Effect of zero-valent iron on biological denitrification in the autotrophic denitrification system

This study investigated nitrate removal using biological denitrification by the iron-reducing bacteria strain CC76 combined with zero-valent iron (ZVI) in simulated groundwater under anaerobic conditions. The mechanism of nitrate reduction as well as the process of iron cycling by strain CC76 and ZVI were studied. During growth experiments, the strain CC76 showed the ability to utilize Fe²⁺ (electron donor) produced from the stimulated corrosion of ZVI for the nitrate removal. ZVI exerted inhibitive effects on the growth of strain CC76 in the early stage. However, the strain CC76 was able to tolerate the presence of ZVI in the long term. Moreover, three factors (temperature, initial pH, and ZVI concentration) were selected as effective factors and were optimized using a central composite design of response surface methodology. Based on the statistical analysis, a temperature of 30.44 °C, initial pH of 6.11, and ZVI concentration of 5.89 g/L were determined to be the optimum values. The effect of Fe²⁺/ZVI ratio was also explored and compared with ZVI alone, a certain amount of a mixture of Fe²⁺ and ZVI showed a higher nitrate removal ability. Moreover, scanning electron microscopy and X-ray diffraction analyses showed the corrosion of ZVI occurred after reaction in the autotrophic denitrification system.     

Degradation of Acid Orange 7 by Gliding Arc Discharge Plasma in Combination with Advanced Fenton Catalysis

A new plasma–catalysis process of gliding arc discharge (GAD) plasma with zero–valent iron (ZVI) was examined. Because GAD plasma creates an acidic environment, solid iron releases ferrous ions which act as a catalyst for the decomposition of the hydrogen peroxide. A comparative study of the catalytic effects between Fe²⁺ and Fe⁰ in GAD plasma was investigated. The decolorization reactions of Acid Orange 7 (AO7) followed pseudo–first–order kinetics. And the rate constants for the process of GAD with ZVI was increased by 30% and by 19%, respectively, compared with the process of GAD alone and the process of GAD with ferrous. The investigations of solution pH and hydrogen peroxide both demonstrated that the GAD plasma induced conditions are much suitable for advanced Fenton reactions. The corrosion of ZVI in GAD plasma can give continuous ferrous ions to sustain Fenton reaction. Also, ZVI was demonstrated to have favorable reusable feature.     

Characteristics and Kinetics of Nitrobenzene Reduction by Sucrose-modified Nanoiron

Sucrose-modified nanoscale zero-valent iron(SM-NZVI) was prepared with liquid phase reducing method, and characterized by transmission electron microscopy(TEM) and X-ray diffraction(XRD) for the shape and structure. The size of SM-NZVI particles was about 100―150 nm and they displayed better dispersity. The degradation of nitrobenzene(NB) in water by SM-NZVI was carried out in batch experiments. The results indicate that the efficiency of NB reduction via SM-NZVI increased by 44.24% compared with that via NZVI, and coexistent Ca²⁺, Mg²⁺, HCO₃^- and other ions showed little effect on NB reduction but negative influence on aniline(AN) production. Furthermore, the kinetic researches indicate that NB reduction with SM-NZVI could be described by pseudo first-order kinetic model at different initial pH values and iron dosage. The oxidation products of iron were mainly Fe₃O₄ and Fe₂O₃ with irregular shape.     

负载零价铁膨胀石墨的合成及对水中NO3-去除的效果与机制

以网络状孔型结构发达的膨胀石墨（EG）为载体,采用化学沉积法制备了负载零价铁（ZVI）的膨胀石墨（EG-ZVI）.利用扫描电子显微镜（SEM）、X射线衍射（XRD）仪及X射线光电子能谱仪（XPS）等对负载及反应前后的EG-ZVI进行表征,探究了EG-ZVI对硝酸根（NO₃^-）的去除效果并对其反应产物及机理进行了分析.结果表明,亚微米级零价铁已负载到EG石墨表面,且分布均匀;与EG相比,EG-ZVI对NO₃^-的去除能力显著提升,其去除率是EG的2.3倍.得益于铁碳原电池效应,EG-ZVI对pH依赖性比零价铁低,即使在pH=9的条件下,NO₃^-去除率依然能达到65%以上,是单独用零价铁处理时的1.83倍;EG-ZVI去除NO₃^-是吸附和还原过程共同作用的结果,符合三级动力学模型,其还原过程由负载在EG表面的零价铁发生腐蚀提供电子,从而还原NO₃^-产生以NH₄⁺-N为主的含氮化合物;EG-ZVI对NO₃^-具有较强的还原吸附作用,并能解决零价铁在反应过程中生成惰性层或金属氢氧化物导致去除效率低的缺陷,使其在含NO₃^-废水的处理中具有较高的应用潜力.     

Amplification effects of magnetic field on hydroxylamine-promoted ZVI/H2O2 near-neutral Fenton like system

This study has demonstrated an interesting amplification effect of magnetic field（MF） on the hydroxylamine（HA）-promoted zero valent iron（ZVI）/H2 O₂ Fenton-like system.Sulfamethoxazole（SMX） could be efficiently degraded at near neutral pH.Conditional parameters affecting the SMX degradation in the ZVI/H₂ O₂/HA/MF system,e.g.,pH and the dosages of ZVI,HA and H₂ O₂,were investigated.Unlike the acid-favorable ZVI/H₂ O₂ and ...     

Effect of selected ligands on the U(VI) immobilization by zerovalent iron

Summary Theeffect ofCl^-, CO₃^2-, EDTA, NO₂^-, NO₃^-, PO₄^3-, SO₄^2-, and humic substances (HS)on the U(VI)co-precipitation from aqueous solutions by zerovalent iron (ZVI) was investigated in the neutral pH range.Batch experiments without shaking were conducted for 14 days mostly with five different ZVI materials (15 g/l), selected ligands (10mM) and an U(VI) solution (20 mg/l, 0.084mM). Apart from Cl^-, all tested ligands induced a decrease ofU(VI)coprecipitation. This decrease is attributed to the surface adsorption and complexation of the ligands at the reactive sites on the surface of ZVI and their corrosion products. The decrease ofU(VI)removal was not uniform with the five ZVI materials. Generally, groundwater with elevated EDTA concentration could not be remediated with the ZVI barrier technology. The response of the system on the pre-treating by two ZVI materials in 250mM HCl indicated that in situ generated corrosion products favor an irreversible U(VI) uptake. Thus for the long term performance of ZVI barrier, the iron dissolution should continue in such a way that fresh iron oxide be always available for U(VI) coprecipitation.     

Determination of nitrobenzene by differential pulse voltammetry and its application in wastewater analysis

A new method for the determination of nitrobenzene (NB) by differential pulse voltammetry (DPV) based on an adsorptive stripping technique was developed. Cyclic voltammetry (CV) was used in a comparative investigation into the electrochemical reduction of NB at a glassy carbon electrode (GCE). With this electrode, the sharp peak of NB appeared at −0.71 V (vs. Ag/AgCl). The experimental parameters were optimized. Studies on the effect of pH on the peak height and peak potential were carried out over the pH range ca. 9.0–11.5 with sodium carbonate/sodium hydrogen carbonate buffer solution. A solution of pH 9.9 was chosen as analytical medium. Cathodic peak currents were found to be linearly related to the concentration of NB over the range ca. 12.3–1.23 × 10⁴ μg L⁻¹ with relative standard deviations of ca. 3.26–6.75%. The detection limit of NB in water was 5.42 μg L⁻¹. The interference of organic and inorganic species on the voltammetric response was also studied. The proposed method was applied to the determination of NB in wastewater samples with an average recovery of ca. 95.9–102.4%.     

A Pyrene‐Linked Cavity within a β‐Barrel Protein Promotes an Asymmetric Diels–Alder Reaction

A unique π‐expanded reaction cavity tethering a polycyclic moiety which provides a platform for substrate binding was constructed within the robust β‐barrel structure of nitrobindin (NB). NB variants with cavities of different sizes and shapes are coupled with N ‐(1‐pyrenyl)maleimide ( Pyr ) to prepare a series of NB‐ Pyr conjugates. The orientation of the pyrene moiety is fixed within the cavity by the coupling reaction. The fluorescent quenching analysis of NB‐ Pyr indicates that azachalcone ( aza ), which is a dienophile for a Diels–Alder (DA) reaction, is efficiently incorporated within the pyrene‐linked reaction cavity by the aromatic interaction. The DA reaction between aza and cyclopentadiene proceeds within the reaction cavity of NB‐ Pyr in the presence of Cu^II ion in high yield and high enantio‐ and regioselectivity.     

Keggin型杂多阴离子PW11O39Fe(III)(H2O)4-电催化降解硝基苯

以Keggin型铁取代杂多阴离子PW11O39Fe(III)(H2O)4－ (PW11Fe)代替传统电芬顿(electro-Fenton)方法中的Fe3＋作为电催化剂, 构成一个新颖的电催化体系并用于中性水溶液中硝基苯的降解. 结果表明, 含有1.0 mmol•L－1硝基苯和1.0 mmol•L－1 PW11Fe的混合磷酸盐溶液(pH 6.86), 在－0.5 V电位和60 mL•min－1 O2流速下反应100 min, 硝基苯便完全降解. 降解的准一级表观速率常数与硝基苯的初始浓度有关, 当硝基苯的初始浓度为1.0, 2.0和5.0 mmol•L－1时, kobs分别为7.18×10－2, 3.57×10－2和1.47×10－2 min－1. 降解反应100 min的TOC(有机碳总量)去除率约为35%, 表明硝基苯的降解过程伴随着矿化.     

Removal of the Harmful Nitrate Anions from Potable Water Using Different Methods and Materials,including Zero-Valent Iron

Drinking water containing nitrate ions at a higher concentration level of more than 10 mg/L, according to the World Health Organization (WHO), poses a considerable peril to humans. This danger lies in its reduction of nitrite ions. These ions cause methemoglobinemia during the oxidation of hemoglobin into methemoglobin. Many protocols can be applied to the remediation of nitrate ions from hydra solutions such as Zn metal and amino sulfonic acid. Furthermore, the electrochemical process is a potent protocol that is useful for this purpose. Designing varying parameters, such as the type of cathodic electrode (Sn, Al, Fe, Cu), the type of electrolyte, and its concentration, temperature, pH, and current density, can give the best conditions to eliminate the nitrate as a pollutant. Moreover, the use of accessible, functional, and inexpensive adsorbents such as granular ferric hydroxide, modified zeolite, rice chaff, chitosan, perlite, red mud, and activated carbon are considered a possible approach for nitrate removal. Additionally, biological denitrification is considered one of the most promising methodologies attributable to its outstanding performance. Among these powerful methods and materials exist zero-valent iron (ZVI), which is used effectively in the deletion process of nitrate ions. Non-precious synthesis pathways are utilized to reduce the Fe²⁺ or Fe³⁺ ions by borohydride to obtain ZVI. The structural and morphological characteristics of ZVI are elucidated using UV–Vis spectroscopy, zeta potential, XRD, FE-SEM, and TEM. The adsorptive properties are estimated through batch experiments, which are achieved to control the feasibility of ZVI as an adsorbent under the effects of Fe⁰ dose, concentration of NO₃⁻ ions, and pH. The obtained literature findings recommend that ZVI is an appropriate applicant adsorbent for the remediation of nitrate ions.     

Ag(I)‐Catalyzed Chlorination of Linezolid during Water Treatment: Kinetics and Mechanism

The kinetic and mechanistic study of Ag(I)‐catalyzed chlorination of linezolid (LNZ) by free available chlorine (FAC) was investigated at environmentally relevant pH 4.0–9.0. Apparent second‐order rate constants decreased with an increase in pH of the reaction mixture. The apparent second‐order rate constant for uncatalyzed reaction, e.g., k″_app = 8.15 dm³ mol⁻¹ s⁻¹ at pH 4.0 and k″_app. = 0.076 dm³ mol⁻¹ s⁻¹ at pH 9.0 and 25 ± 0.2°C and for Ag(I) catalyzed reaction total apparent second‐order rate constant, e.g., k″_app = 51.50 dm³ mol⁻¹ s⁻¹ at pH 4.0 and k″_app. = 1.03 dm³ mol⁻¹ s⁻¹ at pH 9.0 and 25 ± 0.2°C. The Ag(I) catalyst accelerates the reaction of LNZ with FAC by 10‐fold. A mechanism involving electrophilic halogenation has been proposed based on the kinetic data and LC/ESI/MS spectra. The influence of temperature on the rate of reaction was studied; the rate constants were found to increase with an increase in temperature. The thermodynamic activation parameters E_a, ΔH^#, ΔS^#, and ΔG^# were evaluated for the reaction and discussed. The influence of catalyst, initially added product, dielectric constant, and ionic strength on the rate of reaction was also investigated. The monochlorinated substituted product along with degraded one was formed by the reaction of LNZ with FAC.     

DNA Interaction with 17α‐Ethinylestradiol Studied Using Electrochemical Biosensors and Biosensing in Solution

The synthetic estrogen 17α‐ethinylestradiol (EE2) is an active component of oral contraceptives. It is considered as an endocrine disrupting compound that, once incorporated into an organism, affects the hormonal balance of animals and humans. In this study we characterized the DNA‐EE2 interaction using an electrochemical biosensor and biosensing in solution phase with the double stranded DNA from salmon sperm and deoxyguanosine monophosphate (dGMP). Differential pulse voltammetry method has been applied based on voltammetric anodic responses of the deoxyguanine (dGuo) and deoxyadenine (dAdo) as well as EE2 in the medium of phosphate buffer solution pH 7.0. Binding of EE2 to the nucleobases leads to a decrease of their anodic signals. Association constant for DNA‐EE2 interaction has been estimated to be about 1.1 ? 10³ L mol^?1 and 1.4 ? 10³ L mol^?1 for dGuo and dAdo responses, respectively. The association is reversible as indicated by decrease of the EE2 response in pure buffer solution due to leaching of EE2 from the surface attached DNA. The DNA‐EE2 association has been confirmed also by UV‐vis spectrometric experiments.     

Amperometric Determination of Creatinine with a Dialysis Membrane‐Covered Nitrobenzene/Water Interface for Urine Analysis

The ion transfer of creatinine (CRE) at a polarized nitrobenzene (NB)/water (W) interface has been studied. When the pH of the W phase is in the range of 1.2 to 4.0, a well‐defined voltammetric wave is observed for a simple transfer of CRE⁺ (protonated form) at the NB/W interface. This transfer reaction has been applied to develop an amperometric method for the determination of CRE in urine. In this system, the NB/W interface is covered with a dialysis membrane to prevent possible interference from urine proteins. The concentration of CRE in a urine control has successfully been determined.     

Water-soluble palladium nanoparticles as an active catalyst for highly selective hydrogenation of nitrobenzene to aniline

Palladium (Pd) nanoparticles (NPs) stabilized by tri-block copolymer polyoxyethylene–polyoxypropylene–polyoxyethylene (P123) micelles were synthesized in water using a hydrogenation reduction method. Well-dispersed P123 micelles in the aqueous phase favored the stabilization of Pd NPs. The P123–Pd micellar catalyst was first applied in the liquid phase hydrogenation of nitrobenzene (NB), showing excellent catalytic activity, and the only reaction product detected was aniline (AN). Using water as the reaction medium and under mild conditions, both the preparation of catalysts and NB hydrogenation were convenient and environmentally friendly. Under the optimal conditions, the isolated catalyst phase could be recycled at least five times, and the catalytic activity and selectivity remained unchanged. A reaction scheme was suggested. First-order kinetics was determined at 3.0 MPa hydrogen pressure and temperature 30–75 °C, and the activation energy was 40.18 kJ mol^?1. This work provides an environmentally benign and effective method for the hydrogenation of NB to AN.     

Sorption—desorption studies of anionic dyes on alumina pretreated with acids

Sorption—desorption behaviour of the anionic dyes naphthol blue-black (NB) and lissamine green ‘BN’ (LG) on chromatographic alumina, pretreated with mineral acids, is described. Alumina samples of surface-phase pH 1.0–8.0 were prepared and studied for their sorption behaviour. The sorption was found to vary with surface pH of the substrate and acid used for pretreatment. Quantitative sorption was shown at pH ⩽ 4.0 (NB) and pH ⩽ 3.5 (LG) on Al₂O₃ treated with HNO₃ [Al₂O₃(n)], and maximum sorption occurred at pH 5.0 (NB) and pH 5.5 (LG) on Al₂O₃ treated with H₂SO₄ [Al₂O₃(s)] and pH 2.5 (NB) and pH 3.0 (LG) on Al₂O₃ treated with H₃PO₄ [Al₂O₃(p)]. Variation in sorption with time (10 min-72, h), temperature (30–60°C) and regeneration of the substrates with aqueous electrolytes is also reported. Desorption efficacy of anions was in the order: PO³⁻₄ > SO²⁻₄ > NO⁻₃. The acid-treatment, and hence the specifically adsorbed anions (NO⁻₃, SO²⁻₄, PO³⁻₄), appears to modify the sorption properties of alumina significantly. It appears that the controlling force for adsorption is predominantly ion exchange. A few synthetic mixtures of the dyes were separated by column chromatography, using inorganic electrolytes as eluents.     

Insights into the synergy of zero-valent iron and copper oxide in persulfate oxidation of Orange G solutions

The degradation of Orange G (OG) by persulfate (PS, S₂O₈ ^2?) activated with dual catalysts that combined zero-valent iron (ZVI) and copper oxide (CuO) was investigated through batch experiments. Effects of pH, initial OG concentration, persulfate dosages, and dosages of dual catalysts on OG degradation were also examined. Higher persulfate concentration and catalysts dosages resulted in higher OG degrading rates. The OG degradation was higher under acidic conditions (pH 3.0 and 5.0) when compared to alkaline conditions. The constituents and the morphology of the catalysts coating before and after reaction were also investigated with X-ray diffraction and scanning electron microscopy. Radical mechanism was studied and three radical scavengers [methanol (MA), tert-butanol (TBA), phenol] were used to determine the type of major active species taking part in the degradation of OG. It was assumed that the \({\text{SO}}_{4}^{ \cdot - }\) or \({\text{HO}} \cdot\) played a major role in the OG degradation. In conclusion, the ZVI/CuO/PS system is a good candidate for use in detoxifying water contaminants.     

Enzymatic Production of Glutathione Coupling with an ATP Regeneration System Based on Polyphosphate Kinase

Glutathione (GSH) is an important reducing agent in the living cells. It is synthesized by a two-step reaction and requires two molecules of adenosine triphosphate (ATP) for one molecule GSH. The enzymatic cascade reaction in vitro is a promising approach to achieve a high titer and limit side reactions; although, a cost-effective phosphate donor for ATP regeneration is required. Triphosphate (PolyP₍₃₎), tetraphosphate (PolyP₍₄₎), and hexametaphosphate (PolyP₍₆₎) were investigated in this study. Triphosphate inhibited the bifunctional GSH synthetase (GshF) from Streptococcus agalactiae, while no significant inhibition was observed by adding hexametaphosphate. The polyphosphate kinase from Corynebacterium glutamicum was hence investigated to use hexametaphosphate for regeneration of ATP. Further, the orthogonal experiment, which includes seven factors (buffer concentration, pH value, ADP concentration, GshF dosage, polyphosphate kinase (PPK) dosage, reaction temperature, substrate ratio of amino acid, and reaction times), indicated that the capacity of buffer is the most significant factor of the reaction conditions for enzymatic production of glutathione coupling with a PPK-based ATP regeneration system. After optimizing the Mg²⁺ concentration, the reaction was scaled up to 250 mL in a stirred reactor with pH feedback control to stabilize the pH value of reaction system and nitrogen protection to avoid the oxidation of product. A yield of 12.32 g/L was achieved. This work provided a potential GshF-based enzymatic way coupling the PPK-based ATP regeneration to product GSH in the optimal conditions towards cost-effectiveness at the industrial scale.     

Treatment of industrial contaminants with zero-valent iron- and zero-valent aluminium-activated persulfate: a case study with 3,5-dichlorophenol and 2,4-dichloroaniline

Zero-valent iron (ZVI)- and zero-valent aluminium (ZVA)-activated persulfate (PS) oxidation procedure was applied to remove the industrial pollutants 3,5-dichlorophenol (3,5-DCP; 12.27 µM) and 2,4-dichloroaniline (2,4-DCA; 12.34 µM) from aqueous solutions. The effects of PS concentration and pH were investigated to optimize heterogeneous treatment systems. Negligible removals were obtained for both pollutants by individual applications of nanoparticles (1 g/L) and PS (1.00 mM). PS activation with ZVI resulted in 59% (1.00 mM PS; 1 g/L ZVI; pH 5.0; 120 min) and 100% (0.75 mM PS; 1 g/L ZVI; pH 5.0; 80 min) 3,5-DCP and 2,4-DCA removals, respectively. The ZVA/PS treatment system gave rise to only 31% 3,5-DCP (1.00 mM PS; 1 g/L ZVA; pH 3.0; 120 min) and 47% 2,4-DCA (0.25 mM PS; 1 g/L ZVA; pH 3.0; 120 min) removals. The pH decreases from 5.0 to 3.0 and from 3.0 to 1.5 enhanced contaminant removals for ZVI/PS and ZVA/PS treatments, respectively. Pollutant removal rates were in correlation with the consumption rates of the oxidants. Metal ion (Al, Fe) release increased in the presence of PS and with decreasing pH.     

Synthesis,Characterization, and Catalytic Activity of New Cu(II) Complexes of Schiff Base: Effective Catalysts for Decolorization of Acid Red 37 Dye Solution

In this paper, three new Cu(II) Schiff base complexes with three different anions (acetate, chloride, and nitrate) were successfully synthesized and characterized by elemental analysis, mass spectra, molar conductance, FT‐IR, NMR,UV–vis spectroscopy, magnetic moment, ESR, and thermal analysis. The catalytic performances of these complexes in decolorization of azo dye, Acid Red 37, were evaluated. Copper(II) complexes were found to be an efficient catalyst for decolorization of Acid Red 37 in the presence of hydrogen peroxide. The catalytic investigation revealed that the Cu(II) complex with acetate anion (complex 1 ) performed the highest catalytic activity. The kinetics of the decolorization of AR37 with this catalyst was studied, and the observed rate constant was determined. The effects of different reaction parameters such as catalyst dosage, solution pH, initial concentration of H₂O₂, dye solution, and reaction temperature on the reaction rate constant were studied. The best reacting conditions should be catalyst dosage = 0.004 g, initial pH 4.0, [H₂O₂]₀ = 0.8 M, and [AR37]₀ = 1.16 M at temperature 25°C. Under these conditions, about 99% of AR37 was decolorized within 60 min. The results indicated that the Cu(II) complex with the acetate anion is a promising catalyst for wastewater treatment.     

Copolymerization of ethylene and norbornene using cyclopentadienylzirconium trichloride activated by isobutyl‐modified methylaluminoxane

The copolymerization of ethylene (E) and norbornene (NB) was investigated using the commercially available and inexpensive catalyst system, cyclopentadienylzirconium trichloride (CpZrCl₃)/isobutyl‐modified methylaluminoxane (MMAO), at a moderate polymerization temperature in toluene. For the CpZrCl₃ catalyst system activated by aluminoxane with a 40 mol % methyl group and a 60 mol % isobutyl group (MMAO), the quantities of the charged NB and the polymerization temperature significantly affected the molecular weights, polydispersities, and NB contents of the obtained copolymers and the copolymerization activities in all the experiments. As the charged NB increased and thereby the NB/E molar ratio increased, the NB content in the copolymer increased and reached a maximum value of 71 mol %. The CpZrCl₃/MMAO ([Al]/[Zr] = 1000) catalyst system with the [NB] of 2.77 mol L^?1 and ethylene of 0.70 MPa at 50 °C showed the highest activity of 1690 kg mol_Zr^?1 h^?1 and molecular weight of 21,100 g mol^?1. The ¹³C NMR analysis showed that the CpZrCl₃/MMAO catalyst system produced the E‐NB random copolymer with a number of NB homosequences such as the NN dyad and NNN triad. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7411–7418, 2008