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.
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ABSTRACT: The aim of the present work was to study the Pb(II) ions adsorption by entrapped silica nanopowders within calcium alginate to determine the isotherm, kinetic and thermodynamic of the adsorption process. According to the results, an optimal initial pH of 5.0 was found for the Pb(II) adsorption. The adsorbed Pb(II) ions reached to 36.51 mg/g as the contact time increased to 180 min at an initial Pb(II) concentration of 50 mg/L. However, a contact time of 90 min was selected as equilibrium time because of no significant increase in Pb(II) adsorption after this time. The results of isotherm and kinetic studies showed the Langmuir isotherm and pseudo-second order kinetic model were the best fitted models (R2 > 0.999). The maximum adsorption capacity for Pb(II) adsorption onto entrapped silica nanopowders was estimated to be 83.33 mg/g. According to the Dubinin–Radushkevich (D–R) isotherm model, Pb(II) adsorption onto the composite follows a chemical mechanism (E = 10 kJ/mol). Negative ΔG° and ΔH° values indicated spontaneous and exothermic nature of the Pb(II) adsorption onto entrapped silica nanopowders, respectively. In addition, the results of continuous flow mode study exhibited that increasing empty-bed contact time (EBCT) from 5 to 20 min resulted in increasing the specific throughput (St) from 8.42 to 11.22 mL/g, respectively.Journal of the Taiwan Institute of Chemical Engineers 01/2014; 45(3):973–980. · 2.64 Impact Factor
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ABSTRACT: Abstract The effect of non-functionalized and amino-functionalized multiwall carbon nanotube (CNT) exposure, as well as the impact of CNT presence on coexistent pesticide accumulation, was investigated in lettuce (Lactuca sativa L.). Lettuce seeds were sown directly into CNT-amended vermiculite (1000 mg L(-1)) to monitor phytotoxicity during germination and growth. During growth, lettuce seedlings were subsequently exposed to chlordane (cis-chlordane [CS], trans-chlordane [TC] and trans-nonachlor [TN]) and p,p'-DDE (all at 100 ng/L) in the irrigation solution for a 19-d growth period. CNT exposure did not significantly influence seed germination (82-96%) or plant growth. Similarly, pesticide exposure had no impact on plant growth, total pigment production or tissue lipid peroxidation. After 19 d, the root content of total chlordane and p,p'-DDE was 390 and 73.8 µg g(-1), respectively; in plants not exposed to CNTs, the shoot levels were 1.58 and 0.40 µg g(-1), respectively. The presence and type of CNT significantly influenced pesticide availability to lettuce seedlings. Non-functionalized CNT decreased the root and shoot pesticide content by 88% and 78%, respectively, but amino-functionalized CNT effects were significantly more modest, with decreases of 57% in the roots and 23% in the shoots, respectively. The presence of humic acid completely reversed the reduced accumulation of pesticides induced by amino-functionalized CNT, likely due to strong competition over adsorption sites on the nanomaterial (NM). These findings have implications for food safety and for the use of engineered NMs in agriculture, especially with leafy vegetables.Nanotoxicology 04/2014; · 7.84 Impact Factor
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ABSTRACT: Atrazine is one of the most heavily used herbicide worldwide. Atrazine has been detected in ground and surface waters in many countries beyond permissible limits due to its low vapor pressure, long persistence, and low biodegradability. This study aims to develop a bacterial biomass which can be used as biosorbent to remove the atrazine from waters easily and cost-effectively. Here, fourteen bacterial strains were isolated from soil having the history of atrazine contamination and batch experiments were carried with biosorbents prepared from various bacterial isolates. The biosorbent BS-1 developed from strain C1 was found be the best for the removal of atrazine.Clean Technologies and Environmental Policy 01/2013; · 1.83 Impact Factor