scholarly journals Chemical Reduction of Nitrate by Zero-Valent Iron: Shrinking-Core versus Surface Kinetics Models

2020 ◽  
Vol 17 (4) ◽  
pp. 1241 ◽  
Author(s):  
Maria Villen-Guzman ◽  
Juan Manuel Paz-Garcia ◽  
Brahim Arhoun ◽  
Maria del Mar Cerrillo-Gonzalez ◽  
Jose Miguel Rodriguez-Maroto ◽  
...  
Keyword(s):  
Nitrate Reduction ◽  
Chemical Reduction ◽  
Permeable Reactive Barriers ◽  
Zero Valent Iron ◽  
Sound Design ◽  
Surface Kinetics ◽  
Ph Values ◽  
Stirred Reactor ◽  
Constant Ph ◽  
Shrinking Core

Zero valent iron (ZVI) is being used in permeable reactive barriers (PRB) for the removal of oxidant contaminants, from nitrate to chlorinated organics. A sound design of these barriers requires a good understanding of kinetics. Here we present a study of the kinetics of nitrate reduction under relatively low values of pH, from 2 to 4.5. We use a particle size of 0.42 mm, which is within the recommended size for PRBs (0.2 mm to 2.0 mm). In order to avoid possible mass-transfer limitations, a well-stirred reactor coupled with a fluidized bed reactor was used. The experiments were performed at constant pH values using a pH controller that allows to accurately track the amount of acid added. Since the reduction of H + to H 2 by the oxidation of ZVI will always be present for these pH values, blank experiments (without nitrate) were performed and the rate of this H + reduction obtained. This rate of reduction was studied using three kinetic models: a regular empirical one, the Shrinking-Core Model (SCM), and the Surface Kinetics Model (SKM). The best performance was obtained from the SKM model. Therefore, this model was also used to study the results for the nitrate reduction, also with satisfactory results. In both cases, some assumptions are introduced to maintain a moderate number of fitting parameters.

Fate of nitrogen species in nitrate reduction by nanoscale zero valent iron and characterization of the reaction kinetics

2010 ◽  
Vol 61 (3) ◽  
pp. 705-712 ◽  
Author(s):  
Y. H. Hwang ◽  
D. G. Kim ◽  
Y. T. Ahn ◽  
C. M. Moon ◽  
H. S. Shin
Keyword(s):  
Nitrate Reduction ◽  
Chemical Reduction ◽  
Reduction Rate ◽  
Zero Valent Iron ◽  
Ammonium Ion ◽  
Alkaline Condition ◽  
Order Kinetic ◽  
Nitrogen Species ◽  
Nanoscale Zero Valent Iron ◽  
Fate Of Nitrogen

This study investigates the fate of nitrogen species during nitrate reduction by nanoscale zero valent iron (NZVI) as well as the related kinetics. The NZVI used for the experiments was prepared by chemical reduction without a stabilizing agent. The pseudo first order kinetic constant of nitrate reduction at 30°C with an NZVI/nitrate ratio of 1.25:1, which were the reference conditions of this study, was 4.08 h−1 (R2 = 0.955). A nitrogen mass balance was established by quantitative analysis of aqueous-phase and gas-phase nitrogen species. The results confirm that the nitrate was converted to ammonium ion, that ammonia stripping subsequently occurred under a strong alkaline condition, and that the total amount of aqueous nitrogen was consequently reduced. The nitrate reduction rate also increased with a lower pH and a higher temperature when microscale ZVI was used. However, in contrast to the reaction by microscale ZVI, the nitrate reduction rate by NZVI was higher for an unbuffered condition, possibly due to the abundance of surface atoms and the smaller size.

scholarly journals Chemical reduction of nitrate by zerovalent iron nanoparticles adsorbed radiation-grafted copolymer matrix

Nukleonika ◽  
2017 ◽  
Vol 62 (4) ◽  
pp. 269-275 ◽  
Author(s):  
Sanduni Y. Ratnayake ◽  
Anoma K. Ratnayake ◽  
Dieter Schild ◽  
Edward Maczka ◽  
Elzbieta Jartych ◽  
...  
Keyword(s):  
Drinking Water ◽  
Nitrate Reduction ◽  
Iron Nanoparticles ◽  
Chemical Reduction ◽  
Reduction Process ◽  
Green Technology ◽  
Zerovalent Iron ◽  
Grafted Copolymer ◽  
Ph Values ◽  
Zerovalent Iron Nanoparticles

Abstract This research specifically focused on the development of a novel methodology to reduce excess nitrate in drinking water utilizing zerovalent iron nanoparticles (nZVI)-stabilized radiation-grafted copolymer matrix. nZVI was synthesized by borohydrate reduction of FeCl3 and stabilized on acrylic acid (AAc)-grafted non-woven polyethylene/polypropylene (NWPE/PP-g-AAc) copolymer matrix, which was grafted using gamma radiation. The use of nZVI for environmental applications is challenging because of the formation of an oxide layer rapidly in the presence of oxygen. Therefore, radiation-grafted NWPE/PP synthetic fabric was used as the functional carrier to anchor nZVI and enhance its spreading and stability. The chemical reduction of nitrate by nZVI-adsorbed NWPE/PP-g-AAc (nZVI-Ads-NWP) fabric was examined in batch experiments at different pH values. At low pH values, the protective layers on nZVI particles can be readily dissolved, exposing the pure iron particles for efficient chemical reduction of nitrate. After about 24 h, at pH 3, almost 96% of nitrate was degraded, suggesting that this reduction process is an acid-driven, surface-mediated process. The nZVI-water interface has been characterized by the 1-pK Basic Stern Model (BSM). An Eley-Rideal like mechanism well described the nitrate reduction kinetics. In accordance with green technology, the newly synthesized nZVI-Ads-NWP has great potential for improving nitrate reduction processes required for the drinking water industry.

INTEGRATING NANOSCALE ZERO-VALENT IRON AND TITANIUM DIOXIDE FOR NUTRIENT REMOVAL IN STORMWATER SYSTEMS

NANO ◽  
2008 ◽  
Vol 03 (04) ◽  
pp. 297-300 ◽  
Author(s):  
NI-BIN CHANG ◽  
MARTY WANIELISTA ◽  
FAHIM HOSSAIN ◽  
LEI ZHAI ◽  
KUEN-SONG LIN
Keyword(s):  
Titanium Dioxide ◽  
Water Reuse ◽  
Algal Blooms ◽  
Chemical Reduction ◽  
Nitrate Removal ◽  
Packed Bed ◽  
The United States ◽  
Zero Valent Iron ◽  
Nanoscale Zero Valent Iron ◽  
Freshwater Bodies

Nutrients, such as nitrate, nitrite, and phosphorus, are common contaminants in many aquatic systems in the United States. Ammonia and nitrate are both regulated by the drinking water standards in the US primarily because excess levels of nitrate might cause methemoglobinemia. Phosphorus might become sources of the eutrophication problems associated with toxic algae in the freshwater bodies. Toxic algal blooms can cause severe acute and chronic public health problems. Chemical reduction of nitrate by using zero-valent iron started as early as 1964, and considerable research reports relating to this technology to nanomaterial were extensively reported in 1990s making the use of nanoscale zero-valent iron (NZVI) particles for nitrate removal become one of the most popular technologies in this field. The purpose of the present study was to examine the potential of integrating green sorption media, such as sawdust, limestone, tire crumb, and sand/silt, with two types of nanoparticles, including NZVI and Titanium Dioxide ( TiO 2), for nitrate removal in an engineering process. The study consists of running packed bed column tests followed by the addition of NZVI and TiO 2 to improve nitrate and phosphorus removal efficiency. Preliminary results in this paper show that the potential and advanced study may support the creation of design criteria of stormwater and groundwater treatment systems for water reuse in the future.

Nitrate reduction over nanoscale zero-valent iron prepared by hydrogen reduction of goethite

2012 ◽  
Vol 133 (1) ◽  
pp. 205-211 ◽  
Author(s):  
H.B. Liu ◽  
T.H. Chen ◽  
D.Y. Chang ◽  
D. Chen ◽  
Y. Liu ◽  
...  
Keyword(s):  
Nitrate Reduction ◽  
Hydrogen Reduction ◽  
Zero Valent Iron ◽  
Nanoscale Zero Valent Iron

scholarly journals Production of butyric acid at constant pH by a solventogenic strain of Clostridium beijerinckii

2020 ◽  
Vol 38 (No. 3) ◽  
pp. 185-191 ◽  
Author(s):  
Marek Drahokoupil ◽  
Petra Patáková
Keyword(s):  
Flow Cytometry ◽  
Butyric Acid ◽  
Population Viability ◽  
Clostridium Beijerinckii ◽  
Clostridium Tyrobutyricum ◽  
Fluorescence Staining ◽  
Low Concentration ◽  
Ph Values ◽  
Constant Ph ◽  
Acetone Butanol Ethanol

A solventogenic strain of Clostridium beijerinckii, NRRL B-598, was cultured for the production of butyric acid as the main fermentation product. However, unlike typical acetone-butanol-ethanol (ABE) fermentations, where pH is not regulated, in this study the pH was kept constant during fermentation. From the five pH values tested, 6.0, 6.5, 7.0, 7.5 and 8.0, pH 6.5 and 7.0 resulted in the highest concentrations of butyric acid, at 9.69 ± 0.09 g L–1 and 11.5 ± 0.39 g L–1, respectively. However, a low concentration of solvents, 1.8 ± 0.22 g L–1, was only reached at pH 7.0. These results are comparable with those from typical butyric acid producers, i.e. Clostridium butyricum and Clostridium tyrobutyricum strains. At pH 7.0, we succeeded in suppressing sporulation and prolonging the population viability, which was confirmed by flow cytometry combined with double fluorescence staining.

Common oxidants activate the reactivity of zero-valent iron (ZVI) and hence remarkably enhance nitrate reduction from water

2015 ◽  
Vol 146 ◽  
pp. 227-234 ◽  
Author(s):  
Xuejun Guo ◽  
Zhe Yang ◽  
Hong Liu ◽  
Xiaofang Lv ◽  
Qiansi Tu ◽  
...  
Keyword(s):  
Nitrate Reduction ◽  
Zero Valent Iron
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