Journal of Oleo Science Copyright ©2012 by Japan Oil Chemists’ Society J. Oleo Sci. 61, (10) 593-600 (2012) Development of Novel Carbon Fiber produced from Waste Fiber by Cabonization Naohito Kawasaki＊ , Hisato Tominaga, Fumihiko Ogata, Kenji Inoue and Moe Kankawa Faculty of Pharmacy, Kinki University, (3-4-1, Kowakae, Higashi-Osaka, Osaka 577-8502, JAPAN) Abstract: The volume of waste fiber has increased rapidly in recent years, and this trend is expected to continue. In this study, therefore, we attempted to convert waste fiber to carbonaceous materials by carbonization and investigated the basic properties of the resulting carbonized fibers. The results demonstrated that pores tend to form and specific surface areas change substantially, depending on the carbonization conditions. The carbonization conditions resulting in the largest specific surface areas included a temperature increase and retention times of 2 h. Carbonization temperatures resulting in the maximum values of 1000℃ were 900–1000℃ for wool and 1000℃ for both polyester and cotton. In particular, the specific surface area of cotton after carbonization at 1000℃ was 1253 m2/g, and scanning electron microscopy (SEM) micrographs showed that cotton retained its fibrous form after carbonization. Thus, it is possible to inexpensively convert waste fibers to carbonaceous material by carbonization. The results indicate that for cotton fiber in particular, the practical application of this process to the production of low-cost fibrous activated carbon would be possible, since cotton fiber retains its fibrous form under carbonization. Key words: Waste Fiber; Carbonization; Pore Size Distribution; Conversion 1 INTRODUCTION responsibility in their pursuit of profits. However, recycling In recent years, increases in population and industrial rates for fiber products have not been rising, largely activity have led to many mutually related problems world- because of consumer resistance to the use of recycled wide concerning the environment, resources, and energy. products and the cost of recycling. Essentially, material cycle systems undergo breakdowns, People have used wool, cotton, and other natural fibers and effective use of waste materials as resources can con- throughout recorded history. The development of chemical tribute to the integrity of these systems. fibers began in 1884, and today they account for 60％ of With the declining prices of fiber products, their life the total volume of fiber use. Most of the chemical fibers cycle has shortened. In Japan alone, the annual volume of are petroleum-based polymers, and its effective utilization fiber waste discharge has reached some two million tons, is highly desirable. and the product life cycle has substantially shortened. Activated carbon, which is produced from materials such Moreover, the rapid rise in fiber imports appears to be as palm shell, petroleum pitch, and coal, is widely used for causing a rise in oversupply, dead stock, and subsequent the adsorption of organic compounds and harmful sub- disposal of unsold products. Approximately 10％ of all fiber stances4－7）. Fibrous activated carbon is characterized by a products are recycled, mostly in the form of incineration higher specific surface area, adsorption rate, and adsorp- and land reclamation. Other forms of recycling include tion efficiency than granular activated carbon8, 9）, but its chemical decomposition and regeneration of polyester production process is also more complex and expensive. In （PE）fiber, reuse of cotton as an automotive insulation ma- recent years, a trend has emerged for the production of terial, and export of used clothing to Southeast Asia and low-cost, useful carbonaceous materials from biomasses other regions. The use of these products as a reinforcing such as apricot shells10）, rubber wood sawdust11, 12）, material in walls and other applications has also been re- bamboo13）, jute fiber14）, and other agricultural by-products. ported1－3）. In recent years, in an effort to expand clothing An investigation has also been carried out on the produc- recycling, corporations have been asked to exercise social tion of activated carbon from cotton yarn using 4％ calcium ＊Correspondence to: Naohito Kawasaki, Professor Faculty of Pharmacy, Department of Pharmacy 3-4-1, Kowakae, Higashi-Osaka, Osaka 577-8502, JAPAN E-mail: [email protected] Accepted May 24, 2012 (recieved for review February 27, 2012) Journal of Oleo Science ISSN 1345-8957 print / ISSN 1347-3352 online http://www.jstage.jst.go.jp/browse/jos/ http://mc.manusriptcentral.com/jjocs 593 N. Kawasaki, H. Tominaga, F. Ogata et al. phosphate as an activator, and its ability to adsorb p-ni- sure of 0.025-0.99 and the desorption isotherm at a relative troaniline15, 16）has also been investigated. The various pressure of 0.1-0.99 were determined at the temperature methods of activated charcoal production that have been of liquid nitrogen. Then, the values were calculated by the reported generally include not only carbonization but also Dollimore-Heal method18）. The pores were considered to activation by processing with steam or chemical substanc- be cylindrical, and the average pore diameter（D）was cal- es. In the present study, we produced carbonaceous mate- culated using Eq.（2）from the specific surface area（S）and rials from various waste fibers by carbonization without ac- the pore volum（e P）19）. tivation. A method for carbonaceous material production 4P D＝ （2） without activation has important advantages, including low S energy consumption and low environmental burden. The present study focused on the conversion of waste 2.3 Chemical properties of carbonaceous materials fibers to carbonaceous materials. Carbonaceous materials Base consumption was determined using the method of were produced from waste fibers, and their specific surface Boehm et al.20, 21）. A 0.1-g sample of the carbonaceous ma- area, pore volume, surface chemical properties, and effi- terial was weighed and placed in a vial, to which 20 mL of ciency in reduction of carbon dioxide emissions were in- 0.05 mol/L sodium hydroxide solution（Wako Pure Chemical vestigated. Industries, Osaka, Japan）was added; this was followed by shaking the vial at 100 rpm and 25℃ for 24 h. The solution was then filtered using 0.45-μm glass fiber filter paper（Ad- vantec, Tokyo, Japan）. The filtrate was titrated with 0.01 2 EXPERIMENTAL mol/L hydrochloric acid solution（Wako Pure Chemical In- 2.1 Production of carbonaceous materials dustries, Osaka, Japan）, using methyl red as the indicator, The carbonaceous materials were produced essentially and the base consumption was calculated using Eq.（3）. as follows. Wool, PE, or cotton was placed in a magnetic （0.05×a－0.01×b） B＝ （3） furnace under a nitrogen gas flow of 1 L/min, and the tem- W perature was increased over 3 h to an end temperature where B is the base consumption（mmol/g）, a is the volume between 400 and 1000℃. The maximum temperature was of the sodium hydroxide solution（mL）, b is the volume of held for 0-2 h, and then, the materials were naturally the hydrochloric acid solution（mL）, and W is the carbona- cooled. The carbonized wool and PE were then pulverized ceous material weight（g）. Base consumption is an indica- and used as an adsorbent, and the cotton was used without tor of the number of carboxyl, phenolic hydroxyl, and other further processing because of its fibrous form. The result- acidic groups and the quantity of acidic substances present ing carbonaceous materials and the original fibers were ob- on the surface of the carbonized fibers. served on a JSM-5200 scanning electron microscope（JEOL, The pH was measured using the Japan Industrial Stan- Ltd., Tokyo, Japan）. dard JIS K1474 test method for activated carbon22）. To 50 The carbonaceous material yields Y（％）were calculated mL of purified water, 0.5 g of adsorbent was added; then, using Eq.（1）, the solution was boiled for 5 min and filtered using 0.45-μm M glass fiber filter paper; finally, the filtrate pH was measured Y＝ ×100 （1） M0 on a digital pH meter（Mettler-Toledo, OH, USA）. where M and M0 are the dry weights（g）of the carbona- ceous material and the original fiber, respectively. The carbon, hydrogen, and nitrogen contents of the fibers and the carbonaceous materials were measured on a 3 RESULTS AND DISCUSSION Micro Corder JM-10（J-Science Co., Ltd., Kyoto, Japan）by 3.1 Surface shape of carbonaceous materials the Pregl-Dumas method. The SEM micrographs in Figs. 1-3 showed that the origi- nal wool and PE fibers lost their fibrous form and under- 2.2 Physical properties of carbonaceous materials went pore formation with an increase in carbonization tem- The specific surface area was obtained by first determin- perature. PE, which is produced by the condensation ing the adsorption isotherm at liquid nitrogen temperature polymerization of dicarboxylic acid and a diol and has a （－195.8℃）with high-purity nitrogen gas（99.999％）as the melting point of approximately 240℃, appeared to enter a adsorption gas on a Nova4200e（Quantachrome, FL, USA）. molten state at 400℃. As a result, the fibers formed an in- Next, curve fitting to the nitrogen adsorption isotherm at a creasing number of small pores with further increase in the relative pressure of 0.05-0.30 was carried out using the carbonization temperature. Cotton, on the other hand, re- Brunauer-Emmett-Teller（BET）equation17）. tained its fibrous form and SEM images showed no discern- Pore size distribution and pore volume were similarly able change with increasing carbonization temperatures. obtained. First, the adsorption isotherm at a relative pres- Since cotton is derived from plants, its main component is 594 J. Oleo Sci. 61, (10) 593-600 (2012) Manufacture of Novel Carbon Fiber No carbonization 400℃ 600℃ 500µm 500µm 500µm 800℃ 900℃ 1000℃ 500µm 500µm 500µm Fig. 1 SEM images of carbonaceous materials produced from wool at different temperatures.