Chemical Reduction Of Nitrate Research Articles

Elucidating distinct roles of chemical reduction and autotrophic denitrification driven by three iron-based materials in nitrate removal from low carbon-to-nitrogen ratio wastewater

Effective nitrate removal is a key challenge when treating low carbon-to-nitrogen ratio wastewater. How to select an effective inorganic electron donor to improve the autotrophic denitrification of nitrate nitrogen has become an area of intense research. In this study, the nitrate removal mechanism of three iron-based materials in the presence and absence of microorganisms was investigated with Fe2+/Fe0 as an electron donor and nitrate as an electron acceptor, and the relationship between the iron materials and denitrifying microorganisms was explored. The results indicated that the nitrogen removal efficiency of each iron-based material coupled sludge systems was higher than that of iron-based material. Furthermore, compared with the sponge iron coupled sludge system (60.6%–70.4%) and magnetite coupled sludge (56.1%–65.3%), the pyrite coupled sludge system had the highest removal efficiency of TN, and the removal efficiency increased from 62.5% to 82.1% with time. The test results of scanning electron microscope, X-ray photoelectron spectroscopy and X-ray diffraction indicated that iron-based materials promoted the attachment of microorganisms and the chemical reduction of nitrate in three iron-based material coupled sludge systems. Furthermore, the pyrite coupled sludge system had the highest nitrite reductase activity and can induce microorganisms to secrete more extracellular polymer substances. Combined with high-throughput sequencing and PICRUSt2 functional predictive analysis software, the total relative abundance of the dominant bacterial in pyrite coupled sludge system was the highest (72.06%) compared with the other iron-based material systems, and the abundance of Blastocatellaceae was relatively high. Overall, these results suggest that the pyrite coupled sludge system was more conducive to long-term stable nitrate removal.

Removal of nitrate from aqueous solution using nano zerovalent iron‐reduced graphene oxide composite: optimization of parameters

AbstractIn this study, nitrate removal from aqueous solution was performed using nano zerovalent iron–reduced graphene (nZVI‐rGO) composite. The effect of operational parameters including initial nitrate concentration, composite dosage, solution pH, and contact time on the removal process was examined using design expert software. Our investigation revealed that the nitrate‐contaminated water can be easily treated by applying the synthesized composite within the short contact time of 1 min. In the presence of nZVI‐rGO composite, about 96% of nitrate reduced to nitrogen gas (~64%) and small amounts of ammonium (~32%) and nitrite (~0.3%) were released. The kinetics results confirmed that the adsorption and chemical reduction of nitrate by the composite are well fitted to the pseudo‐second‐order and pseudo‐first‐order kinetic models, respectively. The thermodynamic results showed that the removal of nitrate by the composite is a spontaneous and endothermic process.

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

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 to by the oxidation of ZVI will always be present for these pH values, blank experiments (without nitrate) were performed and the rate of this 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.

Treatment of mining wastewater polluted with cyanide by coagulation processes: A mechanistic study

In this work, coagulation and electrocoagulation for the removal of cyanide ions contained in synthetic mining wastewater were evaluated paying particular attention to the elucidation of the coagulation mechanisms. Iron and aluminum salts with concentrations ranging from 0.01 to 10 000 mg dm−3 metal were used in chemical coagulation. Experimental data were properly fitted to Freundlich isotherm to elucidate that the main mechanism to remove cyanide during chemical coagulation was adsorption onto coagulant flocs although a maximum cyanide removal percentage of only 25% was attained. Then, electrochemical coagulation with iron and aluminum electrodes was evaluated at 1, 10 and 100 A m−2, obtaining completely different results. Iron electrochemical coagulation leads to the complete cyanide removal regardless of the current density applied, although the TOC removal was much lower than expected. On the contrary, only 60% of cyanide removal was reached by aluminum electrochemical coagulation and its efficiency was found to be highly dependent on the current density applied. Furthermore, no cyanate or hazardous inorganic chlorine species were detected during both electrocoagulation processes. However, chloride was oxidized to hypochlorite and then, it reacted with ammonium ions (contained in mining wastewater or produced by chemical reduction of nitrate by aluminum) to form chloramines. A proposal of coagulation mechanisms during the electrochemical process that explains experimental results was developed which involved the formation of iron-cyanide complexes, charge neutralization, adsorption on a superficially charged metal precipitate and/or enmeshment into a sweep metal floc.

Chemical Reduction of Nitrate Using Nanoscale Bimetallic Iron/Copper Particles

Chemical Reduction of Nitrate Using Nanoscale Bimetallic Iron/Copper Particles

Preparation of Pyramids Structured Silicon as a Support for Nano Sized Zero Valent Iron Particles for Nitrate Removal from Water

In this study, pyramids structured silicon (PSi) has been made from metallurgical grade silicon powder with wet alkaline etching and then chemically activated with nano zero valent iron (NZVI) to eliminate nitrate. The NZVI/PSi composite was characterized by scanning electronic microscopy (SEM), X-ray diffraction(XRD), X-ray fluorescence spectrometer (XRF), energy dispersive X-ray spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR), and UV–Vis spectrophotometry. The size of NZVI particles was between 30–100 nm coated on PSi without clustering of the NZVI particles due to the electromagnetic attraction forces. The synergistic effect of NZVI/PSi composites obviously increased remarkably nitrate removal efficiency than NZVI alone. Chemical reduction of nitrate by zerovalent iron in water requires acidic pH conditions but NZVI/PSi composite can reduce nitrate in water in the pH range of 2–7. Also, removal of nitrate complete in 20 min by NZVI/PSi composite that was shorter than NZVI in 120 min. Above all, this composite completely was separated from solution with external magnetic field.

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

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.

Mechanism of formate-nitrite transporters by dielectric shift of substrate acidity.

Bacterial formate-nitrite transporters (FNTs) regulate the metabolic flow of small, weak mono-acids. Recently, the eukaryotic PfFNT was identified as the malaria parasite's lactate transporter and novel drug target. Despite crystal data, central mechanisms of FNT gating and transport remained unclear. Here, we show elucidation of the FNT transport mechanism by single-step substrate protonation involving an invariant lysine in the periplasmic vestibule. Opposing earlier gating hypotheses and electrophysiology reports, quantification of total uptake by radiolabeled substrate indicates a permanently open conformation of the bacterial formate transporter, FocA, irrespective of the pH Site-directed mutagenesis, heavy water effects, mathematical modeling, and simulations of solvation imply a general, proton motive force-driven FNT transport mechanism: Electrostatic attraction of the acid anion into a hydrophobic vestibule decreases substrate acidity and facilitates protonation by the bulk solvent. We define substrate neutralization by proton transfer for transport via a hydrophobic transport path as a general theme of the Amt/Mep/Rh ammonium and formate-nitrite transporters.

Chemical removal of nitrate from water by aluminum-iron alloys

Zero-valent iron has been intensively investigated in chemical reduction of nitrate in water, but the reduction requires acidic or weak acidic pH conditions and the product of the reduction is exclusively ammonium, an even more toxic substance. Zero-valent aluminum is a stronger reductant than iron, but its use for the reduction of aqueous nitrate requires considerably alkaline pH conditions. In this study, aluminum-iron alloys with an iron content of 10%, 20% and 58% (termed Al-Fe10, Al-Fe20 and Al-Fe58, respectively) were investigated for the reduction of aqueous nitrate. Al-Fe alloys were efficient to reduce nitrate in water in an entire pH range of 2–12 and the reduction proceeded in a pseudo-first order at near neutral pH conditions. The observed reaction rate constant (Kobs) of Al-Fe10 was 3 times higher than that of Fe and the Kobs of Al-Fe20 doubled that of Al-Fe10. The nitrogen selectivity of the reduction by Al-Fe10, Al-Fe20 and Al-Fe58 was 17.6%, 23.9% and 40.3%, respectively at pH 7 and the nitrogen selectivity by Al-Fe20 increased from 18.9% at pH 2–60.3% at pH 12. The enhanced selectivity and reactivity of Al-Fe alloys were likely due to the presence of an intermetallic Al-Fe compound (Al13Fe4).

Efficient nitrate removal using micro‐electrolysis with zero valent iron/activated carbon nanocomposite

ABSTRACTBACKGROUNDIncreasing nitrate concentration in ground water resources due to increased municipal and industrial contaminations is posing a great threat to human health worldwide. Therefore, an efficient technique to remove nitrate from ground water is in high demand.RESULTIn this study, nanoscale zero valent iron (NZVI)/activated carbon (AC) nanocomposite material was successfully synthesized to form a highly efficient micro‐galvanic cell to be used in the chemical reduction of nitrate. Analysis of NZVI‐AC composites were conducted by BET, XRD, SEM, TEM and XPS, while utilizing sodium borohydride as a reducing agent in liquid phase reaction for the reduction of ferrous ions. Several factors during the preparation process were investigated for their effect on the performance of the material when used for the reduction of nitrate in aqueous media. Experiment results demonstrated that the material prepared under optimized preparation conditions can remove up to 94.3% of nitrates with composites at 2.1 g L−1. The final degradation products are mainly N2 and .CONCLUSIONThe composites were found to behave more efficiently for nitrate removal when compared with NZVI. In addition, the production of these new composite materials can be economically scaled up as with NZVI, which is necessary for practical environmental remediation. © 2016 Society of Chemical Industry

Physico-chemical technologies for nitrogen removal from wastewaters: a review

The paper examines the main physico-chemical processes for nitrogen removal from wastewaters, considering both those that have been long known and still widely applied at the industrial scale, and those that are still at the research level. Special attention is paid to the latest technological developments, as well as to operational problems and fields of application. The processes considered are briefly summarized as follows: ammonia air and steam stripping; ammonia vacuum distillation; ammonia precipitation as struvite; ammonia and nitrate removal by selected ion exchange; breakpoint chlorination; chloramine removal by selected activated carbon; ammonia adsorption on charcoal; chemical reduction of nitrate; advanced oxidation processes to convert ammonia and organic-N into nitrogen gas or nitrate. Special attention is given to advanced oxidation processes, as great research efforts are currently addressed to their implementation. These specifically include ozonation, peroxon oxidation, catalytic wet air oxidation, photo-catalytic oxidation and electrochemical oxidation.

Chemical Reduction of Nitrate in Aqueous Solution by Iron Powder

Nitrate is a common groundwater contaminant and poses health and environmental threats. Reductive denitrification of nitrate by zero-valent iron was investigated in unbuffered solutions at 20 °C. Nitrate was effectively removed at low initial solution pH. The reaction was accompanied by the production and then disappearance of a small quantity of nitrite, suggesting that nitrite was the intermediate and subsequently further reduced. A rapid rise in solution pH was also observed during the reaction. At the initial pH of 4, a reduction of 90% in nitrate concentration from 60 to 7.0 mg/L at 60 min was observed. The extent of nitrate removal decreased with increasing solution pH within the tested range of 3 - 6, suggesting that the reaction was an acid-driven process. The extent of nitrate removal also increased with Fe dosage over the range of 5 - 20 g/L, as higher Fe dosages provided more reactive surfaces. It is proposed that protons participate in the nitrate reduction by Fe0 via an initial reduction of protons to reduced hydrogen species followed by a subsequent reaction with nitrate. The hydrolysis of Fe corrosion products (e.g., ferrous ions) produces protons, in particular, near the surfaces of Fe, which drives the reaction to continue.

Poly[β-(1→4)-2-amino-2-deoxy-D-ghicopyranose] based zero valent nickel nanocomposite for efficient reduction of nitrate in water

Chemical reduction of nitrate using metal nanoparticles has received increasing interest due to over-dependence on groundwater and consequence health hazard of the nitrate ion. One major drawback of this technique is the agglomeration of nanoparticles leading to the formation of large flocs. A low cost biopolymeric material, poly [β-(1→4)-2-amino-2-deoxy-D-glucopyranose] (β-PADG) obtained from deacetylated chitin was used as stabilizer to synthesize zero valent nickel (ZVNi) nanoparticles. The β-PADG-ZVNi nanocomposite was characterized using infra red (IR), UV-Vis spectrophotometric techniques and Scanning Electron Microscope (SEM). The morphology of the composite showed that β-PADG stabilized-ZVNi nanoparticles were present as discrete particles. The mean particle size was estimated to be (7.76 ± 2.98) nm and surface area of 87.10 m2/g. The stabilized-ZVNi nanoparticles exhibited markedly greater reactivity for reduction of nitrate in water with 100% conversion within 2 hr contact owing to less agglomeration. Varying the β-PADG–to-ZVNi ratio and the ZVNi-to-nitrate molar ratio generally led to a faster nitrate reduction. About 3.4-fold difference in the specific reaction rate constant suggests that the application of the β-PADG-stabilizer not only increased the specific surface area of the resultant nanoparticles, but also greatly enhanced the surface reactivity of the nanoparticles per unit area.

DECONTAMINATION OF NITRATES AND NITRITES IN WASTEWATER BY ZERO-VALENT IRON NANOPARTICLES

The chemical reduction of nitrate or nitrite species by zero-valent iron nanoparticle (ZVIN) in aqueous solution and related reaction kinetics or mechanisms using fine structure characterization were investigated. Experimentally, ZVIN of this study was prepared by borohydride reduction method at room temperature. The morphology of as-synthesized ZVIN shows that the nearly ball and ultrafine particles ranged of 20–50 nm were observed with FE-SEM analysis. The kinetic model of nitrites or nitrates reductive reaction by ZVIN is proposed as a pseudo-first-order kinetic equation. The nitrite and nitrate removal efficiencies using ZVIN were found 65–83% and 51–68%, respectively, based on three different initial concentrations. By using XRD patterns, the quantitative relationship between nitrite and Fe(III) or Fe(II) becomes similar to the one between nitrate and Fe(III) in the ZVIN study. The possible reason is linked with a faster nitrite reduction by ZVIN. In fact, the occurrence of the relative faster nitrite reductive reaction suggested that the passivation of the ZVIN have a significant contribution to iron corrosion. The XANES spectra show that the nitrites or nitrates reduce to N 2 while oxidizing the ZVIN to Fe 2 O 3 or Fe 3 O 4 electrochemically. It is also very clear that decontamination of nitrate or nitrite species in groundwater via the in-situ remediation with a ZVIN permeable reactive barrier would be environmentally attractive.

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

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.

Synthesis of nanoscale zero-valent iron supported on exfoliated graphite for removal of nitrate

Nano ZVI particles supported on micro-scale exfoliated graphite were prepared by using KBH 4 as reducing agent in the H 2O/ethanol system. The supported ZVI materials generally have higher activity and greater flexibility for environmental remediation applications. The exfoliated graphite as the support was treated beforehand to hydrophilic material. Nano iron particles are deposited onto the rough graphite surface while those were formed by borohydride reduction. The possible nitrate reduction pathways were proposed. The TEM image shows that iron particles are highly dispersed on the surface of graphite and several of iron particles are imbedded in the pit of support surface. In this synthesis, iron particles have a nearly spherical shape with a grain size of 50–100 nm. The surface areas of materials with different iron loadings of 3.5%, 7.0%, 10.0%, 15.0% and 20.0%(mass fraction) are 2.89, 9.55, 8.45, 23.8 and 6.18 m 2·g −1 by BET surface analyzer. The chemical reduction of nitrate by supported nano ZVI in aqueous solution were tested in series batch experiments. Experiment results suggest that NO 3 − can be more rapidly reduced to NH 4 + at neutral pH and anaerobic conditions by supported nano ZVI than unsupported nano ZVI or ZVI scraps. The 15% nano Fe/graphite shows the best reduction efficiency contrasted with other Fe loading particles.

Preparation of spherical iron nanoclusters in ethanol–water solution for nitrate removal

In this study, a higher surface area spherical nanoscale zero valent iron (HNZVI) cluster (80 nm, 54.25 m 2 g −1) was synthesized in ethanol–water mixed solvent in the presence of dispersion agent of polyglycol (PEG). At the same time, a lower surface area nanoscale zero valent iron (LNZVI) particle (80 nm, 8.08 m 2 g −1) was also prepared with only de-ioned water as reaction media. Their structures, compositions and physical properties were characterized by transmission electron microscope (TEM), X-ray diffractometer (XRD), inductively coupled plasma atomic emission spectrophotometer (ICP-AES), and Brunauer–Emmett–Teller (BET) surface area analyzer and the results obtained for these two kinds of nanoscale iron were compared with each other and also with those reported in the literatures. The HNZVI clusters seemed to be accumulated by smaller iron particles (<10 nm). At the same time, whiskers were formed in the final produce. Reactivity of the HNZVI was affirmed via denitrification of nitrate. The factors controlling the reduction of nitrate, such as pH, dissolved oxygen (DO), iron content as well as the initial nitrate concentration were also discussed. Finally, kinetic analysis revealed that chemical reduction of nitrate by HNZVI could not be described by the first- or pseudo-first-order kinetic model.

Chemical reduction of nitrate by nanoscale Fe/Ni bimetallic particles.

Chemical reduction of nitrate by nanoscale Fe/Ni bimetallic particles.

Chemical reduction of nitrate by metallic iron

Research Article| February 01 2004 Chemical reduction of nitrate by metallic iron Jie Chi; Jie Chi 1College of Environmental Science and Engineering, Tianjin University, Tianjin 300072, China Search for other works by this author on: This Site PubMed Google Scholar Shu-Ting Zhang; Shu-Ting Zhang 1College of Environmental Science and Engineering, Tianjin University, Tianjin 300072, China E-mail: shuting_zhang@eyou.com Search for other works by this author on: This Site PubMed Google Scholar Xin Lu; Xin Lu 1College of Environmental Science and Engineering, Tianjin University, Tianjin 300072, China Search for other works by this author on: This Site PubMed Google Scholar Li-Hua Dong; Li-Hua Dong 1College of Environmental Science and Engineering, Tianjin University, Tianjin 300072, China Search for other works by this author on: This Site PubMed Google Scholar Sui-Liang Yao Sui-Liang Yao 2Research Institute of Innovative Technology for the Earth, 9-2, Kizugawadai, Kizu-cho, Soraku-gun, Kyoto 619-0292, Japan Search for other works by this author on: This Site PubMed Google Scholar Journal of Water Supply: Research and Technology-Aqua (2004) 53 (1): 37–41. https://doi.org/10.2166/aqua.2004.0004 Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Share Icon Share Twitter LinkedIn Tools Icon Tools Cite Icon Cite Permissions Search Site Search nav search search input Search input auto suggest search filter All ContentAll JournalsThis Journal Search Advanced Search Citation Jie Chi, Shu-Ting Zhang, Xin Lu, Li-Hua Dong, Sui-Liang Yao; Chemical reduction of nitrate by metallic iron. Journal of Water Supply: Research and Technology-Aqua 1 February 2004; 53 (1): 37–41. doi: https://doi.org/10.2166/aqua.2004.0004 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex The reduction reaction of nitrate by metallic iron under aerobic conditions was investigated in the pH range of 2.0–8.5. The concentration of nitrate, nitrite, ammonia/ammonium and total nitrogen in the reduction solution were monitored. The reduction products of nitrate were ammonia/ammonium remaining in the reduction solution and gaseous nitrogen emitted from the reduction solution. Nitrate predominantly reduced to gaseous nitrogen at the beginning of the reduction reaction, and ammonia/ammonium at the end of the reduction reaction. pH value was an important parameter affecting the reduction of nitrate by metallic iron. At a low pH values, ammonium was the main reduction product, while gaseous nitrogen was the dominant reduction product at high pH values. In the reduction products, gaseous nitrogen was 40.1, 56.0, 68.0, 77.8 and 81.0% after 150-min reduction at pH=2.0, 3.5, 5.0, 7.0 and 8.5, respectively. ammonia, chemical reduction, contaminated water, denitrification, metallic iron, nitrate This content is only available as a PDF. © IWA Publishing 2004 You do not currently have access to this content.

転炉スラグを散布した底泥における硝酸塩の生物学的・化学的還元

転炉スラグを散布した底泥における硝酸塩の生物学的・化学的還元