Removal of EDTA from low pH printed-circuit board wastewater in a fluidized zero valent iron reactor.
Fluidized zero valent iron (ZVI) process was adopted to reduce ethylenediaminetetraacetic acid (EDTA) from low pH printed-circuit board (PCB) wastewater for two reasons: (1) low pH of the wastewater favoring the ZVI reaction; (2) higher ZVI utilization for fluidized process due to abrasive motion of the ZVI. The results showed that the degradation of EDTA was greatly enhanced under acidic pH, longer hydraulic detention time (HRT) and presence of dissolved oxygen (DO). Without addition of oxygen, 65% of EDTA was removed with capacity of 7.33 mg EDTA/g ZVI at pH 2, ZVI dosage of 424 g/L and HRT 10 min. With 6.8 mg/L of DO, 83% of EDTA was reduced with capacity of 19.01 mg EDTA/g ZVI for the same experimental condition. The presence of oxygen/ZVI initiated a Fenton type reaction to reduce EDTA. The end product after EDTA degradation was analyzed by high performance liquid chromoagraphy (HPLC), where propionic acid (C(2)H(5)COOH) was observed, indicating EDTA (oxidation number for carbon is 2) was oxidized to propionic acid (oxidation number for carbon is 3). Nitrogen species was also measured and the nitrogen in EDTA was converted to ammonium instead of nitrate and nitrite.
Chen
Shiao-Shing
SS
Institute of Environmental Engineering and Management, National Taipei University of Technology, No. 1, Sec. 3, Chung-Hsiao E. Rd, Taipei 106, Taiwan. f10919@ntut.edu.tw
Hsu
Hong-Der
HD
Lin
Yi-Jiun
YJ
Chin
Pei-Ying
PY
D000641:Ammonia / Q000737:chemistry / Q000302:isolation & purification; D019149:Bioreactors; D004492:Edetic Acid / Q000737:chemistry* / Q000302:isolation & purification; D004563:Electrochemistry; D006863:Hydrogen-Ion Concentration; D007501:Iron / Q000737:chemistry*; D014865:Waste Disposal, Fluid / Q000295:instrumentation / Q000379:methods*
D000641:Ammonia; D004492:Edetic Acid; D007501:Iron