Effects of natural water ions and humic acid on catalytic nitrate reduction kinetics using an alumina supported Pd-Cu catalyst.
Catalytic nitrate reduction was evaluated for the purpose of drinking water treatment. Common anions present in natural waters and humic acid were evaluated for their effects on NO3(-) hydrogenation over a bimetallic supported catalyst (Pd-Cu/gamma-Al2O3). Groundwater samples, with and without powder activated carbon (PAC) pretreatment, were also evaluated. In the absence of inhibitors the NO3- reduction rate was 2.4 x 10(-01) L/min g cat. However, the addition of constituents (SO4(2-), SO3(2-), HS-, CI-, HCO3-, OH-, and humic acid) on the order of representative concentrations for drinking water decreased the NO3- reduction rate. Sulfite, sulfide, and elevated chloride decreased the NO3- reduction rate by over 2 orders of magnitude. Preferential adsorption of Cl- inhibited NO3- reduction to a greater extent than NO2- reduction. Partial regeneration of catalysts exposed to SO3(2-) was achieved by using a dilute hypochlorite solution, however Cu dissolution occurred. Dissolved constituents in the groundwater sample decreased the NO3- reduction rate to 3.7 x 10(-03) L/min g cat and increased ammonia production. Removal of dissolved organic matter from the groundwater using PAC increased the NO3- reduction rate to 5.06 x 10(-02) L/min g cat and decreased ammonia production. Elemental analyses of catalysts exposed to the natural groundwater suggest that mineral precipitation may also contribute to catalyst fouling.
Chaplin
Brian P
BP
Department of Civil and Environmental Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA.
Roundy
Eric
E
Guy
Kathryn A
KA
Shapley
John R
JR
Werth
Charles J
CJ
D000535:Aluminum / Q000032:analysis*; D002384:Catalysis; D003300:Copper / Q000032:analysis*; D004777:Environment; D006812:Humic Substances / Q000032:analysis*; D007477:Ions; D007700:Kinetics; D007854:Lead / Q000032:analysis*; D009566:Nitrates / Q000032:analysis*; D013440:Sulfides / Q000737:chemistry; D014865:Waste Disposal, Fluid; D014874:Water Pollutants, Chemical; D014881:Water Supply
D006812:Humic Substances; D007477:Ions; D009566:Nitrates; D013440:Sulfides; D014874:Water Pollutants, Chemical; D007854:Lead; D003300:Copper; D000535:Aluminum