Zero-valent Zinc Research Articles

Soluble metal porphyrins - Zero-valent zinc system for effective reductive defluorination of branched per and polyfluoroalkyl substances (PFASs)

Nano zero-valent metals (nZVMs) have been extensively utilized for decades in the reductive remediation of groundwater contaminated with chlorinated organic compounds, owing to their robust reducing capabilities, simple application, and cost-effectiveness. Nevertheless, there remains a dearth of information regarding the efficient reductive defluorination of linear or branched per- and polyfluoroalkyl substances (PFASs) using nZVMs as reductants, largely due to the absence of appropriate catalysts. In this work, various soluble porphyrin ligands [[meso‑tetra(4-carboxyphenyl)porphyrinato]cobalt(III)]Cl·7H2O (CoTCPP), [[meso‑tetra(4-sulfonatophenyl) porphyrinato]cobalt(III)]·9H2O (CoTPPS), and [[meso‑tetra(4-N-methylpyridyl) porphyrinato]cobalt(II)](I)4·4H2O (CoTMpyP) have been explored for defluorination of PFASs in the presence of the nZn0 as reductant. Among these, the cationic CoTMpyP showed best defluorination efficiencies for br-perfluorooctane sulfonate (PFOS) (94%), br-perfluorooctanoic acid (PFOA) (89%), and 3,7-Perfluorodecanoic acid (PFDA) (60%) after 1 day at 70 °C. The defluorination rate constant of this system (CoTMpyP-nZn0) is 88–164 times higher than the VB12-nZn0 system for the investigated br-PFASs. The CoTMpyP-nZn0 also performed effectively at room temperature (55% for br-PFOS, 55% for br-PFOA and 25% for 3,7-PFDA after 1day), demonstrating the great potential of in-situ application. The effect of various solubilizing substituents, electron transfer flow and corresponding PFASs defluorination pathways in the CoTMpyP-nZn0 system were investigated by both experiments and density functional theory (DFT) calculations. SYNOPSISDue to the unavailability of active catalysts, available information on reductive remediation of PFAS by zero-valent metals (ZVMs) is still inadequate. This study explores the effective defluorination of various branched PFASs using soluble porphyrin-ZVM systems and offers a systematic approach for designing the next generation of catalysts for PFAS remediation.

Dispersive liquid-liquid microextraction as a novel enrichment approach for compound-specific carbon isotope analysis of chlorinated phenols.

Compound-specific isotope analysis (CSIA) via gas chromatography-isotope ratio mass spectrometry (GC-IRMS) is a potent tool to elucidate the fate of (semi-)volatile organic contaminants in technical and environmental systems. Yet, due to the comparatively low sensitivity of IRMS, an enrichment step prior to analysis often is inevitable. A promising approach for fast as well as economic analyte extraction and preconcentration prior to CSIA is dispersive liquid-liquid microextraction (DLLME) - a well-established technique in concentration analysis of contaminants from aqueous samples. Here, we present and evaluate the first DLLME method for GC-IRMS exemplified by the analysis of chlorinated phenols (4-chlorophenol, 2,4-dichlorophenol, and 2,4,6-trichlorophenol) as model compounds. The analytes were simultaneously acetylated with acetic anhydride and extracted from the aqueous phase using a binary solvent mixture of acetone and tetrachloroethylene. With this method, reproducible δ13C values were achieved with errors ≤ 0.6‰ (n = 3) for aqueous concentrations down to 100 μg L-1. With preconcentration factors between 130 and 220, the method outperformed conventional liquid-liquid extraction in terms of sample preparation time and resource consumption with comparable reproducibility. Furthermore, we have demonstrated the suitability of the method (i) for the extraction of the analytes from a spiked river water sample and (ii) to quantify kinetic carbon isotope effect for 2,4,6-trichlorophenol during reduction with zero-valent zinc in a laboratory batch experiment. The presented work shows for the first time the potential of DLLME for analyte enrichment prior to CSIA and paves the way for further developments, such as the extraction of other compounds or scaling up to larger sample volumes.

Enhanced dual synergistic mechanism of adsorption and ozone triggering via biochar-derived zero-valent bimetal sites for water purification

Novel zero-valent iron (ZVI) and zero-valent zinc (ZVZ) bimetal-supported biochar (ZF@BC) was developed for heterogeneous catalytic ozonation (HCO), which demonstrated the unique dual synergistic adsorption and catalysis-induced effective O3 triggering and interfacial decontamination. ZF@BC exhibited impressive catalytic and structure stabilities for 2-methyl-4-chlorophenoxyacetic acid (MCPA) degradation during long-lasting HCO, which can resist interference from a complex water quality background. Abundant electron-rich oxygen-containing functional groups and defects on BC contributed to the adsorption of MCPA and O3, respectively, while the introduced ZVZ was anticipated to expedite O3 decomposition by facilitating single-electron transfer reduction of O2 and establishing a robust connection with ZVI. Continuous efficacy of bimetal in three stages enhanced the efficiency of O3 utilization and hydroxyl radicals (•OH) yield, thereby safely mitigating the associated toxicity of MCPA after treatment. The development of O3/ZF@BC introduced a sustainable, long-term decontamination strategy and provided valuable insights for the advancement of HCO.

Modulation of oxygen vacancy and zero-valent zinc in ZnCr2O4 nanofibers by enriching zinc for efficient nitrate reduction

One-step generation and modulation of oxygen vacancies by enriching zinc to substitute chromium ions in ZnCr2O4 nanofibers are proposed to reduce nitrate to ammonia, which meanwhile induces the formation of zero-valent zinc. The catalyst with the most oxygen vacancies achieves an optimal NH3 yield rate of 20.36 mg h−1 mg−1cat. and Faradaic efficiency of 90.21 % at − 1.2 V vs. reversible hydrogen electrode (RHE), and it also has excellent long-term durability and structural stability. Theoretical calculations reveal oxygen vacancies are more favorable to form in ZnCr2O4, which shift the d-band center (εd) of Cr and Zn to higher and lower energy levels, respectively. The free energy for the whole reaction on ZnCr2O4 shows a continuous decreasing tendency, indicating the reaction can spontaneously take place. The results are expected to pave a new avenue to rationally design defective non-noble catalysts for catalyzing nitrate to produce ammonia.

Degradation of 1-alkyl-3-methylimidazolium tetrafluoroborate in an ultrasonic zero-valent zinc and activated carbon micro-electrolysis system

Increased attention has been given to the removal of ionic liquids (ILs) from natural water environments. In this work, 5 kinds of 1-alkyl-3-methylimidazoliumtetrafluoroborate ([Cnmim][BF4] (n = 2, 4, 6, 8, 10)) ILs were degraded in an ultrasonic zero-valent zinc (ZVZ) and activated carbon (AC) micro-electrolysis system. Optimization of degradation conditions and the degradation levels were studied by high performance liquid chromatography, the surface morphology of the ZVZ and AC changed before and after the reaction were observed by scanning electron microscope. The degradation intermediates were detected by gas chromatography- mass spectrometry and ion chromatography, and inferred the degradation pathway. The degradation effect of [C4mim][BF4] was best with ultrasonic assistance, pH 3 and an AC/ZVZ ratio of 1:1. The degradation of [Cnmim][BF4] in aqueous solution exceeded 91.7% in 120 min, and the mineralization level exceeded 88.9%. The surface of smooth and dense ZVZ particles became loose flocculent and the porous surface of AC became larger and rougher after reaction. The degradation pathway suggested that the imidazolium ring was sulfurized or oxidized, and then the ring was opened to form N-alkyl formamide and N-methyl formamide. ZVZ/AC micro-electrolysis combined with ultrasonic irradiation is an effective method to remove ILs, which provides new insight into IL degradation.

Waste-battery-derived multifunctional zinc catalysts for glycolysis and decolorization of polyethylene terephthalate

In this study, novel and easily recyclable catalysts were prepared from waste batteries for efficient glycolysis and decolorization of polyethylene terephthalate (PET) to obtain bis(2-hydroxyethyl) terephthalate (BHET). At 190 °C and 5 h, the PET conversion and BHET yield reach 89.7 and 77.7%, respectively, which are comparable to the values obtained for the commonly used catalyst zinc acetate. Species generated from the reaction between ethylene glycol (EG) and zinc plates (e.g., Zn-glycolate, ZnO, and other metal species on zinc plates) demonstrate excellent catalytic performance. Furthermore, dye molecules released from several commercial-colored PET bottles during glycolysis can be degraded to colorless molecules using zinc plates, thereby facilitating BHET purification. The exposed zero-valent zinc from the zinc plates in EG is responsible for degrading the dye molecules. Finally, the scaled-up PET glycolysis process is conceptually designed using Aspen Plus software. The simulation results suggest that reducing the energy requirement in distillation is necessary for further improvement.

Expanding the calibration range of compound-specific chlorine isotope analysis by the preparation of a 37 Cl-enriched tetrachloroethylene.

The recent development of reliable GC/qMS methods for δ37 Cl compound-specific stable isotope analysis (CSIA) paves the way for dual carbon-chlorine isotope analysis of chlorinated ethenes and thus allows deeper insights into underlying transformation processes/mechanisms. A two-point calibration is indispensable for the precise and correct conversion of raw data to the international δ37 ClSMOC scale. The currently available calibration standards for tetrachloroethylene (PCE) span only a very narrow range from -2.52‰ (EIL2) to +0.29‰ (EIL1), which is considerably smaller than observed δ37 Cl isotope enrichment in (bio-)transformation studies (up to 12‰). We describe the preparation and evaluation of a new 37 Cl-enriched PCE standard to avoid bias in δ37 Cl CSIA arising from extrapolation beyond the calibration range. The preparation comprised: (i) partial PCE reduction by zero-valent zinc in a system of PCE, ethanol (initial volume ratio 3/5) and trace amounts of water followed by (ii) liquid-liquid extraction and (iii) a subsequent fractional distillation to purify the 37 Cl-enriched PCE. The obtained PCE (PCEenriched ) showed a purity of 98.8% (mole fraction) and a δ37 ClSMOC value of +10.8±0.5‰. The evaluation of an experimental dataset with and without extrapolation showed no significant variation. The new PCE standard (PCEenriched ) expands the calibration range to 13.3‰ (previously 2.8‰) and thus prevents potential bias introduced by extrapolation beyond the calibration range.

Efficient Reductive Defluorination of Branched PFOS by Metal-Porphyrin Complexes.

Vitamin B12 (VB12) has been reported to degrade PFOS in the presence of TiIII citrate at 70 °C. Porphyrin-based catalysts have emerged as VB12 analogues and have been successfully used in various fields of research due to their interesting structural and electronic properties. However, there is inadequate information on the use of these porphyrin-based metal complexes in the defluorination of PFOS. We have therefore explored a series of porphyrin-based metal complexes for the degradation of PFOS. CoII-5,10,15,20-tetraphenyl-21H,23H-porphyrin (CoII-TPP), CoII-5,10,15,20-tetrakis(4-methoxyphenyl)-21H,23H-porphyrin (CoII-M-TPP), and CoIII-M-TPP exhibited efficient reductive defluorination of the branched PFOS. Within 5-8 h, these compounds achieved the same level of PFOS defluorination as VB12 achieved in 7-10 days. For branched isomers, the specific removal rate of the CoII-TPP-TiIII citrate system is 64-105 times higher than that for VB12-TiIII citrate. Moreover, the CoII-TPP-TiIII citrate system displayed efficient (51%) defluorination for the branched PFOS (br-PFOS) in 1 day even at room temperature (25 °C). The effects of the iron and cobalt metal centers, reaction pH, and several reductants (NaBH4, nanosized zerovalent zinc (nZn0), and TiIII citrate) were systematically investigated. Based on the analysis of the products and previously published reports, a new possible defluorination pathway of branched PFOS is also proposed.

Activation of O2 by zero-valent zinc assisted with Cu(II) for organics removal: Performance and mechanism

This study proposes a method to activate O2 by accelerating the corrosion process for zero-valent zinc (ZVZ) with the assistance of Cu(II), promoting the consecutive production of reactive oxygen species. The mechanisms for reactive oxygen species generation are clarified with metronidazole (MTZ) as the targeted pollutant. The outcome suggests the association of Cu(Ⅱ) and ZVZ presents an apparent cooperative activity, an enhancement of 85% in MTZ removal is attained for the ZVZ/Cu(Ⅱ) system after 10 min compared to that for ZVZ. Analysis of the mechanisms involved indicates that this improvement is due to the addition of Cu(Ⅱ), which can accelerate the corrosion of ZVZ. In addition, quenching experiments and electron paramagnetic resonance (EPR) technology show that superoxide radicals (·O2−) result in rapid MTZ degradation. The primary component that is liable for O2 activation and a certain amount of H2O2 generation is verified to be ZVZ. Moreover, Cu(I) is detected in the ZVZ/Cu(Ⅱ) system, which arises from a direct reduction pathway driven by ZVZ and an indirect reduction pathway driven by active hydrogen atoms.

Zero valent zinc regulates adipocyte differentiation through calpain family protein and peroxisome proliferator-activated receptor gamma signaling in mouse 3T3-L1 cells

In the present study, the zero valent zinc (ZVZ) was used in the field of tissue regeneration engineering by inducing the preadipocytes into mature adipocytes in mouse 3T3-L1 cells. Initially, the ZVZ nanoparticles was synthesized using chemical reduction method and confirmed by EDS spectrum analysis which showed the presence of zinc ion without any impurities. The XRD and Raman analysis showed the characteristic peaks of zinc with hexagonal structure and the strong phonon band attributed to ZVZ, respectively. The microscopic analysis showed the ZVZ nanoparticles are well dispersed with spherical shape and the size was found to between 85−95 nm. The in vitro cytotoxic activity of ZVZ against 3T3-L1 showed less toxicity in higher concentration and the results were compared with standard adipogenic stimulant dexamethasone. The oil red O staining assay morphologically confirmed the ZVZ induces adipogenesis in 3T3-L1 as well as increase the lipid accumulation during treatment with ZVZ. Moreover, the ZVZ upregulates the expression of adipogenic marker genes such as PPARγ, FABP4 and the calpain family protein during differentiation of preadipocytes into mature adipocytes. Together, the ZVZ regulates the differentiation in 3T3-L1 cells through PPARγ and calpain signaling pathway deciphers the role of ZVZ in tissue regeneration engineering.

Enhanced nitrogen and phosphorus adsorption performance and stabilization by novel panda manure biochar modified by CMC stabilized nZVZ composite in aqueous solution: Mechanisms and application potential

Direct discharge of water containing excessive nitrogen and phosphorus concentrations into the aquatic environment can lead to loss of resources and eutrophication. Biochar prepared by thermochemical treatment of feedstocks, particularly the metal modified biochar, which can be used as a new adsorbent for aquatic environmental treatment. Herein, a novel panda manure biochar (PMBC) modified by carboxymethyl cellulose (CMC) stabilized nano zero-valent zinc (nZVZ-CMC-PMBC) was developed and applied for efficiently removal of NH4+and PO43−. Batch sorption experiments verified the kinetics and equilibrium isotherms of NH4+ and PO43− adsorption, the results showed that PMBC had significantly better adsorption performance on nitrogen and phosphorus compared to bamboo biochar. Moreover nZVZ-CMC-PMBC demonstrated maximum theoretical adsorption capacities of 40.31 mg•g−1 NH4+-N and 154.30 mg•g−1 total phosphorus (TP). Characterization result of SEM-EDS, BET, FTIR, XRD and XPS reveal that PMBC had larger specific surface area and pore diameter than bamboo biochar which confirmed that PMBC contained more adsorption sites. As for nZVZ-CMC-PMBC, crystalline nZVZ flakes are dispersed and impregnated into the frame of CMC-nZVZ- PMBC composite, characterization analysis unveiled the formed complexes on its surface. Therefore, the adsorption mechanism of nZVZ-CMC-PMBC for NH4+-N and TP mainly involved Zn2+ precipitates, surface electrostatic attraction and surface complexation.

XAFS Study of Thermally Oxidated Sapphire Implanted with Zinc Ions

The local structure of Zn in Al2O3 is studied by the X-ray absorption fine structure (XAFS) method after the implantation of Zn ions and thermal oxidation, which results in the formation of nanoparticles in sapphire. Based on the data of X-ray absorption near edge spectra (XANES), it can be concluded that Zn atoms interact with oxygen and the Al2O3 substrate. The sapphire sample implanted with Zn ions and annealed in oxygen at 600°C contains zinc in three different states: ZnO, zinc spinel (ganite) ZnAl2O4, and metallic Zn in the form of nanoparticles. Since the fraction of zero-valent zinc is close to 50%, very small Zn metal clusters consisting of the minimum possible number of chemically bonded atoms are expected to be formed. The average number of Zn–Zn bonds for each zinc atom in them slightly exceeds unity, i.e., Zn dimers dominate in the sapphire matrix.

Debromination of polybrominated diphenyl ethers (PBDEs) by palladized zerovalent zinc particles: Influence factors, pathways and mechanism

We synthesized a novel material, namely palladized zero-valent zinc (Pd/ZVZ), and investigated its efficiency for the degradation of polybrominated diphenyl ethers (PBDEs). The plated Pd significantly enhances the degradation rate of PBDEs by ZVZ at the optimum loading of 1% by weight. In the Pd/ZVZ system, very few lower BDEs were accumulated during the degradation of 2,2′,4,4′- tetrabromodiphenyl ether (BDE-47) and the final product is diphenyl ether, whereas the ZVZ system only debrominates BDE-47 to di-BDE and further debromination becomes very difficult. The degradation rates of BDEs by ZVZ greatly decreased with decreased bromination level, while in Pd/ZVZ system, the degradation rates of PBDEs did not show a significant difference. These indicate different mechanisms. This was confirmed by investigating the debromination pathways of the PBDEs in both systems. We determined that a H-transfer was the dominant mechanism in the Pd/ZVZ system. In addition, the reactivity of Pd/ZVZ to BDE-47 is pH-independent, which has a great advantage for various applications over ZVZ alone. Our study provides a new approach for the remediation of the PBDEs pollution.

Enhanced debromination of 2,2′,4,4′-tetrabromodiphenyl ether (BDE-47) by zero-valent zinc with ascorbic acid

A new technique of zero-valent zinc coupled with ascorbic acid (ZVZ/AA) was developed and applied to debrominate the 2,2′,4,4′-Tetrabromodiphenyl ether (BDE-47), which achieved high conversion and rapid debromination of BDE-47 to less- or non-toxic forms. The reaction conditions were optimized by the addition of 100 mg/L ZVZ particles and 3 mmol/L AA at original solution pH = 4.00 using the solvent of methanol/H2O (v:v = 4:6), which could convert approximately 94% of 5 mg/L BDE-47 into lower-brominated diphenyl ethers within a 90 min at the ZVZ/AA system. The high debromination of BDE-47 was mainly attributed to the effect of AA that inhibits the formation of Zn(II)(hydr)oxide passivation layers and promotes the corrosion of ZVZ, which leads to increase the reactivity of ZVZ. Additionally, ion chromatography and gas chromatography mass spectrometry analyses revealed that bromine ion and lower-debromination diphenyl ethers formed during the reduction of BDE-47. Furthermore, based on the generation of the intermediates products, and its concentration changes over time, it was proposed that the dominant pathway for conversion of BDE-47 was sequential debromination and the final products were diphenyl ethers. These results suggested that the ZVZ/AA system has the potential for highly efficient debromination of BDE-47 from wastewater.

Development and Validation of Technologies for Remediation of 1,2,3-Trichloropropane in Groundwater

1,2,3-Trichloropropane (TCP) is a synthetic chemical with known and suspected human health effects associated with exposure. In response to the identification of TCP in environmental media, several states in the United States (US) have set maximum contaminant levels (MCLs) for TCP in drinking water and guidance values for TCP in groundwater. Current treatment methods for TCP in groundwater are limited and can be cost prohibitive. The purpose of this review is to summarize the state of knowledge on TCP remedial technologies and describe efforts to develop and validate promising treatment methods. In situ chemical reduction (ISCR) and in situ bioremediation (ISB) have shown the most potential for TCP remediation. ISCR of TCP by zero-valent zinc (ZVZ) has been evaluated for several years through bench-scale testing, field-scale column testing, and a pilot-scale ZVZ injection program. Additional injections are ongoing to assess the long-term efficacy of ISCR. ISB under anaerobic conditions has been evaluated in laboratory studies and at the field scale with bioaugmentation. Field-scale evaluation of ISB is also ongoing. This review provides an overview of TCP, including use, physicochemical properties, fate and transport, health effects, and current regulation. The states of treatment technologies for TCP are detailed, including granular activated carbon (GAC), ISCR, ISB, and chemical oxidation. Case studies and notable findings are described for ISCR and ISB. While knowledge gaps remain for ISCR and ISB, results to date for these technologies are encouraging.

Nano zerovalent zinc catalyzed peroxymonosulfate based advanced oxidation technologies for treatment of chlorpyrifos in aqueous solution: A semi-pilot scale study

Chlorpyrifos (CPY), an organophosphate pesticide is largely used throughout the world on different crops for the control of pests and causes severe health and environmental issues. In this study, highly efficient, crystalline, and nm-rang sized zerovalent zinc (nZVZn) catalyst was synthesized and used for removal of chlorpyrifos at semi-pilot scale. The nZVZn showed high activity and caused 55% removal of CPY at 90 min time under the conditions of [CPY] 0 = 10 mg/L, [nZVZn] 0 = 1.0 g/L, and flow rate of the reactor = 0.2 L/min. Using identical conditions of [CPY] 0 , [nZVZn] 0 and flow rate, the use of peroxymonosulfate (PMS) promoted the performance of nZVZn and caused 99.5% removal of CPY at [PMS] 0 = 40 mg/L. The electron spin resonance (ESR) spectroscopy studies revealed that nZVZn catalyzed PMS reactions yield hydroxyl and sulfate radicals that degraded CPY and removal of CPY was suppressed by applying radical scavengers. The nZVZn catalyzed PMS based removal of CPY was optimum at high [PMS] 0 , [nZVZn] 0 and low pH of solution. The flow rate of the pilot plant reactor also influenced the degradation efficiency of CPY. High pH of solution, high [CPY] 0 as well as use of alcohols, NOM, and some inorganic ions inhibited removal of CPY by nZVZn catalyzed PMS. The analysis of degradation products (DPs) of CPY were used to propose degradation pathways of CPY. The high TOC removal of CPY, low leaching of Zn 2+ from Zn 0 into aqueous solution, and toxicity reduction of CPY suggest the nZVZn catalyzed PMS process to be highly effective and environmental benign for treatment of CPY. • Nano zerovalent zinc was used for removal of chlorpyrifos at semi-pilot scale. • Removal of chlorpyrifos by zerovalent zinc was promoted by peroxymonosulfate. • Hydroxyl and sulfate radical rate constants with chlorpyrifos were calculated. • Proposed degradation pathways of chlorpyrifos were suggested. • Toxicities of treated chlorpyrifos solutions and zinc ion leaching were evaluated.

Regenerable bagasse-based carbon activated by in situ formation of zero-valent zinc microparticles for high-performance degradation of amoxicillin in water.

Increasing degradation of amoxicillin in water by low-cost advanced functional activated carbon-based materials derived from bagasse is an effective and economic way to remove the antibiotic residue pollutant and for high-valued utilization and transformation of plant wastes. In this work, bagasse was pyrolyzed and Zn2+ was activated for designing a high-efficiency bagasse-based activated carbon, which was characterized by FTIR, XRD, XPS, SEM, EDS, and ζ potential analyses. These analyses illustrated the mechanism of amoxicillin degradation, and microscale zero-valent zinc in bagasse-based activated carbon has a key role in amoxicillin degradation. Amoxicillin was broken down by reductive degraded radicals, which were produced by microscale zero-valent zinc corrosion in water. After the amoxicillin degradation, the byproduct of zinc hydroxide being adsorbed onto the used bagasse-based activated carbon can provide possibility of sustainable regeneration. Mass spectra analysis illustrated the main degradation products of amoxicillin. The kinetic experiments were adopted to observe the process of amoxicillin degradation, followed by the pseudo-first-order kinetic model. The isotherm experiments demonstrated that the maximum amoxicillin degradation capacity of bagasse-based activated carbon was about 46mgg-1. The bagasse wastes were used as carbon source to design potential advanced activated carbon materials for increasing degradation of amoxicillin in water.

Preparation of Nanosized Zero-Valent zinc (Zn0) Immobilized on ZnO as Redox Nanocomposite for Degradation of Methyl Orange from Aqueous Solution

Introduction: In this study, nanosized zero-valent zinc (Zn0) as a reducing agent, simultaneously synthesized and immobilized on an oxidizing agent, ZnO photocatalyst for degradation of methyl orange (MO) from the aqueous solution. Materials and Methods: The prepared redox nanocomposite (nZn0-ZnO) was characterized by the XRD and SEM techniques. The prepared sample was separated by centrifuging. The preparation process of nZn0-ZnO including synthesis-immobilization, washing, and drying carried out under Argon gas flow. Moreover, the effect of temperature and kinetics reaction was studied. Results: The results showed that degradation efficiency of prepared redox nanocomposite was increased compared to each ZnO nanopowder and Zn0 under the same operational condition. The calculated activation energy for the degradation process was 4.05 KJ.mol-1. Finally, the results showed that the degradation processes followed pseudo first order kinetic model in the basic condition by the relative deviation modulus. Conclusion: As compared to ZnO nanopowder and Zn0, the prepared redox nanocomposite showed high degradation efficiency for the removal of methyl orange from the aqueous solution.

Reduction of nitrate to nitrite in water by acid-washed zero-valent zinc

ABSTRACTThis study examines capability of zero-valent zinc (ZVZ), prepared from acid-washing zinc powder, for reducing nitrate to nitrite under various conditions. While higher dosages of ZVZ and elevated temperatures enhance nitrate reduction, effect of pH is validated as the most important factor to nitrate reduction as the nitrate reduction efficiency and kinetics are significantly enhanced under acidic conditions. However, nitrate reduction by ZVZ is inhibited under alkaline conditions. ZVZ also remains effective for nitrate reduction in the presence of other anions. The findings gained in this study are critical to design and operate nitrate reduction using zero-valent metals.

Removal of Acid Red dye from aqueous solution using zero-valent copper and zero-valent zinc nanoparticles

Removal of Acid Red dye from aqueous solution using zero-valent copper and zero-valent zinc nanoparticles