Molar Ratio Research Articles

A novel approach for recovery of iron from copper slag using calcium salts.

Copper slag is not only a waste but it has many valuable and recoverable metals present in it such as iron. Therefore,this study focuses on the utilization of waste materials i.e.,copper slag and tire char for iron recovery. Four calcium salts, i.e., CaCO3, Ca(OH)2, CaCl2, and CaSO4, with different dosages, reduction temperature, reduction time, and atmospheric conditions were investigated in order to find best reaction mechanism for iron recovery. Among these salts, the optimum conditions were determined: using CaCO3 under 0.384 of CaO/SiO2 molar ratio in a 60-min reduction period at 1473.15K temperature, that gives 91.14% iron recovery. Both FESEM-EDS data and chemical titration showed more than 70% of the highest iron grade in the recovered product. The analysis results indicate that main impurity in the whole procedure was carbon from coal char that reduces the iron grade. This research not only provides a novel way to recover iron from copper slag, but also provides a future direction to handle copper slag and tire char waste materials.

Dry-gel conversion synthesis sponge-based MIL-160 monolith adsorbent at low temperature for water adsorption

The facile synthesis MOFs monolith adsorbent is highly imperative for the economically friendly development of water adsorption. Herein, metal-organic framework material MIL-160 monolith was synthesized by the dry-gel conversion method at low temperature. The effects of curing conditions, dry-gel composition and crystallization temperature on crystal structure, porosity, microstructure and water vapor adsorption/desorption properties were studied. XRD results showed that the MIL-160 powder and monolith adsorbent can be synthesized under the condition that the molar ratio of dry-gel was Al3+: FDCA: NaOH = 1:1:2 at 60 °C (FDCA is the abbreviation of 2,5-Furandicarboxylicacid). The water vapor saturation adsorption capacity and water vapor desorption activation energy of the powder and monolith adsorbent were 0.310, 0.231 g/g at 20 % RH and 72.3, 62.4 kJ/mol, respectively. The convenient dry-gel conversion synthesis of MIL-160 monolith may provide a guidance for the manufacture of high-performance water harvest device.

Ineffectiveness of phosphorus-containing amendments to reduce Pb bioaccessibility in an urban alkaline soil.

Urban soils contaminated by historical and current anthropogenic activities present an alarming human health risk requiring redress. Federal and state governments continue to lower residential soil lead (Pb) screening standards, which will likely require new risk-based approaches to address urban soil Pb contamination. Phosphorus (P) soil amendments have long been presented as a solution to sequester Pb, thereby reducing exposure risk. In this study, P-containing sources (biosolids incinerator ash, poultry litter, biosolids compost, and triple superphosphate) of varying solubilities were assessed as soil amendments to reduce Pb bioaccessibility and serve as an inexpensive remediation strategy for urban soil. Contaminated soil (1624mg kg-1Pb, pH 7.43) from Cleveland, OH, was treated with the four P-containing soil amendments at a 1:5Pb:P molar ratio and two combination treatments at 1:10Pb:P molar ratio and incubated for 3 months. A batch equilibration analysis was also conducted to assess reduction in in vitro bioaccessible Pb (IVBA Pb). Pb bioaccessibility was evaluated using US EPA Method 1340 at pH 1.5 and the Physiologically Based Extraction Test pH 2.5 at 1 and 3 months. In general, treatments were ineffective in reducing IVBA Pb regardless of IVBA extraction method, incubation duration, batch equilibration analyses, or P source. The results of this study suggest P-containing amendments are not suitable to address Pb exposure in the study soil. Site-specific efficacy testing to determine reductions in IVBA Pb from P-containing amendments should be performed before making recommendations for remediation of Pb-contaminated urban soil.

Influence of Structural Properties of Oleic Acid-Capped CdSe/ZnS Quantum Dots in the Detection of Hg2+ Ions.

Oleic acid-capped CdSe/ZnS quantum dots (QDs) were used to investigate their photoluminescence (PL) response to Hg2+ ions as a function of the surface properties of QDs. Three distinctly-size CdSe/ZnS QDs were obtained by varying the molar ratio of shell precursors, which were characterized by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HR-TEM), Fourier-Transform infrared (FT-IR), X-ray photoelectron spectroscopy (XPS), absorption spectroscopy, and time-resolved fluorescence spectroscopy. Results revealed the obtention of zinc blende nanocrystals with sizes ranging from 2.7 to 3.2nm (± 0.5) and ZnS thickness between 0.3 and 1.0 monolayer (ML). The variation of the [S]/[Zn] molar ratio introduced chemical species that act as traps, affecting the PL properties differently. Depending on the thickness of the shell and chemical speciation on surface, Hg2+ ions could induce quenching or enhancement of PL. Detection of mercury ions was evaluated in terms of Stern-Volmer equation, where the limit of detection (LOD) for the PL quenching system was 11.2 nM, while for the PL enhancing systems were 8.98 nM and 10.7 nM. Results demonstrate the performance of oleic acid-capped CdSe/ZnS QDs to detect Hg2+ and their capacity to turn the PL on/off depending on surface properties.

Controlled Migration of Lithium Cations by Diamine Bridges in Water-Processable Polymer-Based Solid-State Electrolyte Memory Layers for Organic Synaptic Transistors.

Synaptic transistors require sufficient retention (memory) performances of current signals to exactly mimic biological synapses. Ion migration has been proposed to achieve high retention characteristics but less attention has been paid to polymer-based solid-state electrolytes (SSEs) for organic synaptic transistors (OSTRs). Here, OSTRs with water-processable polymer-based SSEs, featuring ion migration-controllable molecular bridges, which are prepared by reactions of poly(4-styrenesulfonic acid) (PSSA), diethylenetriamine (DETA), and lithium hydroxide (LiOH) are demonstrated. The ion conductivity of PSSA:LiOH:DETA (1:0.4:X, PLiD) films is remarkably changed by the molar ratio (X) of DETA, which is attributed to the extended distances between the PSSA chains by the DETA bridges. The devices with the PLiD layers deliver noticeably changed hysteresis reaching an optimum at X = 0.2, leading to the longest retention of current signals upon single/double pulses. The long-term potentiation test confirms that the present OSTRs can gradually build up the postsynaptic current by gate pulses of -2V, while the long-term depression can be adjusted by varying the depression gate pulses (≈0.2-1.2V). The artificial neural network simulations disclose that the present OSTRs with the ion migration-controlled PLiD layers can perform synaptic processes with an accuracy of ≈96%.

Mo-Doped Ni/C Catalyst for Improved Simultaneous Production of Hydrogen and Carbon Nanotubes through Ethanol Decomposition

A Mo-Ni/C catalyst was developed and assessed in terms of the decomposition of ethanol to produce multi-wall carbon nanotubes (MWCNTs) and hydrogen. The catalyst utilized different molar ratios of Mo:Ni (1:9, 2:8, and 3:7), with Mo acting as a dopant to enhance the MWCNT yield and Ni acting as the primary active phase for MWCNT formation. Among the tested ratios, the 2:8 Mo:Ni ratio exhibited the optimal performance, yielding 86% hydrogen and high-quality MWCNTs. In addition to hydrogen, the process also generated CO, CH4, and CO2. Gas chromatography (GC) was employed to analyze the influence of the Mo:Ni ratio on gas production and selectivity, while the quality of the resulting MWCNTs was evaluated using SEM, Raman spectroscopy, and TEM analyses.

Affinity Constants of Bovine Serum Albumin for 5 nm Gold Nanoparticles (AuNPs) with ω-Functionalized Thiol Monolayers Determined by Fluorescence Spectroscopy.

A detailed understanding of the binding of serum proteins to small (dcore <10 nm) nanoparticles (NPs) is essential for the mediation of protein corona formation in next generation nanotherapeutics. While a number of studies have investigated the details of protein adsorption on large functionalized NPs, small NPs (with a particle surface area comparable in size to the protein) have not received extensive study. This study determined the affinity constant (Ka) of BSA when binding to three different functionalized 5 nm gold nanoparticles (AuNPs). AuNPs were synthesized using three ω-functionalized thiols (mercaptoethoxy-ethoxy-ethanol (MEEE), mercaptohexanoic acid (MHA), and mercaptopentyltrimethylammonium chloride (MPTMA)), giving rise to particles with three different surface charges. The binding affinity of bovine serum albumin (BSA) to the different AuNP surfaces was investigated using UV-visible absorbance spectroscopy, dynamic light scattering (DLS), and fluorescence quenching titrations. Fluorescence titrations indicated that the affinity of BSA was actually highest for small AuNPs with a negative surface charge (MHA-AuNPs). Interestingly, the positively charged MPTMA-AuNPs showed the lowest Ka for BSA, indicating that electrostatic interactions are likely not the primary driving force in binding of BSA to these small AuNPs. Ka values at 25 °C for MHA, MEEE, and MPTMA-AuNPs were 5.2 ± 0.2 × 107, 3.7 ± 0.2 × 107, and 3.3 ± 0.16 × 107 M-1 in water, respectively. Fluorescence quenching titrations performed in 100 mM NaCl resulted in lower Ka values for the charged AuNPs, while the Ka value for the MEEE-AuNPs remained unchanged. Measurement of the hydrodynamic diameter (Dh) by dynamic light scattering (DLS) suggests that adsorption of 1-2 BSA molecules is sufficient to saturate the AuNP surface. DLS and negative-stain TEM images indicate that, despite the lower observed Ka values, the binding of MPTMA-AuNPs to BSA likely induces significant protein misfolding and may lead to extensive BSA aggregation at specific BSA:AuNP molar ratios.

In vitro colon fermentation behaviors of Ca2+ cross-linked guluronic acid block from sodium alginate.

The degradation of sodium alginate by human gut microbiota was found to be retarded via calcium cross-linking in our previous study. We hypothesized that the guluronic acid block (GB) on the alginate molecule might be the key structural region affecting alginate degradation by the gut microbiota when cross-linked with calcium. This study aims to prove this hypothesis by studying the structural features of the cross-linked GB on its in vitro fecal fermentation behaviors concerning the aspects of total carbohydrate contents, monosaccharide contents, short-chain fatty acids production, calcium state variations, and structural variations. Herein, GB isolated from sodium alginate was cross-linked under ranges of molar ratios of [Ca2+]/[-COOH] that further restricted the degradation by gut microbiota similar to the cross-linked alginates. First, total carbohydrate contents, short-chain fatty acids production, monosaccharides contents, and calcium state analyses confirmed that the degradation of GB by gut microbiota was restricted by calcium cross-linking. Furthermore, the tracking analysis of structural variations during in vitro fermentation revealed that the "granules" structure could further restrict degradation by the gut microbiota, leaving more cross-linked GB fragments surviving in comparison to the "networks" structure. In addition, Bacteroides xylanisolvens showed a significant positive correlation to the "cross-linking porosity (R = 0.825, p < 0.001), which supported our previous findings on fermentation behaviors of cross-linked alginate. Together, guluronic acid blocks are the key structural regions that retard the degradation of sodium alginate by the gut microbiota when cross-linked with calcium.

Thermodynamic and Economic Analyses of a Novel Cooling, Heating and Power Tri-Generation System with Carbon Capture

The combined cooling, heating, and power (CCHP) system has attracted increasing attention due to its potential outstanding performance in thermodynamics, economics, and the environment. However, the conventional CCHP systems are carbon-intensive. To solve this issue, a low-carbon-emission CCHP system (LC-CCHP) is firstly proposed in this work by integrating a sorption-enhanced steam methane reforming (SE-SMR) process. In the LC-CCHP system, CO2 is continuously captured by the calcium loop so that low-carbon energy can be generated. Then, the LC-CCHP system thermodynamic model, mainly consisting of a dual fluidized bed reactor which includes the SE-SMR reactor and a CaCO3 calcination reactor, a hydrogen gas turbine, a CO2 reheater, and a lithium bromide absorption chiller, is built. To prove that the LC-CCHP model is reliable, the system major sub-unit model predictions are compared against data from the literature in terms of thermodynamics and economics. Finally, the effects of reforming temperature (Tref), the steam-to-carbon mole ratio (S/C), the calcium-to-carbon mole ratio (RCC), the equivalent ratio for gas turbine (RAE), and the hydrogen separation ratio (Sfg) on total energy efficiency (ηten), total exergy efficiency (ηtex), and carbon capture capability (Rcm) are detected. It is found that the minimum exergy efficiency of 64.5% exists at the calciner unit, while the maximum exergy efficiency of 78.7% appears at the gas turbine unit. The maximum energy efficiency and coefficient of performance of the absorption chiller are 0.52 and 1.33, respectively. When Tref=600 °C, S/C=4.0, RCC=7.62, RAE=1.20, and Sfg=0.27, the ηten, ηtex, and Rcm of the system can be ~61%, ~68%, and ~96%, and the average specific cost of the system is 0.024 USD/kWh, which is advanced compared with the parallel CCHP systems.

A new DES-mediated synthesis of Henna-based benzopyranophenazines and benzoxanthenetriones

MTPPBr/THFTCA-DES was prepared as a new deep eutectic solvent (DES) from a mixture (molar ratio 7:3) of methyltriphenyl-phosphonium bromide (MTPPBr) and tetrahydrofuran-2,3,4,5-tetra-carboxylic acid (THFTCA), and characterized with various spectroscopic techniques, densitometer, and eutectic point. Then, it was used as a new and powerful catalyst for the synthesis of two sets of biologically important compounds, namely the Henna-based benzopyranophenazines and benzoxan-thenetriones. Solvent-free conditions, short reaction time, high efficiency, and easy recycling and separation of the DES catalyst are among the most important features of the presented method. Also, there is a nice consistency between the proposed structure of the DES compound, the integration values of the 1H NMR peaks, and the ratio of MTPPBr to THFTCA obtained from the eutectic point phase diagram. In addition, the reduction of peak splitting patterns in DES compared to the two primary materials can be good evidence of the formation of hydrogen bonds between the two components.

Production of triacetin from industrially derived purified glycerol: Experimental proof of concept, kinetic model derivation and validation

This study illustrates the purification of end-of-life crude glycerol from a real biodiesel production process and its conversion into triacetin via esterification with acetic acid. Crude glycerol of 50.9 wt% purity was physicochemically treated to 74.3 wt% reducing the content of ashes (16.1 to 9.8 wt%), matter organic non-glycerol (25.6 to 9.8 wt%) and water (7.4 to 6.1 wt%). For esterification, catalyst screening with commercial ion exchange resins and zeolites showed that Amberlyst 36 attained a triacetin yield of 30.1 % and stability after 5 cycles. An increase of temperature, molar ratio, and catalyst loading positively affected the reaction rates and equilibrium, whereas increasing water content in the feedstock only showed effect on the equilibrium leading to lower triacetin yields. After dismissing mass transfer limitations, a thorough study on the reaction kinetics analysed the effect of temperature (100–130 °C), molar excess of acetic acid (6–12) and catalyst loading (2.5–7.5 wt%) on the concentration profiles. Kinetic models based on Langmuir-Hinshelwood-Hougen-Watson and Eley-Rideal equations were formulated to fit the experimental data, where an Eley-Rideal model accounting only for water adsorption fitted best. Deactivation was also contemplated considering the ash content in the substrate, yet the model does not correlate with a loss of catalytic activity. The activation energies for the forward and backward reactions of the in-series esterification reactions are 38.2 – 45.8 kJ mol–1 and 47.0 – 50.3 kJ mol–1, respectively, and the enthalpy for water adsorption is 28.2 kJ mol–1.

3D Nickel–Manganese bimetallic electrocatalysts for an enhanced hydrogen evolution reaction performance in simulated seawater/alkaline natural seawater

In this paper, we report an inexpensive one-step synthesis of self-supported 3D nickel-manganese (NiMn) bimetallic coatings and their application for the hydrogen evolution reaction in simulated seawater (1 M KOH + 0.5 M NaCl) and alkaline natural seawater (1 M KOH + natural seawater). These binary coatings were electrodeposited on a titanium substrate using a facile electrochemical deposition method by a dynamic hydrogen bubble template technique. The as-deposited NiMn coatings with variable Mn amounts produce typical globular and unique porous architecture with abundant pores of different sizes. The activity of these fabricated catalysts towards the hydrogen evolution reaction was investigated by linear sweep voltammetry towards simulated seawater and alkaline natural seawater at different temperatures. The surface morphology and composition of the catalysts were also characterized by scanning electron microscopy and inductively coupled plasma optical emission spectroscopy. The as-prepared NiMn/Ti electrocatalyst, which was electrodeposited using a chemical bath containing Ni2+ and Mn2+ ions with a molar ratio of Ni2+:Mn2+ = 1:5, exhibits excellent hydrogen evolution activity in simulated seawater with an ultra-low overpotential of 64.2 mV to reach a current density of 10 mA cm−2. It is noteworthy that this NiMn/Ti electrocatalyst also achieves a current density of 10 mA cm−2 in alkaline natural seawater with a comparably low overpotential of 79.3 mV. The current densities increase by ca. 1.75–2.35 times with an increase in temperature from 25 °C to 75 °C for hydrogen evolution in both electrolytes. This bimetallic catalyst has shown excellent long-term stability at a constant potential of −0.23 V (vs. RHE) and a constant current density of 10 mA cm−2 for 10 h, which ensures higher durability and robustness for practical application of seawater splitting technology.

Significant Promotional Effect of Nb Doping in Bifunctional Pd/WOx Nanocatalysts on One‐Step Benzene Hydroalkylation

AbstractThe development of high‐efficiency heterogeneous bifunctional metal‐acid catalysts with an appropriate metal‐acid balance for the production of cyclohexylbenzene (CHB) via the one‐step tandem benzene hydroalkylation still faces a dilemma because of the difficulty in inhibiting the over hydrogenation of benzene substrate and cyclohexene intermediate and controlling target product selectivity. In this study, Nb‐doped WOx supported Pd nanocatalysts were developed. It has been shown that doping Nb into WOx supports altered surface properties and microstructures of catalysts, resulting in the generation of more surface acidic sites and defective W−Ov−Nb structures (Ov: oxygen vacancies). As‐constructed Pd‐based nanocatalyst with only 0.1 wt % Pd loading and a Nb/(Nb+W) molar ratio of 0.25 exhibited superior catalytic benzene hydroalkylation performance to undoped supported Pd catalyst, with a much higher yield of CHB (35.6 %) at 220 °C. It was authenticated that highly dispersed Pd sites facilitated the dissociation of hydrogen molecules, defective W−Ov−Nb structures were conductive to the surface transfer of active hydrogen species, a large number of acidic sites favored benzene/cyclohexene intermediate adsorption, and abundant Brønsted acidic sites promoted the alkylation between cyclohexene intermediate formed and benzene. Accordingly, excellent cooperative catalysis between Pd sites, acidic sites, and oxygen vacancies contributed to improved catalytic performance of Nb‐doped WOx supported Pd catalysts in benzene hydroalkylation. This research presents an alternative for the creation of low‐cost practical bifunctional metal‐acid catalysts for highly efficient benzene hydroalkylation.

Cerium(III)phosphotungstate: an efficient catalyst in esterification of fatty acids

In this report, a known heteropolyacid salt (HPAs) cerium (Ⅲ) phosphotungstate was synthesized in a volume ratio of 2:1:2 with a molar ratio of 1:1:1 of each ingredient. These HPAs are further utilized in form of a catalyst to generate biodiesel through the esterification of variable carbon chain length alcohols (methanol, ethanol, n-propanol, isopropanol, n-butanol) and stearic acid at different conditions of reaction. FTIR of the produced biodiesel was also done for the assurance of ester peaks in it. Analysis of some important biodiesel properties (density, dynamic viscosity, acid value, aniline point, boiling point, cloud and pour point, and flash and fire point) etc., to differentiate and validate the results. A large surface area of the catalyst i.e. 121.427 m2/g determined using the BET surface area analyser, supports the fact of outrageous catalytic action in the esterification reaction. The effect of additives was also studied on the properties of resultant biodiesel. The calorific value of the samples was measured at 7320 Kcal/kg without additive and 7512 Kcal/kg after adding toluene (as an additive) in the biodiesel generated in the study. The pour point temperature of the biodiesel with additives was observed even &lt; 20℃.

Metal Levels in Striped Dolphins (Stenella coeruleoalba) and Common Dolphins (Delphinus delphis) Stranded along the Sicilian Coastlines of the Mediterranean Sea

Dolphins, top predators of the aquatic food chain, are used as sentinel species of marine pollution as they are sensitive to environmental changes and able to accumulate a large content of contaminants. Several EU directives promote study of marine mammalians as bio-indicators to evaluate the presence of contaminants in the aquatic environment, such as the Mediterranean Sea, which is rich in environmental pollutants due to its geographic and geo-morphological characteristics. The aim of this study was to evaluate the content of toxic and essential metals and metalloids (Hg, Pb, Cd, As, Se and Zn), through ICP-MS analysis, in organs/tissues (liver, muscle, lung, kidney and skin) of striped dolphins (Stenella coeruleoalba) and common dolphins (Delphinus delphis) stranded along the Sicilian coastlines of the Mediterranean Sea. The results confirm the exposure of dolphins to toxic metals and metalloids, with the highest Hg levels observed in skin and liver, although a low Metal Pollution Index (MPI) was found in all samples of both dolphin species. From a comparative analysis of trace metals and metalloids according to sex and state of development, the highest levels of Cd and As were found in females vs. males and adults vs. juveniles, except for Pb in both species, and significant differences were observed between the two species, size of specimens, and organs/tissues analyzed. The highest Hg levels were correlated to those of essential metals Se and Zn, expressed as molar ratios, to evaluate the potential synergic effect of these detoxifying elements against Hg toxicity. This study confirms the rule of Stenella coeruleoalba and Delphinus delphis as valid sentinel species of the Mediterranean Sea, to verify the trend of metals pollution in this aquatic environment and, consequently, the health of these marine species.

Preparation of MAZ-Type Zeolite with High Silica

The Si/Al molar ratio of MAZ aluminosilicate zeolite prepared by the direct hydrothermal method is generally less than five, thus giving rise to poor thermal and hydrothermal stability for this low-silica zeolite. With the purpose of enhancing the Si/Al molar ratio of MAZ zeolite, post-synthesized methods including acetic acid treatment and steaming treatment, as well as interzeolite transformation from FAU zeolite, were employed to prepare MAZ zeolite with high silica. It was found that steaming treatment was more effective in increasing the Si/Al molar ratio in comparison with acetic acid treatment, affording a maximum Si/Al molar ratio of 16.9 along with a preserved crystallinity of approximately 75%. Additionally, high-silica MAZ zeolite with a Si/Al molar ratio of up to 7.3 was also capable of being directly hydrothermally synthesized using interzeolite transformation from FAU zeolite.

Cold energy storage enhancement and phase transition temperature regulation

The objective of this study is to prepare a highly adjustable ester phase change material (PCM) and further optimize its cold storage properties using a simple and controllable physical method. Initially, lauric acid (LA) and polyethylene glycol 200 (PEG 200) are selected as raw materials, and a non-toxic and environmentally friendly polyethylene glycol laurate (PLE) with a tiny supercooling is prepared under the condition of acid-alcohol molar ratio of 1:3. To further regulate the cold storage property of PLE, a series of PCMs with different melting temperatures are successfully prepared using PLE blended with ethanol (EA). Among them, the lowest melting temperature in the study reaches −15.2 °C, which is about 94.6 % lower compared to −7.81 °C for PLE, and the highest latent heat of melting is 81.56 J/g. It is also observed that the supercooling of a range of samples is also optimized compared to the PLE, with a maximum reduction of 27.1 %. Additionally, the prepared samples not only exhibit excellent stability but also demonstrate outstanding application potential in temperature control and preservation experiments. This innovative achievement provides a richer selection of PCMs for the cold storage field. More crucially, this is the first report utilizing EA to regulate the temperature range of ester-based PCMs. This method is simple, easy to operate, and highly reproducible. It paves the way for the refinement, diversification, and customization of refrigeration technology.

Enhancing water resistance in magnesium oxychloride cement modified with sodium dihydrogen phosphate at low MgO concentrations

Phosphate ions significantly enhance the water resistance of magnesium oxychloride cement (MOC). In this study, MOC was prepared with a MgO/MgCl2 molar ratio of 7 and a H2O/MgCl2 molar ratio of 12, while varying the dosage of sodium dihydrogen phosphate. The aim was to observe the microstructural changes in 5Mg(OH)2·MgCl2·8H2O (Phase 5) crystals and the macroscopic mechanical properties before and after immersion. The research found that phosphate ions increase the content of air-cured Phase 5 and reduce the formation of Mg(OH)2 by lowering the required Mg2+ concentration for Phase 5 production. However, excessive phosphate ions can damage the crystal structure of Phase 5, leading to a decrease in MOC strength. An appropriate amount of phosphate ions increases the output of Phase 5, resulting in a highly dense microstructure, which significantly improves the water resistance of MOC. Additionally, this enhances the pore structure of MOC, making the overall structure more compact and resistant to water penetration. This research offers valuable theoretical insights into Phase 5 crystal variations during air curing and water-immersion damage under low Mg2+ concentrations.

Facile construction of copper-doped metal organic framework as a novel visible light-responsive photocatalyst for contaminant degradation

ABSTRACT Metal–organic frameworks (MOFs) with photocatalytic activity have garnered significant attentions in environmental remediation. Herein, copper-doped zeolitic imidazolate framework-7 (Cu-doped ZIF-7) was synthesized rapidly and easily using a microwave-assisted technique. Various analytical and spectroscopic methods were employed to access the framework, morphology, light absorption, photo-electrochemical and photocatalytic performance of the synthesized materials. Compared to ZIF-7, Cu/ZIF-7 (molar ratio of Cu2+ to Zn2+ is 1:1) demonstrates superior visible light absorption ability, narrower band gap, enhanced charge separation capability, and reduced electron–hole recombination performance. Under visible light irradiation, Cu/ZIF-7 serves as a Fenton-like catalyst and demonstrates exceptional activity for contaminant degradation, while virgin ZIF-7 remains inactive. With the addition of 9.8 mmol H2O2 and exposure to visible light for 30 min, 10 mg of Cu/ZIF-7 can completely decompose RhB solution (10 mg/L, 50 mL). The synergistic effect of the Cu/ZIF-7/H2O2/visible light system is attributed to visible light photocatalysis and Fenton-like reactions. Cu/ZIF-7 demonstrates excellent catalytic performance stability, with only a slight decrease in degradation efficiency from an initial 97.0% to 95.4% over four cycles. Additionally, spin-trapping ESR measurements and active species trapping experiments revealed that h+ and ·OH occupied a significant position for Rhodamine B (RhB) degradation. Degradation intermediate products of Rhodamine B have been identified using UPLC-MS, and the degradation pathways have been proposed and discussed. This work offers a facile and efficient technique for developing MOF-based visible light photocatalysts for water purification.

RuNi/TiZr-MMO Catalysts Derived from Zr-Modified NiTi-LDH for CO-Selective Methanation

CO-selective methanation (CO-SMET) is an efficient hydrogen-rich (H2-rich) gas purification technology for proton exchange membrane fuel cells. It is vital to develop suitable catalysts with good low-temperature activity for CO-SMET reactions. In this study, RuNi/TiZrx-mixed metal oxide (RuNi/TiZrx-MMO) catalysts with different molar ratios of Zr/Ti, derived from a Zr-promoted NiTi-layered double hydroxide (NiTi-LDH) precursor were successfully prepared using the co-precipitation and wet impregnation methods. The RuNi/TiZr0.2-MMO catalyst possesses higher catalytic performance in a lower temperature window of 180–280 °C, which can reduce the CO concentration to be below 10 ppm. The characterization results obtained from XRD, BET, SEM, TEM, XPS, TPR, and TPD suggest that the addition of ZrO2 increases the surface area of the catalyst, improves the dispersion of metallic nanoparticles, increases the reducibility of Ni species on the RuNi/TiZr0.2-MMO catalyst’s surface, and enhances the adsorption and activation ability of CO, resulting in remarkable catalytic performance at lower reaction temperatures. Moreover, the RuNi/TiZr0.2-MMO catalyst demonstrated long-term catalytic stability and carbon resistance.