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Zhang Z.,Zhejiang University | Hao Z.,Zhejiang University | Yang Y.,Zhejiang University | Yang Y.,Zhejiang Chimey Environment Science and Technology Co. | And 3 more authors.
Desalination | Year: 2010

The objective of this current work was to investigate different factors that may affect the denitrification of nitrite in the presence of Fe0 and the denitrification kinetics. Our results show that nitrite can be effectively reduced to innocuous N2 gas and NH4 + by Fe0, no other intermediates were generated during the denitrification of NO2 -. The reduction efficiency of nitrite decreased quickly with increasing initial pH value, increased considerably with increasing temperature, and did not vary much at initial concentrations ranging from 20 to 50 mg L- 1 when the excessive amount of Fe0 is utilized, but it decreased rapidly to 0.0448 min- 1 when the initial nitrite concentration was 100 mg L- 1. The experimental data fit well to a pseudo-first-order model. The kobs changed from 0.0722 to 0.0731 min- 1 when the concentration of nitrite increased from 20 to 50 mg L- 1 in this experiment with a Fe dosage of 10 g L- 1. A larger Fe dosage led to the increase of kobs as the denitrification of nitrite by Fe0 involved reductive reactions on metal surface. The activation energy of nitrite reductive denitrification by Fe0 is determined to be 42.7 kJ mol- 1 in the temperature range between 278 and 308 K. © 2010 Elsevier B.V. All rights reserved.


Zhang J.,Zhejiang University | Hao Z.,Zhejiang University | Zhang Z.,Zhejiang University | Zhang Z.,Taizhou University | And 3 more authors.
Process Safety and Environmental Protection | Year: 2010

Nanoscale zero-valent iron (Fe0) was synthesized for nitrate denitrification. The reduction efficiency of nitrate decreased quickly with increasing initial pH value, increased considerably with the increasing dosage of nanoscale Fe0, and did not vary much with initial nitrate concentrations changing from 20 to 50 mg l-1 when the excessive amount of nanoscale Fe0 was utilized. With reductive denitrification of nitrate by nanoscale Fe0, the removal rate of nitrate reached 96.4% in 30 min with nanoscale Fe0 dosage of 1.0 g l-1 and pHin 6.7, and more than 85% of the nitrate was transformed into ammonia. Kinetics analysis in batch studies demonstrates that the denitrification of nitrate by nanoscale Fe0 involves reaction on the metal surface, which fits well the pseudo-first order reaction with respect to nitrate concentration. The observed reaction rate constant of reductive denitrification of nitrate was determined to be 0.086 min-1 with a nanoscale Fe0 dosage of 1.0 g l-1 and pHin 6.7. Fast and highly effective denitrification can be achieved by nanoscale Fe 0 compared with commercial Fe0 powder, this is due to the extremely high surface area and high reactivity for nanoscale Fe0, which can enhance the denitrification efficiencies remarkably. © 2010 The Institution of Chemical Engineers.


Wang Q.,Zhejiang University | Qian H.,Zhejiang University | Yang Y.,Zhejiang University | Yang Y.,Zhejiang Chimey Environment Science and Technology Co. | And 3 more authors.
Journal of Contaminant Hydrology | Year: 2010

The reduction of hexavalent chromium or Cr(VI) by zero-valent iron (Fe0) nanoparticles has received increasing attention in recent years. However, Fe0 nanoparticles prepared using conventional methods suffered several drawbacks due to their high reactivity towards surrounding media, which led to the formation of much larger flocs and significant loss in reactivity. To overcome these problems, we synthesized Fe0 nanoparticles by applying water-soluble carboxymethyl cellulose (CMC) as a stabilizer. CMC-stabilized Fe0 nanoparticles displayed much less agglomeration but greater Cr(VI) reduced power than those prepared without a stabilizer. At a dose of 0.15 g L-1, CMC-stabilized Fe0 nanoparticles were able to reduce 100% of 10 mg L-1 Cr(VI) in minutes. Several factors that may affect the efficiency of Cr(VI) removal were investigated. These included the concentration of CMC, the concentration of Fe0 nanoparticles, the initial Cr(VI) concentration, the pH value, the reaction temperature and the concentration of the calcium cation in the reaction mixture. Our study suggested that the introduction of an innocuous stabilizer such as CMC could significantly improve the performance of Fe0 nanoparticles for environmental remediation applications. © 2010 Elsevier B.V. All rights reserved.


Xu J.,Zhejiang University | Hao Z.,Zhejiang University | Xie C.,Zhejiang University | Lv X.,Zhejiang University | And 3 more authors.
Desalination | Year: 2012

The reductive efficiency of nitrate by zero-valent iron (Fe 0) was increased under initial neutral conditions through addition of certain amount of Fe 2+. Throughout the process, the NO 3 - and Fe 2+ concentrations displayed a declining trend, but the general process was divided into three stages. It showed that Fe 2+ could accelerate the corrosion of iron surface, accompanied by generating Fe 3O 4, and ionizing H + which played an important role in buffering pH of the system. Fe 3O 4 behaved as a good conductor which favored the electron transfer on iron surface and accelerated the reductive denitrification rate of nitrate with Fe 0 and Fe 2+. © 2011 Elsevier B.V..


Fu H.,Zhejiang University | Fu H.,Zhejiang Provincial Environmental Pollution Control Technology Key Laboratory | Lv X.,Zhejiang University | Yang Y.,Zhejiang University | And 3 more authors.
Desalination and Water Treatment | Year: 2012

In this article, DTC-S, a kind of heavy metal capturing agent, was chosen to evaluate the removal effects of complex copper solutions. The complex copper was 5.0 mg/l. The Cu(II)-NH3 was easily removed due to its similarity of free Cu2+ in aqueous solution, and the suitable conditions were initial pH 9.0, 20 mg/l DTC-S and one hour's precipitation. The Cu(II)-EDTA and Cu(II)-Cit were more stable due to their ligands. To reach the standard, the optimal dosage of DTC-S was doubled, and the initial pH was adjusted between 9.5-11.5. The removal rate slightly decreased when external metal ions existed in Cu(II)-EDTA solution. Infrared spectra and SEM micrographs showed the DTC-S was a dithiocarbamate compound, whose functional groups could chelate copper ions in copper complexations. © 2012 Desalination Publications.

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