Average Pore Volume Research Articles

Adsorption of heavy metals from aqueous solutions by magnetic barium hydroxyapatite nanoparticles

ABSTRACT Magnetic barium hydroxyapatite (Fe3O4@BaHAP) nanoparticles were synthesised and used as a sorbent for the removal of several heavy metal ions from aqueous solutions. The sorbent characterisation was performed by scanning electron microscopy (SEM), X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET), vibrating-sample magnetometer (VSM) and Fourier transform infrared spectroscopy (FTIR) techniques. A homemade device, named continuous collection of magnetic sorbent (CCMS), was designed for efficient removal of heavy metal ions from aqueous solutions and simultaneous collection of the sorbent by a permanent magnet at the end of the process. Results of BET analysis show that average pore diameter, average pore width, pore volume and specific surface area of the Fe3O4@BaHAP NPs were 10.9 nm, 11.6 nm, 0.16 cm3/g and 55.7 m2/g, respectively. Influential parameters on the removal efficiency were investigated and optimised using a central composite design method. The optimised values for solution pH, sorbent amount, stirring and circulating times were 6.2, 150 mg, 13 and 25 min, respectively. Magnetic BaHAP nanoparticles were shown to have higher removal efficiency than BaHAP or Fe3O4 alone. Under optimised conditions, adsorption capacities for Pb2+, Cr3+, Cd2+ and Cu2+ were 99.0, 66.5, 91.2 and 92.1 mg/g, respectively. The results demonstrated that the synthesised magnetic BaHAP nanoparticles can effectively remove several metal ions from contaminated water sources.

Nylon fiber waste as a prominent adsorbent for Congo red dye removal

In this research nylon fibers wastes (NF) were fabricated into porous sheet using a phase inversion technique to be utilized as an adsorbent materials for Congo red dye (CR). The fabricated sheet denoted as NS was characterized using FTIR and XRD. The surface studies of the adsorbent materials using SEM and BET analysis reveals a highly pores structure with an average pore volume 0.61 cc/g and BET surface area of 767 m2/g. The adsorption studies of fabricated NS were employed into CR at different parameters as pH, effect of time and dye concentration. The adsorption isotherm and kinetic studies were more fit to Langmuir and pseudo second order models. The maximum adsorption capacity qmax reached 188 mg/g with removal percentage of 95 for CR concentration of 400 mg/L at pH 6 and 0.025 g NS dose for 10 ml CR solution. The regeneration study reveals a prominent adsorption behavior of NS with removal % of 88.6 for CR (300 mg/L) after four adsorption desorption cycles. Effect of incorporation of NaonFil Clay to NS was studied using Response Surface Methodology (RSM) modeling and reveals that 98.4% removal of CR could be achieved by using 19.35% wt. of fiber with 8.2 g/L dose and zero clay, thus at a predetermined parameters studies of NanoFil clay embedded into NS, there are no significant effect for %R for CR.

Synthesis and characterizations of molybdenum-doped titanium dioxide nanoparticles for photocatalytic removal of chromium (VI) from aqueous solutions

The photocatalytic removal of toxic heavy metals using titanium dioxide nanoparticles is an emerging technology for environmental remediation. Pure and Mo-doped TiO2 nanoparticles were synthesized using a modified sol-gel process, and then characterized by field emission scanning electron microscopy (FE-SEM) and particle size analysis (PSA) to determine their morphology and size, while X-ray diffraction (XRD) and energy-dispersive X-ray spectroscopy (EDS) were used to determine their crystalline phase and composition. Brunauer–Emmett–Teller (BET) analysis was used to measure the surface area and porosity of the synthesized catalysts applying Langmuir and BET models. The catalyst was mainly composed of spherical anatase TiO2 particles, with a diameter in the range of 15–75 nm, and the maximum doping percentage of Mo was 3.3%. The Langmuir surface area of pure and Mo-doped TiO2was 91.63 and 128.73 m2/g, and the average pore volume was 0.029 and 0.032 cm3/g, respectively. The nanomaterials were used in the photocatalytic removal of Cr(VI) from aqueous solutions, and the adsorption isotherms indicated that the catalyst uptake (qe,max) amounts for Mo-doped TiO2 and pure TiO2 were 12.5 and 6.5 mg/L, respectively. Moreover, the equilibrium removal percentage was improved from 41% for pure TiO2 to 90% for Mo-doped TiO2, which confirms that photocatalytic activity is enhanced by doping TiO2 with molybdenum.

The effect of nanomaterials in the treatment of medical waste in hospitals

In recent years, there has been a significant increase in the amount of medical waste produced, which poses a serious threat to the environment. Within such waste, the presence of antibiotics, which are now widely used, poses a potential threat to human health. This paper investigates the ability of Fe–Mn-NAM adsorbent material made from water hyacinth extract, iron chloride, and manganese sulfate, to adsorb the antibiotics norfloxacin (NOR) and ofloxacin (OFLX) in medical solid waste. Experimental results indicated that the specific surface area of the Fe–Mn-NAM nanosorbent material was 32.56 m2/g, with an average pore volume of 0.083 cm3/g and an average pore size of 3.21 nm. The amount of antibiotics adsorbed by Fe–Mn-NAM peaked under weakly alkaline conditions, and the capacity of the material to adsorb NOR significantly exceeded that for OFLX. There was a negative correlation between the amount of Fe–Mn-NAM adsorbent material added and the adsorption of NOR and OFLX, and a positive correlation with the antibiotic removal rate. At the same adsorbent dosage, the amount of adsorption and the removal rate of NOR by the Fe–Mn-NAM adsorbent material were significantly higher than for OFLX. Through electrostatic attraction, hydrogen bonding, surface complexation, and surface hydrophobicity, the Fe–Mn-NAM adsorbent material demonstrated a certain capacity to treat and eliminate NOR and OFLX in medical solid waste.

Experimental and mechanistic study on the removal of lead from solution by sulfuric acid modified steel slag adsorbent

In this study, sulfuric acid modified steel slag (SS-HS) was prepared using a one-step hydrothermal synthesis method, utilizing converter steel slag as the raw material, to remove heavy metal Pb2+ from water. Single-factor experiments were conducted to determine the influence of different factors on the adsorption capacity. The obtained material was characterized using EDS and FT-IR to analyze its composition. Response surface methodology was employed to optimize the preparation conditions of SS-HS, and the optimal conditions were determined as follows: sulfuric acid dosage of 8.07 mL, reaction time of 9.98 h, and reaction temperature of 99.44 ℃. SS-HS was prepared under the optimized conditions obtained from the response surface methodology. The physicochemical properties of the prepared SS-HS were analyzed using SEM, EDS, and BET. It was observed that the specific surface area of SS-HS increased from 8.0041 m2/g to 131.8312 m2/g. The average pore volume was 0.2101 cm3/g and the average pore size was 6.3737 nm for mesoporous material. Additionally, the influence of different adsorption conditions on the adsorption capacity of Pb2+ was investigated. The optimum adsorption conditions reached the maximum adsorption amount of 193.05 mg/g at Pb2+ solution concentration of 700 mg/L, adsorbent mass of 0.03 g, temperature of 55 °C, pH= 5. To further understand the adsorption process, kinetic and isotherm models were established. The results indicated that the adsorption process followed a pseudo-second-order kinetic model and Freundlich isotherm model, suggesting a monolayer chemical adsorption. XPS analysis was employed to determine the composition and valence state of the materials, confirming that the adsorption mechanism of SS-HS primarily involved electrostatic adsorption, ion and ligand exchange, and surface precipitation. This study not only introduces a novel approach for the resource utilization of steel slag but also presents an innovative adsorbent for efficient removal of Pb2+ from aqueous solutions.

Synthesis, physical properties, and carbon dioxide uptake of new metal-sulfamethoxazole complexes

Considerable research is currently being undertaken to reduce atmospheric CO2 levels, and a promising approach is capturing and storing the gas using adsorbents. In this regard, the synthesis and investigation of the potential use of new materials as CO2 storage media has attracted attention from both industry and academia. Metal-organic frameworks have a range of unique chemical and physical properties with many applications. Reported here is the synthesis of three new sulfamethoxazole-metal complexes and their use as models for investigation of the influence of the metal on their ability to absorb CO2. A new Schiff base was first synthesized, in 89 % yield, from the condensation of sulfamethoxazole and 4-(dimethylamino)benzaldehyde under acidic conditions. The reaction of the Schiff base with metal (nickel, copper, and cobalt) chlorides in ethanol under reflux gave the corresponding sulfamethoxazole-metal complexes in 71–80 % yield. Several experiments were conducted to assess the uptake of CO2 under different conditions. The complexes have low surface areas (1.36–5.82 m2/g) and average pore volume and diameters of 0.008–0.018 cm3/g and 2.17–4.08 nm, respectively. They showed some ability to adsorb CO2 (323 K and 40 bars), and the storage capacity was 11.2–26.1 cm3/gm. The cobalt-containing complex had the highest CO2 storage capability (26.1 cm3/g) due to its relatively high surface area (5.82 m2/g), pore volume (0.018 cm3/g), pore diameter (4.08 nm), and surface roughness (11.6) compared to the nickel and copper complexes.

Biochar from Delonix regia pod: consideration of an updraft retort carbonisation process

Retort carbonisation is a novel technology especially suited to the sub-Saharan Africa energy conversion challenges. This study aims to produce and characterise biochar from Delonix Regia pod (DRP) via the retort carbonisation process. The process achieved a Delonix Regia pod biochar (DRPB) yield of 29.48 wt% at a peak temperature of 375 °C and a process time of 150 min. The average pore volume, specific surface area, and average pore size of DRPB were 0.0352 cm3/g, 88.03 m2/g, and 1.6 nm, respectively. Morphological analysis revealed that DRPB had a heterogeneous surface morphology with an average roughness of 12.96 × 103 µm. Functional groups such as C-O, N-O, O-H, C = O, CO-O, and C-H are present in the biochar. DRPB compares well with other retort carbonisation biochar. Potential applications were also discussed based on the biochar properties and the product can be tested for water treatment applications and as an additive for improving the tribological and rheological properties of lubricating oils.

Properties of high-performing horizontal wells in the Midland Basin

What do the best horizontal wells in the Midland Basin Spraberry and Wolfcamp tight oil plays have in common? What differentiates them from less productive wells? In this study, we address these questions with data assembled from a high-resolution geomodel and public and vendor-sourced completions data. From 10,064 tight oil horizontal wells, 101 (1%) of the most productive wells by first-year oil production and 101 of the most productive wells by length-normalized first-year production are selected. We compare the completion, spacing, petrophysical, landing, and fluid properties between the most productive wells and others. Among the discoveries, we find that Wolfcamp A wells are more likely to be in the top 1%, especially those drilled in the carbonate-poor rock. Average hydrocarbon-filled pore volume and oil formation factors still lead to high-performing wells. High pressure is an important consideration for Wolfcamp B top producers. All of the best oil producers have low producing gas-oil ratios. The top 1% of wells are usually the first well in the pad to be completed, and they come from above-average pads. The top 30% of completions lead to the top 1% of wells more often than extremely intense completions. Operators can apply these results to the further development of the Midland Basin. Specifically, they can prioritize development areas in Wolfcamp A with low carbonate abundance and save costs by not implementing extremely intense completions.

Analysis of the Pore Structure and Fractal Characteristics of Coal and Gas Outburst Coal Seams Based on Matrix Compression Correction

The comparative analysis of coal samples under different gas occurrence conditions systematically reveals the pore structure characteristics of coal and gas outburst coal seams. The functional relationship between R0,max and Kc was clarified using mathematical statistical methods, and the pore structure and fractal characteristics of coal and gas outburst coal seams were analyzed on the basis of modified mercury pressure data and fractal analysis. The results show that the functional relationship between R0,max and Kc is consistent with y = 1.59x−0.48, and when the mercury inlet pressure is 10~120 MPa, the coal sample is the most affected by the matrix compression effect. The average pore volume and average specific surface area of the outburst coal samples were 41.71% and 23.09%, which is greater than those of the non-outburst coal samples, respectively, and the specific surface area and pore volume provided by the outburst mining micropores were 46.24% and 81.67%, respectively. The fractal dimension, D, of the coal seam increased with the increase in metamorphism, and compared with low gas mines, the fractal dimension of coal samples in the coal and gas outburst mines was higher, the influence of the matrix compression effect was more obvious, and the heterogeneity was stronger.

Hydrogenation of 2-ethyl-2-hexenal to alcohol over nickel-based catalysts: Effects of nickel content and promoter

The catalytic hydrogenation of 2-ethyl-2-hexenal (EPA) on a nickel-based catalyst via 2-ethyl-2-hexanal as an intermediate product is one of the step in manufacturing 2-ethylhexanol (EH). In this study, a nickel-based catalyst was synthesized using peptization and impregnation method. The catalyst's performance was examined utilizing a batch reactor adjusted for nickel loading and promoters. The surface area of the synthesized catalysts was around 61.5 – 235.2 m2/g with 76.4 Å pore size and 0.19 mL/g average pore volume. The catalyst was tested in an isothermal batch reactor at 120 °C and 30 bar. The nickel-based catalyst with 53%-Ni loading had the highest catalytic activity, with 100% EPA conversion and 81% EH selectivity. In addition, copper has been demonstrated to be the most effective catalyst promoter. The thermodynamic and kinetic approaches were also used in this investigation.

Effect of fouling and cleaning upon the surface charge and porosity of polyethersulphone membranes during coffee brew decaffeination

Filtration processes could offer a viable alternative to use of solvents for the production of reduced caffeine coffee beverages (so called ‘half-decaf’) which have recently gained increased commercial attention. However fouling phenomena and membrane deterioration could significantly alter the process performance; hence fouling and cleaning mitigation strategies must be explored by monitoring key membrane properties such as porosity and surface charge. In this study, multiple cycle filtration of coffee brews for the selective reduction of caffeine has been performed. A commercially available synthetic tight ultrafiltration polyethersulphone (PES) membrane (GP95PP – Alfa Laval) and a bespoke loose nanofiltration mixed matrix PES membrane fabricated, were used for three consecutive fouling and cleaning filtration cycles. The impact and mechanisms of fouling and the cleaning protocol effectiveness were investigated using surface charge, porosity, membrane surface and membrane morphology characterization techniques. Streaming potential studies revealed negative surface zeta potential for the membranes in a pH range of ca. 3.5–8.0. The fouled membrane classes exhibited elevated negative charges, which were partially restored to the pristine levels when chemically cleaned, suggesting the presence of residual negatively charged foulants. Porosity studies revealed the presence of a porous cake layer with an increase of average pore size and pore volume, and a decrease of 10–20 % on the BET surface area of the fouled membranes. Presence of key compounds on the membrane surface and structure was confirmed via EDX and FT-IR spectroscopy. Surface roughness along with SEM microscopy verified the uniform deposition of the foulants with absence of bulky particles. The presence of a cake layer was confirmed via SEM cross-sectional images due to selective thick layer thickness increase of the fouled membranes. Flux differences between the membrane classes can be related to the thickness of the top layer. Flux decreases and flux recovery ratios were also reported over multiple cycles and linked with porosity and other surface properties.

Preparation of foam ceramics from solid wastes: a study on the relationship between firing regime and properties by grey system theory

Foam ceramics were prepared by using 80 wt.% sand shale, 8 wt.% coal fly ash, 8 wt.% steel slag and 4 wt.% magnesite as raw materials and 0.3 wt.% SiC as foam agent. Effects of firing temperature and holding time on performance and phases of foam ceramics were investigated. Grey system theory was used to explore the correlation between pore structure parameters and thermal conductivity. The foam ceramics sintered at 1160 °C for 50 min exhibit the optimal comprehensive properties: bulk density of 0.651 g/cm3, flexural strength of 4.75 MPa, total porosity of 73.58%, closed porosity of 54.16%, and thermal conductivity of 0.081 W/(m·K). The Micro-CT results show that the pores with the average pore volume of 1.083 mm3 are relatively independent and uniform; and the pore wall thickness presents a normal distribution, which is conducive to improving the properties. Among the pore structure parameters, the fractal dimension has the greatest correlation with the thermal conductivity of foam ceramics.

Coconut shell char-based nanocomposites of polyamide-6: An investigation of thermal, morphological, and crystalline properties

This research was intended to investigate the thermal, morphological, and crystalline characteristics of polyamide-6@carbon char-based nanocomposites. The mesoporous nanosized carbon char was prepared in the laboratory via the carbonization method. The parameters of the coconut shell-based biocarbon char were confirmed by surface area and particle size analysis, and X-ray diffraction analysis. The coagulation-processed nanocomposites of polyamide-6 were prepared using synthesized mesoporous carbon char as filler. The obtained filler with a Brunauer–Emmett–Teller surface area of 1517 m2/g and an average pore volume of 2.51 nm was mixed with the polyamide at five different loadings. The coagulation technique was employed for the nanocomposite synthesis. The acquired coagulated nanocomposite was investigated using Fourier transform infrared analysis, thermogravimetric analysis, differential scanning calorimetric technique, and scanning electron microscopy analysis. It was evidenced from the research that loading coconut shell-based carbon char to polyamide-6 can contribute to a 10 °C rise in final degradation temperature with a 4 % loading of filler. The same filler content has contributed to a 5 °C decline in glass transition temperature. A continuous decrease in crystallinity with a rise in the concentration of biochar is indicative of the incorporation of amorphous character. So, it was determined that the thermal, morphological, and crystalline properties have been modified by synthesizing the coagulation-processed nanocomposites with mesoporous biochar of coconut shells.

Characteristics and Factors Influencing Pore Structure in Shale Oil Reservoirs of Different Lithologies in the Jurassic Lianggaoshan Formation of the Yingshan Gas Field in Central Sichuan Basin

Shale in the Jurassic Lianggaoshan Formation in central Sichuan exhibits strong heterogeneity. The study of the pore structure characteristics of different lithologies is crucial to the selection of the target interval. Shale samples of the Lianggaoshan Formation from well YS5 in the central part of the Sichuan Basin were analyzed using scanning electron microscopy, low-temperature nitrogen adsorption, high-pressure mercury injection (HPMI), and large -field splicing method -based scanning electron microscopy (LFS-SEM) to elucidate the pore structure characteristics of shale and their influencing factors. The mineral composition of the reservoir in the study area was diverse, primarily consisting of clay minerals, followed by quartz and calcite. The reservoir space comprised intergranular, granular, and organic matter pores, and oil was observed to fill the reservoir space. Reservoir characteristics varied with the lithological properties. In clayey shale, intergranular pores located in clay mineral particles and pores between pyrite and natural fractures were mainly observed, with a bimodal distribution of pore size and peak distribution of 10–50 nm and >100 nm. The storage space of ash-bearing shale mainly consisted of intragranular pores and intergranular (crystalline) micropores, with pore sizes primarily concentrated in the 10–50 nm range. The storage space in silty shale mainly developed in clastic mineral particles such as quartz, followed by clay mineral intergranular pores with a relatively wide distribution of sizes. Pores were mainly inkbottle-shaped and slit-type/plate-type pores, with an average specific surface area of approximately 6.9046 m2·g−1 and an average pore volume of approximately 0.0150 cm3·g−1. The full-pore capillary pressure curve was established using a combination of gas adsorption–desorption tests and HPMI. The fractal dimension of the sample pore structure was calculated, and a significant linear correlation was found between clay mineral content and the fractal dimension. Thus, the pore structure characteristics were mainly controlled by the content and distribution of clay minerals.

Enhancement of Methylene Blue Adsorption from ZnO/Activated Carbon Nanocompossites Prepared by Pyrolysis of Molten ZnCl2 with Rice Husks

In this work, we synthesized a facile step pyrolysis of ZnO/activated carbon nanocomposites by using molten ZnCl2 and rice husks in oxygen-limited environment. The mass ratio of molten ZnCl2 and rice husks was chosen from 0 to 5 wt.%, the pyrolysis temperature range from 400 to 800 oC. When the mass ratio of molten ZnCl2 and rice husks was equal to 1.0 and the pyrolysis temperature was at 800 oC, the size of ZnO nanoparticles in diameter was found to be of 10-20 nm. The ZnO/activated carbon nanocomposites exhibited a porous structure with the BET surface area, average pore diameter and pore volume of 643.9 m2/g, 4,76 nm and 0.255 cm3/g, respectively. To investigate the adsorption behavior of methylene blue, batch experiments were performed on all samples. The ZnO/activated carbon sample manufactured at a mass ratio of 1.0 and a pyrolysis temperature of 800 oC has the best methylene blue adsorption capability. The Langmuir isotherm was used to calculate the maximum adsorption capacity of methylene blue, which was 814.9 mg/g. Based on the obtained results, one can suggest that ZnO/activated carbon nanocomposites prepared by the facile pyrolysis route from molten ZnCl2 and rice husks possessing eco-friendly behaviour and low productioncost can be used as a potential adsorbent for wastewater treatment.

Integrated pretreatment of poplar biomass employing p-toluenesulfonic acid catalyzed liquid hot water and short-time ball milling for complete conversion to xylooligosaccharides, glucose, and native-like lignin

This work aimed to study an integrated pretreatment technology employing p-toluenesulfonic acid (TsOH)-catalyzed liquid hot water (LHW) and short-time ball milling for the complete conversion of poplar biomass to xylooligosaccharides (XOS), glucose, and native-like lignin. The optimized TsOH-catalyzed LHW pretreatment solubilized 98.5% of hemicellulose at 160 °C for 40 min, releasing 49.8% XOS. Moreover, subsequent ball milling (20 min) maximized the enzymatic hydrolysis of cellulose from 65.8% to 96.5%, owing to the reduced particle sizes and cellulose crystallinity index. The combined pretreatment reduced the crystallinity by 70.9% while enlarging the average pore size and pore volume of the substrate by 29.5% and 52.4%, respectively. The residual lignin after enzymatic hydrolysis was rich in β-O-4 linkages (55.7/100 Ar) with less condensed structures. This lignin exhibited excellent antioxidant activity (RSI of 66.22) and ultraviolet absorbance. Thus, this research suggested a sustainable waste-free biorefinery for the holistic valorization of biomass through two-step biomass fractionation.

Feasibility study of applying a graphene oxide-alginate composite hydrogel to electrokinetic remediation of Cu(II)-contaminated loess as electrodes

Inappropriate handling of heavy metal-containing wastewater resulting from extensive mining and smelting activities causes serious threats to surrounding environments and human health. The electrokinetic (EK) technology has been extensively applied to remediate heavy metal-contaminated sites because of its great manoeuvrability. The electrochemical polarization effect, however, reduces the electron transfer rate and could badly degrade EK removal efficiency. To this end, the present work proposed a novel graphene oxide-alginate composite hydrogel and applied it to copper removal as electrodes in EK remediation. A series of laboratory tests concerning its physical, mechanical, adsorption, and electrochemical properties were conducted. The graphene oxide (GO) particles provide larger average pore size and pore volume than traditional activated carbon electrodes. The surface functional groups, including hydroxyl, carboxyl, and epoxide groups, promote hydrogen bond formation. The GO particles and the calcium alginate are crosslinked with the hydrogen bonds, improving the mechanical properties of the graphene oxide-alginate composite hydrogel. Furthermore, the functional groups also encourage copper adsorption, and a high GO proportion does not necessarily mean an improvement in copper adsorption. The dynamic mechanism of Cu(II) adsorption onto the graphene oxide-alginate composite hydrogel conforms with the pseudo-second-order kinetic model. Moreover, the absence of oxidative and reductive peaks in the cyclic voltammograms is mainly attributed to the non-faradaic nature of the graphene oxide-alginate composite hydrogel, indicating a reduced electrode polarization effect. The Nyquist plot also approves its low resistance nature. The results were then compared against other electrodes to highlight the relative merits of the proposed graphene oxide-alginate composite hydrogel electrode.

Solid-state processed novel germanium/reduced graphene oxide composite: Its detailed characterization, formation mechanism and excellent Li storage ability

By using a simple solid-state reduction process, germanium oxide (GeO2) and graphene oxide (GO) are reduced to germanium (Ge) and reduced graphene oxide (rGO), respectively, to form Ge/rGO composite. Transmission electron microscopy showed that clusters of Ge nanoparticles are decorated on the graphene layers of rGO. Detailed x-ray diffraction, Raman scattering, and x-ray photoelectron spectroscopic analyses confirmed Ge/rGO composite formation. The thermal stability of Ge/rGO composite and the reduction mechanism through which the composite is formed are experimentally elucidated. Further, Brunauer–Emmett–Teller (BET) specific surface area, average pore volume, and average pore size of Ge/rGO composite are measured to be ∼115 m2/g, ∼0.4 cm3/g, and ∼14 nm, respectively. The thermal analysis quantified the amount of rGO in the Ge/rGO composite to be ∼66%. As-synthesized Ge/rGO composite is tested as anode material in Li-ion batteries. When cycled at 160 mA/g current density and in the 0.005–3.0 V voltage range, the composite showed an excellent reversible capacity of ∼539 mAh/g that corresponds to 98% capacity retention at the end of the 100th cycle. The Ge/rGO composite also showed high reversible capacity retention, good rate capability, and excellent cycle life when tested at 80 and 320 mA/g in the same voltage range. The redox peaks in the cyclic voltammetry (CV) curves revealed that alloying-dealloying and electrochemical adsorption-desorption mechanisms are the primary reasons for the lithium-ions storage by Ge and rGO, respectively. A constant area under the CV curves throughout the test indicated the stable capacity. Also, the CV results align with the galvanostatic cycling results.

Ultrasonic-assisted, rapid preparation of mesoporous MnCO3 for electrochemical supercapacitor applications: A novel approach

Accounting for the methods opted in the preparation of nanoscale materials with high surface rea, average pore size and volume needs high energy and time-consuming processes. This work discloses a quick, scalable, and simple co-precipitation method for synthesizing MnCO3 for use in supercapacitors as a working electrode using MnSO4 and (NH4)HCO3 as the manganese and carbonate sources, respectively. As-synthesized sample is subjected to sonication at different periods for evaluating the effect of capacitance and the size of MnCO3 particles. Investigations using X-ray diffraction and X-ray photoelectron spectroscopy proves that MnCO3 can form the rhodochrosite phase and microscopical analyses reveals that nanograins smaller than 10 nm aggregated into spherical particles that were submicron in size. N2 adsorption–desorption isotherm isotherms validates the mesoporosity of MnCO3. The Galvanostatic charge–discharge cycling and cyclic voltammetry techniques examine the capacitance characteristics of mesoporous MnCO3 in both 0.1 Mg(ClO4)2 and Na2SO4 aqueous solutions. Mesoporous MnCO3 delivers a specific capacitance of 188F g−1 and 124F g−1 at a specific current of 0.33 A g−1 in both Mg(ClO4)2 and Na2SO4 aqueous solutions with a loading level of 1.5 mg cm−2. Additionally, mesoporous MnCO3 shows strong rate capability and stable cycle-life over 10,000 cycles. These demonstrates the mesoporous nanomaterials with high surface area and volume can enhance the energy storage capacitance of a supercapacitor.

Efficient [Fe-Imidazole@SiO2] Nanohybrids for Catalytic H2 Production from Formic Acid.

Three imidazole-based hybrid materials, coded as IGOPS, IPS and impyridine@SiO2 nanohybrids, were prepared via the covalent immobilization of N-ligands onto a mesoporous nano-SiO2 matrix for H2 generation from formic acid (FA). BET and HRTEM demonstrated that the immobilization of the imidazole derivative onto SiO2 has a significant effect on the SSA, average pore volume, and particle size distribution. In the context of FA dehydrogenation, their catalytic activity (TONs, TOFs), stability, and reusability were assessed. Additionally, the homologous homogeneous counterparts were evaluated for comparison purposes. Mapping the redox potential of solution Eh vs. SHE revealed that poly-phosphine PP3 plays an essential role in FA dehydrogenation. On the basis of performance and stability, [Fe2+/IGOPS/PP3] demonstrated superior activity compared to other heterogeneous catalysts, producing 9.82 L of gases (VH2 + CO2) with TONs = 31,778, albeit with low recyclability. In contrast, [Fe2+/IPS/PP3] showed the highest stability, retaining considerable performance after three consecutive uses. With VH2 + CO2 = 7.8 L, [Fe2+/impyridine@SiO2/PP3] activity decreased, and it was no longer recyclable. However, the homogeneous equivalent of [Fe2+/impyridine/PP3] was completely inactive. Raman, FT/IR, and UV/Vis spectroscopy demonstrated that the reduced recyclability of [Fe2+/IGOPS/PP3] and [Fe2+/impyridine@SiO2/PP3] nanohybrids is due to the reductive cleavage of their C-O-C bonds during catalysis. An alternative grafting procedure is proposed, applying here to the grafting of IPS, resulting in its higher stability. The accumulation of water derived from substrate's feeding causes the inhibition of catalysis. In the case of [Fe2+-imidazole@SiO2] nanohybrids, simple washing and drying result in their re-activation, overcoming the water inhibition. Thus, the low-cost imidazole-based nanohybrids IGOPS and IPS are capable of forming [Fe2+/IGOPS/PP3] and [Fe2+/IPS/PP3] heterogeneous catalytic systems with high stability and performance for FA dehydrogenation.