scholarly journals Single and combined removal of Cr(VI) and Cd(II) by nanoscale zero-valent iron in the absence and presence of EDDS

2017 ◽  
Vol 76 (5) ◽  
pp. 1261-1271 ◽  
Author(s):  
Haoran Dong ◽  
Yalan Zeng ◽  
Yankai Xie ◽  
Qi He ◽  
Feng Zhao ◽  
...  
Keyword(s):  
Dissolved Oxygen ◽  
Zero Valent Iron ◽  
Inhibition Effect ◽  
Insignificant Effect ◽  
Removal Process ◽  
Nanoscale Zero Valent Iron ◽  
Effects Of Ph ◽  
Alkaline Conditions ◽  
Acidic Conditions ◽  
Ph Dependent

This study examined the feasibility of nanoscale zero-valent iron (nZVI) for the single and combined removal of Cr(VI) and Cd(II) with or without ethylene diamine disuccinic acid (EDDS). The effects of pH and dissolved oxygen (DO) on the removal process were investigated. Results show that the single removal of either Cr(VI) or Cd(II) by nZVI was pH dependent, where the higher Cr(VI) removal was achieved under acidic conditions, whereas the higher Cd(II) removal was achieved under alkaline conditions. The presence of DO enhanced Cd(II) removal but inhibited Cr(VI) removal under alkaline conditions. In the co-existence of Cr(VI) and Cd(II), it was found that Cd(II) exerted insignificant effect on Cr(VI) removal, while the presence of Cr(VI) remarkably enhanced the Cd(II) removal. The addition of EDDS exhibited different influences on Cr(VI) and Cd(II) removal, which were associated with pH and DO. The EDDS enhanced Cr(VI) removal at pH 5.6–9.0 in the absence of DO, but decreased Cr(VI) removal at pH 9.0 in the presence of DO. For the removal of Cd(II) at pH 5.6–7.0, either facilitation or inhibition effect of EDDS was observed, depending on EDDS concentration and the co-existence of Cr(VI). However, Cd(II) removal was always significantly inhibited by EDDS at pH 9.0.

Dissolved oxygen and nitrate effects on the reduction and removal of divalent mercury by pumice supported nanoscale zero-valent iron

2018 ◽  
Vol 4 (10) ◽  
pp. 1651-1661 ◽  
Author(s):  
Ghulam Hussain Qasim ◽  
Sangwook Lee ◽  
Giehyeon Lee ◽  
Woojin Lee ◽  
Yongseok Hong ◽  
...  
Keyword(s):  
Dissolved Oxygen ◽  
Zero Valent Iron ◽  
Nanoscale Zero Valent Iron

Absence of dissolved oxygen and presence of nitrate in groundwater increases Hg(0) during the Hg(ii) removal using pumice supported nZVI.

Effects of pH on photocatalysis of 2,4,6-trichlorophenol in aqueous TiO2 suspensions

1994 ◽  
Vol 30 (9) ◽  
pp. 47-57 ◽  
Author(s):  
Shuzo Tanaka ◽  
Uttam Kumar Saha
Keyword(s):  
Sodium Chloride ◽  
Degradation Rate ◽  
Parent Compound ◽  
Photocatalytic Decomposition ◽  
Illumination Time ◽  
Effects Of Ph ◽  
Alkaline Conditions ◽  
Na Ions ◽  
Acidic Conditions

The effects of pH on the photocatalytic decomposition of 2,4,6-trichlorophenol (TCP) were investigated in the presence of titanium dioxide suspensions illuminated by a high pressure mercury lamp over the wavelength range of 302-405 nm. Higher degradation rate was observed under alkaline conditions than acidic conditions. Although a rapid adsorption of TCP onto the TiO2 surface was observed at low pH and no adsorption at high pH, the role of adsorption of TCP was found insignificant in photocatalysis. With sodium chloride addition, a decrease in reaction rate was observed at pH 5 due to Cl− ions inhibition, but at pH 10 the same anions had no adverse effect on the measured photocatalytic efficiency and Na+ ions enhanced the degradation rate of TCP. With no oxygen, however, the photocatalytic decomposition of TCP in sodium chloride solution gives lower degradation rate than with dissolved oxygen and no sodium chloride at various pH. Complete mineralization requires a longer illumination time than the decomposition of the parent compound. A mechanism for the reaction based on photogeneration of hydroxyl radicals was proposed.

scholarly journals The Removal of Uranium onto Nanoscale Zero-Valent Iron Particles in Anoxic Batch Systems

2014 ◽  
Vol 2014 ◽  
pp. 1-9 ◽  
Author(s):  
Richard A. Crane ◽  
Thomas B. Scott
Keyword(s):  
Dissolved Oxygen ◽  
Mine Water ◽  
Inductively Coupled Plasma ◽  
Corrosion Behaviour ◽  
Zero Valent Iron ◽  
Iron Particles ◽  
Near Surface ◽  
Batch Systems ◽  
Batch System ◽  
Nanoscale Zero Valent Iron

The removal of uranium (U) onto nanoscale zero-valent iron particles has been studied for uranium-bearing mine water and synthetic uranyl solutions in the presence and absence of dissolved oxygen. The work has been conducted in order to investigate the differential nanoparticle corrosion behaviour and associated mechanisms of U removal behaviour in conditions representative of near-surface and deep groundwater systems. Batch systems were analysed over a 28-day reaction period during which the liquid and nanoparticulate solids were periodically analysed to determine chemical evolution of the solutions and particulates. Analysis of aqueous samples using inductively coupled plasma mass spectrometry recorded near-total U removal after 1 hour of reaction in all systems studied. However, in the latter stages of the reaction (after 48 hours), significant rerelease of uranium was recorded for the mine water batch system with dissolved O2present. In contrast, less than 2% uranium rerelease was recorded for the anoxic batch system. Concurrent analysis of extracted nanoparticle solids using X-ray diffraction recorded significantly slower corrosion of the nanoparticles in the anoxic batch system, with residual metallic iron maintained until after 28 days of reaction compared to only 7 days of reaction in systems with dissolved O2present. Results provide clear evidence that the corrosion lifespan and associated U6+removal efficacy of nanoscale zero-valent iron replace enhanced in the absence of dissolved oxygen.

The decreasing aggregation of nanoscale zero-valent iron induced by trivalent chromium

2017 ◽  
Vol 14 (2) ◽  
pp. 99
Author(s):  
Danlie Jiang ◽  
Xialin Hu ◽  
Rui Wang ◽  
Yujing Wang ◽  
Daqiang Yin
Keyword(s):  
Aquatic Environment ◽  
Groundwater Remediation ◽  
Trivalent Chromium ◽  
Zero Valent Iron ◽  
Environmental Behaviour ◽  
Magnetic Attraction ◽  
Aggregation Behaviour ◽  
Nanoscale Zero Valent Iron ◽  
Magnetite Content ◽  
Acidic Conditions

Environmental contextNanoscale zero-valent iron is a promising material for environmental engineering and groundwater remediation. However, the environmental behaviour and fate of nanoscale iron that is essential for applications and risk assessment is still uncertain. We report a study on the aggregation behaviour and mobility of nanoscale iron in the aquatic environment using colloidal chemical methods. AbstractDespite high magnetisation, nanoscale zero-valent iron (nZVI) exhibits weak aggregation when treating hexavalent chromium (CrVI) (0.02mmol L–1) under anaerobic circumstances, which leads to the enhancement of its mobility in the aquatic environment. To elucidate such an unexpected phenomenon, the influences of different valences of chromium on the aggregation behaviour of nZVI were examined. Results indicate that trivalent chromium (CrIII) greatly decreases the aggregation of nZVI in acidic conditions (pH 5), while little influence is observed at a higher pH (pH 7). We suggest that such influences are mainly a result of precipitation on the surface of nZVI particles, which prevents the formation of chain-like aggregates. Accordingly, although the particles are highly magnetic (magnetite content >70%, saturation magnetisation=363 kA m–1), the magnetic attraction between aggregates and particles is not strong enough to promote further aggregation. Furthermore, the Cr(OH)3 shell blocks collisions between particles and greatly enhances their zeta-potential, which also assists in preventing aggregation. Our results suggest that heavy metals can significantly affect the environmental behaviours of nanoparticles.

scholarly journals Photooxidation Contribution Study on the Decomposition of Azo Dyes in Aqueous Solutions by VUV-Based AOPs

2011 ◽  
Vol 2011 ◽  
pp. 1-8 ◽  
Author(s):  
Chih-Ming Ma ◽  
Gui-Bing Hong ◽  
Hua-Wei Chen ◽  
Nguyen-Thi Hang ◽  
Yung-Shuen Shen
Keyword(s):  
Azo Dyes ◽  
Ph Value ◽  
Reaction Rates ◽  
Degradation Of Dyes ◽  
Degradation Rates ◽  
Effects Of Ph ◽  
Alkaline Conditions ◽  
Acidic Conditions ◽  
High Concentrations ◽  
Acid Blue

The effects of pH value, VUV intensity, initial dye concentration, initial H2O2concentration, and TiO2loading dose on the degradation of three azo dyes: acid Orange 8, acid Blue 29, and acid Blue 113 were studied to explore and compare the treatment efficiencies among the adopted AOPs. It was found that pH played an important role in the degradation of dyes using VUV irradiation. For VUV/H2O2, VUV/TiO2, and VUV/TiO2/H2O2processes, the decoloration rates of the three azo dyes were more efficient under acidic conditions relative to alkaline conditions. The degradation rates of dyes increased with increasing concentrations of H2O2, but reaction rates were retarded at high concentrations of H2O2because the H2O2compound acted as a scavenger of the hydroxyl radical. In this paper, three azo dyes were decomposed efficiently by VUV irradiation only demonstrating the effectiveness of VUV direct photolysis.

Effects of pH value and calcium hardness on the removal of 1,1,1-trichloroethane by immobilized nanoscale zero-valent iron on silica based supports

Chemosphere ◽  
2018 ◽  
Vol 211 ◽  
pp. 102-111 ◽  
Author(s):  
Shuai Chen ◽  
Carolina Belver ◽  
Hui Li ◽  
Lu Yao Ren ◽  
Yong Di Liu ◽  
...  
Keyword(s):  
Ph Value ◽  
Zero Valent Iron ◽  
Nanoscale Zero Valent Iron ◽  
Effects Of Ph
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