Transport and retention of zinc oxide nanoparticles in porous media: effects of natural organic matter versus natural organic ligands at circumneutral pH.
The potential toxicity of nanoparticles (NPs) has received considerable attention, but there is little knowledge relating to the fate and transport of engineered ZnO NPs in the environment. Column experiments were performed at pH 7.3-7.6 to generate effluent concentrations and retention profiles for assessing the fate and transport of ZnO NPs (PZC=9.3, nominal size 20 nm) in saturated quartz sands (256 μm) in the presence of low natural organic matter (NOM) concentrations (1 mg/L humic and fulvic acids) and millimolar natural organic ligands (NOL) levels (formic, oxalic, and citric acids). At circumneutral pHs, ZnO NPs were positively charged and immobile in sand. The presence of NOM decreased the attachment efficiency facilitating ZnO transport through sand columns. Conversely, ZnO transport in the presence of formic and oxalic acids was only slightly improved when compared to ZnO in DI water; whereas, citric acid showed no improvement. The distinct difference between NOM and NOL may have important implications with regard to ZnO transport in the subsurface environment. Experimental results suggested the presence of both favorable and unfavorable nanoparticle interactions causes significant deviations from classical colloid filtration theory (CFT).
Ground Water and Ecosystems Restoration Division, National Risk Management Research Laboratory, Office of Research and Development, United States Environmental Protection Agency, 919 Kerr Research Drive, Ada, OK 74820, USA. Electronic address: edwdjones@hotmail.com.
Edward H
EH
Jones
Ground Water and Ecosystems Restoration Division, National Risk Management Research Laboratory, Office of Research and Development, United States Environmental Protection Agency, 919 Kerr Research Drive, Ada, OK 74820, USA.
Chunming
C
Su
D001578:Benzopyrans / Q000737:chemistry; D019343:Citric Acid / Q000737:chemistry; D005374:Filtration; D005561:Formates / Q000737:chemistry; D006812:Humic Substances; D006863:Hydrogen-Ion Concentration; D008024:Ligands; D046529:Microscopy, Electron, Transmission; D053758:Nanoparticles / Q000032:analysis* / Q000737:chemistry / Q000648:ultrastructure; D019815:Oxalic Acid / Q000737:chemistry; D010316:Particle Size; D016062:Porosity; D011791:Quartz; D014874:Water Pollutants, Chemical / Q000032:analysis* / Q000737:chemistry; D015034:Zinc Oxide / Q000032:analysis* / Q000737:chemistry
D001578:Benzopyrans; D005561:Formates; D006812:Humic Substances; D008024:Ligands; D014874:Water Pollutants, Chemical; C030544:formic acid; D011791:Quartz; D019343:Citric Acid; D019815:Oxalic Acid; D015034:Zinc Oxide; C005023:fulvic acid
Fate and transport; Nanoparticles; Natural organic ligands; Natural organic matter; Zinc oxide