Journal of Central South University (Science and Technology) Aug. 2010

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1 41 4 ( ) Vol.41 No Journal of Central South University (Science and Technology) Aug EDTA ( ) OH EDTA ph OH EDTA CO2 H2O NH3 ph ml/min S/m 200 ma 1h (TOC) 96.40% 50 TOC 90% X703.1 O646.5 A (2010) Electrochemical degradation of organic wastewater containing EDTA with three-dimensional electrode reactor CHAI Li-yuan, YOU Xiang-yu, SHU Yu-de, YANG Jie, WANG Yun-yan, ZHAO Na (School of Metallurgical Science and Engineering, Central South University, Changsha , China) Abstract: The electrochemical degradation of organic wastewater containing EDTA was investigated using a novel three-dimensional electrode reactor. The results show that using activated carbon as particle electrode, EDTA in organic wastewater can be efficiently removed by OH radicals produced in the reactor, while its removal efficiency is significantly dependent on current, electric conductivity and ph of the wastewater. EDTA is firstly degraded into primary amine during the action of OH radicals, then mineralized into CO2, H2O andnh3. The removal efficiency of total organic carbon (TOC) is 96.40% at 200 ma, 0.15 S/m of electric conductivity, 1 h of electrolysis time, 25, 200 ml/min of influent flow rate, ph 6.0. The removal efficiency of TOC maintains 90% when it is circulated times is 50. Key words: three-dimensional electrode; electro-catalytic oxidation; organic wastewater; OH radical; EDTA-2Na (Advanced oxidation processes) OH [1] OH [2] [3] OH [4] [5] (2009ZX ) ( ) ( ) (2008FJ1013) (1975 ), wyy@mail.csu.edu.cn

2 4 EDTA 1241 [6 7] [8 9] [10 12] [13] EDTA EDTA EDTA ( ) 2 5cm 10 cm ( 830~2 360 µm) 5cm 5cm 10 cm PVC 1 1mm PVC 0.5 cm 5cm DF1797B ~80 V 0~2.5 A 1.2 TOC-VCPH ( ) (TOC) 200 mg/l ph PHS-3B ph ( ) DDS-307 ( ) NEXUS670 ( Nicolet ) TOC η m0 m t η = m 100% (1) m0 TOC mt t TOC g 500 ml TOC Fig.1 Schematic diagram of a three-dimensional electrode reactor EDTA

3 1242 ( ) 41 EDTA 3 TOC 86.79% 4 TOC 86.79% 50% TOC 95% [14] O2 H2O OH +H + +e (2) 2 EDTA Fig.2 Effect of temperature on adsorption capacity of EDTA adsorbed using activated carbon ph ma 500 ml 2h TOC 3 I=100 ma, σ =0.20 S/m, t =1 h, θ=25, v =200 ml/min, ph =8.0 3 TOC Fig.3 Effect of used times of activated carbon on TOC removal efficiency OH O +H + +e (3) 2O O2 (4) (2) OH OH +e (5) OH +OH O +H2O+e (6) 2O O2 (7) (6) (5) (2) (5) 2.80 V ( 4) 3000~3500cm cm 1 N H cm 1 N H cm 1 N H [15] NH3 EDTA EDTA R3N( ) R2NH( ) H2NR( ) NH4 + +HOOC COOH CO2+H2O+ NH3 Gilbert [16] EDTA

4 4 EDTA 1243 I =100 ma, σ =0.20 S/m, t =1 h, θ=25, v=200 ml/min, ph =8.0 4 Fig.4 Infrared spectrum of activated carbon after electrolysis reaction Na2SO S/m 0.15 S/m 60 min 94.71% 0.40 S/m 60 min 84.03% 0.15 S/m [17] ml TOC 5 5 TOC 200 ml/min 20% 275 ml/min 25% 200 ml/min I =100 ma, t =1 h, θ=25, v=200 ml/min, ph =8.0 σ/(s m 1 ): ; ; ; TOC Fig.6 Effect of electric conductivity on TOC removal efficiency I =100 ma, σ =0.20 S/m, t =1 h, θ=25, ph =8.0 v/(ml min 1 ): 1 125; 2 200; TOC Fig.5 Effect of influent flow on TOC removal efficiency ma 60 min 96.40% 500~800 ma 60 min 92% 1100mA 60 min 75.22% TOC 200~800 ma TOC (ph=9.0) (6) (5) EDTA TOC 1100mA (5) (6)

5 1244 TOC σ =0.20 S/m, t =1 h, θ=25, v=200 ml/min, ph =8.0 I/mA: 1 200; 2 500; 3 800; TOC Fig.7 Effect of current on TOC removal efficiency ph ph TOC 8 8 ph 4~11 TOC 85%~90% ph 3 TOC 80% 40% ph 3 Tafel RT [18] 2 (2) F (3) (4) 8 ph 11 TOC RT ph Tafel [18] 2 F ( ) 41 (5) (6) (7) EDTA ph 3~7 (3) ph 7~10 (6) ph 3~10 TOC TOC 9 9 TOC TOC min TOC 95.26% min TOC 77.48% 25 Tafel [18] 1 RT (7) (5) (6) 4 F EDTA 8 45 EDTA 45 (7) I =100 ma, σ =0.20 S/m, t =1 h, v =200 ml/min, ph =8.0 θ/ :1 25; 2 35; 3 45; TOC Fig.9 Effect of inlet water temperature on TOC removal efficiency I =100 ma, σ =2.0 ms/cm, t =1 h, θ=25, V =200 ml/min ph: 1 6; 2 9; 3 12; ph TOC Fig.8 Effect of inlet water ph on TOC removal efficiency 3 (1) TOC 90%

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