Mo Adsorption Research Articles

Quantum anomalous Hall effect with high Chern numbers in functionalized square-octagon Sb monolayers

The quantum anomalous Hall (QAH) effect has attracted continuous attention due to its intriguing properties and potential applications in future electronics. Here, we present our investigation of the electronic and topological properties of a square-octagon Sb monolayer with Mo atoms adsorbed (Mo@so-Sb) using first-principles calculations. Our studies reveal how a trivial insulator can be first engineered into an unusual bipolar magnetic semiconductor (BMS) and then further tuned by strain into a spintronics-favorable half semiconductor (HS) or half metal. Remarkably, with 3.7% compressive strain applied, we achieve a QAH state in Mo@so-Sb with a high Chern number (C = 4) which is much larger than that (C = ±1 or ±2) of the previously predicted Chern insulators. This QAH state is characterized by the appearance of four gapless chiral edge states within the nontrivial band gap, enabling a robust multi-channel low-power-consumption transport. Its nontrivial topology primarily originates from the band inversion between the non-degenerate Mo 4d and Sb 5p orbitals. Additionally, we demonstrate the interesting BMS, HS, and QAH states can be controlled by the Mo adsorption concentrations. Our findings not only provide a versatile means of transforming trivial insulators into the desired spintronics-favorable and topological states, but also open new possibilities for high-performance electronic devices.

Adsorption Properties of a Polyamine Special Ion Exchange Resin for Removing Molybdenum from Ammonium Tungstate Solutions

A polyamine special ion exchange resin was used to adsorb Mo from ammonium tungstate solutions. The effects of adsorption time, S2− concentration, adsorption temperature, CO32− concentration, mass ratio of WO3 to Mo, and Mo concentration on the Mo and WO3 adsorption capacities were investigated. Energy dispersive spectrometer plane scans were used to study the distributions of Mo, W, S, and Na on the loaded polyamine special ion exchange resin and the desorbed polyamine special ion exchange resin. The results showed that the polyamine special ion exchange resin performed well during adsorption and desorption. Under the optimum conditions for the static adsorption experiments, the adsorption capacities for Mo and WO3 were 99.29 mg/mL and 31.97 mg/mL, respectively, and the desorption rates for Mo and WO3 were 99.35% and 99.43%, respectively. Adsorption and desorption of molybdenum and tungsten on the polyamine special ion exchange resin were investigated by dynamic adsorption experiments with an ammonium tungstate solution containing 125.0 g/L WO3, 12.50 g/L Mo, 15.65 g/L S2−, and 0 g/L CO32−. The adsorption capacities for Mo and WO3 were 53.48 mg/mL and 9.79 mg/mL, and the adsorption rates for Mo and WO3 were 99.05% and 1.81%, respectively. The loaded polyamine special resin was desorbed with a 45 g/L sodium hydroxide solution, and the dynamic desorption rates for Mo and WO3 were 99.02% and 99.29%, respectively.

Changes in molybdenum bioaccessibility in four spiked soils with respect to soil pH and organic matter

Investigation of the inherent relationship between soil physicochemical properties and pollutant's bioaccessibility (BAc) by analyzing different soil types may produce erroneous results or bias, owing to the complexity of natural soil characteristics. However, use of single factor analysis (e.g., soil pH, organic matter) facilitates evaluation of the transition. In this study, the inherent relationship between soil properties and the BAc of molybdenum (Mo) was evaluated in two typical variable-charge soils (Ferralosol and Ferrosol) and constant-charge soils (Alfisol and Inceptisol) spiked with Mo after adjusting their pH and organic carbon content. The Unified Bioaccessibility Research Group of Europe (BARGE) Method (UBM) was applied to evaluate the BAc of Mo in the gastric and intestinal phase (GP and IP, respectively). Isothermal adsorption experiment, Tessier sequential extraction, and field emission scanning electron microscope-energy dispersive spectroscopy (FESEM-EDS) analysis were conducted on these spiked soils. The results indicated that the BAc of Mo in IP (27.42–80.41%) was significantly higher than that in GP (2.52–28.53%). A significantly lower level of BAc of Mo was found in the variable-charge soils, when compared with that in the constant-charge soils. Furthermore, significant negative correlations were identified between the BAc and adsorption of Mo, which decreased with soil pH. These negative correlations can be attributed to the increase in soil negative charge density and enhancement of Mo desorption by hydroxyl, which reinforce the repulsion between Mo and soil particles with increasing soil pH; this was further confirmed by the decrease in Mo adsorption with Alfisol pH. The Mo fractions and FESEM-EDS patterns confirmed that the BAc of Mo in GP was negatively correlated with soil organic carbon (SOC) content, possibly owing to an increase in Mo retention by SOC. These findings indicated that the health risk of Mo contamination in low pH and SOC-rich variable-charge soil is relatively low, thus providing references for rationalizing risk assessment and remediating Mo-polluted soil.

Synthesis of p(HEMA-co-AETAC) nanocomposite hydrogel with vinyl-function montmorillonite nanoparticles and effective removal of methyl orange from aqueous solution

It has become crucial to develop new adsorbents to remove toxic dye wastes from wastewater to protect our existing aquatic ecosystem. Here, to remove methyl orange azo dye from aqueous solutions, a new p(HEMA-co-AETAC)/VMt nanocomposite hydrogel was prepared by using 2-hydroxyethyl methacrylate and [2-(acryloyloxy)ethyl]trimethylammonium chloride monomers using vinyl-based montmorillonite crosslinker. Obtained new types of crosslinker and nanocomposite hydrogels have been characterized by various analysis methods. In addition, the effects of crosslinker amount, monomer amount and pH on the swelling behavior of nanocomposite hydrogel were investigated. The effects of essential parameters such as contact time, initial dye concentration, pH effect of the solution, adsorbent amount, and temperature on adsorption were evaluated. It was determined that there was no significant change in the adsorption ability of the nanocomposite hydrogel in the pH range of 3–10. Experimental results showed that the Langmuir isotherm model fit better, and the calculated maximum adsorption capacity was 961.54 mg/g. In addition, it was determined that vinyl-based montmorillonite used as a crosslinker supported MO adsorption. p(HEMA-co-AETAC)/VMt nanocomposite hydrogel may be a new type of adsorbent to remove toxic synthetic dye residues from aqueous media.

Green synthesis of alumina nanoparticle using Hibiscus rosa-sinensis leaf extract as a candidate for molybdenum-99 adsorbent

Al2O3 nanoparticle is effectively used as an adsorbent for the low specific activity of molybdenum-99 (99Mo). The Al2O3 nanoparticle was synthesized by the green synthesis method using Hibiscus rosa-sinensis leaf extract (HRE). The Al2O3 nanoparticle synthesized using 10% of the HRE has a crystallite size of 4.9 nm, a surface area of 254.6 m2/g, a pore size of 9.1 nm, a pore volume of 0.58 cm3/g and has a Mo adsorption capacity of 43.4 ± 6.1 mg Mo/g.

Removal of Molybdenum from Contaminated Groundwater Using Carbide-Derived Carbon

In the present work, the removal of Mo from aqueous solutions and real groundwater by using the novel high-surface-area adsorbent carbide-derived carbon (CDC) was performed. The adsorbent was characterized using X-ray photoelectron spectroscopy (XPS), X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS), Brunauer, Emmett, and Teller (BET) surface area analysis, and Fourier-transform infrared spectroscopy (FTIR). The effect of the operational parameters (contact time, CDC loading, Mo concentration, and pH) on the adsorptive performance of the sorbent in the batch adsorption mode was studied. The experimental work revealed that the adsorption of Mo onto CDC is a very fast process and provides 99% Mo removal in less than 30 min. The adsorption process was pH-dependent, achieving the maximum adsorptive removal at a pH range of 3–5. The highest adsorption capacity corresponded to 16.24 mg/g at a Mo concentration of 10 ppm, adsorbent loading of 0.6 g/L, and pH 3. Four models were used to analyze the adsorption isotherms of Mo onto CDC, which were Freundlich, Langmuir, Temkin, and Sips. The obtained adsorption results were also processed using four adsorption kinetic models: intra-particle diffusion, Elovich, second-order, and pseudo-first-order. The adsorption of Mo onto CDC was found to fit the Freundlich isotherm model, as confirmed by the highest R2 values (0.9118) and lowest SSE (0.4777), indicating the heterogeneous multilayer adsorption of Mo onto CDC. Likewise, the experimental adsorption data were found to be more consistent with the pseudo-second-order model. The main adsorption mechanisms contributing to Mo adsorption were found to be electrostatic interactions and ligand–ligand exchange, in addition to surface complexation or ion exchange between Mo ions and oxygen-containing groups on the CDC’s surface. Moreover, the removal efficiency under acidic conditions (pH: 3) was found to be stable and high (>99%), regardless of the Mo concentration (0.5–10 ppm) due to the characteristic PZC corresponding to CDC (pH 9.9). A performance test of the CDC using both real groundwater and GW spiked with 570 µg/L Mo showed an almost complete removal of Mo from GW. The regeneration tests confirmed that adsorbed Mo can be recovered from CDC by pH adjustment and the regenerated CDC can be reused.

Adsorption behavior of molybdenum onto K-doped γ-Al2O3 and iron clay nanocomposite

Abstract Adsorption of molybdenum was carried out on two materials; potassium doped γ-Al2O3 (KA) and bentonite iron oxide composite (BIOC) with purpose of using in production of chromatographic 99mTc generators, for KA absorbent, different ranges of potassium loadings have been considered, for BIOC solid the used weight ratio was (Bentonite/Fe = 2/1). Samples were characterized by XRD and WDXRF. Adsorption of MoxOy z− species was carried out at pH 2.5 and 25 °C, effects of contact time and pH were studied. The Mo adsorption data onto used materials were well fitted using Freundlich and Langmuir models. Doped alumina samples showed higher adsorption capacities (∼90 mg g−1) than the usual alumina used in generator technology (∼60 mg g−1), whereas adsorption capacities of BIOC solid were in the range of (∼75 mg g−1).

Eco-friendly ZIF-67/rice straw-derived cellulose acetate electrospun nanofiber mats for efficient CO2 capturing and selectivity removal of methyl orange dye

Electrospun nanofiber membranes are ubiquitous in the ecological environment due to the high specific surface area and porosity, excellent functionality and recycling. Surface enriched ZIF-67 that incorporated into electrospun rice straw-derived cellulose acetate (RSCA) nanofibers mats were synthesized using a facile in-situ growth strategy. The RSCA was achieved by the acetylation reaction of rice straw-derived cellulose, which was extracted from the recycled waste agricultural rice straw by green solvent. The structures and properties of ZIF-67/RSCA were investigated to reveal the mechanism of in-situ growth method. ZIF-67/RSCA mat shows efficient CO2 capture and water treatment performance. The achieved ZIF-67/RSCA-0.1 M nanofiber membrane possesses optimal capacities for CO2 (1.33 mmol/g at 273 K and 101 kPa), which reached to 70% of ZIF-67 powders. MO adsorption capacity of ZIF-67/RSCA-0.1 M membrane was matched with the pseudo-second-order kinetic model, and their equilibrium adsorption capacity towards MO was found to be 11.20 mg/g at room temperature, which is about 15 times as that of pure RSCA nanofibers membrane (0.77 mg/g). Moreover, the ZIF-67/RSCA could selectively adsorb the MO, while it cannot remove the MB pollutant. The detailed analysis of BET and Zeta potential indicated that larger specific surface area and positive potential of ZIF-67/RSCA were favorable for efficient adsorption and selectivity. We believe the approach to fabricate ZIF-67/RSCA nanofibers membrane using the rice straw for removing CO2 and MO is a win-win strategy for the application of agricultural waste to environmental pollution.

Multi-usable titanium dioxide and poly(vinylidene fluoride) composite foam photocatalyst for degradation of organic pollutants

Multi-usable photocatalyst foam was prepared by coagulating poly(vinylidene fluoride)–titanium dioxide (PVDF-TiO2) composite solution with water-spray. X-ray diffraction, ultraviolet–visible, infrared and X-ray photoelectron spectra were confirmed the inclusion of TiO2 in PVDF-TiO2 foam (PTF). PVDF did not affected the band gap and characteristic light absorption of TiO2. Whereas, TiO2 decreased the crystallinity of PVDF matrix. As per thermogravimetric analysis, coagulation of 8 ml composite solution containing 0.3 g of PVDF and 25, 50, 75, and 100 mg of TiO2 resulted the PTF with 2.75, 13.77, 17.56, and 21.93 wt% TiO2, respectively. Due to phase separation, TiO2 were coated on the surface of PTF. Methyl orange (MO, 10 µM) was used as a model pollutant. PTF with 0–13.77 wt% TiO2 showed significant MO adsorption under dark and ultraviolet A light. Adsorption was almost nullified in case of PTF with 17.56, and 21.93 wt% TiO2, and the photooxidation was prevailed. The photocatalytic efficiency of PTF with 17 wt% TiO2 was stable during 50 reuse cycles. Physiochemical characterization of multi-used PTF confirmed that TiO2 NPs were not leached out during reuse. Aforementioned findings suggest that PTF can be a potential reusable photocatalyst for practical water decontamination process.

Surface modification of acid-functionalized mesoporous gamma-alumina for non-fission 99Mo/99mTc generator

Mesoporous gamma-alumina (MGA) was synthesized for neutron-activated 99Mo adsorbent. Acid functionalization of the MGA was carried out to enhance the Mo adsorption capacity and the 99Mo breakthrough profile. The acid-treated MGA has a more positive particle charge, rougher surface, smaller particle and pore size, larger surface area, and wider pore distance. The acid-treated MGA has a Mo adsorption capacity of 82.8 ± 6.3 mg Mo/g and resulted in 99mTc eluate with the 99Mo breakthrough at the acceptable level.

Extremely light molybdenum isotope signature of sediments in the Mariana Trench

Molybdenum (Mo) isotope signature (δ98/95Mo) of marine sediments is a powerful proxy for constraining marine redox conditions and early diagenetic processes. Oxic pelagic sediments have been increasingly acknowledged as an important sink for Mo in its global cycling, however, the mechanisms controlling Mo enrichment and isotope fractionation during early diagenesis in this environment are not fully understood. In this study, four sedimentary cores were sampled by full-ocean-depth lander system in the Mariana Trench, aiming to explore the processes controlling Mo partitioning in the sediments of the deepest ocean in the world. Sediments from four locations exhibit a wide range of authigenic Mo contents (Moauth, relative to continental crust), varying from 1.98 to 43 μg/g. A positive relation between Mo and Mn contents was identified for these sediments, which suggests that Mo are mainly hosted in Fe-Mn (oxyhydr)oxides. In addition, negative correlations between δ98/95Mo values and Mo/Mn ratios are found at each site. The δ98/95Mo values of the sediments vary from −1.71 ± 0.05 to −0.15 ± 0.04‰, revealing similar trends towards lighter values with burial depth from three sites. However, throughout the sediment core TY41 obtained from Mariana Trench, the δ98/95Mo values of sediment remain nearly constant around −0.55‰. Supported by the abundant Fe (oxyhydr)oxides throughout this site, it is likely the sediment is affected by enhanced fluid exchange across sediment-seawater interface, and the δ98/95Mo values of dissolved Mo in pore water resemble seawater signature. Therefore, the Mo isotopic offset between dissolved Mo and sediment is similar to the expected fractionation during the adsorption to Mn oxides (~ + 3.0‰) and hematite (~ + 2.2‰), which suggests that most of the dissolved Mo is scavenged by Mn oxides and/or hematite. The extremely light δ98/95 Mo values of sediments in deeper parts of the cores coincide with enhanced Mo accumulation. This indicates an even lighter isotope signature of dissolved Mo in pore water during the re-precipitation of Fe-Mn (oxyhydr)oxides upon an isotopic equilibrium for Mo adsorption to metal oxides. Both the patterns of both dissolved oxygen and nitrate suggest that the study sites are located within the nitrate reduction zone and Mn reduction occur at deeper depths below the studied interval. Therefore, the source of the isotopically light dissolved Mo in pore water was explained by the preferential release of isotopically lighter Mo from Fe-Mn (oxyhydr)oxides during the enhanced dissolution at deeper depth. In contrast, at the shallower depths of these cores (expect for core TY41), the higher δ98/95 Mo values towards seawater-sediment interface suggest the dissolved Mo is more impacted by the seawater exchange. This study provides a deeper insight into the diagenetic Mo cycling in trench environments, with Fe-Mn (oxyhydr)oxides rich sediments as an important sink for Mo.

Efficient preparation of phosphazene chitosan derivatives and its applications for the adsorption of molybdenum from spent hydrodesulfurization catalyst

In this study, the phosphazene chitosan derivative was manufactured and characterized. adsorption of molybdenum (Mo) from solutions using prepared working material as sorbent was examined. Nuclear magnetic resonance spectroscopy (1HNMR), Carbon-13 (13CNMR) nuclear magnetic resonance, Gas Chromatography–Mass Spectrometry (GC–MS), Phosphorus-31 nuclear magnetic resonance (31P-NMR), scanning electron microscopy (SEM), Brunauer–Emmett–Teller analysis (BET surface area) and Fourier-transform infrared spectroscopy (FTIR) were used to characterize and confirm the prepared adsorbent. Many variables, including pH of the aqueous solution, the amount of adsorbent dosed, initial concentration of Mo(VI), contact time, and temperature were examined using the batch adsorption technique. When Mo(VI) is exposed to foreign ions, its desorption behavior changes. (Cr6+, Cl−, Co2+, Fe3+, and sulfate) were investigated. Cr6+ had a greater impact on the adsorption process in compared with other foreign ions. The maximum capability for Mo(VI) adsorption on the created adsorbent was 305.07 ± 2.36 mg/g, which was obtained at room temperature. The adsorption isotherms were best fitted with the Freundlich isotherm model. The kinetic data fitted well with the pseudo-second-order equation. The thermodynamic studies found that the adsorption was an exothermic and spontaneous process in nature.

Photo-Fenton Degradation of Methyl Orange with Dunino Halloysite as a Source of Iron

The Fenton reaction is one of the most important processes for water and soil remediation, although this process has some drawbacks such as the use of H2O2 in large amounts, the formation of sludge due to the use of iron salts, and the need for acid pH values. Here we present the use of a natural clay, modified by acid treatment, as a heterogeneous catalyst to replace soluble iron salts and to avoid the use of water peroxide, resulting in a considerable increase in the attractiveness of the process. Halloysite (HT) clay from the Dunino mine consists of alumina and silica layers with the presence of iron species acting as a source of Fe ions. The etching of alumina layers using hydrochloric acid induces the release of iron species (mainly ions) in the solution, giving rise to the photodegradation activity of organic contaminants in water (i.e., Methyl Orange, MO) under UV irradiation without the need for hydrogen peroxide and avoiding the formation of sludges. MO adsorption properties and MO photodegradation ability were investigated for untreated and acid treated samples, respectively, to achieve the optimal process conditions. MO was not adsorbed on the clay’s surface due to electrostatic repulsion, but a complete degradation was observed after three hours under UV irradiation. The kinetics of photodegradation and the values of the half-life time are presented as a measure of the degradation rate. The proposed process shows a new route for effective remediation of water containing biologically active organic substances dissolved in it.

Adsorption of octahedral mono-molybdate and poly-molybdate onto hematite: A multi-technique approach

Molybdenum (Mo) is a key trace element and a contaminant in many environments including mine tailings and acid mine drainage systems. Under oxic conditions Mo exists in a number of forms, including mono-molybdate (Mo(VI)O42-) and various poly-molybdate species (e.g. Mo(VI)7O246-) depending on the geochemical conditions (e.g. pH). The mobility and bioavailability of Mo is often controlled by sorption to mineral surfaces, including iron (oxyhydr)oxides e.g. hematite (Fe2O3). This study uses adsorption isotherms, PHREEQC geochemical modeling, Attenuated Total Reflection-Fourier Transform Infrared Spectroscopy (ATR-FTIR), and X-ray Absorption Spectroscopy (XAS) to holistically characterise the molecular scale adsorption of molybdate to hematite as a function of pH (3−12) and Mo(VI) concentration (0.01 × 10−4 - 2 × 10−3 M). PHREEQC and ATR-FTIR indicated both pH and Mo concentration are important variables when forming mono- vs. poly- molybdate and suggest low pH (≤ 4) and high Mo(VI) concentration (≥ 5 × 10−4 M) contribute to the formation of a poly-molybdate surface species on the hematite surface. XAS found Mo adsorbed to hematite via an inner-sphere corner-sharing bidentate binuclear complex with an octahedral mono-molybdate structure at a Mo concentration of 0.6 × 10−4 M across the pH range, and at a Mo(VI) concentration of 5 × 10−4 M and pH over 5. This is the first direct observation of octahedrally coordinated Mo(VI) adsorption species on hematite, and this information has broad implications for the mobility and transport of Mo as a contaminant in the environment.

Engineering Commercial TiO2 Powder into Tailored Beads for Efficient Water Purification.

In this study, efficient commercial photocatalyst (Degussa P25) nanoparticles were effectively dispersed and stabilized in alginate, a metal binding biopolymer. Taking advantage of alginate’s superior metal chelating properties, copper nanoparticle-decorated photocatalysts were developed after a pyrolytic or calcination-sintering procedure, yielding ceramic beads with enhanced photocatalytic and mechanical properties, excellent resistance to attrition, and optimized handling compared to powdered photocatalysts. The morphological and structural characteristics were studied using LN2 porosimetry, SEM, and XRD. The abatement of an organic pollutant (Methyl Orange, MO) was explored in the dark and under UV irradiation via batch experiments. The final properties of the photocatalytic beads were defined by both the synthesis procedure and the heat treatment conditions, allowing for their further optimization. It was found that the pyrolytic carbon residuals enabled the adhesion of the TiO2 nanoparticles, acting as binder, and increased the MO adsorption capacity, leading to increased local concentration in the photocatalyst vicinity. Well dispersed Cu nanoparticles were also found to enhance photocatalytic activity. The prepared photocatalysts exhibited increased MO adsorption capacity (up to 3.0 mg/g) and also high photocatalytic efficiency of about 50% MO removal from water solutions, reaching an overall MO rejection of about 80%, at short contact times (3 h). Finally, the prepared photocatalysts kept their efficiency for at least four successive photocatalytic cycles.

Insights into the role of metal cation substitution on the anionic dye removal performance of CoAl-LDH

The preparation of the adsorbent plays an important role in the adsorption technology, especially the selection of adsorbents with high specific surface area and special structure is particularly critical to the entire adsorption process. Herein, a series of ternary LDHs was designed via a facile hydrothermal method, and in another word, all derived from binary CoAl-LDH by substituting with another transition metals(Ni, Zn, Fe), used as adsorbents to remove MO and CR. The adsorption capacity of the obtained ternary LDHs are better than that of the pristine CoAl-LDH, and CoNiAl-LDH stands out with the higher adsorption capacity than other ternary LDHs samples whether the dye is MO or CR. Then the effect of initial dye concentration, pH and temperature on its MO adsorption performance was systematically studied. The maximum adsorption capacity reached more than 330 mg/g under the optimal conditions (25 °C, pH=3). This work may provide a method to design the advanced adsorbents design for further enhancing the adsorption activity in the field of water environmental protection.

Mechanisms Responsible for Adsorption of Molybdate ions on Alumina for the Production of Medical Radioisotopes

Abstract In this work, the mechanisms responsible for the adsorption of molybdate ions on alumina are investigated using in-depth surface analyses of alumina specimens immersed in solutions containing different molybdate ions at different pH values. The obtained results reveal that when alumina is immersed in an acidic solution containing molybdate ions, the hydroxyl groups present on the surface are removed to generate positively charged sites, and molybdate ions (MoO42− or AlMo6O24H63−) are adsorbed via an electrostatic interaction. Alumina dissolves slightly in an acidic solution to form AlMo6O24H63−, which is more easily desorbed than MoO42−. Furthermore, the enhancement in the Mo adsorption or desorption property may be achieved by enriching the surface of the alumina adsorbent with many –OH groups and optimizing Mo solution to adsorb molybdate ions on alumina as MoO42− ions. These findings will assist researchers in engineering more efficient and stable alumina-based adsorbents for molybdenum adsorption used in medical radioisotope (99Mo/99mTc) generators.

Synthesis and characterization of mesoporous gamma-alumina by glucose as soft-template for molybdenum-99 adsorption: high and low molar ratio of water to aluminium isopropoxide effect

The mesoporous gamma-alumina is a good material for metal adsorption. Its textural properties are excellent, mainly for molybdenum-99 radioisotopes adsorption as part of 99Mo/99mTc generator in nuclear medicine. In this work, we have prepared mesoporous gamma-alumina by sol-gel treatment in the presence of glucose as a soft template. The molar ratio of reactant (water: aluminium isopropoxide(AIP)) was applied in the high and low ratios (150:1 and 25:1). The resulted mesoporous gamma-alumina was investigated using characterization analysis of X-ray diffraction, Nitrogen adsorption-desorption, and FTIR. The results indicate that the mesoporous gamma-alumina in the high molar ratio of water to AIP had a higher surface area and better crystallinity than the low molar ratio of reactants. Furthermore, in the Mo adsorption test, the mesoporous gamma-alumina with the high molar ratio posed a higher Mo adsorption capacity up to 55.69 mg Mo g−1 adsorbent. In the future, the molar ratio of reactants should be tuned in the range of around 150:1 to obtain the optimal Mo adsorption capacities of the resulted mesoporous gamma-alumina using the glucose template.

Observation of surface precipitation of ferric molybdate on ferrihydrite: Implication for the mobility and fate of molybdate in natural and hydrometallurgical environments

Adsorption of molybdate (Mo(VI)) on the surfaces of ferrihydrite is one of the most critical processes that control its mobility and fate in the environment. However, the sorption mechanism and the effect of pH on the speciation of Mo(VI) on ferrihydrite surfaces are not well understood. In this study, X-ray diffraction (XRD), Raman, Fourier transform infrared (FTIR), and Mo K-edge and L3-edge X-ray absorption spectroscopy (XAS) have been utilized to characterize the Mo(VI) species sorbed on ferrihydrite under various pH conditions. XRD, Raman, and FTIR results show that at acidic pH, surface precipitation of poorly crystalline ferric molybdate (PCFM) occurs under apparently undersaturated conditions (theoretical log IAP < log Ksp) and is enhanced by the aging process, whereas Mo(VI) is mainly present as surface adsorbed species at circum-neutral pH. The Mo K-edge and L3-edge X-ray absorption near edge structure (XANES) analyses show that a mixture of tetrahedrally and octahedrally coordinated Mo(VI) simultaneously exists at pH 3–7 and the octahedral Mo(VI) species decreases with increasing pH. The Mo-Fe interatomic distances (3.52–3.56 Å) derived from EXAFS fittings suggest the corner-sharing complexation of both MoO4 and MoO6 with FeO6 octahedra. As the pH decreases from 7 to 3, the coordination number of the Mo-Fe shell (CNMo-Fe) increases from 0.6(3) to 1.9(3), possibly due to the gradual transformation of surface adsorbed Mo(VI) to PCFM. These findings on the observation of Mo(VI) complexation, surface precipitation, and their marked pH dependence during the Mo(VI) adsorption on ferrihydrite have important implications for both understanding the mobility and fate of Mo(VI) in natural and hydrometallurgical industry impacted environments and developing optimal applications for the remediation of Mo contamination in aqueous environments.

Selective capture of toxic anionic dyes of a novel prepared DMDAAC-grafted chitosan/genipin/cellulose hydrogel beads with antibacterial activity

Novel eco-friendly and green dimethyldiallylammonium chloride (DMDAAC) grafted chitosan/genipin/cellulose hydrogel beads (CCBG-g-PDMDAAC), were fabricated as selective adsorbents for anionic dyes. The physical and chemical structural changes of the prepared hydrogels were evaluated by FTIR, XRD, SEM and TG-DSC analysis. Results showed CCBG-g-PDMDAAC efficiently and selectively adsorb anionic dyes (Reactive Red 195-RR195 and Methyl orange-MO) from mixture of dye solutions. Endowed chitosan-based hydrogels the advantage of acid insolubility and good adsorption. RR195 and MO adsorption process were described better with pseudo-second-order kinetic model and Langmuir isotherm model with a maximum adsorption capacity of 1333.52 and 190.48 mg/g, respectively, indicating that monolayer chemisorption controlled the sorption process. Moreover, the hydrogels exhibited nice reusability and against S. aureus and E. coli. The hydrogels are promising for the potential application in wastewater treatment and antibacterial simultaneously.