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Gao Y.-Q.,Tongji University | Gao N.-Y.,Tongji University | Deng Y.,Montclair State University | Gu J.-S.,Shanghai Urban Construction Investment Development Corporation | And 2 more authors.
Water Environment Research | Year: 2012

Adsorption of microcystin-LR (MC-LR) from water using iron oxide (α-Fe2O3) nanoparticles was investigated in this study. Adsorption of MC-LR adsorption was well-described by a pseudo second order kinetics model and Freundlich and Langmuir isotherm equations at 15 to 35°C. Thermodynamic analysis showed that the Gibbs free energy was negative, whereas standard enthalpy and entropy changes were positive at this temperature range. These findings suggest that the adsorption of MC-LR on iron oxide nanoparticles was spontaneous and endothermic. The effects of initial pH, inorganic cations, and competing compounds with carboxyl groups on absorption of MC-LR were also evaluated. Typically, adsorption efficiency decreased with increasing pH from 2 to 11. Sodium ions did not appear to significantly affect MC-LR adsorption, whereas calcium ions slightly enhanced the MC-LR adsorption capacity of the iron oxide nanoparticles. Moreover, the inhibiting effect of competing organic compounds was increased with increasing numbers of carboxyl groups, as follows: citric acid (3) > oxalic acid (2) > benzoic acid (1). Source


Gao Y.-Q.,Tongji University | Gao N.-Y.,Tongji University | Deng Y.,Montclair State University | Gu J.-S.,Shanghai Urban Construction Investment Development Corporation | And 2 more authors.
Ultrasonics Sonochemistry | Year: 2013

In this study, the major factors affecting sonolytic degradation of sulfamethazine (SMT), a typical pharmaceutically active compound, in water were evaluated. The factors tested included two operational parameters (i.e. initial SMT concentration and ultrasonic power), three dissolved gases (i.e. Ar, O 2 and N2), five most frequently found anions in water (NO3-,Cl-,SO42-,HCO3-andBr-), ferrous ion (Fe 2+), and four alcohols (methanol, ethanol, isopropyl alcohol, tert-butyl alcohol). Typically, the degradation rate was increased with the increasing initial SMT concentration and power. The degradation rate was accelerated in the presence of argon or oxygen, but inhibited by nitrogen. Effects of anions on the ultrasonic treatment were species-dependent. The SMT degradation rate was slightly inhibited by NO3-,Cl-,and,SO42- but significantly improved by HCO3-andBr-. The negative effects of alcohols acted as hydroxyl radicals scavengers with the following order: tert-butyl alcohol > isopropyl alcohol > ethanol > methanol. The synergetic effect of ferrous ion was mainly due to production of additional hydroxyl radicals (·OH) through Fenton chemistry. LC/MS/MS analysis indicated that the degradation of SMT by ultrasonic irradiation is mainly ascribed to ·OH oxidation. Of interest, although the SMT could be rapidly degraded by ultrasonic irradiation, the degradation products were rarely mineralized. For example, ∼100% of 180 μM SMT was decomposed, but only 8.31% TOC was reduced, within 2 h at an irradiation frequency of 800 kHz and a power of 100 W. However, the products became much biodegradable (BOD 5/COD was increased from 0.04 to 0.45). Therefore, an aerobic biological treatment may be an appropriate post-treatment to further decompose the SMT degradation products. © 2013 Elsevier B.V. All rights reserved. Source

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