title: Chemical reduction of an unbuffered nitrate solution using catalyzed and uncatalyzed nanoscale iron particles.
abstract: 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.
authors.affiliation: Research Center for Environmental Pollution Prevention and Control Technology, Graduate Institute of Environmental Engineering, National Taiwan University, Taipei.
authors.forename: Ya Hsuan
authors.initials: YH
authors.lastname: Liou
authors.forename: Shang-Lien
authors.initials: SL
authors.lastname: Lo
authors.forename: Chin-Jung
authors.initials: CJ
authors.lastname: Lin
authors.forename: Wen Hui
authors.initials: WH
authors.lastname: Kuan
authors.forename: Shih Chi
authors.initials: SC
authors.lastname: Weng
mesh_terms: 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
chemical_list: D002021:Buffers; D007220:Industrial Waste; D009566:Nitrates; D009573:Nitrites; D014874:Water Pollutants, Chemical; D003300:Copper; D007501:Iron