この論文は国立情報学研究所の学術雑誌公開支援事業により電子化されました。Japanese cedar (Cryptomeria japonica D. Don) wood powder was carbonized at varying temperatures from 400° to 2,400℃ and used to remove mercury from 5 ppm mercuric chloride solutions. The removal efficiency of the carbonized wood materials changed depending on the carbonization temperature. The carbonization temperatures that provided wood powder with high removal capacity ranged from 600° to 1,400℃. Low removal of mercury from the aqueous solutions was observed for carbonization temperatures below 400° and above 1,600℃. The specific surface area of the carbonized wood materials was highly correlated with the capacity to remove mercury

HATA, Toshimitsu

IMAMURA, Yuji

ISHIHARA, Shigehisa

KAJIMOTO, Takeshi

PULIDO-NOVICIO, Lilibeth

Kyoto University Research Information Repository

Title<Original>Removal of Mercury from Aqueous Solutions ofMercuric Chloride Using Wood Powder Carbonized at HighTemperatureAuthor(s)PULIDO-NOVICIO, Lilibeth; HATA, Toshimitsu;KAJIMOTO, Takeshi; IMAMURA, Yuji; ISHIHARA,ShigehisaCitationWood research : bulletin of the Wood Research Institute KyotoUniversity (1998), 85: 48-55Issue Date1998-09-30URL http://hdl.handle.net/2433/53184RightType Departmental Bulletin PaperTextversionpublisherKyoto UniversityOriginal.Removal of Mercury from Aqueous Solutionsof Mercuric Chloride Using Wood PowderCarbonized at High Temperature*lLilibeth PULIDO-NoVICIO*2, Toshimitsu HATA*2, Takeshi KAJIMOTO*3,Yuji IMAMURA*2 and Shigehisa ISHIHARA*4(Received May 31, 1998)Abstract--Japanese cedar (Cryptomeriajaponica D. Don) wood powder was carbonized at varyingtemperatures from 400° to 2,400°C and used to remove mercury from 5 ppm mercuric chloridesolutions. The removal efficiency of the carbonized wood materials changed depending on thecarbonization temperature. The carbonization temperatures that provided wood powder with highremoval capacity ranged from 600° to 1,400°C. Low removal of mercury from t,he aqueoussolutions was observed for carbonization temperatures below 400° and above 1,600°C. The specificsurface area of the carbonized wood materials was highly correlated with the capacity to removemercury.Keywords: Cryptomeria japonica, carbonization temperature, mercury, removal, specific surface area1. IntroductionIndustrialization has led to progressively higher demands for pollution-controlmeasures. Recently, increasing attention has focused on the industrial application ofcharcoal especially for the adsorption of organic pollutants and heavy metals. To increasethe adsorptive properties of this material, it is manufactured as activated carbon which hasbeen extensively used in water and air purification due to its superior adsorptive propertiescharacterized by high surface area and microporosity as well as high degree of surfaceactivityl-3) .Heavy metals are potential hazards in the field of environmental pollution controlbecause of their toxicity and harmful effects. The removal of metal ions is thereforedesirable to prevent these hazardous effects in the environment. Chemical precipitation,solvent extraction, ion exchance, photocatalysis etc. are some of the several methods devisedto date to remove metal ions4-6). However, adsorption over adsorbents is still the mostcommonly used method for this purpose. Considering the high cost involved in preparing*' This work was presented at the 48th Annual Meeting of the Japan Wood Research Society at ShizoukaCity, April, 1998.*2 Laboratory of Wood Composite.*3 Wakayama Industrial Technology Center, Wakayama City.*4 Former Professor, Laboratory of Wood Composite.-48 -PULIDO-NoVICIO et at.: Removal of Mercury from Aqueous Solutions of Mercuric Chlorideactivated carbon, interest has focused on the utilization of ordinary charcoal instead ofactivated carbon.In our previous studies, we used carbonized wood materials for removal of mercuryfrom aqueous solutions of this metal. Mercury, which is toxic, quite mobile and active inbiochemical metabolism, is still spreading in the environment of surface and ground watersystems7- 11 ). Wood powder and that carbonized at 200°, 600° and 1,000°C removedmercury within the concentration range of 1-10 ppm; mercury was preferentially removedeven when mixed with other heavy metals. Wood powder carbonized at 1,000°C showedthe best removal of heavy metals among the wood-based materials examined, evencompared to activated carbon, in both single and mixed solutions9 ). Further, thiscarbonized material can remove mercury from aqueous solutions of different types ofmercury compounds 10).In this study, the removal capacity of this wood species carbonized at temperatureabove 1,000°C was determined using mercuric chloride as the adsorbate material.2. Materials and Methods2.1 MaterialsThe materials used were wood powder ofJapanese cedar (Cryptomeriajaponica D. Don)carbonized at 400°, 600°, 1,000°, 1,200°, 1,400°, 1,600°, 2,000° and 2,400°C. Mercuricchloride (HgC12) was used as the heavy metal compound for the removal experiments.2.2 Carbonization processThe wood powder which was passed through a no. 20 mesh sieve, was ovendried at10SoC and then carbonized seperately at a temperature of 400°, 600°, 1,0000, 1,200°, 1,400°,1,600°, 2,000° or 2,400°C. For 400°,600° and 1,000°C carbonization, nitrogen (N2 ) gas waspassed at 100 ml/min. through the furnace and the temperature was raised at a heating rateof 4°C until the target temperature was attained. Argon gas was used for the carbonizationof other materials at the same heating rate. The wood material was kept for 1 hour at thetarget temperature before the heater and gas flow were turned off. The carbonized woodmaterial was taken out of the furnace after cooling overnight.2.3 Surface area measurementThe surface area of the carbonized wood was measured using BELSORP 36. TheBET (Brunaeur-Emmet-Teller) multi-point method was used to determine the surface area.Nitrogen gas at 77°K was used to determine the adsorption isotherms.2.4 Scanning electron microscopyThe surface characteristics of raw wood powder and carbonized wood power ofJapanese cedar were observed directly by scanning electron microscopy (SEM) after coating- 49--,---. WOOD RESEARCH No. 85 (1998)•.•.•.•.•.•.•.•.•.•. $100ca 506~ 25~,~ 07:e:~-==!RJ10075.-....~ : ."-'"a 50.>0se 25....s::(I) .~-,'0~. 0 [((25) ;---,-----r----r---r-----.o 500 1000 1500 2000 2500Carbonization temperature(\JC)Fig. 2. Relationship between percent removal ofmercury in 5 ppm mercuric chloridesolution and Japanese cedar woodpowder carbonized at different tempe-ratures. Legend: ......0...... 1 hsoaking, ----<>- 4 h soaking,---0--- 24 h soaking.5010 20 30 40Soaking time (h)-25 ;---r---,r--.,.......-~-~oFig. 1. Percent removal ofmercury after soakingcarbonized Japanese cedar wood powderin 5 ppm mercuric chloride solution.Legend: ,6. 400°C*, 0 ..1,400°C*, - - -+- -- 600°C*,-r']- 1,600°C*, ---0---1,OOO°C*, - - -EB- -- 2,OOO°C*,----<>- 1,200°C*, ---"\7---2,400°C*. Note: *-carbonizationtemperature.with gold. Japanese cedar wood was cut into cross· and radial sections using a·microtomeafter carbonization and examined by SEM.2.5 Removal experimentAn aqueous solution of 5 ppm of mercuric chloride was prepared on a weight by weight(w/w) basis of mercury.. Carbonized wood material (500 mg each) was added to 50 ml ofthe solution and continuously shaken for 1, 4, 8, 24 or 48 h in a thermostatically controlledwater bath at 30°C. The mixtures were filtered and then the concentrations of mercury inthe samples ware measured using an. inductively coupled plasma (ICP) apparatus.3. Results and Discussion3.1 Effects of carbonization temperature on the removal of mercuryFig. 1 shows the removal of mercury from 5 ppm mercuric chloride solutions usingJapanese cedar carbonized wood powder. When the wood materials carbonized at 600°,1,000°, 1,200° and 1,400°C were soaked in the solutions, mercury was removed faster thanwhen those carbonized at 400°, 1,600°, 2,000° and 2,400°C were used. Wood powdercarbonized at 600°, 1,000°, 1,200° and 1,400°C removed about 99% of the mercury after 1 h- 50-PULIDO-NoVICIO et at.: Removal of Mercury from Aqueous Solutions of Mercuric ChlorideTable 1. Yield and specific surface area of carbonized Japanese cedar wood powderCarbonization temperature (OC)4006001,0001,4001,6002,400Yield (%)29.828.026.926.626.426.3Specific surface area (m2/g)27.400343.800563.310255.1004.1392.261of soaking whereas it took about 24 h to reach almost the same level of removal using thatcarbonized at 400°C. The wood powder carbonized at temperatures between 1,600° and2,400°C removed only about 25% of the mercury even after 24 h of soaking.We demonstrated previously that that raw wood powder also removed a considerableamount of mercury at about 80% within one hour lO), but carbonization improved itscapacity to remove mercury with better removal efficiency when carbonized at above 600°C.This suggested that the removal capacity of wood powder was dependent on the finalcarbonization temperature. As the final carbonization temperature increased, the amountof the metal removed increased. However, marked reductions in mercury removal weredetected using wood materials carbonized at temperatures above 1,600°C (Fig. 2). Theseobservations indicated that there is an optimum temperature range for carbonization ofwood to remove metals from solution.3.2 Yield and specific surface area of carbonized wood materialsTable 1 shows the yield and specific surface area of carbonized wood materials. Theyield of charcoal decreased as the carbonization temperature increased. However, startingfrom the carbonization temperature of 1,000°C, almost the same yield was observed. Ourprevious report noted that specific surface area of raw wood powder without anycarbonization was 0.541 m2/g and it increased by carbonization9). Distinct difference inspecific surface area was detected between materials carbonized at 400° and 600°C,indicating incomplete carbonization at the former temperature. Carbonization at 600°,1,000° and 1,400°C resulted in high specific surface area, suggesting that the large amount ofheat energy supplied during carbonization promoted an increase in specific surface area.On the other hand, the specific surface areas of the wood materials carbonized at 1,600° and2,400°C were markedly reduced. The changes in specific surface area were stronglycorrelated with the capacity for removal of mercury from the solutions. From these resultsit was concluded that specific surface area of the wood materials contributed to the capacityto remove mercury from solution.Thermal conversion of wood changes the performance properties of the product.Within a given increase in carbonization temperature, both chemical and physical- 51-WOOD RESEARCH No. 85 (1998)Fig. 3. Scanning electron micrographs of the surfaces of raw wood powder (A & B),and wood powder carbonized at 1,OOO°C (C & D) and at 2,400°C (E & F).conversions occur. From 100° to about 3;000°C, several reactions take place affecting theperformance of this material!). Wood begins to lose water of constitution at about IOSoCand weight loss is slow up to 200°C. From 200°C to 280°C, carbon dioxide, water vaporand acetic acid are released resulting in endothermic reaction. From 280° to SOO°C, rapidpyrolysis occurs and if oxygen is present the products iIlaybe oxidized in highly exothermic- S2-PULIDO-NoVICIO et at.: Removal of Mercury from Aqueous Solutions of Mercuric ChlorideFig. 4. Scanning electron micrographs of cross-sections (A, B, and C) and radialsections (D) of Japanese cedar wood carbonized at I,OOO°C.reactions. Combustible gases are liberated and charcoal IS being formed.Carbonization is said to be completed with the temperature range of 4000 to 6009C..:.12,~3).Emission of these combustible gases is considered to promote the formation of micropores inthe wood cells walls. As carbonization temperature was increased, the remaining volatile- 53-WOOD RESEARCH No. 85 (1998)substances, mainly tar, evaporated and considerable number ofpores were cleared resultingin the increase of specific surface area.On analysis of the chemical structure of wood charcoal by X-ray diffraction, peaksoriginating from cellulose crystalline structure disappeared when the wood was carbonizedat 300°C, and no· clear,gi;ffr(iction peaks were detected at temperatures below 1,400°Csuggesting no grapllhi~~.~i:~ri':in the charcoal14) • In this previous report, the X-raydiffraction patte~~~n~n~~dgradually with increases in te!TIperature above 1,400°C, possiblydue to ultrast.~u~~u:~~lbhanges in the charcoal. Graphitization of wood is assumed to beginat a carbonizi:(lg t~mperature of about I,800°C 1) and carbon units are suggested to bere~rranged';les.J1lting in the decrease of specific surface area. The micro and ultra pores inthe wood ~enwans which contributed in the removal of mercury were assumed to be formedby carbo11.:ization and reform~d and/or rearranged by heating.3.3 Microstructural observations by SEMF'ig. 3 shows an over view ofcarbonized wood powder and enlarged view of their surfacecharacteristics by SEM. After carbonization, the size of the wood powder became smallerand the surfaces of the samples became smooth possibly because the wood suffered fromthermal degradation and decomposition. The original fibrillar arrangement of the woodstructure was destroyed resulting in fragile walls within a smooth amorphous wall. Aftercarbonization at 2,400°C, needle- or powder-like fragments were recognized adhering tothe surfaces of wood powder. With sufficient heating, wood charcoal was considered to betransformed into graphite, so that the fragments were assumed to be responsible for thegraphitic properties of the carbonized wood." Cross- and radial sectional views ofJapanese cedar wood carbonized at 1,OOO°C areshown in Fig. 4. No significant differences were observed in the cellular arrangement ofearlywood and latewood or in cell wall features such as pit structures between r,aw wood andcarbonized wood. However, glass-like fractured surfaces of cross-sections were clearlydbserved for the tracheid cell walls possibly due to decomposition of the cellulose fibrillar-structure.References1) S. ISHIHARA: Polymeric Materials Encyclopedia, 2C, 956-961 (1996).2) B. SINGH, S. MADHUSUDHANAN, V. DUBEY, R. NATH and N.B.S.N. RAo: Carbon, 34, No.3, 327-330(1996).3) A. SERON, H. BENADDI, F. BEGUIN, E. FRACKOWIAK, J.L. BRETELLE, M.C. THIRY, T.J. BANDOSZ, J.JAGIELLO and J.A. SCHWARZ: Carbon, 34, No.4, 481-487 (1996).4) K. SEKI, N. SAITO and M. AOYAMA: Wood Sci. and Technol, 31, 441-447 (1997).5) K. TENNAKONE, C.T.K. THAMINIMULLE, S. SENADEERA and A.R. KUMARASINGHE: j. Photochem. Photobiol.A. Chern., 70, 193-195 (1993).6) M.R. PRAIRE, L.R. EVANs, B.M~ STANGE and S.L. MARTINEZ: Environ. Sci. Technol., 27, 1776-1782- 54-PULIDO-NoVICIO et al.: Removal of Mercury from Aqueous Solutions of Mercuric Chloride(1993).7) G.]. GRANT: "Encyclopedia of Inorganic Chemistry" ed. R.B. King. John Wiley & Sons, Ltd., England,2136-2164 (1994).8) S. LINDBERG, P.M. STOKES, E. GOLDBERG and C. WREN: "Lead, Mercury, Cadmium and Arsenic in theEnvironment" ed. T.C. Hutchinson and K.M. Meema. John Wiley & Sons Ltd., Great Britain, 17-33(1987) .9) L.L. PULIDO, T. HATA, Y. IMAMURA, S. ISHIHARA and T. KAJIMOTO: J. Wood Sci., 44, No.3, 237-243(1998) .10) L.P. NOVICIO, T. HATA, T. KAJIMOTO, Y. IMAMURA and S. ISHIHARA: Resources Processing Journal(accepted).11) L.L. PULIDO, B.B. BISANA, T. HATA, Y. IMAMURA, S. ISHIHARA and T. KAJIMOTO: Wood Research, No. 84,54-61 (1997).12) J. REED WELKER: J. Fire & Flammability, 1, 12-29 (1970).13) E.]. SOLTES and T.]. ELDER: "Organic Chemicals from Biomass" ed. I.S. Goldstein. CRC Press, Inc.,Boca Raton, Florida, 63-99 (1981).14) K. NISHIMIYA, T. HATA, Y. IMAMURA and S. ISHIHARA: J. Wood Sci., 44, 1, 56-61 (1998).- 55-

<Original>Removal of Mercury from Aqueous Solutions of Mercuric Chloride Using Wood Powder Carbonized at High Temperature

http://repository.kulib.kyoto-u.ac.jp/dspace/bitstream/2433/53184/1/KJ00000018023.pdf

<Original>Removal of Mercury from Aqueous Solutions of Mercuric Chloride Using Wood Powder Carbonized at High Temperature

Abstract

Similar works

Full text

Available Versions

Kyoto University Research Information Repository