KR102538781B1 - 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, comprising a three-layer structure of upper, middle, and lower layers. A fiberboard filter containing wood bark activated carbon for absorption and adsorption of fine dust, volatile organic compounds, and heavy metals is provided, wherein the upper and lower layers contain only wood fibers, and the middle layer contains a randomly mixed mixture of wood fibers and activated carbon.

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 wood bark activated carbon for absorption and adsorption of fine dust, volatile organic compounds, and heavy metals, and a method for manufacturing the same.

In a situation where indoor and outdoor air quality deterioration due to the inflow and occurrence of fine dust reduces people's satisfaction with life and causes health anxiety, it is urgent to prepare countermeasures that can efficiently reduce fine dust existing in various indoor and outdoor spaces. In particular, subway platforms, underground tunnels, train interiors, etc., which are related to subways, are enclosed spaces, making it difficult to discharge fine dust and harmful substances generated from various pollutants or from outside, and natural ventilation is not possible. and directly or indirectly adversely affect the health of subway workers. However, since it is impossible to strictly control pollutant emission sources, the application of emission source management measures to solve this problem has been limited to date. It is a situation where a plan is needed.

As a commercialized technology to reduce fine dust to date, a method to control pollutants of various sizes by using a membrane with fine pores as a filter is mainly used. Scrubbers, etc. are also applied individually or jointly (Yeo, 2016). However, the above technologies have disadvantages such as not being able to handle fast flow rates and thus not being applicable to large facilities, low fine dust removal efficiency, short filter lifespan, and high filter replacement costs (Lee, 2019). On the other hand, since the dry filtration filter is an air cleaning technology that mainly reduces only fine dust, it reduces only a limited amount of volatile organic compounds and heavy metals harmful to the human body existing in indoor and outdoor spaces. In addition, 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), so it takes a long time to biodegrade when landfilled, resulting in soil contamination and mass production. of waste, and when incinerated, it generates a large amount of carbon dioxide, which is the main cause of global warming (Bok, 2018; Marketsandmarkets, 2020). Therefore, it is necessary to develop a high-efficiency and low-cost new collection and filtration technology using regenerated fibers as raw materials for filtering, which can replace synthetic fiber nonwoven fabrics.

Looking at the technology trends being developed at home and abroad in relation to fine dust reduction, overall, technology for practical use, such as fine dust treatment materials, process development technology, and ICT-based air pollutant management, is mainly being secured (Ha & Lee , 2018). In particular, in Korea, we are concentrating on identifying the causes of elimination reactions by material, developing material source technology and major core technology for materials/processes, and focusing on removing primary emissions (dust collection) and secondary generation (denitrification and desulfurization) precursors. this is aligned In addition, rather than the development of emission reduction technology, technology development for dust collectors that can drastically reduce fine dust emissions while minimizing the installation space at the source of fine dust is in progress. However, since the reduction target 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 to improve existing facilities and performance of dust collection technology. In the case of foreign countries, the highest level of fine dust reduction technology is developing various facilities related to post-exhaust treatment devices for industrial facilities in Germany and Sweden, centering on the United States and Japan, where ultrafine dust regulations have been strengthened, but indoor and outdoor ultrafine dust reduction The development of 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 practicality and cost.

The present invention is a wood bark activated carbon-containing fiberboard filter formed of a three-layer structure of an upper layer, a middle layer, and a lower layer, wherein the upper and lower layers contain only wood fibers, and the middle layer contains a mixture of wood fibers and activated carbon randomly mixed. An impregnated fiberboard filter is provided. Without limitation, the fiberboard filter according to the present invention is provided with a plurality of vents penetrating the upper, middle and lower layers. In the filter according to the present invention, the weight ratio of activated carbon is 20% to 40% by weight 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 filter according to the present invention efficiently reduces volatile organic compounds (VOCs) and heavy metals, including fine dust existing in indoor and outdoor spaces. In addition, it is possible to respond to the Convention on Climate Change by reducing greenhouse gas emissions by converting waste filtration filters into solid biofuels, in addition to creating a foundation for commercialization through realization of recycling of living/slaughter/industrial wastes and waste reduction.

1 is a schematic diagram of a spiked caul plate for manufacturing 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 filter and manufacturing method for replacing synthetic fiber-based nonwoven fabric for absorption/adsorption of fine dust, VOC, and heavy metals.

It is required to develop technology to replace the raw material of the filtration filter, which is currently mainly manufactured with non-woven fabric, which is a synthetic fiber, with renewable vegetable fiber. Among vegetable fibers, wood fiber is judged to be the most suitable raw material for filtration filters based on the quantity and price that can be supplied in Korea, but it is converted into a form such as non-woven fabric by combining it in parallel, cross, and arbitrary ways through mechanical, chemical, and thermal processes. 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 fiber in the form of a low-density fiberboard and using it as a filter. However, filters manufactured using only wood fibers are expected to have limitations in filtration of pollutants such as volatile organic compounds (VOCs) and heavy metals present in various indoor and outdoor spaces. A method of manufacturing in the form of a fiberboard by adding excellent activated carbon as a medium is sought. A plan to use unused wood by-products as a raw material for the activated carbon used in filter manufacturing has been proposed in consideration of economic feasibility and recycling of waste. Since the filter made of wood fiber and wood-based activated carbon is in the form of a fiber board, it must have a certain level of strength, and for this purpose, an adhesive is required. Since the fiber raw material used in manufacturing the filter is a carbon-neutral wood-based resource, the used/collected filter can be used as a solid biofuel. Therefore, it is manufactured using a natural adhesive rather than a petrochemical synthetic resin adhesive used in conventional fiberboard manufacturing. A plan to do so emerged. 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 it will be possible to produce filter filters at a very low cost in addition to efficient recycling and value-adding of waste resources as well as reduction of waste generation. As a raw material that satisfies these conditions, a method of using human hair, pig hair, pig blood, and wood bark, which is generated in large quantities as waste at home and abroad, as a raw material for adhesives has been proposed.

The present invention is described below with reference to specific examples, but is not limited thereto.

Materials and Methods

1.1 Disclosed materials

Wood fiber (moisture content: 10 ± 1%) and emulsion wax (solid content: 43 ± 1%) used in the manufacture of the fiberboard type filter were supplied free of charge from UNID Co., Ltd. (Jeonbuk, Gunsan).

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

Sodium hydroxide and oxalic acid used for hydrolysis of HH, PH, and PB and sodium borate added for preservative purposes were purchased from Lab Story Science (Chungbuk, Cheongju) and used as reagents for chemical experiments. In order to impart flame retardant performance to the fiberboard filter, the phosphoric acid flame retardant added to the adhesive was supplied from Happy Homewood Tech Co., Ltd. (Muan, Jeonnam) and used. On the other hand, phenol formaldehyde (hereinafter referred to as PF), which was used as a control for comparison of adhesive performance with the prepared protein-based natural adhesive, had a solid content of 50% and a viscosity of 200 m Pa s, and was manufactured in Gangnam Hwaseong (Gyeonggi, Korea). Anyang).

Activated carbon added to adsorb VOCs and heavy metals in the fiberboard filter was manufactured using larch and cypress bark, which are unused wood by-products in Korea, and are provided free of charge by the Forestry Cooperative Federation’s Dongbu Wood Distribution Center and Happy Homewood Tech Co., Ltd. (Muan, Jeonnam), respectively. was supplied with In addition, charcoal (cork oak active-carbon, COA), which is not sold because it partially contains bark, was supplied free of charge from Good Charcoal (Seoul, Songpa), which produces oak charcoal for meat roasting, and used as activated carbon. Coconut shell active-carbon (CSA) and coconut shell active-carbon (CSA) were used to compare the adsorption capacities of larch bark active-carbon (LBA), cypress bark active-carbon (CBA), and COA for VOCs and heavy metals. Activated carbon embedded in the integral filter for air purifiers from S company was purchased from Eco Life & Health Co., Ltd. (Daegu, Nam-gu) and S company's internet shopping mall, respectively, and used as controls.

1.2 Preparation of adhesive components

To use HH and PH as raw materials for adhesives, liquefaction is required. To this end, 200 g of HH and PH were slowly added to a 5% NaOH (AK) aqueous solution (350 ml), respectively, at 95 ± 2.5 ° C. Minutes of hydrolysis were performed (Yang & Ahn, 2017; Park et al., 2017). In order to remove bubbles generated during the hydrolysis reaction, 15 drops of a defoamer (Defoamer-NW) manufactured by Ilshin Chemical (Goryung, Gyeongbuk) were added using a plastic pipette with a capacity of 3 ml. The solid content of human hair (HH-AK) and pork hair alkaline hydrolysate (PH-AK) obtained by the hydrolysis reaction was 35 - 40%, the pH was about 12.8, and the viscosity was measured in the range of 500 mPa s at 25 ℃. In addition, insufficiently hydrolyzed human hair and pork hair were removed through a sorting process, so that no problems such as clogging of the nozzles occurred during spraying.

Unlike HH and PH, since PB is in a liquid state, a direct hydrolysis reaction was performed after stirring sufficiently. Since the pH of HH-AK and PH-AK is higher than 12, the necessity of adding a curing agent to lower the pH was raised to shorten the curing reaction, and as a result, acid hydrolyzate of PB was used as a curing agent. Acid hydrolyzate of PB (PB-AC) is not an inorganic acid containing chlorine, sulfur, and nitrogen to be used as solid biofuel for thermal power plants after the use and collection of fiberboard filters manufactured using protein-based natural adhesives. It was reacted with an organic acid, HOOCCOOH. For the hydrolysis reaction, after adding 5% oxalic acid based on the PB solid content to sufficiently stirred PB, the reaction was performed at 90 ± 5 ° C for 0.5 hour to obtain a hydrolyzate (PB-AC) (Yang et al., 2017; Yang & Ahn, 2017). The solid content of PB-AC was measured to be 19.3% and the pH was 2.1, and upon completion of the reaction, it was in the form of mud, making it impossible to measure the viscosity.

When an adhesive composed of only protein-based components is used for fiberboard manufacturing, there is a concern about a decrease in strength, so phenolic compounds such as tannins are extracted from bark and added to the adhesive. To this end, larch bark crushed to a certain size was primarily reacted in hot water at 95 ± 2 ° C for 4 hours, and then concentrated hydrolyzate (LB-HE) was obtained through evaporation. The solid content of the LB-HE thus obtained was measured to be around 38%, the viscosity was 1,000 m Pa s or more, and the pH was 5.4. This extraction process takes a long time and the amount that can be secured is small. As a solution to this, a large amount of LB-HE was secured by requesting the Health Center, and the specific method is as follows. After putting about 7 kg of larch bark with enough water in a boiling water heater (50 liter), 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 put into a press to obtain an additional liquid extract. After removing large-sized residues from this liquid extract three times with a sorting sieve, it was packed in a pouch. The solid content of LB-HE stored in the pouch was about 5%, and prior to adhesive preparation, it was concentrated to around 38% through an evaporation process 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 decay.

1.3 Adhesive preparation

An adhesive for manufacturing a fiberboard filter was prepared by reacting HH-AK, PH-AK, PB-AC and/or LB-HE. Through the results of previous studies, HH-AK/PH-AK/PB-AC/LB-HE was classified as 40/40/10/10, 40/40/20/0, 35/35/10/20, 35/ An adhesive was prepared by adjusting to 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 decay, so after preparing a 20% concentration sodium borate aqueous solution, 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 raw material for various purposes, so it is thought to be harmless to the human body (Thevenon et al., 2010 ). In order to impart flame retardant performance to the fiberboard filter to be manufactured, 15 drops of a phosphoric acid flame retardant solution provided by Happy Homewood Tech Co., Ltd. were added to the adhesive.

1.4 Preparation of activated carbon and elemental analysis

To secure large quantities of LBA and CBA, a steel drum with a capacity of 200 liters was used, and the process is as follows. After cutting the upper and lower parts of the drum, four 2.5 cm high wooden beams were erected at the inner corners as supports. 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 to be used for carbonization. After bending the top of the drum as much as possible using a tool so that the upper part of the drum is directed outward, the skirt drum is covered, and then an iron pipe with a diameter of 60 mm is installed on the top of the drum to discharge the vaporized material and used as an exhaust port. A carbonization furnace was buried at the bottom of two thirds of the drum, and the contents consisting of 1 part slaked lime, 2 parts briquettes, and 1 part red clay 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 provided free of charge was currently on sale, so it was not possible to specifically secure the manufacturing process from the supplier, 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 a copper layer of a quartz tube to convert into gaseous molecules (CO ₂ , N ₂ , H ₂ O) that are easy to analyze for each element. After separating each of these mixed gases while passing through a gas chromatography column, they were quantitatively converted into electrical signals by a thermal conductivity detector. Finally, after preparing a calibration curve using standard samples, the contents of carbon, hydrogen, and nitrogen for each sample were measured, and the results of elemental analysis were expressed as the average value of three repetitions.

1.5 Heavy metals and volatile organic compounds in activated carbon adsorption capacity Assessment Methods

Prior to the evaluation of adsorption capacity, 50 g of activated carbon stored overnight in an oven at 95 ± 2.5 ° C. was placed in a nonwoven fabric bag, and then sealed and stored in a zipper bag. After exposing it to various indoor and outdoor spaces (smoking rooms, metal processing companies, corridors of buildings near subway stations, sawmills, underground parking lots) for more than a week, it is collected and collected according to the Enforcement Decree of the Environmental Health Act. The amount of zinc was measured. That is, after removing all components except for ash by using 65% nitric acid solution (HNO ₃ ) from the activated carbon after exposure, the 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 content of copper was obtained by examining 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 to measure the adsorption capacity of heavy metals was 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 VOCs were quantitatively analyzed by thermal desorption-gas chromatography-MS method. The VOCs adsorption performance test method of activated carbon is to put an activated carbon sample that is not exposed to the external environment into a fixed frame, vaporize the liquid VOCs (benzene, toluene, ethylbenzene, xylene, styrene) standard substance at 200 ℃, and then The sample was passed through a fixing frame in which an activated carbon sample was installed. Gas samples before and after the passage of activated carbon were collected with Tenax TA adsorption tubes and quantitatively analyzed using thermal desorption GC/MS.

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

1.6 Manufacture of fiberboard filters

In order to determine the target density of the fiberboard filter, the heating pressure time of 6, 10, or 12 minutes at various content ratios (4, 8, 10, 14%), the temperature and pressure of the heating press ^were fixed at 180 ℃ and 24 kg/cm After adjusting the amount of activated carbon in ^the fiberboard to 30 wt%, 40 wt%, or 50 wt% in the condition of A thick fiberboard (25 cm x 25 cm) was prepared using a closed thermocompressor. The target density of the fiberboard filter was determined to be 200 kg/m ³ or more based on the results of strength and air permeability of the fiberboard thus manufactured. However, the air permeability of the fiberboard thus manufactured was low. To solve this problem, as shown in FIG. 1, a spiked caul plate capable of manufacturing a fiberboard having up to 64 conical vents (diameter: 10 mm or less) was made of special stainless steel. produced. Using this, a fiberboard filter was manufactured in the following manner.

Put a certain amount of wood fibers into a 60 liter plastic bucket according to the specified dimensions and target density, spray 2% wax emulsion based on the total dry weight of the wood fibers using a sprayer for high-viscosity paint, and then apply the amount of adhesive calculated at the fixed content rate. was sprayed. Describing the molding process, first, 25% of the total weight of wood fibers to which the adhesive was sprayed was molded while being uniformly distributed in a thermopress mold with a spiked caul plate, and then a mixture of 50% of the total weight of wood fibers and activated carbon was sequentially molded on top of it. Finally, the remaining 25% weight of wood fiber was molded on it. After placing the flat caul plate on the molded wood fiber and activated carbon mat, hot pressing was performed at a pressure of 24 kg/cm ² at a temperature of 180 °C for 12 minutes. On the other hand, the PF resin used as a control was hot-pressed for 7 minutes with a 5% paper content under the same hot press temperature and pressure to prepare a fiber board. 2-3 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 put in a zipper bag and stored until the performance test.

1.7 Strength comparison of fiberboard filters and pollutant emission measurement

The strength of the manufactured fiberboard filter was compared by type by measuring the bending strength while applying a load to the surface of the test piece at an average rate of 10 min/mm in accordance with the National Institute of Forest Science notice "Specifications and Quality Standards for Wood Products" (National Institute of Forest Science , 2015). Pollutant emission was measured according to the test method for eco-friendly building material certification. It was measured according to the Indoor Air Quality Process Test Standards (No. 2020-19), Volatile Organic Compounds and Formaldehyde Test Methods Emitted from Building Materials-Small Chamber Method (ES 02131.1d) announced by the National Institute of Environmental Research. In the emission test, the total volatile organic compounds (TVOC, molecular weight of substances between C ₆ and C ₁₆ Total), benzene, toluene, ethylbenzene, xylene, styrene, formaldehyde and acetaldehyde emissions were measured.

1.8 Fine dust in the fiberboard filter absorption capacity evaluation

It was carried out according to the National Institute of Environmental Research Notice (No. 2020-30) air pollution process test standard, dust measurement method in the environmental atmosphere-high-capacity air sampling technique (ES 01604.1).

The weight of the fiberboard, Korean paper, and quartz filter for dust measurement treated with constant temperature and humidity for more than 7 days at (20 ± 5) ℃ and (20 ± 5) % was measured. On the day when the fine dust advisory was issued, dust was collected from the outside on the 2nd floor of Building 201, Seoul National University, 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, and the fine dust absorption capacity was measured by measuring the weight change. 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, heavy metals were adsorbed in all samples except for the low aluminum content in the samples exposed to smoking rooms and underground parking lots. appeared to be In particular, it was measured that about 10 times more iron and aluminum were adsorbed in the exposed CSA at the sawmill and the passageway connected to the open window of the building about 30 m away from the outdoor subway station than the non-exposed CSA. 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 not enough VOCs physically and chemically bound to the activated carbon. On the other hand, TVOC and some 5VOC were detected in the exposed activated carbon vaporized at 150 °C.

In order to accurately measure the VOC adsorbed on the activated carbon, the vaporized VOC was forcibly passed through the sample sufficiently purified in an oven before measuring the VOC adsorption capacity of the activated carbon, and the amount of VOC before and after passage was measured. As a result, CSA, COA, and SAA were measured to adsorb more than 99% of 5VOC. However, the 5VOC adsorption 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 the 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 air can be reduced. On the other hand, it was determined that the low VOC adsorption capacity of LBA and CBA was the result of insufficient carbonization by using briquettes with low calorific value, so lignite with high calorific value was used for carbonization. As a result of measuring the VOC adsorption capacity of the LBA-L and CBA-L thus prepared, the TVOCs adsorption capacity was 92.0% and 95.5%, respectively, which was significantly higher than that of LBA and CBA and higher than that of SAA. In addition, TVOC and 5VOC adsorption capacities were higher than those of CSA or COA or had no difference. 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

In order to confirm the conclusion that the adsorbability of heavy metals and VOCs of the activated carbon carbonized with lignite is superior to that of briquettes, carbon, hydrogen, and nitrogen analyzes were performed for each activated carbon. Compared to 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 many research results, it was confirmed that the adsorption capacity of activated carbon for VOCs and heavy metals was proportional to the carbon content.

1.4 Characteristics of adhesives

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 37 wt% or more of HH-AK and PH-AK, 20 wt% or more of PB-AC, and 38 wt% or more of LB-HE, and the total was about 35%. As a result of measuring the viscosity of the adhesive prepared under these conditions using a viscoelasticity meter (ARES, TA Instruments, USA), the viscosity was similar to that of urea-formaldehyde, a thermosetting adhesive for wood-based composite materials.

Looking at the curing behavior measured while raising the temperature from room temperature to 200 ℃ at a rate of 2 ℃ / min using the above viscoelasticity meter (ARES, TA Instruments, USA), there was no change in storage modulus in the temperature range of 40 - 90 ℃ , in the range of 90 - 100 ℃, the effect of evaporation of moisture began to appear. After 100 ℃, the storage modulus increased as the temperature increased, confirming the viscoelastic properties of most thermosetting adhesives.

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

First, the fiberboard manufactured with a density of 200 kg/m ³ had excellent flexural strength, but had a problem in air permeability. In the case of the fiber board manufactured by lowering the density to 100 and 125 kg/m ³ , the air permeability was improved, but the strength was very low, and it was found to be unsuitable for the target density. Although the flexural strength of fiberboards manufactured with target densities of 150 and 180 kg/m ³ by increasing the target density increased, it was judged that air permeability should be improved along with partial destruction during manufacturing and transportation. Next, the flexural strength of the fiberboards manufactured with 4%, 8%, 10%, and 14% paper content with the target density fixed at 200 kg/m ³ showed a tendency to increase with the increase of the paper content. Through the results of previous studies for determining the target density and the loading rate, the target density and the loading rate of the fiberboard filter were determined to be 200 kg/m ³ or more and 8% or 10%, respectively.

Under the above conditions, when the fiberboard was prepared by adding 30 wt%, 40 wt%, and 50 wt% of activated carbon based on the dry weight of the fiberboard filter, the effect on the strength was not significant at 30 wt% and 40 wt%, but at 50 wt% The % addition had a negative effect on strength. Therefore, the amount of activated carbon added was determined to be up to 40 wt%. On the other hand, as a result of visually confirming the strength by the distribution of activated carbon within the fiberboard, random addition did not significantly affect the strength, but it is expected that the problem of desorption of the activated carbon present on the surface layer of the fiberboard during the manufacturing and transportation process will occur. excluded from Next, it was prepared by adding activated carbon to the middle layer in the thickness direction of the fiberboard in a single layer, but since the adhesive was not applied to the activated carbon, it was separated from the center of the fiberboard during cutting to prepare a test piece. Based on these results, it was decided to manufacture a three-layer fiberboard by using only wood fibers for the surface layers (upper and lower layers) of the fiberboard and randomly mixing wood fibers and activated carbon for the core layer (middle layer). On the other hand, as a result of confirming the effect of the particle size of activated carbon on the strength of the fiberboard filter, in the fiberboard manufactured by adding 50 wt% of powdered activated carbon (< 4 mesh) to the thickness direction intermediate layer in a single layer, compared to the total dry weight of the fiberboard, A phenomenon of separation from the center layer occurred during cutting to prepare the test piece. However, in the case of a fiberboard made of particulate activated carbon (> 2 mesh) under the same conditions, separation due to cutting did not occur. Therefore, in terms of strength, it was decided to manufacture a fiber board 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 core layer with wood fibers at a target density of 200 kg/m ³ , high density and low air permeability were obtained at regular intervals to compensate for this. It was perforated using an electric drill to have vents of the same diameter. Through this, air permeability is improved, but it is judged that there will be a lot of fine dust and VOC/heavy metals that pass through without being absorbed or adsorbed, so a low target density fiber board that is not perforated between two perforated fiber boards and/or a filter paper (Korean paper) at the bottom It was decided to use the fiberboard filter set composed of as a filter for the absorption/adsorption of fine dust/VOC/heavy metal for indoor and outdoor use. On the other hand, since the fiber board has a low density (200 kg/m ³ ), there is an external problem that the fiber swells around the vent during the perforation process, so a plan to increase the target density to 250 kg/m ³ and spikes on the pressure plate during the hot pressure process have been developed. It was decided to investigate a method of bonding to produce vented fiberboard.

1.6 coconut shell Selection of manufacturing conditions by activated carbon-added fiberboard filter strength

1.6.1 Target density and added amount of activated carbon

First, in order to determine the hot pressing time, the fiberboard prepared with a target density of 200 kg/m ³ , activated carbon content of 40 wt%, and a 10% paper content with a hot pressing time of 6 minutes had low strength and was easily broken as a whole. occurred (FIG. 2, A). Although the strength of the fiberboard manufactured by extending the hot pressing time to 12 minutes was improved, the corner portion was broken in some cases in the process of handling the manufactured board (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 greatly improved compared to that manufactured at 200 kg/m ³ , and overall handling was very easy (FIG. 2, C). Next, it was found that the fiberboard manufactured by adjusting the target density to 250 kg/m ³ had sufficient strength to be handled (FIG. 2, D).

Next, using HH-AK / PH-AK / PB-AC / LB-HE = 40 wt% / 40 wt% / 10 wt% / 10 wt% as an adhesive for fiberboard production, the target with 40 wt% of activated carbon The flexural strengths of the fiberboards manufactured by adjusting the density to 200 kg/m ³ and 250 kg/m ³ and hot-pressing at 180 °C for 12 minutes were measured as 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 Paper content rate

Using the same adhesive as above, the content ratio was adjusted to 8%, 10%, and 12% with 40 wt% of activated carbon to prepare a target density of 200 kg / m ³ , 180 ° C., and a hot pressure temperature and time of 12 minutes. The flexural strength of the fiberboard was 0.43, 0.23 and 0.32 kgf/cm ² , which was the highest at 8% fat content (8%/10%: p = 0.04; 8%/12%: p = 0.33), both 10% and 12%. It was analyzed that there was no difference in the index (p = 0.27). Since the fiberboard filter, which will be collected after use, will be used as a solid biofuel, it was decided to fix the content ratio at 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, a target density of 250 kg/m ³ , an activated carbon content of 40 wt%, a coating ratio of 8%, and a hot pressure temperature and time of 180 ° C and 12 minutes were fixed, and then various kinds of adhesives were applied to prepare a fiber board. The flexural strength was measured, and the fiberboards manufactured with the remaining types of adhesives 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 control fiber board prepared with 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 clogged frequently during application, which was caused by the 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 the molecular weight increased, which was assumed to be a phenomenon that was excluded from the adhesive for manufacturing fiberboard. 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 were higher than those 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, 35 wt% HH-AK/35 wt% PH-AK/10 wt% PB-AC/20 wt% LB-HE was used as an adhesive for manufacturing fiberboard.

1.6 Pollutant emissions from fiberboard filters

Looking at the types of contaminants emitted from the fiberboard made with the adhesive, total volatile organic compounds (TVOC), which is the sum of substances between C6 and C16, and 5VOC, which is the sum of benzene, toluene, ethylbenzene, xylene, and styrene, formaldehyde, and acet With aldehyde, the results are shown in Table 5. There was no emitted 5VOC at all, TVOC was significantly lower than the highest grade standard in the HB eco-friendly building material rating standard, and aldehydes were also investigated 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 of the Ministry of Environment.

1.7 of the fiberboard filter VOCs reduction

Looking at the results of measuring the VOC reduction ability of the fiberboard filter prepared by adding CSA and COA as activated carbon, all activated carbon-added fiberboard filters manufactured in the present invention, including filters made only from wood fibers, were compared with the non-woven fabric filter of S company air purifier. It was confirmed that it had a high VOC reduction ability by comparison. However, when looking at the results of measuring the VOC reduction ability of only the activated carbon, it is expected that the VOC reduction ability of the S company filter is lower than that of the activated carbon-added fiberboard filter prepared in the present invention from the low VOC adsorption capacity of the S company activated carbon. Next, the VOC reduction ability of the fiberboard filter prepared without activated carbon was lower than that of the fiberboard filter prepared with activated carbon, and through this result, it was confirmed that activated carbon plays an important role in the adsorption and filtration of VOCs in the fiberboard filter.

As a result of examining the TVOC and 5VOC reduction capacities of the fiberboard filters prepared by adjusting the addition amount of CSA activated carbon to 30 wt% and 40 wt% with the target density fixed at 200 and 250 kg/m ³ , respectively, 30 wt% There was no difference with increase, but at 40 wt%, it decreased with increase in wood cloth density. This is thought to be the result of low air permeability of the fiberboard filter itself manufactured with high density except for the ventilation hole. Based on this result, 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 -20 wt% It was determined to be prepared by adjusting to %.

On the other hand, when looking at the VOC reduction performance measurement results of the fiberboard filters prepared using CSA and COA, respectively, the TVOCs and 5VOC reduction abilities of the COA-added fiberboard filter were generally higher than those 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 was not large, the reason for the difference in VOC reduction capacity of the fiberboard filter was presumed to be due to some interaction between COA and wood fibers in the fiberboard filter.

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

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

1.8 Fine dust in the fiberboard filter reduction

As a result of measuring the fine dust reduction ability of the fiberboard filter prepared in the present invention, most of the activated carbon-added fiberboard and / or filter paper manufactured in the present invention had a higher fine dust reduction ability than 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 exhibited high fine dust reduction ability. Therefore, it was confirmed that the fine dust reduction ability of the fiberboard filter was confirmed, but unlike the quartz filter, in the case of fiberboard and filter paper, it was thought that the adsorption of moisture present in the air could affect the fine dust reduction ability because most of the fiberboard and filter paper were composed of hydrophilic natural fibers. The weight change rate of the fiberboard filter according to 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 decreased again to 20%, it was measured that the weight increased by less than 0.5% from the initial weight. In addition to this result, in order to measure the fine dust reduction ability of the fiberboard and filter paper, it was stored in a constant temperature and humidity room at 25 ℃ and 20% humidity for 24 hours, and then the weight was measured. The impact is expected to be extremely limited.

On the other hand, according to the result of comparing the fine dust reduction ability of each fiberboard filter set, it was confirmed that the fine dust reduction ability was high under all the fiberboard manufacturing conditions investigated by the present inventors, and in particular, 30 wt%-200 kg/m In the case of ³ and 40 wt%-250 kg/m ³ COA-added fiberboard, it was found to have very good TVOCs and 5VOC reduction capabilities. Therefore, it is determined that the filter set composed of the fiberboard and the 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 absorption/adsorption of pollutants such as fine dust, VOC, and heavy metals in the air 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 groups CSA and SAA, including indoor spaces such as subway trains and platforms where ventilation is difficult. It is expected that many metal components will also be present in In addition, a large amount of TVOCs and 5VOCs were detected in this activated carbon, and when used as a raw material for filter manufacturing, it is thought that it will sufficiently play a role in reducing VOCs present in a certain space. Through the carbon content analysis, it was possible to confirm the adsorption capacity of heavy metals and VOCs of the activated carbon. To manufacture a filter using activated carbon as a carrier, a fiberboard was manufactured using lignocellulosic fibers as a substrate. If it is appropriately adjusted, it is thought that there will be no problem at all from the viewpoint of the supplier and the user. 35 wt% of HH-AK, 35 wt% of PH-AK, 10 wt% of PB-AC, and 20 wt% of LB- Adhesives formulated with HE were found to be most suitable for fabricating fiberboard filters. On the other hand, in order to improve air permeability in the manufacture of fiberboard, it was manufactured using spiked caul plates to have vents of constant spacing and diameter, through which sufficient air permeability could be secured. On the other hand, in the perforated fiberboard manufactured by applying the adhesive, a paper content of 8%, a target density of 200 and 250 kg/m ³ , and an activated carbon content in the fiberboard of 20, 30, and 40 wt% were confirmed as optimal manufacturing conditions. Since this fiberboard is manufactured with protein-based natural adhesive, it has met the highest standard of eco-friendly board grade and HB mark of the Ministry of Environment. As a result of confirming the VOC reduction ability of the fiberboard filter set composed of the fiberboard and the filter paper manufactured 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 m ³ -20 wt%, 150 kg / m ³ It was determined to be prepared by adjusting to -20 wt%. In this condition, the fiberboards prepared with COA, LBA-L and CBA-L showed very good TVOCs and 5VOC reduction ability. Also, when looking at the fine dust reduction results for this fiberboard filter set, it was very excellent compared to the quartz filter. In particular, the 30 wt%-200 kg/m ³ and 40 wt%-250 kg/m ³ COA-added fiberboards have excellent TVOCs and 5VOC reducing abilities.

references

Yeo Guk-hyeon. 2016. Fine dust management technology trend, Korea Environmental Industry and Technology Institute, Konetic Report 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]

Sujin Ha, Hyungyu Lee. 2018. Fine Dust Technology Trend - Focusing on dust collection and reduction technology, Science and Technology Employment Agency, S&T Market Report No. 64.

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Bok Jin Line. 2018. Technological product trend of sanitary and medical nonwoven fabric, latest nonwoven fabric technology development trend seminar, Korea Textile Industry Association.

Lee Jong-ryul, Baek Chan-wook. 2018. (Ultra) Fine Dust Status and Busan's Future Response Strategy, 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 and tecnolog

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Claims (7)

A fiberboard filter containing wood bark activated carbon, formed of a three-layer structure of an upper layer, a middle layer, and a lower layer, wherein the upper and lower layers contain only wood fibers, and the middle layer includes a mixture in which wood fibers and activated carbon are randomly mixed, wherein the mixture includes wood fibers and A fiberboard filter containing activated carbon of wood bark for absorption and adsorption of fine dust, volatile organic compounds and heavy metals, mixed with activated carbon using hydrolyzates of natural raw materials selected from human hair, pig hair and pig blood, and natural adhesives including larch hot water extract . The fiberboard filter according to claim 1, wherein a plurality of vents are provided through the upper, middle and lower layers. 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 . delete A fiberboard filter assembly in which the fiberboard filter of claim 1 is sandwiched 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.

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