Dechlorination of Organic Compounds Contained in Hazardous Wastes

Chapter 14

Downloaded by UNIV OF CALIFORNIA SANTA BARBARA on September 6, 2015 | http://pubs.acs.org Publication Date: March 8, 1990 | doi: 10.1021/bk-1990-0422.ch014

Dechlorination of Organic Compounds Contained in Hazardous Wastes Potassium Hydroxide with Polyethylene Glycol Reagent 1

1

1

1

1

T. O. Tiernan , D. J. Wagel, G. F. VanNess, J. H. Garrett , J. G. Solch, and C. Rogers 1Department of Chemistry, Wright State University, Dayton, OH 45435 R i s k Reduction Engineering Laboratory, U.S. Environmental Protection Agency, Cincinnati, OH 45268 2

2

Laboratory and field tests have demonstrated that a chemical reagent prepared by reacting potassium hydroxide with polyethylene glycol (KPEG) effectively dechlorinates polychlorinated dibenzo-p-dioxins (PCDD) and polychlorinated dibenzofurans (PCDF) which are contained in liquid hazardous wastes or which are sorbed on spent activated carbon. The present paper is concerned primarily with the effects of treatment duration, reaction temperature, the presence of water and volatile materials, and the quantity of the KPEG reagent on the efficiency of the KPEG dechlorination reaction with PCDD/PCDF in such waste materials. The results of these studies indicate that the concentrations of PCDD/PCDF in waste liquids can be reduced to levels of less than one part-per-billion by direct treatment with KPEG. In the case of the contaminated carbon matrix, however, direct KPEG treatment is somewhat less effective, and reduction of PCDD/PCDF to such concentrations appears to be best achieved by first extracting the carbon matrix with an appropriate solvent, and then treating the extract with KPEG. Chlorinated organic chemicals constitute a significant portion of the hazardous materials which are accumulating in the environment as the result of manufacturing processes and improper waste disposal practices. Among such chlorinated compounds, the polychlorinated dibenzo-p-dioxins (PCDD), polychlorinated dibenzofurans (PCDF), and polychlorinated biphenyls (PCB) are important because of their toxicity, and the degree of public concern over their presence and transport in water, air and soils. Since the toxicity of PCDD, PCDF, PCB and other chlorocarbon congeners can generally be significantly reduced by removing chlorine atoms from these 0097-6156/90/0422-0236$06.00/0 © 1990 American Chemical Society In Emerging Technologies in Hazardous Waste Management; Tedder, D., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1990.


14. TIERNANETAL.

Dechlorination ofOrganic Compounds

237

m o l e c u l e s , waste treatment processes which r e s u l t i n d e c h l o r i n a t i o n o f t h e s e compounds a r e o f g r e a t i n t e r e s t . One s u c h p r o c e s s entails treatment of wastes w i t h appropriate chemical reagents. A chemical d e c h l o r i n a t i o n p r o c e s s has s e v e r a l a d v a n t a g e s . In p r i n c i p l e , simple and r e l a t i v e l y i n e x p e n s i v e r e a g e n t s c a n be u s e d , and t h e w a s t e and t h e r e a g e n t c a n be c o m b i n e d a t t h e t r e a t m e n t s i t e . Consequently, t h e p r o c e s s c a n be s c a l e d t o a s i z e w h i c h i s a p p r o p r i a t e t o e i t h e r small or large q u a n t i t i e s of waste. Using recently developed r e a g e n t s , d e h a l o g e n a t i o n r e a c t i o n s c a n be a c c o m p l i s h e d a t m o d e r a t e temperatures. T h i s s i m p l i f i e s the design of r e a c t o r s r e q u i r e d for such t r e a t m e n t and r e d u c e s the need f o r c o n t r o l l i n g v o l a t i l e emissions. A l s o , such processes are o b v i o u s l y economical i n terms o f t h e amount o f e n e r g y r e q u i r e d f o r t h e p r o c e s s . A l l of these factors suggest lower costs for chemical d e c h l o r i n a t i o n processes than are r e q u i r e d for i n c i n e r a t i o n or o t h e r processes which necessitate large fixed plant investments, and a r e c o n f i n e d t o a given s i t e . D e h a l o g e n a t i o n r e a c t i o n s a r e w e l l known i n o r g a n i c chemistry, but d e c h l o r i n a t i o n i s seldom used for preparative purposes. Traditionally, dechlorination reactions require strong bases or r e d u c i n g a g e n t s , o f t e n r e q u i r e h i g h t e m p e r a t u r e s , and are sometimes v i o l e n t and d i f f i c u l t to c o n t r o l . Moreover, such processes f r e q u e n t l y r e s u l t i n rearrangement o f the c h l o r i n e s u b s t i t u e n t s on the chlorinated species being t r e a t e d , rather than complete dechlorination. However, a s i m p l e , low temperature dehalogenation p r o c e s s has r e c e n t l y been d e s c r i b e d ( 1 , 2 ) . The d e c h l o r i n a t i n g reagent i n t h i s c a s e i s p r e p a r e d by c o m b i n i n g a p o l y e t h y l e n e g l y c o l (PEG) w i t h s o l i d p o t a s s i u m h y d r o x i d e ( a p p r o x i m a t e l y two moles of KOH f o r e a c h m o l e o f PEG) a n d h e a t i n g t h e m i x t u r e a t 9 0 - 1 0 0 ° C f o r a p p r o x i m a t e l y one h o u r . The r e s u l t i n g a c t i v e s p e c i e s i s apparently a p o t a s s i u m a l k o x i d e ( K P E G ) , w h i c h may f o r m a n e t h e r following d i s p l a c e m e n t o f c h l o r i d e from the c h l o r i n a t e d m o l e c u l e . The e f f e c t i v e n e s s o f t h e KPEG r e a g e n t has already been demonstrated in several studies. The i n i t i a l investigations e s t a b l i s h e d t h a t t h i s r e a g e n t c a n d e c h l o r i n a t e some aliphatic c h l o r i n a t e d compounds, as w e l l as c e r t a i n a r o m a t i c chlorinated c o m p o u n d s , s u c h as PCB ( 3 ) . Further studies conducted i n our l a b o r a t o r y d e m o n s t r a t e d t h a t KPEG c a n e f f e c t i v e l y dechlorinate 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) a n d o t h e r PCDD a n d PCDF a t m o d e r a t e t e m p e r a t u r e s , when t h e s e compounds a r e c o n t a i n e d e i t h e r in pure s o l u t i o n s or i n complex chemical waste m i x t u r e s . These laboratory scale experiments were s u b s e q u e n t l y s c a l e d up and u t i l i z e d b y t h e U . S . E n v i r o n m e n t a l P r o t e c t i o n A g e n c y (EPA) i n f i e l d t e s t s t o t r e a t s e v e r a l t h o u s a n d g a l l o n s o f l i q u i d w a s t e s (as w e l l as s e v e r a l tons of s o i l s c o n t a i n i n g t h e s e wastes) w h i c h were contaminated with relatively high concentrations of various c h l o r o c a r b o n s , i n c l u d i n g PCDD, P C D F , PCB o t h e r c h l o r i n a t e d o r g a n i c s (4). As t e s t i n g o f t h e KPEG r e a g e n t p r o c e e d s , several different a p p l i c a t i o n s are being e x p l o r e d . One p r o b l e m o f i n c r e a s i n g c o n c e r n i s the g e n e r a t i o n o f hazardous waste by s m a l l i n d u s t r i e s , research f a c i l i t i e s , and l a b o r a t o r i e s a c c o m p l i s h i n g a n a l y s e s o f l a r g e numbers of samples c o n t a i n i n g hazardous compounds. The c o s t s f o r d i s p o s a l by t h e s e f a c i l i t i e s o f w a s t e s c o n t a m i n a t e d w i t h c h l o r i n a t e d o r g a n i c s

In Emerging Technologies in Hazardous Waste Management; Tedder, D., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1990.


238

EMERGING TECHNOLOGIES IN HAZARDOUS WASTE MANAGEMENT

i s q u i t e h i g h , and d i s p o s a l o f w a s t e s c o n t a m i n a t e d w i t h PCDD/PCDF i s a l w a y s d i f f i c u l t , and at t i m e s i m p o s s i b l e . Because the s c a l e of the KPEG r e a c t i o n c a n e a s i l y b e a d j u s t e d t o a c c o m m o d a t e t h e v o l u m e o f contaminated waste, on-site d e c h l o r i n a t i o n of laboratory wastes c o u l d p r o v e t o b e a n i m p o r t a n t a p p l i c a t i o n o f t h i s KPEG t r e a t m e n t process. The s t u d i e s d e s c r i b e d h e r e i n w e r e d e s i g n e d t o y i e l d a b e t t e r u n d e r s t a n d i n g o f t h e o p e r a t i n g c o n d i t i o n s w h i c h a r e most e f f e c t i v e f o r d e c h l o r i n a t i o n o f P C D D / P C D F u s i n g t h e KPEG r e a g e n t . As noted above, e f f e c t i v e procedures have p r e v i o u s l y been e s t a b l i s h e d for the t r e a t m e n t of s e v e r a l complex c h e m i c a l wastes and s o i l s c o n t a m i n a t e d w i t h t h e s e w a s t e s (4). The p r e s e n t p a p e r i s c o n c e r n e d mainly with experiments intended to define optimum reaction c o n d i t i o n s f o r d e s t r u c t i o n o f PCDD/PCDF and o t h e r chlorocarbons which are s o r b e d on spent a c t i v a t e d c a r b o n . While the l a t t e r i s a difficult task, a viable chemical process for regeneration of a c t i v a t e d c a r b o n w h i c h has been u s e d t o remove t o x i c c h l o r o c a r b o n s from wastewater s h o u l d m a r k e d l y r e d u c e t h e c o s t o f wastewater treatment. Experimental Laboratory Reaction Vessel. The l a b o r a t o r y e x p e r i m e n t s described h e r e i n were conducted i n c o n t r o l l e d - a c c e s s l a b o r a t o r i e s by p e r s o n n e l wearing s a f e t y garments and o r g a n i c v a p o r r e m o v i n g breathing apparatus. The r e a c t i o n s were a c c o m p l i s h e d e i t h e r i n a g l o v e b o x w i t h c a r b o n and p a r t i c u l a t e f i l t e r s on the o u t l e t , o r i n s i d e a h i g h flow rate chemical hood. The a l l - g l a s s r e a c t i o n v e s s e l u s e d i n t h e s e s t u d i e s was a 5 0 0 m L , t h i c k - w a l l r e a c t i o n k e t t l e w h i c h fits into a heating mantle. The g l a s s c o v e r o f t h e k e t t l e h a d four ground g l a s s openings which p r o v i d e access f o r a v a r i a b l e r a t e s t i r r e r , a thermometer, a w a t e r - c o o l e d condenser and a sample i n t r o d u c t i o n p o r t or a purge gas i n l e t . During the laboratory t e s t s , t h e s t i r r e r was o p e r a t e d a t a p p r o x i m a t e l y 1 0 0 r p m , t h e m a n t l e t e m p e r a t u r e was a d j u s t e d t o meet t h e e x p e r i m e n t a l r e q u i r e m e n t s , a n d t h e c o n d e n s e r was o p e r a t e d e i t h e r i n a v e r t i c a l p o s i t i o n s o a s to c o n t i n u o u s l y r e t u r n m a t e r i a l s v o l a t i l i z e d from the r e a c t i o n m i x t u r e t o t h e r e a c t i o n f l a s k , o r t h e c o n d e n s e r was p o s i t i o n e d a t a 30 d e g r e e a n g l e downward w i t h r e s p e c t t o t h e f l a s k , i n o r d e r t o a l l o w v o l a t i l e m a t e r i a l s t o c o n d e n s e a n d b e c o l l e c t e d i n a s e p a r a t e 2 5 0 mL collection flask. The t e m p e r a t u r e o f t h e r e a c t i o n m i x t u r e was m o n i t o r e d w i t h a t h e r m o m e t e r , t h e t i p o f w h i c h was i m m e r s e d i n t h e r e a c t i o n m i x t u r e , a n d t h e h e a t i n g m a n t l e t e m p e r a t u r e was m e a s u r e d w i t h a thermocouple p l a c e d between the g l a s s k e t t l e and the h e a t i n g mantle. D u r i n g t h e t r e a t m e n t p r o c e s s , t h e r e a c t i o n v e s s e l was s e a l e d a n d a n a c t i v a t e d c h a r c o a l t r a p was a t t a c h e d t o t h e c o n d e n s e r outlet. Procedures for Analysis of Reaction Products. I n some e x p e r i m e n t s , t i m e - r e s o l v e d s t u d i e s were c o n d u c t e d . At selected i n t e r v a l s during t h e s e t e s t s , and a t the c o n c l u s i o n o f each e x p e r i m e n t , a l i q u o t s o f the r e a c t i o n m i x t u r e were removed and t r a n s f e r r e d to separate bottles. The a l i q u o t s were i m m e d i a t e l y w e i g h e d and a s u f f i c i e n t q u a n t i t y o f 50% s u l f u r i c a c i d w a s a d d e d t o p r o d u c e a n a c i d i c


14. TIERNAN ET AL.

Dechlorination of Organic Compounds

solution, thus quenching the d e c h l o r i n a t i o n r e a c t i o n . These a l i q u o t s of the r e a c t i o n mixture were s p i k e d w i t h C-labelled PCDD/PCDF i s o m e r s t a n d a r d s r e p r e s e n t a t i v e of the t e t r a through o c t a c h l o r i n a t e d congener groups o f t h e s e compounds. Depending on t h e a n a l y s e s t o be p e r f o r m e d , o t h e r s t a n d a r d s s u c h as i s o t o p i c a l l y l a b e l l e d PCB a n d c h l o r o b e n z e n e s were a l s o added t o t h e a l i q u o t s o f the r e a c t i o n m i x t u r e . The q u e n c h e d r e a c t i o n p r o d u c t s , which i n c l u d e d any s o l i d m a t e r i a l , were m i x e d w i t h s u f f i c i e n t s o d i u m s u l f a t e t o p r o d u c e a f r e e l y f l o w i n g powder ( t y p i c a l l y , 8 g o f sodium s u l f a t e was m i x e d w i t h e a c h g r a m o f s a m p l e ) a n d t h e s a m p l e / s o d i u m s u l f a t e m i x t u r e was t h e n s u b j e c t e d t o S o x h l e t e x t r a c t i o n f o r a p e r i o d o f 16 h o u r s u s i n g b e n z e n e / a c e t o n e (1/1) as the e x t r a c t i o n solvent. I t s h o u l d be n o t e d t h a t S o x h l e t e x t r a c t i o n , r a t h e r than less rigorous extraction procedures, i s required to effectively remove PCDD/PCDF from t h e c a r b o n m a t r i x . L i q u i d portions of the quenched r e a c t i o n m i x t u r e a l i q u o t s ( c o n t a i n i n g no s o l i d material) were e x t r a c t e d r e p e t i t i v e l y w i t h s e v e r a l p o r t i o n s o f h e x a n e . The S o x h l e t e x t r a c t s were t h e n c o n c e n t r a t e d and r e d i l u t e d w i t h hexane, and t h e s e e x t r a c t s , as w e l l as t h e e x t r a c t s o f t h e l i q u i d r e a c t i o n p r o d u c t s , were p r e p a r e d u s i n g p r o c e d u r e s w h i c h have been d e s c r i b e d i n d e t a i l elsewhere (5,6). B r i e f l y , these preparation procedures i n i t i a l l y i n v o l v e d s e q u e n t i a l e x t r a c t i o n o f t h e s a m p l e w i t h 3 0 mL q u a n t i t i e s o f 20% p o t a s s i u m h y d r o x i d e , w a t e r , c o n c e n t r a t e d sulfuric acid, and w a t e r . The r e a c t i o n m i x t u r e e x t r a c t s were then chromatographed on a m u l t i - l a y e r s i l i c a column u s i n g hexane as the eluting solvent. Following concentration, the extracts were chromatographed on a three-gram a c t i v a t e d b a s i c a l u m i n a c o l u m n , from w h i c h a f r a c t i o n c o n t a i n i n g P C B was i s o l a t e d b y e l u t i n g w i t h 8% m e t h y l e n e c h l o r i d e i n h e x a n e , a n d a f r a c t i o n c o n t a i n i n g PCDD/PCDF was t h e n c o l l e c t e d b y e l u t i n g t h e c o l u m n w i t h 50% m e t h y l e n e c h l o r i d e i n hexane. The PCDD/PCDF f r a c t i o n was i n t r o d u c e d o n t o a P X - 2 1 c h a r c o a l / c e l i t e 5 4 5 c o l u m n , f r o m w h i c h t h e P C D D / P C D F f r a c t i o n was u l t i m a t e l y recovered by back e l u t i o n w i t h toluene. Another a c t i v a t e d b a s i c a l u m i n a c o l u m n was t h e n u s e d t o p r e p a r e t h e f i n a l P C D D / P C D F f r a c t i o n w h i c h was c o n c e n t r a t e d t o n e a r d r y n e s s . Prior to a n a l y s i s t h e e x t r a c t was r e d i l u t e d w i t h a t r i d e c a n e solution c o n t a i n i n g i s o t o p i c a l l y l a b e l e d 1 , 2 , 3 , 4 - T C D D and 1 , 2 , 7 , 8 t e t r a c h l o r o d i b e n z o f u r a n (TCDF) ( C - o r C l - l a b e l l e d compounds). 1


239

1

3

3

3 7

PCDD/PCDF i n the samples were q u a n t i f i e d u s i n g a h i g h r e s o l u t i o n g a s c h r o m a t o g r a p h c o u p l e d t o a mass s p e c t r o m e t e r (GC-MS). The c o m p u t e r c o n t r o l l e d mass s p e c t r o m e t e r was o p e r a t e d i n the s e l e c t e d i o n mode, a n d two o r more m a s s e s w e r e m o n i t o r e d f o r e a c h C - l a b e l l e d PCDD/PCDF i n t e r n a l s t a n d a r d and f o r each native PCDD/PCDF compound t o be q u a n t i f i e d . The PCDD/PCDF i s o m e r s were s e p a r a t e d o n a 6 0 m D B - 5 f u s e d s i l i c a c a p i l l a r y GC c o l u m n w h i c h y i e l d e d d a t a on t h e 2 , 3 , 7 , 8 - T C D D isomer as w e l l as on t h e total t e t r a - t h r o u g h o c t a c h l o r i n a t e d congener groups o f t h e s e compounds. A d d i t i o n a l c a p i l l a r y GC c o l u m n s w e r e u s e d t o o b t a i n i s o m e r s p e c i f i c d a t a on the 2 , 3 , 7 , 8 - s u b s t i t u t e d PCDD/PCDF i s o m e r s , i n c a s e s where t h i s was d e s i r e d . These methods y i e l d e d l o w p a r t - p e r - t r i l l i o n d e t e c t i o n l i m i t s f o r PCDD a n d P C D F . The s a m p l e s d e r i v e d from t h e l a b o r a t o r y and f i e l d treatment t e s t s were g e n e r a l l y a n a l y z e d f o r t e t r a - , p e n t a - , h e x a - , h e p t a - and octa-CDD/CDF, and the success o f t h e d e c h l o r i n a t i o n p r o c e s s was 1 3



240


gauged b y t h e e x t e n t t o w h i c h t h e c o n c e n t r a t i o n s o f t h e s e compounds were r e d u c e d i n the t r e a t e d samples as compared t o the untreated samples. Further s t u d i e s are i n progress to determine the u l t i m a t e d e s t r u c t i o n p r o d u c t s o f t h e KPEG r e a c t i o n . I t s h o u l d be m e n t i o n e d t h a t w h i l e t h e u l t i m a t e reaction p r o d u c t s ( o t h e r t h a n r e s i d u a l PCDD/PCDF) from t h e s t u d i e s d e s c r i b e d h e r e i n a r e s t i l l not known, the g r o s s p r o d u c t m i x t u r e s r e s u l t i n g f r o m KPEG t r e a t m e n t o f p u r e 2 , 3 , 7 , 8 - T C D D , a s w e l l a s t r e a t m e n t o f a h a z a r d o u s w a s t e c o n t a i n i n g 120 p a r t s - p e r - b i l l i o n (ppb) o f 2 , 3 , 7 , 8 TCDD h a v e b e e n e v a l u a t e d f o r t o x i c o l o g i c a l e f f e c t s . The c o n c l u s i o n s from t h e s e t e s t s i n d i c a t e d t h a t the p r o d u c t s of the r e a c t i o n were n o t m u t a g e n i c a n d w e r e n o t t o x i c t o a q u a t i c o r g a n i s m s o r mammals (4). S t u d i e s i n v o l v i n g t h e K P E G - t r e a t e d 2 , 3 , 7 , 8 - T C D D showed t h a t the r e a c t i o n p r o d u c t s were l e s s t o x i c t o the g u i n e a p i g by a f a c t o r o f 350 t h a n t h e u n t r e a t e d 2 , 3 , 7 , 8 - T C D D . Waste Samples Used i n Treatment T e s t s . The c h e m i c a l w a s t e s a m p l e s s u b j e c t e d t o KPEG t r e a t m e n t i n t h e c o u r s e o f t h e s t u d i e s d e s c r i b e d h e r e i n were o b t a i n e d from a c t u a l h a z a r d o u s w a s t e s i t e s . The pentachlorophenol ( P C P ) - p e t r o l e u m o i l w a s t e s a m p l e was c o l l e c t e d from a 9000 g a l l o n t a n k at a f o r m e r w o o d - p r e s e r v i n g p l a n t site located i n Montana. T h i s w a s t e c o n t a i n e d a b o u t 3% P C P , a s w e l l a s h i g h c o n c e n t r a t i o n s o f t h e e n t i r e c h l o r i n a t e d s p e c t r u m o f PCDD/PCDF (up t o a b o u t 80 p p m ) , w h i c h made o n - s i t e treatment the only p r a c t i c a l remedial procedure. The c o n t a m i n a t e d a c t i v a t e d c a r b o n t e s t e d h e r e was o b t a i n e d f r o m a f a c i l i t y w h i c h t r e a t s aqueous l e a c h a t e from a hazardous waste l a n d f i l l . This carbon contained fine particulate material and was saturated with water ( a p p r o x i m a t e l y 35% b y w e i g h t ) . R e s u l t s and

Discussion

KPEG T r e a t m e n t o f P C P W o o d - P r e s e r v i n g W a s t e s i n L a b o r a t o r y a n d F i e l d Tests. As noted above, a PCP-petroleum o i l w o o d - p r e s e r v i n g waste was o n e o f t h e h a z a r d o u s w a s t e m a t e r i a l s t e s t e d i n t h e KPEG s t u d i e s . The r e s u l t s o f t h e a n a l y s i s o f a s a m p l e o f t h e u n t r e a t e d w a s t e f r o m t h i s s i t e are presented i n Table I . Laboratory KPEG-treatment t e s t s on t h i s w a s t e were c o n d u c t e d a t t e m p e r a t u r e s o f 70°C and 1 0 0 ° C , w i t h a l i q u o t s o f t h e r e a c t i o n m i x t u r e b e i n g w i t h d r a w n f o r a n a l y s e s a t 15 minute i n t e r v a l s . I n t h e s e l a b o r a t o r y e x p e r i m e n t s , 20 g o f w a s t e w e r e c o m b i n e d w i t h 1 g o f p o t a s s i u m h y d r o x i d e a n d 21 g o f KPEG reagent. T h e KPEG r e a g e n t u s e d h e r e was p r e p a r e d b y m i x i n g t w o moles o f s o l i d p o t a s s i u m h y d r o x i d e w i t h each mole o f PEG-400 and h e a t i n g t h e m i x t u r e a t 9 0 - 1 0 0 ° C f o r one h o u r . P o r t i o n s of the data from t h e s e t e s t s a r e shown i n T a b l e I and i n d i c a t e t h a t , a t b o t h o f the r e a c t i o n temperatures noted, n e a r l y complete d e s t r u c t i o n of the P C D D / P C D F i s o m e r s was a c c o m p l i s h e d w i t h i n 30 m i n u t e s . Obviously, t h e r e i s some t r a d e - o f f h e r e b e t w e e n r e a c t i o n t i m e a n d t e m p e r a t u r e . T r e a t m e n t o f 9 0 0 0 g a l l o n s o f t h i s same w a s t e was s u b s e q u e n t l y a c c o m p l i s h e d b y U . S . EPA a t t h e f i e l d s i t e , u s i n g a t r u c k - m o u n t e d stainless s t e e l batch reactor. T h i s 2 7 0 0 g a l l o n r e a c t o r was h e a t e d by a b o i l e r w h i c h c i r c u l a t e d steam t h r o u g h a h e a t e x c h a n g e r . The f i e l d t r e a t m e n t e n t a i l e d m i x i n g 6 0 0 g a l l o n s o f KPEG w i t h 1 4 0 0 - 2 0 0 0 g a l l o n s of waste i n the truck-mounted r e a c t o r . The t e m p e r a t u r e o f



Average d e t e c t i o n l i m i t

for

5 batches

(0.64) (0.69) (0.98) (0.81) (0.66)

ND ND ND ND ND ND ND ND ND ND

110 ND ( 0 . 6 0 ) 2.7 ND ( 0 . 9 1 ) ND ( 3 . 2 )

16 ND ( 0 . 4 7 ) 3.0 2.6 ND ( 3 . 6 )

330 ND ( 0 . 4 3 ) 4.9 5.8 ND ( 3 . 6 )

150 500 3900 5400 6200

TCDF PeCDF HxCDF HpCDF OCDF

(0.35) (0.29) (0.76) (1.1) (1.6)

(0.64) (0.64) (0.57) (0.33) (0.84)

ND ND ND ND ND ND ( 0 . 2 8 ) ND ( 0 . 4 1 ) ND ( 2 . 4 ) 1.4 2.6

ND ( 1 . 3 ) ND ( 2 . 1 ) ND ( 3 . 4 ) 2.3 4.1

ND ( 0 . 3 7 ) ND ( 0 . 9 2 ) ND ( 1 . 8 ) 2.1 4.0

ND ( 0 . 4 6 ) ND ( 1 . 0 ) ND ( 1 . 8 ) 11 6.5

a

Composite R e s u l t s from F i v e B a t c h Treatments at the F i e l d S i t e

420 820 3000 21000 84000

Untreated Waste

Laboratory Treatment 30 m i n . 1 0 0 ° C

Laboratory Treatment 15 m i n . 1 0 0 ° C

Laboratory Treatment 30 m i n . 7 0 ° C

Laboratory Treatment 15 m i n , 7 0 ° C

tfifiU

Concentration

I. C o n c e n t r a t i o n s o f P C D D / P C D F i n P C P - P e t r o l e u m O i l Wood P r e s e r v i n g W a s t e B e f o r e Treatment and F o l l o w i n g L a b o r a t o r y and F i e l d KPEG T r e a t m e n t T e s t s

TCDD PeCDD HxCDD HpCDD OCDD

Total Congeners

Table



242


t h i s m i x t u r e was m a i n t a i n e d a t 1 5 0 ° C f o r a p e r i o d o f 1 . 5 hours. Following this treatment, p o r t i o n s of the treated waste were a n a l y z e d and no d e t e c t a b l e l e v e l s o f PCDD/PCDF were f o u n d i n t h e treated waste. The r e s u l t s o f t h e s e f i e l d t e s t t r e a t m e n t s a r e a l s o summarized i n T a b l e I . The d a t a p r e s e n t e d f o r t h e l a t t e r a r e b a s e d on t h e a v e r a g e r e s u l t s o f f i v e s e p a r a t e t r e a t e d b a t c h e s o f w a s t e . The f i e l d t r e a t m e n t c o n d i t i o n s u s e d h e r e w e r e somewhat m o r e r i g o r o u s than the l a b o r a t o r y c o n d i t i o n s i n terms of the temperatures used, and t h i s r e s u l t e d i n c o m p l e t e d e c h l o r i n a t i o n o f t h e t e t r a through o c t a c h l o r i n a t e d PCDD/PCDF i n t h e w a s t e . Laboratory Study of the E f f e c t s o f R e a c t i o n T i m e o n KPEG T r e a t m e n t of Contaminated C a r b o n . T h e e f f e c t s o f r e a c t i o n t i m e o n t h e KPEG d e c h l o r i n a t i o n o f PCDD/PCDF w h i c h h a d been t r a p p e d o n a c t i v a t e d carbon i n the c o u r s e o f wastewater c l e a n u p were a l s o i n v e s t i g a t e d . A 1:1 m i x t u r e b y w e i g h t o f c a r b o n a n d KPEG was u s e d i n t h e s e t e s t s , and the temperature o f t h e r e a c t i o n m i x t u r e was i n c r e a s e d until water and o t h e r v o l a t i l e s p r e s e n t i n the c o n t a m i n a t e d c a r b o n samples refluxed. The c o n d e n s e r a t t a c h e d t o t h e r e a c t i o n v e s s e l was p o s i t i o n e d i n the v e r t i c a l p o s i t i o n i n t h i s c a s e , so t h a t the v o l a t i l i z e d m a t e r i a l s were condensed and r e t u r n e d t o the r e a c t i o n kettle continuously. The t e m p e r a t u r e f o r e a c h t e s t i n t h i s s e r i e s was m a i n t a i n e d a t 1 0 0 ° C . A l i q u o t s o f the r e a c t i o n m i x t u r e were removed from the r e a c t i o n v e s s e l at v a r i o u s t i m e i n t e r v a l s and a n a l y z e d f o r PCDD/PCDF. Table I I presents a s e l e c t e d p o r t i o n of the d a t a from t h e s e t e s t s , and shows t h e c o n c e n t r a t i o n s o f PCDD/PCDF present i n the c o n t a m i n a t e d c a r b o n b e f o r e KPEG t r e a t m e n t and following treatment f o r p e r i o d s o f 4 h o u r s a n d 72 hours, respectively. T h e t o t a l P C D D / P C D F c o n c e n t r a t i o n s ( t h e sum o f a l l c o n g e n e r g r o u p s ) d e c r e a s e d b y 14% d u r i n g t h e f o u r h o u r treatment, w h i l e t r e a t m e n t f o r 72 h o u r s r e s u l t e d i n a 60% d e c r e a s e . As c a n be s e e n from T a b l e I I , t h e d e c r e a s e i n t o t a l PCDD/PCDF c o n c e n t r a t i o n s d u r i n g t h e 7 2 - h o u r t r e a t m e n t was a c c o m p a n i e d b y a n i n c r e a s e i n t h e c o n c e n t r a t i o n s of the lower c h l o r i n a t e d (tetraand penta-) c o n g e n e r s , as compared t o the l e v e l s o f t h e s e i n t h e untreated sample. S i n c e t h e o v e r a l l r e p l i c a b i l i t y o f t h e s e e x p e r i m e n t s was f o u n d t o be on t h e o r d e r o f ± 3 0 % , i t c a n be s e e n t h a t these i n c r e a s e s a r e g e n e r a l l y much l a r g e r t h a n t h o s e w h i c h w o u l d r e s u l t from the combined v a r i a b i l i t y i n the sample, the treatment p r o c e d u r e s and the a n a l y s e s . A p p a r e n t l y the higher c h l o r i n a t e d PCDD/PCDF ( h e x a - , h e p t a , - o c t a - ) have been s t r i p p e d o f c h l o r i n e a t o m s b y t h e KPEG r e a g e n t , y i e l d i n g e l e v a t e d c o n c e n t r a t i o n s o f t h e lower c h l o r i n a t e d congeners, which have not yet been further d e c h l o r i n a t e d , u n d e r t h e s e c o n d i t i o n s , when t h e r e a c t i o n i s s t o p p e d a t 72 h o u r s . S i m i l a r r e s u l t s were o b s e r v e d i n our e a r l i e r s t u d i e s o f KPEG t r e a t m e n t o f P C P w a s t e s c o n t a i n i n g P C D D / P C D F . Continuing the r e a c t i o n f o r a longer p e r i o d of time or u s i n g a higher r e a c t i o n temperature s h o u l d d r i v e the dechlorination reaction toward completion. T h e p r e s e n c e o f w a t e r i n t h e c a r b o n - K P E G m i x t u r e may b e a f a c t o r which impedes t h e s e r e a c t i o n s . Clearly, the activated carbon i s a v e r y d i f f e r e n t m a t r i x from the waste o i l s and c o n t a m i n a t e d s o i l s a m p l e s c o n t a i n i n g PCDD/PCDF and P C B , f o r w h i c h e a r l i e r s t u d i e s h a v e a l r e a d y d e m o n s t r a t e d t h a t KPEG t r e a t m e n t can fully d e c h l o r i n a t e the tetrathrough o c t a c h l o r i n a t e d congeners.



14.

TIERNAN ET AL.

Table in

243


II. C o n c e n t r a t i o n and P e r c e n t D e s t r u c t i o n o f PCDD/PCDF C o n t a m i n a t e d C a r b o n B e f o r e a n d A f t e r KPEG T r e a t m e n t D e m o n s t r a t i n g E f f e c t o f R e a c t i o n Time Concentration ( D P b )

Total Congeners

Untreated Contaminated Carbon


1500 100 920 540 ND ( 4 3 0 )

TCDF PeCDF HxCDF HpCDF OCDF Total

% of T o t a l PCDD/PCDF Dechlorinated

Following Treatment at 100°C f o r 72 h o u r s

770 24 640 560 13

1600 ND (60) ND (39) ND (13) ND (12)

170 16 7.9 1600 360

280 62 ND ( 5 . 0 ) ND ( 1 0 0 ) ND (18)

4800

4200

1900

—

13%

470 450 190 350 280 PCDD/PCDF

Following Treatment at 100°C for 4 hours

60%


244



F u r t h e r experiments w i t h the contaminated carbon are i n progress to i n v e s t i g a t e the e f f e c t s o f water and r e a c t i o n t e m p e r a t u r e on the KPEG d e c h l o r i n a t i o n r e a c t i o n . The r e s u l t s d e s c r i b e d above demonstrate the need f o r c a r e f u l l a b o r a t o r y t e s t s t o e v a l u a t e waste matrices p r i o r to f i e l d treatment i n order to d e f i n e operating parameters which w i l l r e s u l t i n f u l l d e c h l o r i n a t i o n of the toxic contaminants. Laboratory Study o f t h e E f f e c t s o f Water and O t h e r V o l a t i l e s on t h e KPEG T r e a t m e n t of Contaminated Carbon. The c o n t a m i n a t e d carbon w h i c h h a d b e e n t r e a t e d w i t h KPEG f o r a p e r i o d o f f o u r h o u r s i n t h e e x p e r i m e n t d i s c u s s e d a b o v e was t r e a t e d a s e c o n d t i m e u n d e r d i f f e r e n t conditions. During t h i s second t e s t , the condenser attached to the r e a c t i o n v e s s e l was p o s i t i o n e d s o t h a t the components which v o l a t i l i z e d a s t h e r e a c t i o n m i x t u r e was h e a t e d w e r e c o n d e n s e d i n t o a separate c o l l e c t i o n vessel. A f t e r 1.5 h o u r s , t h e s e v o l a t i l e s were c o m p l e t e l y removed from the m i x t u r e and the t e m p e r a t u r e o f the m i x t u r e r o s e t o 1 4 6 ° C , w i t h no i n c r e a s e i n t h e t e m p e r a t u r e o f the heating mantle. The m i x t u r e was m a i n t a i n e d a t 146°C for an additional 2 hours. In a separate experiment, the v o l a t i l e components p r e s e n t i n a n o t h e r a l i q u o t o f the o r i g i n a l c o n t a m i n a t e d c a r b o n were removed by d i s t i l l a t i o n p r i o r t o t h e a d d i t i o n o f t h e KPEG r e a g e n t . Following r e m o v a l o f t h e v o l a t i l e s , t h e KPEG was a d d e d a n d t h e reaction m i x t u r e was h e a t e d f o r f o u r h o u r s a t a t e m p e r a t u r e o f 1 3 5 ° C . T a b l e I I I compares t h e o b s e r v e d c o n c e n t r a t i o n s o f PCDD/PCDF i n t h e p r o d u c t s from t h e two e x p e r i m e n t s j u s t d e s c r i b e d t o t h e initial c o n c e n t r a t i o n s o f t h e s e compounds i n t h e c o n t a m i n a t e d c a r b o n and t o the c o r r e s p o n d i n g r e s u l t s o b t a i n e d from the four hour, 100°C d i r e c t t r e a t m e n t e x p e r i m e n t w h i c h was d e s c r i b e d i n t h e p r e v i o u s s e c t i o n . The r e s u l t s s u m m a r i z e d i n T a b l e I I I i n d i c a t e t h a t t h e r e m o v a l o f t h e water and o t h e r v o l a t i l e s from the sample w h i c h had been p r e v i o u s l y t r e a t e d w i t h KPEG f o r f o u r h o u r s , w i t h a c o n c u r r e n t i n c r e a s e i n t h e temperature o f the r e a c t i o n m i x t u r e from 100°C t o 146°C, r e s u l t e d i n d e c h l o r i n a t i o n o f 81% o f t h e t o t a l P C D D / P C D F c o n g e n e r s p r e s e n t i n the carbon. J u s t a s was o b s e r v e d f o r t h e 7 2 - h o u r KPEG t r e a t m e n t e x p e r i m e n t ( w i t h n o r e m o v a l o f v o l a t i l e s ) w h i c h was d i s c u s s e d i n t h e p r e v i o u s s e c t i o n , however, most of the r e s i d u a l PCDD/PCDF contamination consists of the lower chlorinated congeners, i n d i c a t i n g t h a t the r e a c t i o n has not r e a c h e d c o m p l e t i o n . The e x p e r i m e n t i n w h i c h t h e w a t e r was r e m o v e d p r i o r t o a d d i t i o n o f t h e KPEG r e s u l t e d i n t h e d e c h l o r i n a t i o n o f 60% o f t h e t o t a l P C D D / P C D F p r e s e n t on the c a r b o n . While the r e s i d u a l concentrations of lower c h l o r i n a t e d congener groups were not as h i g h as i n the experiment j u s t d i s c u s s e d , the concentrations of higher c h l o r i n a t e d congeners was g r e a t e r . The r e s u l t s o f t h e l a t t e r t e s t w o u l d a l s o have been a f f e c t e d b y t h e somewhat l o w e r r e a c t i o n t e m p e r a t u r e ( 1 3 5 ° C ) which was a c h i e v e d i n t h e l a s t v o l a t i l e r e m o v a l e x p e r i m e n t d e s c r i b e d h e r e . A n a l y s e s o f t h e d i s t i l l a t e from t h e s e two e x p e r i m e n t s i n d i c a t e d t h a t most o f t h e PCDD/PCDF c o n g e n e r s were n o n - d e t e c t a b l e , ensuring that t h e PCDD/PCDF h a d a c t u a l l y been d e c h l o r i n a t e d and n o t s i m p l y removed from the r e a c t i o n m i x t u r e a l o n g w i t h the v o l a t i l e s . While these experiments c l e a r l y demonstrate that the removal of the v o l a t i l e s from t h e r e a c t i o n m i x t u r e r e s u l t s i n more c o m p l e t e d e s t r u c t i o n i n a



% destruction of T o t a l PCDD/PCDF 115

Total PCDD/PCDF

TCDF PeCDF HxCDF HpCDF OCDF


Total Congener

4800

470 450 190 350 280

1500 100 920 540 ND ( 4 3 0 )


13%

4200

170 16 7.9 1600 360

770 24 640 560 13

Water Not Removed, Treated at 100°C for 4 hours

81%

920

120 15 15 13 12

740 ND ( 1 . 2 ) ND ( 1 . 2 ) ND ( 1 . 8 ) 1.9

W a t e r Removed Following Addition of KPEG, Treated at 146°C for 3.5 hours

Concentration (ppb)

60%

1900

42 29 75 630 ND

(74)

(13)

Removed Addition KPEG, at 135°C 4 hours

75 43 950 21 ND

Water Before of Treated for

Table I I I . C o n c e n t r a t i o n and P e r c e n t D e s t r u c t i o n o f PCDD/PCDF i n C o n t a m i n a t e d C a r b o n B e f o r e a n d A f t e r T r e a t m e n t o f KPEG D e m o n s t r a t i n g E f f e c t of Removing Water from R e a c t i o n M i x t u r e



246


s i g n i f i c a n t l y s h o r t e r p e r i o d o f t i m e , t h i s i s p r o b a b l y due t o the concurrent i n c r e a s e i n the temperature of the r e a c t i o n mixture which occurs. These r e s u l t s do n o t i n d i c a t e a c l e a r c h o i c e b e t w e e n removal of the v o l a t i l e s before or a f t e r the i n t r o d u c t i o n of the KPEG i n t e r m s o f e f f i c i e n c y o f t h e d e c h l o r i n a t i o n . The p r e s e n c e o f water i n the t r e a t m e n t m i x t u r e has been s u g g e s t e d as a p o s s i b l e e x p l a n a t i o n for the incomplete d e c h l o r i n a t i o n of 2,3,7,8-TCDD i n a c o n t a m i n a t e d (120 ppb) w a s t e sample c o n s i s t i n g o f s o l v e n t s , o i l and w a t e r d u r i n g l a r g e r s c a l e KPEG f i e l d t e s t s (4). In these field t e s t s , retreatment of the i n i t i a l l y t r e a t e d waste w i t h a d d i t i o n a l KPEG r e d u c e d t h e c o n c e n t r a t i o n o f 2 , 3 , 7 , 8 - T C D D t o a non-detectable level. Laboratory Study of the E f f e c t s of t h e Q u a n t i t y o f KPEG R e a g e n t o n the D e c h l o r i n a t i o n R e a c t i o n . R e d u c i n g t h e q u a n t i t y o f KPEG w h i c h i s used to t r e a t a waste sample a l s o r e d u c e s the f i n a l volume o f t r e a t e d m a t e r i a l and s i m p l i f i e s the n e u t r a l i z a t i o n o f the r e a c t i o n m i x t u r e w h i c h w o u l d u l t i m a t e l y be r e q u i r e d t o r e n d e r the highly a l k a l i n e treatment products safe for conventional d i s p o s a l . Using t h e c o n t a m i n a t e d c a r b o n m a t r i x , a n e x p e r i m e n t was c o n d u c t e d w i t h a c a r b o n t o KPEG r a t i o o f 2 0 : 1 , much h i g h e r t h a n t h a t u s e d i n the experiments already described. A n e x c e s s o f p o t a s s i u m h y d r o x i d e was a d d e d t o t h e c a r b o n i n t h i s c a s e , a n d t h e s a m p l e was h e a t e d a t 1 2 0 ° C f o r 72 h o u r s . The r e s u l t s o f t h i s t e s t a r e p r e s e n t e d i n T a b l e I V . These d a t a i n d i c a t e t h a t , as w i t h o t h e r treatments discussed e a r l i e r , d e c h l o r i n a t i o n of the h i g h e r c h l o r i n a t e d PCDD/PCDF i s e s s e n t i a l l y c o m p l e t e , b u t some o f t h e t e t r a - a n d p e n t a c h l o r i n a t e d congeners remain after the 72-hour t r e a t m e n t . These results demonstrate, however, t h a t the r e a c t i o n i s not s i g n i f i c a n t l y impeded b y u s i n g a r e l a t i v e l y l o w p r o p o r t i o n o f KPEG a s c o m p a r e d t o c a r b o n . R e c e n t f i e l d t r e a t m e n t t e s t s o n P C B - c o n t a m i n a t e d s o i l s c o n t a i n i n g up t o 2 2 0 0 p p b o f PCB w h i c h w e r e c o n d u c t e d b y U . S . E P A h a v e s h o w n t h a t e f f e c t i v e d e c h l o r i n a t i o n o f PCB c a n b e a c h i e v e d e v e n w i t h s o i l - t o KPEG r a t i o s a s h i g h a s 1 0 0 : 1 . Laboratory Study of KPEG T r e a t m e n t of the E x t r a c t of a Contaminated Carbon Sample. An a l t e r n a t i v e approach for d e c h l o r i n a t i n g PCDD/PCDF s o r b e d on a c t i v a t e d carbon entails e x t r a c t i o n o f t h e PCDD/PCDF and o t h e r e x t r a c t a b l e m a t e r i a l s present i n the c a r b o n u s i n g an a p p r o p r i a t e solvent, f o l l o w e d by KPEG treatment of the e x t r a c t . S u c h a t e s t was c o n d u c t e d p r e v i o u s l y , u s i n g m e t h y l e n e c h l o r i d e / a c e t o n e ( 1 / 1 ) t o e x t r a c t t h e PCDD/PCDF from the carbon. T h e r e s u l t a n t e x t r a c t was t h e n t r e a t e d w i t h KPEG a t 145°C f o r four h o u r s . T h e r e s u l t o f t h i s e x p e r i m e n t was a r e d u c t i o n of a l l PCDD/PCDF c o n g e n e r s to non-detectable concentrations (Tiernan, T. 0 . ; Wagel, D. J . ; VanNess, G. F . ; G a r r e t t , J. H.; S o l c h , J . G . ; R o g e r s , C . J . ; Chemosphere, i n p r e s s ) . These r e s u l t s suggest that extractable organic material present on the contaminated carbon i s not r e s p o n s i b l e f o r impeding d e c h l o r i n a t i o n of the activated-carbon-bound PCDD/PCDF isomers. Possibly, inhomogeneity of the carbon m a t r i x and/or incomplete mixing and c o n t a c t o f t h e KPEG r e a g e n t w i t h t h e c a r b o n may a c c o u n t f o r the i n c o m p l e t e d e s t r u c t i o n o f t h e P C D D / P C D F w h i c h was o b s e r v e d i n t h e



14.

TIERNAN ET AL.

247


T a b l e I V . C o n c e n t r a t i o n and D e s t r u c t i o n E f f i c i e n c y f o r t h e PCDD/PCDF C o n g e n e r s B e f o r e and A f t e r T r e a t m e n t Using a 20:1 R a t i o of Contaminated Carbon:KPEG Concentration

Total Congener TCDD PeCDD HxCDD HpCDD OCDD

1500 100 920 540 ND ( 4 3 0 )

TCDF PeCDF HxCDF HpCDF OCDF Total


470 450 190 350 280 PCDD/PCDF

% Destruction o f T o t a l PCDD/PCDF

4800

F o l l o w i n g Treatment w i t h KPEG a t 1 2 0 ° C f o r 72 h o u r s 980 ND ND ND ND

(60) (6.0) (4.1) (2.2)

270 11.4 ND (7) ND ( 1 0 0 ) ND ( 1 3 ) 1260

74%


248



tests described e a r l i e r . Additional to explore t h i s p o s s i b i l i t y .

experiments

were

accomplished

L a b o r a t o r y S t u d y o f t h e E f f e c t s o f I m p r o v i n g t h e M i x i n g o f t h e KPEG Reagent and the C o n t a m i n a t e d Carbon D u r i n g T r e a t m e n t . The somewhat l i m i t e d d e c h l o r i n a t i o n o f P C D D / P C D F c o n g e n e r s w h i c h was o b s e r v e d when c o n t a m i n a t e d c a r b o n c o n t a i n i n g t h e s e c o m p o u n d s was d i r e c t l y t r e a t e d w i t h KPEG may r e s u l t f r o m t h e i n a b i l i t y o f t h e KPEG to p e n e t r a t e the m a t r i x and e f f e c t i v e l y c o n t a c t t h e carbon-bound PCDD/PCDF. I n an e f f o r t t o more c o m p l e t e l y d i s t r i b u t e the d e c h l o r i n a t i n g r e a g e n t t h r o u g h t h e c a r b o n m a t r i x , a n e x p e r i m e n t was c o n d u c t e d i n w h i c h 1 0 0 g o f t h e c o n t a m i n a t e d c a r b o n was t h o r o u g h l y m i x e d w i t h 90 mL o f w a t e r , 10 mL o f P E G - 4 0 0 a n d 1 2 . 5 g o f s o d i u m hydroxide. The w a t e r and o t h e r v o l a t i l e s w e r e t h e n r e m o v e d b y d i s t i l l a t i o n o f t h e m i x t u r e a n d t h e r e s i d u a l c a r b o n a n d KPEG w e r e heated to a temperature of 170°C f o r a p e r i o d o f s i x h o u r s . This procedure e f f e c t i v e l y i n c o r p o r a t e s both the removal of the v o l a t i l e components and t h e h i g h e r r e a c t i o n t e m p e r a t u r e s w h i c h were shown t o enhance the d e c h l o r i n a t i o n p r o c e s s i n the p r e v i o u s e x p e r i m e n t s . The m e a s u r e d c o n c e n t r a t i o n s o f t h e PCDD/PCDF i n t h e r e a c t i o n m i x t u r e , as d e t e r m i n e d by a n a l y s e s f o l l o w i n g t h i s t r e a t m e n t , a r e summarized i n Table V. The e x t e n t o f d e c h l o r i n a t i o n o f t h e t o t a l P C D D / P C D F c o n g e n e r s a c h i e v e d i n t h i s t e s t was 82%, w h i c h i s q u i t e s i m i l a r t o the best o v e r a l l r e s u l t s o b t a i n e d i n the previous treatment experiments. A s i n t h e s e o t h e r e a r l i e r e x p e r i m e n t s , t h e TCDD a n d TCDF c o n g e n e r s s o r b e d o n t h e a c t i v a t e d c a r b o n a p p e a r t o r e s i s t the d e c h l o r i n a t i o n p r o c e s s , t h e p r e s e n t r e s u l t s s h o w i n g 49% d e s t r u c t i o n o f t h e TCDD c o n g e n e r s a n d 77% d e s t r u c t i o n o f t h e TCDF c o n g e n e r s . I t i s w e l l known t h a t TCDD a n d TCDF b i n d q u i t e s t r o n g l y t o a n a c t i v a t e d carbon m a t r i x . In fact, i n the course of analyses of samples t o d e t e r m i n e the c o n t e n t o f t h e s e compounds, t h e s e i s o m e r s are s e p a r a t e d from o t h e r i n t e r f e r e n c e s by s o r p t i o n on a P X - 2 1 c h a r c o a l chromatography c o l u m n , as b r i e f l y n o t e d i n the e x p e r i m e n t a l section. Once s o r b e d on t h e c a r b o n , t h e s e i s o m e r s r e s i s t e l u t i o n , even by r e l a t i v e l y s t r o n g s o l v e n t s , and a r e removed e f f i c i e n t l y o n l y when e l u t e d w i t h t o l u e n e . This suggests that i n future experiments w i t h t h e c o n t a m i n a t e d c a r b o n , i t may be u s e f u l t o e m p l o y a n u n c h l o r i n a t e d c o - s o l v e n t i n t h e KPEG p r o c e s s , w h i c h m i g h t d i s p l a c e the PCDD/PCDF from the carbon s i t e s and p e r m i t subsequent d e c h l o r i n a t i o n o f t h e TCDD a n d TCDF i s o m e r s i n t h e KPEG s o l u t i o n . E x p e r i m e n t s t o e v a l u a t e t h i s w i l l be i n i t i a t e d s h o r t l y . E f f e c t i v e n e s s o f KPEG R e a g e n t on 2 , 3 , 7 , 8 - S u b s t i t u t e d P C D D / P C D F Isomers i n Contaminated Carbon. It i s a l s o of i n t e r e s t to determine t h e e f f e c t i v e n e s s o f t h e KPEG p r o c e s s f o r d e c h l o r i n a t i o n o f s p e c i f i c PCDD/PCDF i s o m e r s , i n p a r t i c u l a r the 2,3,7,8-substituted isomers w h i c h a r e t h e more t o x i c compounds. Data which demonstrate the r e s u l t s o f KPEG t r e a t m e n t i n d e c h l o r i n a t i n g s p e c i f i c 2 , 3 , 7 , 8 i s o m e r s are presented i n Table V I . These r e s u l t s were o b t a i n e d f o l l o w i n g t h e l a b o r a t o r y e x p e r i m e n t i n w h i c h t h e c o n t a m i n a t e d c a r b o n was t r e a t e d d i r e c t l y w i t h t h e KPEG r e a g e n t a t 1 0 0 ° C f o r f o u r hours. D e c h l o r i n a t i o n of the 2 , 3 , 7 , 8 - s u b s t i t u t e d isomers of the penta-, h e x a - , and h e p t a - c h l o r i n a t e d c o n g e n e r g r o u p s i s s e e n t o be e s s e n t i a l l y complete, w h i l e the d e s t r u c t i o n e f f i c i e n c y f o r the



14.

TIERNANETAL.

249


Table V. Concentrations of PCDD/PCDF in Untreated and KPEG-Treated Contaminated C a r b o n Carbon Was Treated by Dispersing KPEG in a Water Slurry and Then Removing Water and V o l a t i l e s by D i s t i l l a t i o n Prior to Elevating Mixture Temperature to F i n a l Reaction Temperature

Concentration (ppb)

Total Congener

Untreated Contaminated Carbon 1500 100 920 540 ND (430)


470 450 190 350 280

TCDF PeCDF HxCDF HpCDF OCDF Total PCDD/PCDF Congeners % Destruction

4800

Treated Carbon 6 hours at 170°C 750 ND ND ND ND

(2.2) (2.8) (2.5) (4.3)

109 6.0 ND (1.3) ND (22) ND (66)

870 82%



250


to

Table V I . Comparison of Residuals o f T o t a l PCDD/PCDF Congener Groups R e s i d u a l s of 2 , 3 , 7 , 8 - S u b s t i t u t e d Isomers of Those F o l l o w i n g D i r e c t KPEG T r e a t m e n t o f S p e n t C a r b o n C o n t a i n i n g T h e s e Compounds

PCDD/PCDF C o n g e n e r Groups and S p e c i f i c PCDD/PCDF I s o m e r s Total

Total

Total

Total

Total

Total

Total

Groups

Residual %

TCDD 2,3,7,8-TCDD

52

HxCDD 1,2,3,4,7,8-HxCDD 1,2,3,6,7,8-HxCDD

69

HpCDD 1,2,3,4,6,7,8-HpCDD

—a

TCDF 2,3,7,8-TCDF

35

58

SO.79 S O . 16

S O . 02

31

PeCDF 2,3,4,7,8-PeCDF

3.5

HxCDF 1,2,3,4,7,8-HxCDF

4.2

10

SO.39 —a

HpCDF 1,2,3,4,7,8,9-HpCDF

SO.11

a T r e a t m e n t r e s u l t e d i n an the t o t a l congener group

increase

in

the

concentrations

of


251 14. TIERNANETAL. Dechlorination oj Organic Compounds


2,3,7,8-tetrachlorinated isomers is approximately the same as that achieved for the corresponding congener group as a whole. These results are significant because most of the toxicity which results from PCDD/PCDF contamination is the result of the presence of the 2,3,7,8-substituted isomers. By removing these isomers, the toxicity of the treated material can be significantly reduced even if the concentrations of other PCDD/PCDF isomers in the various congener groups are not reduced to non-detectable levels.

Literature Cited 1. Kimura, Y.; Regen, S. L.; "Polyethylene Glycols Are Extraordinary Catalysts in Liquid-Liquid Two-Phase Dehydrohalogenation"; J. Org. Chem. 1982, 47, 2493-4. 2. Kimura, Y.; Regen, S. L.; "Poly(ethylene glycols) and Poly (ethylene glycol)-Grafted Copolymers Are Extraordinary Catalysts for Dehydrohalogenation Under Two-Phase and ThreePhase Conditions"; J. Org. Chem. 1983 48, 195-8. 3. Rogers, C. J.; Kornel, Α.; U.S. Patent No. 4 675 464, 1987. 4. Tiernan, T. O.; Wagel, D. J.; Garrett, J. H.; VanNess, G. F.; Solch, J. G.; Harden, L. A.; Rogers, C. J.; "Laboratory and Field Tests to Demonstrate the Efficacy of KPEG Reagent for Detoxification of Hazardous Wastes Containing Polychlorinated Dibenzo-p-dioxins (PCDD) and Dibenzofurans (PCDF) and Soils Contaminated with Such Chemical Wastes"; Chemosphere, 1989, 18, 835-41. 5. Solch, J. G.; Ferguson, G. L.; Tiernan, T. O.; VanNess, G. F.; Garrett, J. H.; Wagel, D. J.; Taylor, M. L.; "Analytical Methodology for Determination of 2,3,7,8-tetrachlorodibenzo-p -dioxin in Soils"; In Chlorinated Dioxins and Dibenzofurans in the Total Environment II; Keith, L. H.; Rappe, C.; Choudhary, G.; Eds.; Butterworth Publishers: Boston, Massachusetts, 1985, pp. 377-97. 6. Tiernan, T. O.; "Analytical Chemistry of Polychlorinated Dibenzo-p-dioxins and Dibenzofurans: A Review of the Current Status"; In Chlorinated Dioxins and Dibenzofurans in the Tot Environment; Choudhary, G.; Keith, L. H.; Rappe, C.; Eds.; Butterworth Publishers: Boston, Massachusetts, 1983, pp. 21137. RECEIVED November 10, 1989


Dechlorination of Organic Compounds Contained in Hazardous Wastes

Recommend Documents