The role of clay minerals in the reduction of nitrate in groundwater by zero-valent iron.
Bench-scale batch experiments were performed to investigate the feasibility of using different types of clay minerals (bentonite, fuller's earth, and biotite) with zero-valent iron for their potential utility in enhancing nitrate reduction and ammonium control. Kinetics experiments performed with deionized water (DW) and groundwater (GW) revealed nitrate reduction by Fe(0) proceeded at significantly faster rate in GW than in DW, and such a difference was attributed to the formation of green rust in GW. The amendment of the minerals at the dose of 25 g L(-1) in Fe(0) reaction in GW resulted in approximately 41%, 43%, and 33% more removal of nitrate in 64 h reaction for bentonite, fuller's earth, and biotite, respectively, compared to Fe(0) alone reaction. The presumed role of the minerals in the rate enhancement was to provide sites for the formation of surface bound green rust. Bentonite and fuller's earth also effectively removed ammonium produced from nitrate reduction by adsorption, with the removal efficiencies significantly increased with the increase in mineral dose above 5:1 Fe(0) to mineral mass ratio. Such a removal of ammonium was not observed for biotite, presumably due to its lack of swelling property. Equilibrium adsorption experiments indicated bentonite and fuller's earth had maximum ammonium adsorption capacity of 5.6 and 2.1 mg g(-1), respectively.
Cho
Dong-Wan
DW
Department of Environmental Engineering, Yonsei University, Wonju, Gangwon-do 220-710, South Korea.
Chon
Chul-Min
CM
Jeon
Byong-Hun
BH
Kim
Yongje
Y
Khan
Moonis Ali
MA
Song
Hocheol
H
D000538:Aluminum Silicates / Q000737:chemistry*; D000077215:Clay; D052918:Environmental Restoration and Remediation / Q000379:methods*; D007501:Iron / Q000737:chemistry*; D009566:Nitrates / Q000032:analysis / Q000737:chemistry*; D000644:Quaternary Ammonium Compounds / Q000032:analysis / Q000737:chemistry; D014874:Water Pollutants, Chemical / Q000032:analysis / Q000737:chemistry*
D000538:Aluminum Silicates; D009566:Nitrates; D000644:Quaternary Ammonium Compounds; D014874:Water Pollutants, Chemical; D007501:Iron; D000077215:Clay