In order to manufacture a filter filter supporting activated carbon, a fiberboard was prepared using lignocellulose fibers as a substrate. If it is properly adjusted, I think that there will be no problems at all from the point of view of suppliers and users. Considering the strength of the fiberboard prepared by applying the adhesive prepared in various configurations and the manufacturing cost of the adhesive, 35 wt% of HH-AK, 35 wt% of PH-AK, 10 wt% of PB-AC, and 20 wt% of LB- Adhesives prepared with HE were found to be the most suitable for manufacturing fiberboard filters. On the other hand, in the manufacture of fiberboard, spiked caul plates were used to have vents of regular intervals and diameters to improve ventilation, and through this, sufficient ventilation was ensured. On the other hand, in the perforated fiberboard manufactured by applying the adhesive, a coverage of 8%, target densities of 200 and 250 kg/m ³ , and activated carbon content in the fiberboard of 20, 30, and 40 wt% were confirmed as optimal manufacturing conditions. Since this fiberboard is manufactured with a protein-based natural adhesive, it has met the environment-friendly board grade of the Ministry of Environment and the highest grade standard of the HB mark. As a result of confirming the VOC reduction ability of the fiberboard filter set composed of the fiberboard and filter paper prepared in this way, the target density of the fiberboard - the amount of activated carbon added was 250 kg/m ³ -40 wt%, 200 kg/m ³ -30 wt%, 200 kg/ m ³ -20 wt%, 150 kg/m ³ It was determined to be prepared by adjusting -20 wt%. In this condition, the fiberboard manufactured with COA, LBA-L, and CBA-L was found to have very good TVOCs and 5VOC reduction ability. In addition, when looking at the results of the fine dust reduction performance of this fiberboard filter set, it was very good compared to the quartz filter. In particular, 30 wt%-200 kg/m ³ and 40 wt%-250 kg/m ³ COA-added fiberboard have excellent TVOCs and 5VOC reduction capabilities.

references

Yeo Guk-hyun. 2016. Fine dust management technology trends, Korea Environmental Industry and Technology Institute, Konetic Report No. 2016-112.

Changhwan Lee. 2019. Development technology and evaluation method by filter type, Korea Textile Development Institute, http://super.textopia.or.kr:8888/newsletter/170404/lib0201.pdf. [accessed at January 13, 2020]

Haejin Ha, Hyungyu Lee. 2018. Fine dust technology trends - Focusing on dust collection and reduction technology, Science and Technology Job Promotion Agency, S&T Market Report No. 64.

Marketsandmarkets. 2020. Non-Woven Fabrics Market, https://www.marketsandmarkets.com/Market-Reports/non-woven-fabrics-market-101727296.html. [accessed at January 15, 2021]

double line. 2018. Technological product trend of non-woven fabric for hygiene and medical use, the latest non-woven fiber technology development trend seminar, Korea Textile Industry Association.

Jong-ryul Lee, Chan-wook Baek. 2018. (Secondary) Current status of fine dust and future response strategies in Busan, Busan Institute of Science and Technology Planning and Evaluation, BISTEP 2018-4.

12(3): 253-257.Thevenon, M., Tondi, G., Pizzi, A. 2010. Environmentally friendly wood preservative system based on polymerized tannin resin-boric acid for outdoor application, Maderas. Ciencia y tecnolog

12(3): 253-257.

National Forest Science Academy. 2015. Specifications and Quality Standards for Wood Products - Fibreboard, National Institute of Forestry and Science, No. 2015.

Claims (7)

A fiberboard filter containing activated carbon from wood bark, formed of a three-layer structure of an upper layer, a middle layer and a lower layer, containing only wood fibers in the upper and lower layers, and a mixture in which wood fibers and activated carbon are randomly mixed in the middle layer, fine dust, volatile organic matter Fiberboard filter containing activated carbon from wood bark for absorption and absorption of compounds and heavy metals. The fiberboard filter according to claim 1, wherein a plurality of vents passing through the upper layer, the middle layer and the lower layer are provided. The fiberboard filter according to claim 1, wherein the weight ratio of the activated carbon is 20% to 40% by weight based on the filter. The fiberboard filter according to claim 1, wherein the filter has a density of 150 kg/m ³ to 250 kg/m ³ . The fiberboard filter according to claim 1, wherein the mixture is mixed using a natural adhesive comprising wood fiber and activated carbon, a hydrolyzate of natural raw materials selected from human hair, pig hair and pig blood, and a larch hot water extract. A fiberboard filter assembly in which the fiberboard filter of claim 1 is interposed between two sheets of the fiberboard filter of claim 2. A fiberboard filter assembly in which the fiberboard filter of claim 2 is overlapped, and the filter paper is attached to the bottom surface.

Images