Zero-valent Metal Research Articles

Formally Zerovalent Bis(arene) Germylene Complexes of Zirconium and Hafnium.

Tetrachlorides of zirconium- and hafnium form adducts (2,3) with an intramolecular germylene phosphine Lewis pair. Two electron reduction treating the adducts with [MesNacnacMg]2 gives the low valent metal complexes (4, 5) featuring η6-Trip coordination at the Zr(II) and Hf(II) metal atom. Reduction of the M(II)-complexes gives the zerovalent metal complexes of zirconium (6) and hafnium (7), which have been structurally characterized. Two arene moieties and the germylene exhibit metal coordination. Puckered coordination of a P-phenyl unit was observed for both derivatives 6 and 7. Four electron reduction of a reaction mixture of metal tetrachloride with the germylene-phosphine Lewis pair also gives the zerovalent complexes in good yield. Carbonyl complexes were synthesized treating the reduced metal complexes with carbon monoxide. Dimethylbutadiene shows a reaction with an arene moiety and the coordinated germylene ligand of the zerovalent complexes. A cyclohexadienyl and a triorganogermate ligand are formed. For zirconium this reaction is reversible at room temperature.

Efficient activation of sodium percarbonate by hydroxylamine-enhanced zero-valent transition metals for the removal of AZO: performance, free radical generation and mechanism

Azoxystrobin (AZO) fungicides are novel organic pollutants which are stable in water environment. These pollutants can be degraded using low cost zero-valent metals (zero-valent iron (ZVI) and zero-valent copper (ZVC)) to activate sodium percarbonate (SPC), and the introduction of hydroxylamine (HA) can effectively improve the reaction efficiency of this system. According to the experimental results, HA significantly promoted the regeneration of Fe2+ and Cu+ in the decomposed solution of SPC, significantly accelerating the formation of hydroxyl radicals (•OH) and facilitating the degradation of AZO. Under optimal conditions, when pH = 3, the rate of AZO removal by the HA/ZVI/SPC system reached 99.0 % in 15 min, while the HA/ZVC/SPC system required 50 min to reach 99.1 % removal. Both of the tested HA/zero-valent metal/SPC processes produced •OH, carbonate radicals (CO3·-), superoxide radicals (O2·-) and singlet oxygen (1O2), among which, •OH appeared to be the main reactant responsible for AZO removal. Furthermore, it was found that •OH reacted with trace levels of carbonate ions to generate other reactive oxygen species and promote AZO degradation. The addition of HA not only slowed down the surface passivation of zero-valent metals, but also promoted the conversion of high-valent metal ions to low-valent metal ions, resulting in the generation of more reactive oxygen species within the system. In addition, the degradation intermediates were identified by LC-MS analysis and density-functional theory (DFT), allowing the possible AZO degradation pathways to be proposed.

Recent Developments in the Adsorption of Heavy Metal Ions from Aqueous Solutions Using Various Nanomaterials.

Water pollution is caused by heavy metals, minerals, and dyes. It has become a global environmental problem. There are numerous methods for removing different types of pollutants from wastewater. Adsorption is viewed as the most promising and financially viable option. Nanostructured materials are used as effective materials for adsorption techniques to extract metal ions from wastewater. Many types of nanomaterials, such as zero-valent metals, metal oxides, carbon nanomaterials, and magnetic nanocomposites, are used as adsorbents. Magnetic nanocomposites as adsorbents have magnetic properties and abundant active functional groups, and unique nanomaterials endow them with better properties than nonmagnetic materials (classic adsorbents). Nonmagnetic materials (classic adsorbents) typically have limitations such as limited adsorption capacity, adsorbent recovery, poor selective adsorption, and secondary treatment. Magnetic nanocomposites are easy to recover, have strong selectivity and high adsorption capacity, are safe and economical, and have always been a hotspot for research. A large amount of data has been collected in this review, which is based on an extensive study of the synthesis, characterization, and adsorption capacity for the elimination of ions from wastewater and their separation from water. The effects of several experimental parameters on metal ion removal, including contact duration, temperature, adsorbent dose, pH, starting ion concentration, and ionic strength, have also been investigated. In addition, a variety of illustrations are used to describe the various adsorption kinetics and adsorption isotherm models, providing insight into the adsorption process.

Cu-Ag nanoparticles-dispersed and microchannel textured-laser induced graphene: A chemiresistive aptasensor for thrombin

Thrombin is a key enzyme of the clotting cascade, which can convert soluble fibrinogen to insoluble fibrin. A rapid and accurate sensor is required to give easy access to patients and healthy individuals to monitor their thrombin levels. In this study, a Cu and Ag bimetal nanoparticles (NPs)-dispersed and microchannel textured-laser induced graphene (Cu-Ag-LIG)-based chemiresistive aptasensor is developed. The sensor substrate was synthesized via the suspension polymerization of phenol and formaldehyde, with the in situ inclusion of the metal salts in the reaction mixture. Laser ablation converted the carbon containing polymeric groups to sp2 hybridized graphitic carbon and the metal salts to zero-valent metal NPs. Laser ablation was also used to create microchannels on the graphene surface to ensure the uniform distribution of the analyte. Ag NPs facilitated the binding of thrombin binding aptamer (TBA) via covalent bond, while Cu NPs provided structural support. The aptasensor showed a linear response over the 0.1 – 50 units/mL-thrombin concentration range. The sensor response was unaffected by common interfering biomolecules such as glucose, bovine serum albumin, urea, trypsin, and cholesterol. This study showcases the broader and often overlooked significance of chemiresistive sensors not only in healthcare but also across various scientific domains, offering avenues for transformative advancements in diagnostic technologies.

Synthesis and characterization of Selenicereus undatus extract mediated nano-Bi2O3 and its application in the adsorption of Rhodamine B dye

Betacyanins (BC) are reddish-purple pigments widely found in the peels of white-fleshed dragon fruit (Selenicereus undatus) and peels and pulps of red-fleshed dragon fruit (Selenicereus costaricensis). BC pigments are good anti-oxidants that inhibit the formation of reactive oxygen species (ROS) in plants and thereby promote the reduction of metal ions to zero-valent metals. It also acts as a good stabilizing and capping agent in the synthesis of nanoparticles. Hence, this research aims to extract, and quantize the content of BC from the peels of Selenicereus undatus, to fabricate betacyanin-rich- Selenicereus undatus (SU) modified bismuth oxide nanoparticles (Bi2O3 NPs) and characterize using UV-Vis, FTIR, XRD, SEM, EDAX, and BET. The quantity and stability of the betacyanin are optimized using various parameters like time, temperature, solvent ratio, pH, etc., through a UV-Vis spectrophotometer at 538 nm. Synthesized SU-Bi2O3 NPs aim to alleviate synthetic dye contaminants through adsorption- an efficient route for water remediation. The nano-adsorbent Bi2O3 NPs showed an increase in dye adsorption with an increase in reaction time, temperature, and Bi2O3 NPs dosage, enabling efficient removal of dyes such as Rhodamine B (RhB) dyes.

Ternary Ag3AuS2 Nanocrystals for Thin-Film Solar Cells.

The concept of clean and pollution-free energy development has promoted the rise of environmentally friendly silver-based chalcogenide nanocrystal (NC) solar cells, but currently reported silver-based NCs need complex synthesis processes at high temperatures that may bring zerovalent noble metal impurities for their high redox potentials. In this study, we report a facile synthesis of novel Ag3AuS2 NCs by injecting highly active oleylamine sulfur complexes as sulfur sources into metal precursor solutions at low temperatures of 60 °C. The obtained Ag3AuS2 NCs exhibit broad absorption spectra and high molar extinction coefficients (106 M-1 cm-1). Then, the Ag3AuS2 NCs are applied as the light-absorbing active layer in environmentally friendly thin-film solar cells. By introducing a hybrid mixture of charge acceptors and donors (NCs/P3HT hybrid film) at the interface, the device gains an absorption increment and enhanced charge extraction, achieving a final power conversion efficiency of 3.38%. This work demonstrates the enormous potential of Ag3AuS2 NCs from low-temperature preparation for photovoltaic applications.

Exploring the electronic influence on coordination complexes formed from appended pyrrolidine azothioformamide ligands and copper(I) salts

Redox-active arylazothioformamide (ATF) ligands have seen attention through their unique coordination complexes formed with salts of late transition metals and their known ability to oxidatively dissolve zerovalent metals. When mixed with Cu(I) salts, ATF ligands form both 2:1 and 2:2 coordination complexes remaining neutral without undergoing any redox event. Herein, a series of para-substituted pyrrolidine-ATFs were synthesized, incorporating both electron-donating groups (i.e., -OMe and -Me) as well as electron-withdrawing groups (i.e., -CF3, and -CN). These ligands were then mixed with Cu(I) salts, including CuBr, CuI, and [(CH3CN)4Cu](BF4) to form coordination complexes. The resulting complexes underwent thorough characterization, with several producing X-ray quality crystals for detailed structural analysis. Both strong and weak intermolecular interactions were found through Hirshfeld surface analysis and the redox activity of the complexes was probed using cyclic voltammetry in the voltage range of -1.8 to 1.8 V. Through a UV–Vis titration study, the binding interactions between the ligand host and Cu(I) metal salt guest molecules were determined and ranged from 4,000 – 100,000 M-1. Computational modeling was employed to calculate the change in Gibbs free energy (ΔG) for the formation of the complexes, revealing the optimal orientations between the ligand and the metal. These studies have confirmed that para-substituted pyrrolidine-ATFs containing electron-donating groups exhibit a higher binding affinity towards Cu(I) metal salts compared to those with electron-withdrawing groups. With a thorough understanding of ATF-metal coordination, further ligand design can lead to exciting new catalysts and/or selective metal dissolution agents.

Antibacterial composite films of oxidized alginate-chitosan-ZnO anchored Cu nanoparticles for the degradation of organic pollutants

The growing population and urbanization have adversely affected the environment including water. The waste water from industries has affected not only human but also animals. The availability of clean water is one of the foremost needs for living organism. This makes very urgent to find reliable solutions for cleaning waste water. These days catalysis is one the best solutions to remove and degrade organic pollutants. In this work, porous composite polymer films have been designed through facile method which were employed to stabilize zero-valent metal nanoparticles (NPs). The sustainable, environmentally friendly polymer matrix with attached metal NPs was applied for the effective catalytic degradation of both phenolic compounds and organic dyes. The different composite films consist of ZnO NPs embedded in an Oxidized Alginate-Chitosan (OAlg-CS) biomatrix named as OAlg-CS/ZnO with various percentages of ZnO as a support for metallic Cu NPs. The ZnO NPs have been incorporated into OAlg-CS polymer with 10, 15, and 20 wt% and are designated as OAlg-CS/ZnO-10, OAlg-CS/ZnO-15, OAlg-CS/ZnO-20. Various analytical techniques were utilized to investigate the shape, morphology, elemental composition, functional groups and stability of the composite films. All these polymer nanocomposite films were then evaluated for removal of model organic pollutants comprising p-nitrophenol (4-NP), methylene blue (MB), and methyl orange (MO). The Kapp value for 4-NP was 2.19 × 10−1 min−1, 4.68 × 10−1 min−1 for MO and 8.99× 10−1 min−1 for MB. The experimental results demonstrated that OAlg-CS/ZnO-20 films show the highest catalytic activity as compared to OAlg-CS/ZnO, OAlg-CS/ZnO-10, and OAlg-CS/ZnO-15. The order of rate constants for nitrophenol and dyes using OAlg-CS/ZnO-20 was found to be MB ˃ MO ˃ 4-NP, showing the selectivity of these composite films. The prepared composite films were also investigated for their antibacterial activity against Gram-positive and Gram-negative bacteria and all the films exhibited good anti-bacterial activity, with OAlg-CS/ZnO-20 showed the highest anti-bacterial activity.

Plasma Jet Mediated Reduction of Metal Salt

We demonstrate electrodeposition where the plasma acts as both an electrolyte and electrode, to deposit metallic conductive coatings. In conventional electroplating metal ions are reduced at a working electrode with an applied electrochemical potential. Here an RF atmospheric pressure plasma jet (APPJ) is able to induce a electrochemical reduction due to the presence of free electrons. The advantage of this method is demonstrated by the ability to deposit conducting metal tracks on delicate surfaces including insulators and polymers. The small size and gaseous nature of the plasma allows deposition in difficult geometries with precise spatial control.The reduction process occurs within the plasma. As the aerosolized metal salt crystals interact with the plasma, the free electrons reduce the metal and the hydrogen combines with the anion producing a water soluble acid. The metal reduction takes place within the plasma jet, as show by varying the plasma power and determining the amount of zerovalent metal deposited. Even at low powers, <6 W, the plasma was able to fully reduce the silver, however the copper requires plasma powers of 12 W and above in order to be fully reduced. Once reduced the deposited tracks were shown to be conductive with around 20 % and around 5 % of bulk conductivity for silver and copper respectively. A sintering process occurs also within the plasma, leaving a contiguous track of fused particles of zerovalent metal producing the conducting tracks. The technique is demonstrated mainly for copper and silver, however multiple other metals were capable of being deposited. In addition to the conductivity, the track adherence was tested both using a Scotch Tape© pull test and an in-house constructed scratch test. The track was completely unaffected by the tape pull and the stylus type scratch test showed that the films were scratch resistant up to a pressure up to of 420 kg cm-2, with no measurable drop in conductivity.The APPJ is an accessible, low power, sustainable, precise electroplating device, capable of depositing pure metallic films onto a variety of surfaces. Furthermore, we demonstrate deposition on rough surfaces such as damaged fiberglass, as well as sensitive surfaces including plant tissue and pigskin, with limited damage to the surface.Figure 1. a) showing the deposition setup including nebuliser, salt solution injection, gas flow and power supply. An optical image of the APPJ during deposition operation is included, as well as Schlieren imagine showing the laminar gas flow. b) A silver Hilbert curve printed onto Kapton 0.05 mm thickness via the plasma deposition technique, in a single step process, with no sample prep or post processing. c) Copper deposited on porcine skin showing conductance as part of a LED circuit. Figure 1

Exploring the potential of surface-modified alginate beads for catalytic removal of environmental pollutants and hydrogen gas generation

In this study, hydrogel beads were fabricated using alginate (Algt) polymer containing dispersed nickel phthalocyanine (NTC) nanomaterial. The viscous solution of Algt and NTC was poured dropwise into a divalent Ca2+ ions, resulting in the formation of hydrogel beads known as NTC@Algt-BDs. The surface of the NTC@Algt-BDs was further modified by coating them with different types of metal ions, yielding metal-coated M+/NTC@Algt-BDs. The adsorbed metal ions i.e., Cu+2, Ag+, Ni+2, Co+2, and Fe+3 were subsequently reduced to zero-valent metal nanoparticles (M0) by NaBH4. The prepared beads were characterized using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Initially, M0/NTC@Algt-BDs were examined for the catalytic reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP). Among them, Cu0/NTC@Algt-BDs catalyst exhibited the highest reduction rate and therefore, investigated for reduction of different nitrophenols (NPs) and dyes, including 2-nitrophenol (2-NP), 2,6-dinitrophenol (2,6-DNP), methyl orange (MO), potassium ferrocyanide (PFC), congo red (CR), and acridine orange (ArO). The highest reduction rates of 2.019 and 1.394 min−1 were observed for MO and 2-NP, respectively. Furthermore, the fabricated catalysts were employed for the efficient production of H2 gas by NaBH4 methanolysis. Among which the Ag0/NTC@Algt-BDs catalyst showed excellent catalytic production of H2 gas, exhibiting the lowest activation energy (Ea) of 25.169 kJ/mol at ambient temperature. Furthermore, the impact of NaBH4 amount, and catalyst dosage on the reduction of 2-NP and H2 gas production was conducted whereas the effect of temperature on methanolysis of NaBH4 for evolution of H2 gas was studied. The amount of H2 gas was confirmed by GC-TCD system. Additionally, the recyclability of the catalyst was investigated, as it garnered significant research interest.

Enhancing stability of mononuclear Pt atoms via chloride-to-bromide ligand exchange for hydrosilylation reaction

Single atom catalysts (SACs) offer high atom efficiency with highly selective reaction pathway. Various strategies have been developed to synthesize SACs, among which thermally stable metal centers are usually in high oxidation while they are susceptible to facile sintering in reduced state or under reducing conditions. One of the strategies developed very recently to achieve stable zero valent metal atoms is based on the selection of ligands with moderate coordination strength with the metal center. In this work, the crucial importance of ligand to the stability of single Pt0 atoms is investigated. While HCl and diether have been found to be able to stabilize single Pt0 atoms by forming Pt1@HCl adducts, HBr coordinated Pt single atom (Pt1@HBr) obtained by simply exchanging HCl with HBr shows increased thermal stability over the Pt1@HCl under H2 atmosphere at elevated temperature, as evidenced by DRFITs of CO chemisorption and HRTEM. This work offers a facile approach to tune the stability of Pt single atoms while keeping the structure of active sites of single atom center to achieve excellent catalytic performance, using hydrosilylation in the demonstrative studies.

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.

Metallo-Glycodendrimeric Materials against Enterotoxigenic Escherichia coli.

Conjugation of carbohydrates to nanomaterials has been extensively studied and recognized as an alternative in the biomedical field. Dendrimers synthesized with mannose at the end group and with entrapped zero-valent copper/silver could be a potential candidate against bacterial proliferation. This study is aimed at investigating the bactericidal activity of metal-glycodendrimers. The Cu(I)-catalyzed azide-alkyne cycloaddition (CuAAC) reaction was used to synthesize a new mannosylated dendrimer containing 12 mannopyranoside residues in the periphery. The enterotoxigenic Escherichia coli fimbriae 4 (ETEC:F4) viability, measured at 600 nm, showed the half-inhibitory concentration (IC50) of metal-free glycodendrimers (D), copper-loaded glycodendrimers (D:Cu) and silver-loaded glycodendrimers (D:Ag) closed to 4.5 × 101, 3.5 × 101 and to 1.0 × 10-2 µg/mL, respectively, and minimum inhibitory concentration (MIC) of D, D:Cu and D:Ag of 2.0, 1.5 and 1.0 × 10-4 µg/mL, respectively. The release of bacteria contents onto broth and the inhibition of ETEC:F4 biofilm formation increased with the number of metallo-glycodendrimer materials, with a special interest in silver-containing nanomaterial, which had the highest activity, suggesting that glycodendrimer-based materials interfered with bacteria-bacteria or bacteria-polystyrene interactions, with bacteria metabolism and can disrupt bacteria cell walls. Our findings identify metal-mannose-dendrimers as potent bactericidal agents and emphasize the effect of entrapped zero-valent metal against ETEC:F4.

Doped Cu0 and sulfidation induced transition from R-O• to •OH in peracetic acid activation by sulfidated nano zero-valent iron-copper

Peracetic acid (PAA) has emerged as a new effective oxidant for various contaminants degradation through advanced oxidation process (AOP). In this study, sulfidated nano zero-valent iron-copper (S-nZVIC) with low Cu doping and sulfidation was synthesized for PAA activation, resulting in more efficient degradation of sulfamethoxazole (SMX, 20 μM) and other contaminants using a low dose of catalyst (0.05 g/L) and oxidant (100 μM). The characterization results suggested that S-nZVIC presented a more uniform size and distribution with fewer metal oxides, as the agglomeration and oxidation were inhibited. More significantly, doped Cu0 and sulfidation significantly enhanced the generation and contribution of •OH but decreased that of R-O• in S-nZVIC/PAA/SMX system compared with that of nZVIC and S-nZVI, accounting for the relatively high degradation efficiency of 97.7% in S-nZVIC/PAA/SMX system compared with 85.7% and 78.9% in nZVIC/PAA/SMX and S-nZVI/PAA/SMX system, respectively. The mechanisms underlying these changes were that (i) doped Cu° could promote the regeneration of Fe(Ⅱ) for strengthened PAA activation through mediating Fe(Ⅱ)/Fe(Ⅲ) cycle by Cu(Ⅰ)/Cu(Ⅱ) cycle; (ii) S species might consume part of R-O•, resulting in a decreased contribution of R-O• in SMX degradation; (iii) sulfidation increased the electrical conductivity, thus facilitating the electron transfer from S-nZVIC to PAA. Consequently, the dominant reactive oxygen species transited from R-O• to •OH to degrade SMX more efficiently. The degradation pathways, intermediate products and toxicity were further analyzed through density functional theory (DFT) calculations, liquid chromatography-mass spectrometry (LC-MS) and T.E.S.T software analysis, which proved the environmental friendliness of this process. In addition, S-nZVIC exhibited high stability, recyclability and degradation efficiency over a wide pH range (3.0∼9.0). This work provides a new insight into the rational design and modification of nano zero-valent metals for efficient wastewater treatment through adjusting the dominant reactive oxygen species (ROS) into the more active free radicals.

In-situ precipitation zero-valent Co on Co2VO4 to activate oxygen vacancies and enhance bimetallic ions redox for efficient detection toward Hg(II)

Despite the widespread utilization of variable valence metals in electrochemistry, it is still a formidable challenge to enhance the valence conversion efficiency to achieve excellent catalytic activity without introducing heterophase elements. Herein, the in-situ precipitation of Co particles on Co2VO4 not only enhanced the concentration of oxygen vacancies (Ov) but also generated a greater number of low-valence metals, thereby enabling efficient reduction towards Hg(II). The electroanalysis results demonstrate that the sensitivity of Co/Co2VO4 towards Hg(II) was measured at an impressive value of 1987.74 μA μM−1 cm−2, significantly surpassing previously reported results. Further research reveals that Ov acted as the main adsorption site to capture Hg(II). The redox reactions of Co2+/Co3+ and V3+/V4+ played a synergistic role in the reduction of Hg(II), accompanied by the continuous supply of electrons from zero-valent Co to expedite the valence cycle. The Co/Co2VO4/GCE presented remarkable selectivity towards Hg(II), with excellent stability, reproducibility, and anti-interference capability. The electrode also exhibited minimal sensitivity fluctuations towards Hg(II) in real water samples, underscoring its practicality for environmental applications. This study elucidates the mechanism underlying the surface redox reaction of metal oxides facilitated by zero-valent metals, providing us with new strategies for further design of efficient and practical sensors.

Desalination of Seawater, Synthetic Saline Irrigation Water and Produced Water Using Nano Zero Valent Metals: Results from a Pilot-Scale Desalination System

Two pilot-scale desalination systems employing carbon modified nano-sized, zero valent metals (n-ZVMs) were manufactured and tested to determine (1) the degree to which high-salt water (20 to 130 mS) could be desalinated and (2) if this degree of desalination could be maintained throughout an extended treatment period. The two pilot systems (referred to as Generation 1 and Generation 2) consisted of parallel lines of four individual reactors in series, a settling tank and an activated carbon cell at the end of each reactor line. The system capacity was 300 gal in Generation 1 and 600 gal in Generation 2 with a total hydraulic residence time of 6 h per reactor line (one hour per cell/tank). A slurry of n-ZVMs manufactured from mixtures of ferrous sulfate and green or black tea extract was introduced in the first reactor on each line to yield approximately 5 to 45 g of nano metal per 100 L of influent salt water based on dosing experiments required to achieve maximum salt removal at each of the three influent salt contents used, 28 mS, 44 mS and 123 mS. Once dosing was set, continuous runs (14 days, 23 days and 9 days) were carried out. The results demonstrated that maximum removal occurred with 10 g/100 L of salt for the 30 mS salt solution, 16 g/100 L of salt for the 40 mS influent water and 40 g/100 L for the 130 mS influent. Salt removal (expressed as Na+ and Cl− removed) approached 78% for the 30 mS influent and 41 mS influent, respectively, while removal for the highest concentration salt influent (130 mS) approached 81%. Continuous operation over the extended time-period showed no significant decrease in salt removal with a typical day to day variation of no more than 10%, suggesting that this approach to desalination could rapidly provide usable water from saline aquifers, seawater or even produced water.

Degradation of hydroxypropyl guar gum by dual oxidant system catalyzed by hydrotalcite supported zero-valent transition metal

Degradation of hydroxypropyl guar gum by dual oxidant system catalyzed by hydrotalcite supported zero-valent transition metal

Modeling the Role in pH on Contaminant Sequestration by Zerovalent Metals: Chromate Reduction by Zerovalent Magnesium.

The role of pH in sequestration of Cr(VI) by zerovalent magnesium (ZVMg) was characterized by global fitting of a kinetic model to time-series data from unbuffered batch experiments with varying initial pH values. At initial pH values ranging from 2.0 to 6.8, ZVMg (0.5 g/L) completely reduced Cr(VI) (18.1 μM) within 24 h, during which time pH rapidly increased to a plateau value of ∼10. Time-series correlation analysis of the pH and aqueous Cr(VI), Cr(III), and Mg(II) concentration data suggested that these conditions are controlled by combinations of reactions (involving Mg0 oxidative dissolution and Cr(VI) sequestration) that evolve over the time course of each experiment. Since this is also likely to occur during any engineering applications of ZVMg for remediation, we developed a kinetic model for dynamic pH changes coupled with ZVMg corrosion processes. Using this model, the synchronous changes in Cr(VI) and Mg(II) concentrations were fully predicted based on the Langmuir-Hinshelwood kinetics and transition-state theory, respectively. The reactivity of ZVMg was different in two pH regimes that were pH-dependent at pH < 4 and pH-independent at the higher pH. This contrasting pH effect could be ascribed to the shift of the primary oxidant of ZVMg from H+ to H2O at the lower and higher pH regimes, respectively.

Fe and Cu Intercalations Enhance SERS of MoO3 through Different Mechanistic Pathways.

Surface Enhanced Raman spectroscopy (SERS) is a molecular-specific analytical technique with various applications. Although electromagnetic (EM) and chemical (CM) mechanisms have been proposed to be the main origins of SERS, exploring highly sensitive SERS substrates with well-defined mechanistic pathways remains challenging. Since surface and electronic structures of substrates were crucial for SERS activity, zero-valent transition metals (Fe and Cu) were intercalated into MoO3 to modulate its surface and electronic structures, leading to unexceptional high enhancement factors (1.0×108 and 1.1×1010 for Fe-MoO3 and Cu-MoO3 , respectively) with decent reproducibility and stability. Interestingly, different mechanistic pathways (CM and EM) were proposed for Fe-MoO3 and Cu-MoO3 according to mechanistic investigations. The different mechanisms of Fe-MoO3 and Cu-MoO3 were rationalized by the electronic structures of the intercalated Fe(0) and Cu(0), which modulates the surface and electronic structures of Fe-MoO3 and Cu-MoO3 to differentiate their SERS mechanisms.

Trends in selective hydrogenation

In spite of being commercialized for well over a century, hydrogenation is still a subject of intensive research and development. A patent landscape analysis showed high growth rates for topics related to climate change, bio-renewables, low waste and recyclability. The current paper describes trends, providing examples on the effect of structure sensitivity, on novel intermetallic active phases and on discoveries initiated by modelling. Due to increased processing costs and a negative environmental impact of undesirable by-products, the present focus favours high selectivity over activity. A relatively new class of materials showing an exponential growth in publications, these are the so-called intermetallics. These materials are defined as compounds formed by at least two metals, with – at least partly – ordered crystal structures which are different from the ones of the constituting elements. Non-metallic active phases formed by interaction of a metal ion and a (reducible) support may have a superior hydrogenation performance compared to the corresponding zero-valent metals. Aided by Density Functional Theory modelling (DFT) new, often intermetallic catalysts like Ni5Ga3 were identified which sparked a great number of follow-up studies.