A Novel Photoelectrocatalytic Reactor and Photoelectrocatalytic Advanced Oxidation of Formic Acid

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1 24 5 Vol 24 No 5 Chinese Journal of Catalysis May 2003 : (2003) : ,2, 1, 2, 2, 1 1, (1,, ; 2, ) :,, COD 2,,, TiO 2, :,,,,, : O643/ X7 : A A Novel Photoelectrocatalytic Reactor and Photoelectrocatalytic Advanced Oxidation of Formic Acid AN Taicheng 1,2 3, ZHANG Wenbing 1, ZHU Xihai 2, XIONG Ya 2, SHENG Guoying 1, FU J iamo 1 ( 1 S tate Key L aboratory of Organic Geochemist ry, Guangz hou Institute of Geochemist ry, The Chinese Academy of Sciences, Guangz hou , Guangdong, China ; 2 School of Chemist ry and Chemical Engineering, Zhongshan U niversity, Guangz hou , Guangdong, China) Abstract : A novel poly2f unctional slurry p hotoelect rocatalytic reactor, in which titanium plate was used not only as a gas distributor but also as a cathode of reactor, was designed and characterized by the photocurrent enhance2 ment and COD removal efficiency Bot h t he current s of p hotoelect rochemical and elect rochemical processes in2 creased significantly with the increase of the applied voltage Moreover, the former is always higher than the lat2 ter, even the sum of the latter and the photocurrent, indicating that there exists a synergetic effect in the cur2 rents By comparison of the COD removal kinetics for the three processes, direct electro2oxidation, photocataly2 sis and p hotoelect rocatalysis, an apparent p hotoelect rochemical synergic effect in COD removal was observed in the new reactor for treatment of wastewater containing formic acid The effects of various factors, such as ap2 plied cell voltage, catalyst concent ration and air2flow, on t he p hotoelect rocatalytic were investigated The COD removal efficiency increases in the range of less than 5 V, then no more change ex2 ists with the increase of applied voltage, but the catalyst amount in the new reactor is very sparing, being far smaller than that in other reactors The sparged air in the photoelectrocatalytic reactor not only can efficiently enhance the mass transfer and the collision of photoexcited TiO 2 particles in slurry with the electrode surface, but also can make electric field facilitate to capture the photogenerated electrons Key words : p hotocatalysis, p hotoelect rocatalysis, p hotoelect rocatalytic reactor, formic acid, wastewater t reat2 ment, chemical oxygen demand : :,, 1972,, : Tel : (020) ; Fax : (020) ; E2mail : ac cn : ( ), (A ), (O GL ) China Academic Journal Electronic Publishing House All rights reserved

2 5 : 339,, [13 ], [2,4,5 ], [69 ] [10 ] [11 ] 2, U = 1010 V q V (air) = t = 30 min 1 1 COD [12 ] TiO 2 Degussa P25 (AP) (20 mmol/ L, COD = 320 mg/ L ) min, ;, TiO 2, TiO 2 [13 ] UV2PC2501 ( ), S520 ( ),W YK 303 ( ),500 W ( ) M Y62 ( ) mm PVC ( 40m ) ml TiO 2 1 Fig 1 Schematic diagram of photoelectrocatalytic reactor set2up (1) Inlet of recycled water ; (2) High pressure mercury lamp ; (3) CHI650A electrochemical system ; (4) Sampling outlet ; (5) Inlet of compressed air ; (6) Base of reactor ; (7) Micropore Ti plate cathode ; (8) TiO 2 slurry ; (9) Al foil ; (10) Outer pyrex cylinder ; (11) Porous Ti cirque anode ; (12) Double2walled quartz U2tube ; (13) Outlet of recycled water 100 L/ h, TiO 2 ( TiO 2 ) = 011 g/ L p H = 2 ( 200) Fig 2 SEM image of microporous Ti plate used as electrode China Academic Journal Electronic Publishing House All rights reserved

3 [14 ] 2,, 3, 1 mm 4 2 Fig 4 Current2voltage curves in photoelectrocatalytic reactor 3 Fig 3 Photograph of air bubbles in photoelectrocatalytic reactor (3413A), , nm [15,16 ] Bard [1618 ], [19 TiO 2 ] TiO 2 ( ) ;, [20 ] [21 ] s [22 ] TiO 2 (Pt ) 6,, [17 ] COD ( min - 1 ) ( min - 1 ) 4 COD ( , min - 1 ), China Academic Journal Electronic Publishing House All rights reserved

4 5 : Fig 5 UV2Vis spectra of formic acid during photoelectrocatalytic degradation COD Fig 6 Reaction kinetics of COD removal for different processes 7 Fig 7 Effect of cell voltage on photoelectrocatalytic [23 ] Lea [11 ] ; 1 g/ L,Assabane [23 ], 8 COD TiO 2, V COD ; 510 V, COD (9815 %) 6219 %COD 3516 % Vinodgopal [4 ] 7 COD 4 8 Fig 8 Effect of catalyst concentration on photoelectrocatalytic China Academic Journal Electronic Publishing House All rights reserved

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