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ผู้เขียน หัวข้อ: A device that converts aqueous ammonia into nitrogen gas  (อ่าน 2755 ครั้ง)
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« เมื่อ: พฤษภาคม 02, 2014, 02:28:55 PM »

A device that converts aqueous ammonia into nitrogen gas


Ramsey Kropp a, Dean Tompkins c,d, Timothy Barry c,d, Walter Zeltner d,
Greg Pepping a,1, Marc Anderson a,d, Terence Barry b,d,*
a Environmental Chemistry and Technology Program, University of Wisconsin - Madison, 660 N. Park St., Madison, WI 53706, United States
b Department of Animal Sciences, Aquaculture Research Laboratory, University of Wisconsin - Madison, 660 N. Park St., Madison, WI 53706, United States
c Water Science and Engineering Laboratory, University of Wisconsin - Madison, 660 N. Park St., Madison, WI 53706, United States
d AquaMost, LLC, 5519 Sedgemeadow Road, Middleton, WI 53562, United States2


A B S T R A C T

A photoelectrocatalytic oxidation (PECO)3 device was developed for converting aqueous ammonia into nitrogen gas. The device uses a germicidal UV lamp to activate a titania (TiO2)-coated anode (photoanode) that is connected to a titanium or platinum wire cathode to form an electrolytic cell. When a small bias (2 V DC) was applied between the anode and cathode, ammonia (3 oxidation state) was oxidized primarily into nitrogen gas (0 oxidation state) rather than nitrite (+3 oxidation state) or nitrate (+5 oxidation state). The ammonia oxidation rate changed as a function of the crystalline structure of the
titania coating on the anode, the salinity of the water, the applied voltage, and the disruption of boundary layers near the photoanode surface. There was no ammonia removal in water without at least some NaCl in solution, suggesting that the device works by converting chloride ions into chlorine and hypochlorous acid, which then react with ammonia to form nitrogen gas. Varying the pH between pH = 5 and pH = 10 had no effect on the rate of ammonia removal. A continuous flow-through PECO reactor was tested using aquariums spiked with ammonium chloride or stocked with seawater-adapted tilapia fed a high protein diet, and found to effectively remove ammonia and limit nitrite and nitrate accumulation in the tanks.

Keywords:Ammonia, Titanium dioxide, Photoelectrocatalytic oxidation, Recirculation aquaculture, Aquaculture, Aquarium, Biofiltration, Nitrate, Nitrite
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