Chemical reduction of an unbuffered nitrate solution using catalyzed and uncatalyzed nanoscale iron particles.
Uncatalyzed and catalyzed nanoscale Fe(0) systems were employed for the denitrification of unbuffered 40 mgN L(-1) nitrate solutions at initial neutral pH. Compared to microscale Fe(0) (<100 mesh), the efficiency and rate of nitrate removal using uncatalyzed and catalyzed nano-Fe(0) were highly promoted, in which the maximum promoted rate was obtained using copper-catalyzed nano-Fe(0) (nano-Cu/Fe). Nitrate first-order degradation rate constants (k(obs)) decreased significantly (>70%) with aged nano-Fe(0) and aged nano-Cu/Fe, and were recovered with NaBH(4) as reductants at levels of about 85 and 75%, respectively. Activation energies (E(a)) of nitrate reduction over the temperature range of 10-60 degrees C were 42.5 kJ mol(-1) for microscale Fe(0), 25.8 kJ mol(-1) for nano-Fe(0) and 16.8 kJ mol(-1) for nano-Cu/Fe. Unlike microscale Fe(0), the kinetics of denitrification by nano-Fe(0) and nano-Cu/Fe began to show characteristics of mass transport in addition to chemical reaction control. Ammonium was the predominant end product in all the systems. However, as for nitrite, 40% of the degraded nitrate persisted in the nano-Cu/Fe system. Thus, relative to nano-Cu/Fe, nano-Fe(0) is a potential reductant for denitrification of groundwater as far as toxic nitrite generation is concern.
Liou
Ya Hsuan
YH
Research Center for Environmental Pollution Prevention and Control Technology, Graduate Institute of Environmental Engineering, National Taiwan University, Taipei.
Lo
Shang-Lien
SL
Lin
Chin-Jung
CJ
Kuan
Wen Hui
WH
Weng
Shih Chi
SC
D000327:Adsorption; D002021:Buffers; D003300:Copper; D007220:Industrial Waste; D007501:Iron; D049329:Nanostructures; D009566:Nitrates / Q000032:analysis; D009573:Nitrites / Q000032:analysis; D013696:Temperature; D014874:Water Pollutants, Chemical
D002021:Buffers; D007220:Industrial Waste; D009566:Nitrates; D009573:Nitrites; D014874:Water Pollutants, Chemical; D003300:Copper; D007501:Iron