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1 Korean Chem. Eng. Res., Vol. 42, No. 1, February, 2004, pp (II) ( , ) Characteristics of a Continuous Denitration Process Combining Chemical and Electrolytic Systems with Accompanying the Precipitation of Metal ions Kwang-Wook Kim, Soo-Ho Kim and Eil-Hee Lee Korea Atomic Energy Research Institute, 150, Dukjin-dong, Yuseong-gu, Daejeon , Korea (Received 29 September 2003; accepted 12 December 2003) -! "! #$%. - & '( 2.0 M )*+, M /01 23, $%. # 89: Zr, Mo, Nd, Fe ;& < = 3 >?@+ A1 BC-D, )* E Mo & F3 G H!+ IJKL%. F( M / N O PQ R, S " T UV W?@+ AX Y OS 1.65Z [ = PQ R\ 0.1 M R. \] ^_ `ab-d, Y[ Zr, Mo S& \] c& d-. ee 95%, 83%01 Rf/g%. T UV F( M / OS W?@+ hg / N O i j k UVl \m-d Y n?o #k UVl \m%. Abstract This work has studied the characteristics of destruction of nitric acid and precipitation of several metal ions in a continuous denitration process combining a denitration by formic acid and a residual acid-electrolytic trimming system. The process could treat continuously and effectively a feeding nitric acid of 2.0 M to below about 0.1 M. The metal ions of Zr, Mo, Fe, and Nd did not affect the electrodes at the step of electrolytic trimming of the residual acid after denitration by formic acid. The Mo ion in electrolytic solution enhanced the generation of nitrite ion during the electrolytic reaction. The mole ratio of formic acid to nitric acid fed into the continuous denitration reactor using formic acid affected much the final acidity, the precipitation yields of metal ions, the precipitate morphology. At the ratio of 1.65, the process had the lowest final acidity of less than 0.1 M, and the precipitation yields of Zr and Mo reached 95% and 83%, respectively as the highest values. Only the precipitate generated in the mole ratio of formic acid to nitric acid between 1.5 and 1.7 had a needle-shaped morphology, otherwise it was granular-shaped. Key words: Denitration, Electrolysis, Precipitation, Formic Acid, Nitric Acid 1.! " # $%! &' () * +, -./ :; <4 =8>?@A BC DEF[1-8],! G0 H6!9I J K! "' L@ -.4M. HN JAERII!!' +,- O PQ! 40! R I S" T/ ; UVWC[3, 4] WXYW P Q!I R / Z[\] U7 ^\] 6_`a4 b R c d e(!'i fg h 8i4 ; To whom correspondence should be addressed. nkwkim@kaeri.re.kr %j f kvm. N lm 4n lmi op[ R 6 _-I!q PQ! ;%r\] stu 4v st7!i = PQ! w x -y 1.5 4z\] O {( $%>! ", q \] }~ 7 PQ! e n- j I J> ;7 ƒ1!j n G0O PQ! n"r\] "` ;%[ j -n" R + G0O ;%[ PQ! R gˆ kvm[9, 10]. PQ! R /!!' + 4 I ŠG I y Zr, Moq Œ I HŽ ŠG n #" ^ r\] M. Zrq Mo qi 3 z(third phase) * :zj(emulsification) h z H\ u I a r\] Q š] Zrq Mo * - œ ` \]ž c% 8Ÿj -A M. 26

2 F N lmi 4n lmi U PQ!I ;%[ PQ! R -n" " + gˆ ko ;%[ PQ! R O! n-j r " ;I 4 4 R qi 567 X%4 n 5 k- O n4 X% Zr, Mo, Fe Œ ª Nd h X% 4 ;%[ PQ! R -n" " + I n 5q n" 6_-I 4«X%4 n " 4 7 M. 2. N ;I G0 4n lmi G0 ± 5H ^\ ][9, 10] 125 ml Pyrex column4 G07 \u PQ! R 6_` ' 96 o C] +,- O 6_- ŽI thermocouple4 ²t 7 column Ž heating tape] )³ M. 6_- ŽI PQ!q! stg u R q n A Rµ[ n+g 7 M. R 6_-I st7! &' 2.0 M] z I! : 1.0 ml/min4 7'¹ syringe pump] +,V\u, 4v st7 PQ!/! w x º] +,- O 25.9 M &' PQ!4 syringe pump] 5` I st7 M. ;%[ PQ! R 6_-» 0 O! " - O Ž¼ 18 ml ½/ n" 6_- 3P ;%\] ;¾V\u, PQ! R 6_ qi X%4 n4 567 À xá _- Â» n 4 n" 6_-] «g ^ Ã - O PQ! R 6_-± n" 6_- G4I +(settling tank) VM. n" 6_-I G07 Ä \] IrO 2 n [11-14], Å \] mesh Ti G0V 4v Æ n Çr / ÈÈ É 23 cm 2 4 n a / 5 mm] VM. PQ!I R ` 0? X%4 n k- O n4ª =Ê] Zr, Mo, Fe 4 =Ê] Nd 2.0 M!I 0 "`Ë R =z 0\] G0V Table 1I G0 ª &' ± j +4»» M. R q!q PQ!!' Auto-titrator(Kyoto Electronics AT-400)± TOC Ì-(Shimadzu TOC-5000A) + O ÈÈ Ì V\u, 6_?I K7 ÍÎÏ,!, D! 4 h/ Ion chromatograph(dionex ICS-90) G0O Ì VM. 0? X% 4 &' ICP(Induced Couple Plazma Spectroscopy: Jobinyvon JY38 Plus) G0O ÌVM. 3. PQ! R qi X%4 4 n7 À PQ! R c O! n"` 0?I y X% 4 4 n I µð g ˆ4 M. Œ š] X%4 n4 67 ;%[ PQ! R -n" " + ÑÒI Ó N ;I Ô7 =z X %4 4 Ti Å I µ4 7 ^ Õ - O Ti Å I = 4«0 voltammogram4 Ö7 Œ ¾qg Fig. 1I»» Table 1. Elements and their concentration in simulated solution Element Concentration Chemical formula H M HNO 3 Zr M ZrO(NO 3 ) 2 Mo M (NH 4 ) 6 Mo 7 O 24 4H 2 O Fe M Fe(NO 3 ) 3 9H 2 O Nd M Nd(NO 3 ) 3 6H 2 O - 27 Fig. 1. Linear voltammograms of 2.0 M nitric acid solutions with and without metal ions at Ti cathode.! background M. Fe, Nd, Zr4 : 0 i-v œ/ 2.0 M 0 i-v œq Nr\] Ø4g ÙM. Œ» Mog «a À 0.2 V VI Ú Ûª nü Ý k4 JK nü' Þ/ &'! 0I nüi xo M ßW ^4 S M. 4^/ Mo 4 4 X%\] Ûª7 ^I ^4», Mo 4 I! 0 àji ^\] KÈA M. {( =z X%4 4 ÛªI " Å I µ4 7 W Õ - O 4«0 Ti-IrO 2 n á âi 20a 80 ma/cm 2 \] n " 6_ `ã c Å \] G0 Ti n ÊÇ EPMA(electron probe micreoanalyzer)] Ì ¾q, Ti 4 Â X% ' ä37w åå ÑÒr\] Õ VM. 4 =z X%4 4 PQ! q! n" " qi e X%\] Ûª7 q4 Ù M ^ QM. F Mog «a 0I 0.2 V VI S 7 nü Mo 4 4 Mo X%\] Ûª7 ^I - O»» ^4 Dæ n ÊÇI 0 àji ^\] KÈ M. Œ š] Mog «a À 0.2 V VI S 7 nü! ÛªI D! q k4 [ (1) 6_q c % 6_ [ (2)± (3) # D!q!j Ûª 6_\] 2 M[15, 16]. + NO 3 + 3H + 2e = HNO 2 + H 2 O E o = +0.94( V vs SHE) HNO 2 + H + + e = NO+ H 2 O E o = +0.97( V vs SHE) + NO+ NO 3 + 2H + e = 2HNO 2 E o = ( V vs SHE) HNO 3 + 2NO+ H 2 O= 3HNO 2 4 Õ - O 1.0 M!I 0.5 M D!4 ç 0I = voltammogram4 Ö7 Œ ¾qg Fig. 2I»» M. Fig. 1 Mog ç V VI nü q 1À :G ¾q» M. Fig. 2I =z 0 è-žé D! 4 0I y V\š] Fig V VI nü [ (2)- (4) 6_I nü] KÈÐ M. [ (1)4»! D!\] Ûª 6_ %' êë ^\] ìôí \š][15, 16] Fig. 1I Mo 4 4 y À 0.2 V VI S 7 nü Mo 4 Â ½0I " [ (1) 6_4 ƒî7 H8 D!4 K7 4c K D!4 [ (2)-[ (4) c% Ûª 6 Korean Chem. Eng. Res., Vol. 42, No. 1, February, 2004 (1) (2) (3) (4)

3 28 Fig. 2. Linear voltammograms of 1.0 M nitric acid solution and of a mixture of 1.0 M nitric acid and 0.5 M nitrite ion at Ti cathode. Fig. 4. Amounts of nitrite ion generated in 2.0 M nitric acid solutions of with each metal ion for 15 minutes by Ti cathode at 400 ma/cm 2. Fig. 3. Linear voltammograms of the solutions of several nitric acid concentrations with Mo ion of M at Ti cathode. _I nü] KÈ M. Mog «a 0 À JK n I nüg, Mog Ù!C 0I S 7 nü km ï/ ^/ [ (2)-(4)I kð H8 D!4 4 7Ç ñ5 ƒ16 _I M D!4 K7 K D!4 f%r\] Û ª 7- O [ (2)± [ (3)I kð4 0? 4 Î I F n ÊÇ &'g (7 JK Wò n Üg ßW ^\] KÈ M. 4 Õ - O Mo 4 &' M] H~ z I! &' 0.5 MŽé 2.0 M YW àj`ã 0I =O voltammogram4 Ö7 Œ ¾q Fig. 3I»» M. Îó! 0I Mo 4 4 ô À Fig V VI k ^q Þ4 D! Ûª n Üg S 4 7!&'g )Ç JK nüg H~ ß õ S A M. 4z ¾q]Žé Nd, Fe, Zr 0I 0.2 V VI Ûª nüg S 4 7W å, Mog : 0 IC 0.2 V VI Ûª nüg S 7 ^/ Mo Mö X% 4 Fe, Nd, ZrI xo [ (1)! è- Ûª 6_ ƒî` 4]Žé K7 D! Ûª 6_ vm\] KÈ7u, 4v JK nü ) D! Ûª6_4 ƒî7ç n ÊÇq 0? 4 Î` - vm\] KÈ M. Mo 4 4 ç 0I!4 D!\] Ûª 6_4 ƒî M ^ Õ - O Fe, Nd, Zr, Mo 4 4 ÈÈ «a! Ti-IrO 2 n" 6_-I 400 ma/cm 2 \] n" "O 15 5ø 6_-I K D! &' ÖO kù Œ ¾qg Fig. 4I»» M. X%4 4 ç 7W å/! 0I» Fe, Nd, Zr C : 0I K D! Ä/ xú» Mog : 0I É 2û 4z D!4 T4 Kü S A M. 4 ¾q]Žé Fe, Nd, ZrI xo Mo 4 /! Ûª6_ ƒî` WC n" Ûª6_I " n ÊÇI µ 7W å M ^ Õ A M. 4z ¾q ýþ\] Mo, Zr, Fe, Nd 4 : 2.0 M! ml/min : q 4v PQ!/! w x 1.75] O 96 o C ] :W7 ;%[ R op 6_- #q~, #q O! ma/cm 2 nüg ÿ7u 50 o C] :W7 3+ IrO 2 - Ti n 6_- ~ O O! ;%r\] "7~ q ~ VM. X%4 «4 567 À, ;%[ PQ! R 6_-I n4 6_- ni H~ H»u 6 _- I! Å z\] O =Ž n 4 R 6 _- I n4 7WC HŽ ~ xá 56I " n" 6_- \] g ^4 S 7 PQ! R 6_-± n"+ G4I + O Œ + zhc4 n" 6_-I s t7'¹ O ÑÒ UVM. PQ! R 6_-± n"+ G4 I + I' O PQ!q! n" " q?i' 0!' )I ö n4 n" â I H» n ÊÇI n 4 Å ÑÒr\] S A M. O - n ÊÇI n / =z X%4 4 n-j r\] Û ª7 µ ^4 Dæ ni 8Ÿ µ4 n ÊÇ è Å JK-± ~ Ç ~ ßí ª z n \] ~ ª ü ÑÒr\] S A M. Fig. 5I X% 4 n4 H» ;%[ PQ! R 6_- I PQ!/! w xi ö!',! PQ! àj± N lm 4n lm ¾q [9, 10] X% 4 4 Ù À ;%[ R ¾qg»» M. X% 4 n4 H» À n 4 Ù À± :G k4 MC Ö!' Ý4 nr\] É 0.1 M M ' <4»» M. 4^/ X%4 4 y 0!' Ö r` X%4 Š"I Ì Ø * n ÊÇI HŽ µ X%4 H ^\] 2 M.!' PQ!/! w xg H v g ï/ Ý k4 PQ! x4 gç! &' ïdwwc q

4 - 29 Fig. 5. Changes of total acidity, nitric acid, and formic acid at the continuous denitration reactor in the cases with and without the precipitation of metal ions with a change of mole ratio of formic acid to nitric acid. \] ÿ O PQ!I "!' ~ g ^4 S M. Fig. 6I PQ!q! x4 1.75] R 6_-I ÿ7 À R 6_- 3P n" 6_-I `ai ö!' PQ!,! &' àjg»» M. N lm 4n lmi k n4 567W å ;%[ PQ! R -n" " ¾q± [9] :G~ R 6_-» n" 6_-I É 30 'I zz I ' ^ M. è- 2.0 M!4 st7 z I R 6_-± È n" â» 0!' ÈÈ 1.54 M, 0.72 M, 0.42 M, 0.15 M\] X%4 4 n4 567 ÀI' N ;I ø ;%[ PQ! R -n" " + #" > ;%[\]!!' ì M. Fig. 7I Fig. 6 ;%[ R 6_-± 3P n" âi zz Fig. 7. Changes of several species at each step of the continuous denitration reactor and the electrolytic cells accompanying the precipitation of metal ions at a mole ratio of formic acid to nitric acid of PQ!,!,!, D! ÍÎÏ 4 &' àj Ý4»» M. ÍÎÏ 4 / PQ! R 8fI &' ½WC JK ^4 S 7, * X%4 n4 Ù ;%[ PQ! R -n" " + ÑÒ U N lm 4n lm[9] ¾q p Å! " qi K7 D! HŽg ÍÎÏ 4 \] àû7 n" â I r4 7 ^ S A M. D! &' PQ! R 6_-I É 10 3 M '] K 7» n" âi ÿ> Ùõ M. 4 4: R 6_-I JK D!4» Å n" 6_I " K7 D!/ n" âi Å 6_I " ÍÎÏ 4 \] nû7» N lmi p 4 Ù À Ä I!j Î7 n" â I r4 7W å- vm4m. Æ n" â 4cI 0!q PQ! I!'g! 4 (nitrate) &'km ïdî ^p k4 ^/ n" â Å I D!4 ÍÎED] Ûª7 4 ÍÎED Fig. 6. Changes of total acidity, nitric acid and formic acid at each step of the continuous denitration reactor and the electrolytic cells accompanying the precipitation of metal ions with a change of denitration time at a mole ratio of formic acid to nitric acid of Korean Chem. Eng. Res., Vol. 42, No. 1, February, 2004

5 30 Fig. 8. Changes of total acidities at each step of the continuous denitration reactor and the electrolytic cells accompanying the precipitation of metal ions at several mole ratios of formic acid to nitric acid. g phg ï/ À ÍÎÏ 4 \] y - O 0 4 &' ÎV- vm4m[9]., 0! 4 =Ž4 ÍÎÏ 4 I G07! 4 C4 }ù- vm4m. Fig. 8I ;%[ PQ! R 6_-I ÿ7 PQ!/! w xg àja v PQ! R 6_- È n" 6_-I!' àjg»» M. Fig. 5I kð4 PQ!/! w xg ga ¹ PQ! R 6_-» 0I O PQ! &' g O! &' )7š], PQ! R 6_-I ÿ7 PQ!/! w xg àjüi F n" 6_-] :t7!q PQ! &'g ÔW, 4n lmi ÿ ^p IrO 2 -Ti n" 6_ -I PQ! " %'g! " %'km É 1.5û 4z š][9, 10] 4 ½0I " e n" 6_-» 0 e!' ;%[ PQ! R 6_-I ÿ7 PQ!/! xg 1.65H v e(g 7 z k M. Fig. 9I ;%[ PQ! R 6_-I ÿ7 PQ!/! w xg àja v PQ! R 6_- È n" 6_-I Zr, Mo, Fe, Nd nq!' àjg»» M. PQ! R 6_-I Zr, Mo n/ PQ!/! w xg 1.25I ÈÈ 70%, 60% '4» PQ!/! w xg g I F go 1.65I 95%, 83% '] g <4»» \u PQ!/! w xg 2.0H À PQ! R 6_-I O! &'g <DW- vmi n / M` ) M. > PQ!/! x4 1.65I Mö À± PQ! R c O! n" " qi 2 gr n/ 1À r~ H} M. nr\] Fe n/ 10-15% '4u, Nd n/ 1-4% '] n4 1À r ~ H} M. Œ» n" 6_4 îu7!'g > ïdw 0.1 M 'I Fe, Zr, Mo n/ 100%I ', Nd À'!'g 0MI gy v n4 90% ' YW 'ü M. 4 ¾q]Žé PQ! R qi X %4 n/ 6_-I ÿ7 PQ!/! w x± PQ! R q O! n" c e!'i!å ì M. PQ!/! w xg 1.65I =z X%4 n/ 4n l mi k4 Z[I er nq xú 4M[7]. Fig. 9. Precipitation yields of metal ions and total acidities at each step of the continuous denitration reactor and the electrolytic cells at several mole ratios of formic acid to nitric acid

$R 6_- n morphology kos SEM ¾qg»» M. PQ!/! w xg 1.25I n 4 zq z4 ô 4, PQ!/! w xg 1.5, 1.65I É 2µm - "n z\] Ju, PQ!/! w xg 2.0 4zI 0.1-0.2 µm tñ«4 ¾ 7 1-3 µm MÄ - z tñ n 4 ü M. Fig. 5I Fig.$

6 - 31 Fig. 10. SEM photographs of precipitates generated in the continuous denitration reactor with the mole ratio of formic acid to nitric acid. Fig. 10I ;%[ PQ! R 6_-I ÿ7 PQ!/! w xg àja v PQ! R 6_- n morphology kos SEM ¾qg»» M. PQ!/! w xg 1.25I n 4 zq z4 ô 4, PQ!/! w xg 1.5, 1.65I É 2µm - "n z\] Ju, PQ!/! w xg 2.0 4zI µm tñ«4 ¾ µm MÄ - z tñ n 4 ü M. Fig. 5I Fig. 10 ¾q]Žé N ;I `' ;%[ PQ! R q O! n" " + / Z[I n g WÇ #qr\] e!' 0.1 M-0.5 MYW > +,A Å ì, ŠG! &' +,q Zr, Mo h X%4 - ;%ji #qr\] G0Ð Å Õ A M. 5. ŠG! &' +,u 5`I 0?I y Zr, Mo h X% 4 - -y PQ!I Z[ R 6_ 8i - O ` ;%[ PQ! R - O! n" " + / e!' ;%r\] 0.1 M 4YW # qr\] +,A M. * N ;I Ô Zr, Mo, Nd, Fe h/ O! n" " qi n I r sw åù \u,! 0? Mo 4 / n" 6_qI D! K ƒ î` M. ;%[ PQ! R 6_-I ÿ7 PQ!/! w x g É 1.65H v O! n" " c e!'g g ï~» $M. =z X% 4 n/ PQ! R 6_-I ÿ7 PQ!/! w x± n" 6_-I e!'i!ùm. PQ!/! w xg É 1.65H v Zrq Mo n/ ÈÈ e= 95%± 83%YW 'u Fe É 10%, Nd 4% QCC4 n7 M. PQ! R 6_-I n 6_-I ÿ7 P Q!/! w xi!d PQ!/! w xg G 4I z 4 Œ 4 òi z g M. 1. OECD Final Report, Status and Assessment Report on Actinide and Fission Product Partitioning and Transmutation, Report NEA/ PTS/DOC(98)4(1998). 2. Lelievre, D., Boussier, H., Grouiller, J. P. and Bush, R. P., Perspectives and Cost of Partitioning and Transmutation of Long-Lived Radionuclides, Report EUR-17485(1996). 3. Kondo, Y. and Kubota, M., Precipitation Behavior of Platinum Group Metals from Simulated High Level Liquid Waste in Sequential Denitration Process, J. Nucl. Sci. & Technol., 29(2), 140(1992). 4. Yoo, J. H. and Lee, E. H., Development of Long-Lived Radionuclide Partitioning Technology, Report KAERI/RR-1632/95(1996). 5. Lee, E. H., Hwang, D. S., Kim, K. W., Kwon, S. G. and Yoo, J. H., Denitration Kinetics by Formic Acid Simulated Radwaste Solution, J. Korean Ind. & Eng. Chem., 8(1), 132(1997). 6. Lee, E. H., Hwang, D. S., Kim, K. W., Shin, Y. J. and Yoo, J. H., Removal of Zr and Mo from the Simulated Radwaste Solution(II), J. Korean Ind. & Eng. Chem., 6(5), 882(1995). Korean Chem. Eng. Res., Vol. 42, No. 1, February, 2004

7 32 7. Lee, E. H., Hwang, D. S., Kim, K. W. and Shin, Y. J., Removal of Zr and Mo from the Simulated Radwaste Solution(I), J. Korean Ind. & Eng. Chem., 6(3), 404(1995). 8. Orebaugh, E. G., Denitration of Savannar River Plant waste streams, Report DP-1417(1976). 9. Kim, K. W., Kim, S. H. and Lee, E. H., A Continuous Denitration Process Combining Chemical and Electrolytic Systems for the Destuction of High Concentration of Nitric Acid (I), HWAHAK KONG- HAK, 42(1), 20-25(2004). 10. Kim, K. W., Kim, S. H. and Lee, E. H., Accelerated Denitration by Formic Acid Accompanied with Residual Acid-Electrolytic Trimming, J. Radioanal. Nucl. Chem., 260(1), in press(2004). 11. Kim, K. W., Lee, E. H., Kim, J. S., Shin, K. H. and Kim, K. H., Study on the Electro-Activity and Non-Stochiometry of a Ru-Based Mixed Oxide Electrode, Electrochimica Acta, 46, 915(2001). 12. Kim, K. W., Lee, E. H., Kim, J. S., Shin, K. H. and Kim, K. H., Effect of an Etching Ti Substrate on a Catalytic Oxide Electrode, J. Electrochem. Soc., 148, B111(2001). 13. Kim, K. W., Lee, E. H., Kim, J. S., Shin, K. H., Chung, B. I. and Kim, K. H., Performance Improvement of Ir Oxide Electrode for Organic Destruction, J. Korean Inst. & Chem. Eng, 40(2), 146 (2002). 14. Kim, K. W., Lee, E. H., Kim, J. S., Shin, K. H. and Chung, B. I., A Study on Performance Improvement of Ir Oxide-Coated Titanium Electrode for Organic Destruction, Electrochmica Acta, 47(15), 2524(2002). 15. Kim, K. W., Lee, E. H., Choi, I. K., Yoo, J. H. and Park, H. S., Electrolysis of Nitric Acid by Using a Glassy Carbon Fiber Column Electrode System, J. Radioanal. Nucl. Chem., 245(2), 301(2000). 16. Kim, K. W., Lee, E. H., Choi, I. K., Yoo, J. H. and Park, H. S., A Study on Electrochemical Redox Behavior of Nitric Acid by using a Glassy Carbon Fiber Column Electrode System, J. Korean & Inst. Chem. Eng., 38(2), 149(2000)

- (I) A Continuous Denitration Process Combining Chemical and Electrolytic Systems for the Destruction of High Concentration of Nitric Acid (I)

- (I) A Continuous Denitration Process Combining Chemical and Electrolytic Systems for the Destruction of High Concentration of Nitric Acid (I) Korean Chem. Eng. Res., Vol. 42, No. 1, February, 2004, pp. 20-25 - (I) 305-353 150 (2003 9 29, 2003 12 12 ) A Continuous Denitration Process Combining Chemical and Electrolytic Systems for the Destruction