Normalized Intensity Photon Energy ( eV ) 8960 8980 9000 9020 9040 9060 Cu Fly Ash 4 Fly Ash 3 Fly Ash 2 Fly Ash 1 CuSO 4 CuS CuCO 3 CuCl 2 CuO CuCl Cu 2 O In Japan, about 50 million tons of municipal solid waste ( MSW ) are generated every year and more than 75% of MSW is incinerated. MSW incineration is an excellent technology from the viewpoint of the w e i g h t a n d v o l u m e r e d u c t i o n o f M S W a n d p u b l i c s a n i t a t i o n . H o w e v e r , a p p r o x i m a t e l y 1 0 0 k g o f bottom ash and 30 - 50 kg of fly ash are generated Direct Speciation of Copper, Lead, Antimony, Zinc and Chromium in Municipal Solid Waste Incinerator Fly Ash by X-ray Absorption Fine Structure Spectroscopy Fig. 1. Cu K-edge XANES spectra in fly ash and reference materials. c o n t a i n l a r g e q u a n t i t i e s o f c a l c i u m c o m p o u n d s , b e c a u s e c a l c i u m h y d r o x i d e i s i n j e c t e d b e f o r e t h e b a g f i l t e r f o r a c i d g a s r e m o v a l . T h e X A F S m e a s u r e m e n t s w e r e c a r r i e d o u t a t b e a m l i n e B L 0 1 B 1 . T h e s p e c t r a w e r e c o l l e c t e d i n f l u o r e s c e n c e m o d e a t r o o m t e m p e r a t u r e w i t h a n S i ( 1 1 1 ) o r Si(311) monochromator. The detailed procedure of data reduction has been described elsewhere [2]. Copp er is the most acti ve in the form atio n of d i o x i n a m o n g h e a v y m e t a l c a t a l y s t s . F i g u r e 1 shows Cu K -edge XANES spectra of four kinds of fly ash and reference materials. According to the position of Cu K -edges, Cu (I) the compounds were considered to be contained in MSWI Fly Ash 1 - 3. In the Fly Ash 4 from an ash melting plant, the pre- w h e n 1 t o n o f M S W i s i n c i n e r a t e d . F l y a s h contains many toxic substances, various heavy metals and dioxins. It is usually detoxified and di sp os ed in la nd fi ll s. It is ne ce ss ar y to ve ri fy w h e t h e r t h e c h e m i c a l s t a t e o f h e a v y m e t a l changes into an insoluble state. Fu rt he rm or e, th e fo rm at io n of ch lo ri na te d aromatic compounds from an MSW incinerator ( MSWI ) is known to occur on the surface of fly ash [1]. Some heavy metals act as catalysts. Catalytic activities differ according to the kinds of heavy metal and its species. To evaluate the f o r m a t i o n o f c h l o r i n a t e d a r o m a t i c c o m p o u n d s o n f l y a s h , i t i s n e c e s s a r y t o e x a m i n e t h e species of heavy metal in fly ash. Therefore, in this research, direct speciation of copper, lead, a n t i m o n y a n d z i n c i n f l y a s h t a k e n f r o m t h e M S W I w a s c o n d u c t e d u s i n g X - r a y a b s o r p t i o n fine structure spectroscopy ( XAFS ). The speciation of fly ash and the content of tar get ele men ts are pre sen ted in Tab le I . Fly As h 1 an d 3 we re sa mp le d fr om th e el ec tr os ta ti c precipitators in different continuous stoker-type MS WI s re sp ec ti ve ly . Fl y As h 2 wa s sa mp le d fro m the bag fil ter in a con tin uou s sto ker -ty pe MS WI . Fl y As h 4 wa s sa mp le d fr om th e ba g filter in an ash melting plant. Fly Ash 2 and 4 65 edge peak from the 1 s - 3 d transition appeared at 8 9 7 6 e V a n d t h e c h e m i c a l s t a t e o f c o p p e r w a s e s t i m a t e d t o b e o n l y C u ( I I ) c o m p o u n d s . T h e c o p p e r i n f l y a s h w a s m a i n l y e s t i m a t e d t o b e a mixture of CuCl 2 , CuO and Cu (I) compounds by the X A N E S s p e c t r a . F i g u r e 2 s h o w s k 3 - w e i g h t e d E X A F S s p e c t r a f o r f o u r f l y a s h a n d r e f e r e n c e materials. According to the EXAFS spectra, the fly ash samples were classified into two patterns. As t h e w a v e n u m b e r i n c r e a s e d , t h e E X A F S s p e c t r a became ambiguous in Fly Ash 2 and 3 but clear in F l y A s h 1 a n d 4 . T h e E X A F S s p e c t r a i n d i c a t e d t h a t a C u - C l b o n d e x i s t e d i n F l y A s h 2 a n d 3 i n comparison with those of reference materials. On t h e o t h e r h a n d , t h e d i o x i n c o n c e n t r a t i o n s i n F l y A s h 1 - 4 a r e 1 . 5 , 6 . 7 , 6 . 2 a n d 3 . 5 n g - T E Q / g , r e s p e c t i v e l y . D i o x i n s h a v e 2 1 0 i s o m e r s . O f t h e v a r i o u s i s o m e r s o f d i o x i n s , 1 7 i s o m e r s c a r r y i n g c h l o r i n e a t o m s a t t h e 2 - , 3 - , 7 - , 8 - p o s i t i o n s a r e p a r t i c u l a r l y t o x i c . T h e r e f o r e , t o x i c i t y e q u i v a l e n c y conversion is conducted to obtain a total measure of the toxicity of the mixtures of many isomers. The f a c t o r c a l l e d t o x i c e q u i v a l e n t f a c t o r i n d i c a t e s t h e r e l a t i v e t o x i c i t y r e f e r r i n g t o 2 - , 3 - , 7 - , 8 - t e t r a c h l o r i n a t e d d i b e n z o – p - d i o x i n a s a s t a n d a r d t o y i e l d t o x i c e q u i v a l e n t ( T E Q ) v a l u e [ 3 ] . T h e difference of the EXAFS spectra was considered to h a v e a r e l a t i o n s h i p w i t h t h e d i o x i n c o n c e n t r a t i o n . Namely the Cu compounds in Fly Ash 1 and 4 were d e a c t i v a t e d t o g i v e t h e m a l o w e r a c t i v i t y f o r t h e formation of dioxin than those in Fly Ash 2 and 3. A s f o r o t h e r h e a v y m e t a l s , l e a d w a s m a i n l y estimated to be PbCl 2 in MSWI Fly Ash 1 - 3 and PbO in ash melting plant Fly Ash 4 by Pb L III -edge X A N E S s p e c t r a . T h e s a m e r e s u l t s w e r e a l s o suggested from the EXAFS spectra. According to Zn K -edge XANES spectra, the peak shape of Fly A s h 2 w a s v e r y s i m i l a r t o t h a t o f F l y A s h 3 . Whereas, that of Fly Ash 4 was different from the o t h e r s a n d t h e p e a k p o s i t i o n s h i f t e d t o h i g h e r ph ot on en er gy . Zi nc wa s ma in ly es ti ma te d to be Z n C l 2 i n M S W I F l y A s h 1 - 3 a n d t h e m i x t u r e o f ZnCO 3 , ZnO and ZnCl 2 in ash melting plant Fly Ash 4 . T h e r e w a s n o d i f f e r e n c e i n t h e S b K - e d g e X A N E S s p e c t r a a m o n g t h e m e a s u r e d f l y a s h . Antimony in the fly ash was considered to be Sb (V) Sample Fly Ash 1 Fly Ash 2 Fly Ash 3 Fly Ash 4 Operation Continuous Continuous Continuous Continuous Furnace type Stoker Stoker Stoker Coke bed type ash melting furnace Dust collector ESP BF ESP BF Ac id g as r em ov al C a ( O H ) 2 i n j e c t i o n Wet scrubber C a ( O H ) 2 i n j e c t i o n Cu ( mg / kg ) 1900 1700 3000 1500 Pb ( mg / kg ) 8200 11000 13000 15000 Zn ( mg / kg ) 34000 25000 29000 38000 Sb ( mg / kg ) 1800 1200 1400 940 Dioxins ( ng-TEQ /g) 1.5 6.7 6.2 3.5 ESP : electrostatic precipitator , BF : bag filter, TEQ : toxic equivalent Table I . The specification of fly ash and concentrations of target elements. 66 k 3 χ χ k (Å -1 ) 4 6 8 10 12 Cu Fly Ash 4 Fly Ash 3 Fly Ash 2 Fly Ash 1 CuSO 4 CuS CuCO 3 CuCl 2 CuO CuCl Cu 2 O c o m p o u n d s . T h e E X A F S s p e c t r a i n d i c a t e d t h a t a n t i m o n y c o m b i n e d not only with oxygen but also with chlorine. F r o m t h i s r e s e a r c h , w e w e r e able to obtain the information about t h e s p e c i e s o f h e a v y m e t a l s a n d s u g g e s t t h e r e l a t i o n s h i p b e t w e e n dioxin concentrations and chemical s t a t e s o f c o p p e r c o m p o u n d s i n actual Fly Ash [4]. References [1] L.Stieglitz et al. , ISWA 88 Proc. of 5 th Int. Solid Wastes Conf. 1 (1988) 331. [ 2 ] T . T a n a k a e t a l . , J . C h e m . S o c . F a r a d . Trans. 84 (1988) 2987. [ 3 ] M . V a n d e n B e r g e t a l . , E n v i r o n m e n t a l Health Perspectives 106 (1998) 775. [4] Masaki Takaoka, Nobuo Takeda, Tsunehiro Tanaka, Takashi Yamamoto, Proc. of the 12 th A n n u a l C o n f e r e n c e o f T h e J a p a n S o c i e t y o f Waste Management Experts (2001) 875. F i g . 2 . E X A F S s p e c t r a o f C u i n f l y a s h a n d reference materials. Masaki Takaoka, Takashi Yamamoto and Tsunehiro Tanaka Kyoto University E-mail: takaoka @ epsehost.env.kyoto-u.ac.jp 67
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