Enhanced sorption of strontium radionuclides onto a modified molybdenum titanate composite

A study was conducted to investigate the sorption of 85Sr from aqueous solutions using a fabricated magnesium molybdenum titanate (MgMoTi) composite. The MgMoTi composites were synthesized through the co-precipitation technique and characterized using different analytical tools, including FT-IR, XRD, SEM, and EDX. The sorption studies focused on 85Sr and examined factors such as shaking time, pH, ionic strength, temperature, initial ion concentration, and saturation capacity. The results obtained from the study indicated that, under optimum sorption conditions, the saturation capacity for 85Sr onto S-4 and S-5 was determined to be 23.31 and 37.72 mg g-1, respectively. The sorption of 85Sr exhibited dependence on pH and ionic strength. The kinetics of the sorption process followed the pseudo-2nd-order model, while the thermodynamics revealed an endothermic and spontaneous nature. Desorption studies revealed that 0.1 M HCl was the most effective eluent for the complete recovery of 85Sr. Furthermore, the recycling results demonstrated the excellent recyclability of MgMoTi, suggesting its potential application as a sorbent for the removal of 85Sr from aqueous solutions. Overall, the study highlights MgMoTi as a promising composite with practical utility in the sorption of 85Sr from aqueous solutions.

Recent advances and perspectives for intercalation layered compounds. Part 2: applications in the field of catalysis, environment and health

Intercalation compounds represent a unique class of materials that can be anisotropic (1D and 2D-based topology) or isotropic (3D) through their guest/host superlattice repetitive organisation. Intercalation refers to the reversible introduction of guest species with variable natures into a crystalline host lattice. Different host lattice structures have been used for the preparation of intercalation compounds, and many examples are produced by exploiting the flexibility and the ability of 2D-based hosts to accommodate different guest species, ranging from ions to complex molecules. This reaction is then carried out to allow systematic control and fine tuning of the final properties of the derived compounds, thus allowing them to be used for various applications. This review mainly focuses on the recent applications of intercalation layered compounds (ILCs) based on layered clays, zirconium phosphates, layered double hydroxides and graphene as heterogeneous catalysts, for environmental and health purposes, aiming at collecting and discussing how intercalation processes can be exploited for the selected applications.

Efficient uptake of 85Sr and 60Co using fabricated inorganic sorbent for reducing radiation doses of simulated low-level waste

The present study investigated the sorption behavior of 85Sr and 60Co radionuclides from aqueous solutions onto tin molybdate (SnMo) sorbent. SnMo has been synthesized using the precipitation method and was characterized using four analytical techniques including FT-IR, XRD, SEM, and XRF. The sorption studies applied on 85Sr and 60Co include the effect of shaking time, pH, concentration, and saturation capacity. The experimental data revealed that the sorption process was carried out after equilibrium time (180 min). The saturation capacity for 85Sr and 60Co is measured to be 58.1 and 52.2 mg g-1, respectively. The sorption behavior of studied radionuclides is dependent on pH values. Sorption kinetic better fit with the pseudo-second-order model. Furthermore, the sorption isotherm is better represented by the model proposed by Langmuir. The results of the desorption investigations indicated that the most effective eluents for achieving full recovery of investigated radionuclides were identified. Finally, the recycling results demonstrate the suitability of SnMo for affected sorbing of 85Sr and 60Co from aqueous solutions. All the obtained data clarify that the SnMo sorbent is an effective means of removing 85Sr and 60Co from liquid waste.

Covalently surface-grafting α‑zirconium phosphate nanoplatelets enables collagen fiber matrix with ultraviolet barrier, antibacterial, and flame-retardant properties

Manipulating the dispersibility and reactivity of two-dimensional nanomaterials in collagen fibers (CFs) matrix has aroused attention in the fabrication of multifunctional collagen-based nanocomposites. Here, α‑zirconium phosphate nanoplatelets (ZrP NPs) were surface-functionalized with gallic acid (GA) to afford ZrP-GA NPs for engineering CFs matrix. The influence of ZrP-GA NPs on the ultraviolet barrier, antibacterial, and flame-retardant properties of resultant CFs matrix were investigated. Microstructural analysis revealed that ZrP-GA NPs were dispersed and bound within the collagen fibrils and onto the collagen strands in the CFs matrix. The resultant CFs matrix also maintained typical D-periodic structures of collagen fibrils and native branching and interwoven structures of CFs networks with increased porosity and enhanced ultraviolet barrier properties. Inhibition zone testing presented excellent antibacterial activities of the CFs matrix owing to surface grafting of antibacterial GA. Thanks to enhanced dispersion and binding of ZrP NPs with the CFs matrix by surface-functionalization with GA, the resultant CFs matrix reduced the peak heat release rate and the total heat release by 42.9 % and 39.0 %, respectively, highlighting improved flame-retardant properties. We envision that two-dimensional nanomaterials possess great potential in developing reasonable collagen-based nanocomposites towards the manufacture of emergent multifunctional collagen fibers-based wearable electronics.

The effects of nano-silver loaded zirconium phosphate on antibacterial properties, mechanical properties and biosafety of room temperature curing PMMA materials

Polymethyl methacrylate (PMMA) frequently features in dental restorative materials due to its favorable properties. However, its surface exhibits a propensity for bacterial colonization, and the material can fracture under masticatory pressure. This study incorporated commercially available RHA-1F-II nano-silver loaded zirconium phosphate (Ag-ZrP) into room-temperature cured PMMA at varying mass fractions. Various methods were employed to characterize Ag-ZrP. Subsequently, an examination of the effects of Ag-ZrP on the antimicrobial properties, biosafety, and mechanical properties of PMMA materials was conducted. The results indicated that the antibacterial rate against Streptococcus mutans was enhanced at Ag-ZrP additions of 0%wt, 0.5%wt, 1.0%wt, 1.5%wt, 2.0%wt, 2.5%wt, and 3.0%wt, achieving respective rates of 53.53%, 67.08%, 83.23%, 93.38%, 95.85%, and 98.00%. Similarly, the antibacterial rate against Escherichia coli registered at 31.62%, 50.14%, 64.00%, 75.09%, 86.30%, 92.98%. When Ag-ZrP was introduced at amounts ranging from 1.0% to 1.5%, PMMA materials exhibited peak mechanical properties. However, mechanical strength diminished beyond additions of 2.5%wt to 3.0%wt, relative to the 0%wt group, while PMMA demonstrated no notable cytotoxicity below a 3.0%wt dosage. Thus, it is inferred that optimal antimicrobial and mechanical properties of PMMA materials are achieved with nano-Ag-ZrP (RHA-1F-II) additions of 1.5%wt to 2.0%wt, without eliciting cytotoxicity.

Synthesis and Catalytic Activity for 2, 3, and 4-Nitrophenol Reduction of Green Catalysts Based on Cu, Ag and Au Nanoparticles Deposited on Polydopamine-Magnetite Porous Supports

This work reports on the synthesis of nine materials containing Cu, Ag, Au, and Ag/Cu nanoparticles (NPs) deposited on magnetite particles coated with polydopamine (PDA). Ag NPs were deposited on two PDA@Fe3O4 supports differing in the thickness of the PDA film. The film thickness was adjusted to impart a textural porosity to the material. During synthesis, Ag(I) was reduced with ascorbic acid (HA), photochemically, or with NaBH4, whereas Au(III), with HA, with the PDA cathecol groups, or NaBH4. For the material characterization, TGA, XRD, SEM, EDX, TEM, STEM-HAADF, and DLS were used. The catalytic activity towards reduction of 4-, 3- and 2-nitrophenol was tested and correlated with the synthesis method, film thickness, metal particle size and NO2 group position. An evaluation of the recyclability of the materials was carried out. In general, the catalysts prepared by using soft reducing agents and/or thin PDA films were the most active, while the materials reduced with NaBH4 remained unchanged longer in the reactor. The activity varied in the direction Au > Ag > Cu. However, the Ag-based materials showed a higher recyclability than those based on gold. It is worth noting that the Cu-containing catalyst, the most environmentally friendly, was as active as the best Ag-based catalyst.

Performance of molybdenum vanadate loaded on bentonite for retention of cesium-134 from aqueous solutions

This article studied the sorption behavior of Cs(I) ions from aqueous solutions onto molybdenum vanadate@bentonite (MoV@bentonite) composite. MoV@bentonite has been fabricated using the precipitation method and was characterized by different analytical tools including, FT-IR, XRD, and SEM attached with an EDX unit. The sorption studies applied on Cs(I) ions include the effect of contact time, pH, initial metal concentrations, ionic strength, desorption, and recycling. The experimental results revealed that in the adsorption process carried out after equilibrium time (300 min), saturation capacity has a value of 26.72 mg·g^-1 and the sorption of Cs(I) ions is dependent on pH values and ionic strength. Sorption kinetic better fit with the pseudo-second-order model; sorption isotherms apply to Langmuir, Freundlich, and Dubinin-Radushkevich (D-R) isotherm models. Data of thermodynamic parameters indicate that sorption is spontaneous and endothermic. Recycling experiments show that MoV@bentonite could be used for 7 cycles and the best eluant for the recovery of Cs(I) ions is 0.1 M HCl (76.9%). All the obtained data clarify that MoV@bentonite is considered a promising sorbent for the sorption of Cs(I) ions from aqueous solutions.

Mussel-Inspired Surface Modification of α-Zirconium Phosphate Nanosheets for Anchoring Efficient and Reusable Ultrasmall Au Nanocatalysts

The shortage of powerful functionalities on scalable α-zirconium phosphate (ZrP) materials blocks the facile preparation of highly dispersed and immobilized metal nanocatalysts. We herein present a mild and facile mussel-inspired strategy based on polydopamine (PDA) for the surface modification of ZrP, and hence, the generation of powerful functionalities at a high density for the straightforward reduction of chloroauric acid to Au nanoparticles (AuNPs) and the immobilization of AuNPs. The resulting ternary ZrP@PDA/Au exhibited ultra-small AuNPs with a particle size of around 6.5 nm, as estimated based on TEM images. Consequently, the ZrP@PDA/Au catalyst showed significant activity in the catalytic conversion of 4-nitrophenol (4NP) to 4-aminophenol (4AP), a critical transformation reaction in turning the hazard into valuable intermediates for drug synthesis. The PDA was demonstrated to play a critical role in the fabrication of the highly efficient ZrP@PDA/Au catalyst, far outperforming the ZrP/Au counterpart. The turnover frequency (TOF) achieved by the ZrP@PDA/Au reached as high as 38.10 min^-1, much higher than some reported noble metal-based catalysts. In addition, the ZrP@PDA/Au showed high stability and reusability, of which the catalytic efficiency was not significantly degraded after prolonged storage in solution.

Adsorption of Ag (I) Ions at the Zirconium Phosphate/KNO3 Aqueous Solution Interface

The paper presented the mechanical (MChT), microwave (MWT), and hydrothermal (HTT) methods of zirconium phosphate samples modification in order to improve its adsorption affinity for the Ag (I) ions. The FTIR studies proved that the modification of both gel and xerogel samples with the ultrasonic microwaves causes an increase in the concentration of phosphate groups on the surface of MWT-modified zirconium phosphate: the isoelectric point pHiep = 2.2–2.9 for these samples against 3.9 for the initial sample and pKa2 values were 4.7–5.6 and 6.3, respectively. As resulting from the Ag⁺ ion adsorption studies, the MWT treatment of zirconium phosphate samples caused the greatest affinity of Ag⁺ ions for the surface of MWT zirconium phosphate. Compared with the initial ZrP sample, the shift of the Ag (I) ion adsorption edge towards lower pH values was observed, e.g., with adsorption of Ag (I) ions from the solution with the initial concentration of 1 µmol/dm³ for the initial ZrP sample pH50% = 3.2, while for the sample MWT ZrPxero pH50% = 2.6.

Silver nanomaterials: synthesis and (electro/photo) catalytic applications

In view of their unique characteristics and properties, silver nanomaterials (Ag NMs) have been used not only in the field of nanomedicine but also for diverse advanced catalytic technologies. In this comprehensive review, light is shed on general synthetic approaches encompassing chemical reduction, sonochemical, microwave, and thermal treatment among the preparative methods for the syntheses of Ag-based NMs and their catalytic applications. Additionally, some of the latest innovative approaches such as continuous flow integrated with MW and other benign approaches have been emphasized that ultimately pave the way for sustainability. Moreover, the potential applications of emerging Ag NMs, including sub nanomaterials and single atoms, in the field of liquid-phase catalysis, photocatalysis, and electrocatalysis as well as a positive role of Ag NMs in catalytic reactions are meticulously summarized. The scientific interest in the synthesis and applications of Ag NMs lies in the integrated benefits of their catalytic activity, selectivity, stability, and recovery. Therefore, the rise and journey of Ag NM-based catalysts will inspire a new generation of chemists to tailor and design robust catalysts that can effectively tackle major environmental challenges and help to replace noble metals in advanced catalytic applications. This overview concludes by providing future perspectives on the research into Ag NMs in the arena of electrocatalysis and photocatalysis.

Computational Appraisal of Silver Nanocluster Evolution on Epitaxial Graphene: Implications for CO Sensing

Early stages of silver nucleation on a two-dimensional (2D) substrate, here, monolayer epitaxial graphene (MEG) on SiC, play a critical role in the formation of application-specific Ag nanostructures. Therefore, it is of both fundamental and practical importance to investigate the growth steps when Ag adatoms start to form a new phase. In this work, we exploit density functional theory to study the kinetics of early-stage nuclei Ag n (n = 1-9) assembly of Ag nanoparticles on MEG. We find that the Ag1 monomer tends to occupy hollow site positions of MEG and interacts with the surface mainly through weak dispersion forces. The pseudoepitaxial growth regime is revealed to dominate the formation of the planar silver clusters. The adsorption and nucleation energies of Ag n clusters exhibit evident odd-even oscillations with cluster size, pointing out the preferable adsorption and nucleation of odd-numbered clusters on MEG. The character of the interaction between a chemisorbed Ag3 cluster and MEG makes it possible to consider this trimer as the most stable nucleus for the subsequent growth of Ag nanoparticles. We reveal the general correlation between Ag/MEG interaction and Ag-Ag interaction: with increasing cluster size, the interaction between Ag adatoms increases, while the Ag/MEG interaction decreases. The general trend is also supported by the results of charge population analysis, according to which the average charge per Ag adatom in a Ag n cluster demonstrates a drastic decrement with cluster size increase. 2D-3D structural transition in Ag n clusters was investigated. We anticipate that the present investigation is beneficial by providing a better understanding of the early-stage nucleation of Ag nanoparticles on MEG at the atomic scale. Specific interaction between odd-numbered Ag clusters preadsorbed onto the MEG surface and carbon monoxide (CO) as well as clusters' stability at 300 K is discussed in terms of sensing applications.

Application of electroactive Au/aniline tetramer-graphene oxide composites as a highly efficient reusable catalyst

This study proposes a cost-effective, energy-saving, and green process that uses π-π interactions to modify graphene oxide (GO), and the conjugate structure of aniline tetramer (AT) to enhance the dispersion of GO. Au/aniline tetramer-graphene oxide (Au/ATGO) composites were synthesized and applied as a catalyst in this study. The adsorption of AT on GO, via π-π interaction, formed ATGO composites. Subsequently, the amine group on ATGO was stably anchored on Au nanoparticles (Au NPs) to form Au/ATGO composites. The Au/ATGO composites were characterized and the electroactive properties determined by Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, transmission electron microscopy, and cyclic voltammetry. The Au/ATGO composites showed excellent performance and stability as catalysts when applied for the reduction of nitrophenol to aminophenol within 225 s and the rate constant was 0.02 s-1. The activation energy for the reduction of 4-NP and 2-NP was 48.10 and 68.71 kJ mol-1, respectively. Following a recycling test repeated 20 times, the Au/ATGO composites maintained a conversion rate higher than 94%.

Transparency Change Mechanochromism Based on a Robust PDMS-Hydrogel Bilayer Structure

Hydrogels and polydimethylsiloxane (PDMS) are complementary to each other, since the hydrophobic PDMS provides a more stable and rigid substrate, while the water-rich hydrogel possesses remarkable hydrophilicity, biocompatibility, and similarity to biological tissues. Herein a transparent and stretchable covalently bonded PDMS-hydrogel bilayer (PHB) structure is prepared via in situ free radical copolymerization of acrylamide and allylamine-exfoliated-ZrP (AA-e-ZrP) on a functionalized PDMS surface. The AA-e-ZrP serves as cross-linking nano-patches in the polymer gel network. The covalently bonded structure is constructed through the addition reaction of vinyl groups of PDMS surface and monomers, obtaining a strong interfacial adhesion between the PDMS and the hydrogel. A mechanical-responsive wrinkle surface, which exhibs transparency change mechanochromism, is created via introducing a cross-linked polyvinyl alcohol film atop the PHB structure. A finite element model is implemented to simulate the wrinkle formation process. The implication of the present finding for the interfacial design of the PHB and PDMS-hydrogel-PVA trilayer (PHPT) structures is discussed.

Role of dissolved oxygen in nitroarene reduction by a heterogeneous silver textile catalyst in water

The effects of dissolved oxygen concentration on the rate constant of the 4-nitrophenol reduction reaction with a silver-coated textile as a ‘dip-catalyst’ were studied.