Sorption of atrazine onto humic acids (HAs) coated nanoparticles
ABSTRACT With the development of nanotechnologies, a large number of nano-materials with novel properties are being released into the environment. However, little is known about their fate, transport, toxicity and interactions with organic matters in aqueous environment. In this study, nano-SiO2 or kaolinite, coated with soil humic acid (SHA) and peat humic acid (PHA), were used as sorbents. The original and HA-coated nanoparticles were characterized for particle size, TEM and electrophoretic mobility. Sequential ultrafiltration (UF) was used to characterize the molecular size fractionations of dissolved HAs. Sorption data of atrazine (AT) under various solution concentration, ionic strength and pH were well fitted with Freundlich model. Sorption amount of AT on HA-coated nanoparticles was significantly lower than that on original particles. The sorption maximum appeared at I = 0.001 mol/l (NaNO3), pH 3. Size of nanoparticle aggregates, conformation of HA and specific surface area were factors affecting the sorption process. The compressed conformation of HA was more favorable for HA sorption than expanded one. Size of aggregation was not a determinant factor for the sorption process, while the specific surface areas of nano-sorbent was an important one. Results indicated that HA plays an important role in the transport and toxicity of nanoparticles and AT in aqueous environment.
- SourceAvailable from: Dong-Mei Zhou[show abstract] [hide abstract]
ABSTRACT: Transformation of polychlorinated biphenyls (PCBs) by zero-valent iron represents one of the latest innovative technologies for environmental remediation. The dechlorination of 4-chlorobiphenyl (4-ClBP) by nanoscale zero-valent iron (NZVI) in the presence of humic acid or metal ions was investigated. The results showed that the dechlorination of 4-ClBP by NZVI increased with decreased solution pH. When the initial pH value was 4.0, 5.5, 6.8, and 9.0, the dechlorination efficiencies of 4-ClBP after 48 hr were 53.8%, 47.8%, 35.7%, and 35.6%, respectively. The presence of humic acid inhibited the reduction of 4-ClBP in the first 4 hr, and then significantly accelerated the dechlorination by reaching 86.3% in 48 hr. Divalent metal ions, Co2+, Cu2+, and Ni2+, were reduced and formed bimetals with NZVI, thereby enhanced the dechlorination of 4-ClBP. The dechlorination percentages of 4-ClBP in the presence of 0.1 mmol/L Co2+, Cu2+ and Ni2+ were 66.1%, 66.0% and 64.6% in 48 hr, and then increased to 67.9%, 71.3% and 73.5%, after 96 hr respectively. The dechlorination kinetics of 4-ClBP by the NZVI in all cases followed pseudo-first order model. The results provide a basis for better understanding of the dechlorination mechanisms of PCBs in real environment.Journal of Environmental Sciences 01/2011; 23(8):1286-92. · 1.77 Impact Factor
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ABSTRACT: The aggregation and dispersion behaviors of carbon nanotubes (CNTs) can regulate the environmental spread and fate of CNTs, as well as the organic pollutants adsorbed onto them. In this study, multi-walled carbon nanotubes (MWNTs) and single-walled carbon nanotubes (SWNTs) were surface modified with humic acids from different sources and with surfactants of different ionic types. The dispersion stability of surface modified CNTs was observed by UV-Vis spectrophotometry. The effect of humic acid and surfactant dispersion on the adsorption of atrazine by CNTs was investigated by batch equilibrium experiments. Both humic acid and surfactant could effectively disperse MWNTs, but not SWNTs, into stable suspensions under the studied conditions. Surface modified CNTs had a greatly reduced capacity for adsorption of atrazine. The inhibitory effect of peat humic acid was relatively stronger than that of soil humic acid, but the two surfactants had a similar inhibitory effect on atrazine adsorption by the two CNT types. Increases in surfactant concentration resulted in rapid decreases in the adsorption of atrazine by CNTs when the surfactant concentration was less than 0.5 critical micelle concentration.Journal of Environmental Sciences 01/2010; 22(8):1195-202. · 1.77 Impact Factor
Conference Proceeding: Replacement trim system for the DSVs Sea Cliff and Turtle[show abstract] [hide abstract]
ABSTRACT: Battelle has developed a new method for the active trim or list control of undersea vehicles, using small spheres of tungsten alloy, shifted hydraulically between coils of stainless steel tubing at either end of the vehicle. This system is being developed for installation in the DSV-4 Sea Cliff in the fall of 1996, and subsequently in DSV Turtle. It will replace the traditional mercury trim systems (commonly found in many other undersea vehicles as well), which pose potential health risks to the operations staff, and pollution risks to the environmentOCEANS '95. MTS/IEEE. Challenges of Our Changing Global Environment. Conference Proceedings.; 11/1995