Highly Electroconductive Metal-Polymer Hybrid Foams Based on Silver Nanowires: Manufacturing and Characterization.

Due to their electroconductive properties, flexible open-cell polyurethane foam/silver nanowire (PUF/AgNW) structures can provide an alternative for the construction of cheap pressure transducers with limited lifetimes or used as filter media for air conditioning units, presenting bactericidal and antifungal properties. In this paper, highly electroconductive metal-polymer hybrid foams (MPHFs) based on AgNWs were manufactured and characterized. The electrical resistance of MPHFs with various degrees of AgNW coating was measured during repeated compression. For low degrees of AgNW coating, the decrease in electrical resistance during compression occurs in steps and is not reproducible with repeated compression cycles due to the reduced number of electroconductive zones involved in obtaining electrical conductivity. For high AgNW coating degrees, the decrease in resistance is quasi-linear and reproducible after the first compression cycle. However, after compression, cracks appear in the foam cell structure, which increases the electrical resistance and decreases the mechanical strength. It can be considered that PUFs coated with AgNWs have a compression memory effect and can be used as cheap solutions in industrial processes in which high precision is not required, such as exceeding a maximum admissible load or as ohmic seals for product security.

Highly Efficient Recovery of Ruthenium from Aqueous Solutions by Adsorption Using Dibenzo-30-Crown-10 Doped Chitosan.

Ruthenium, as an industrial by-product or from natural sources, represents an important economical resource due to its specific applications. A complex problem is represented by ruthenium separation during reprocessing operations, therefore, different materials and methods have been proposed. The present study aims to develop a new material with good adsorbent properties able to be used for ruthenium recovery by adsorption from aqueous solutions. Absorbent material was obtained using chitosan (Ch) surface modification with dibenzo-30-crown-10 ether (DB30C10). Chitosan represents a well-known biopolymer with applicability in different adsorptive processes due to the presence of hydroxyl-, carboxyl-, and nitrogen-containing groups in the structure. Additionally, crown ethers are macromolecules with a good complexation capacity for metallic ions. It is expected that the adsorptive efficiency of newly prepared material will be superior to that of the individual components. New synthesized material was characterized using scanning electron microscopy coupled with energy dispersive X-ray (SEM-EDX), Fourier transform infrared spectroscopy (FT-IR), Brunauer-Emmett-Teller surface area analysis (BET), and determination of point of zero charge (pZc). Results obtained from the performed kinetic, thermodynamic, and equilibrium studies confirmed the good adsorptive capacity of the prepared material, Ch-DB30C10, obtaining a maximum adsorption capacity of 52 mg Ru(III) per gram. This adsorption capacity was obtained using a solution with an initial concentration of 275 mg L-1, at pH 2, and 298 K. Ru(III) adsorption kinetics were studied by modeling the obtained experimental data with pseudo-first order and pseudo-second order models. Desorption studies established that the optimum eluent was represented by the 5M HNO3 solution. Based on the performed studies, a mechanism for recovery of ruthenium by adsorption was proposed.

A New Perspective on Adsorbent Materials Based Impregnated MgSiO3 with Crown Ethers for Palladium Recovery.

The study of new useful, efficient and selective structures for the palladium ions' recovery has led to the development of a new series of macromolecules. Thus, this study presents a comparative behavior of two crown benzene ethers that modify the magnesium silicate surface used as adsorbent for palladium. These crown ethers are dibenzo18-crown-6 (DB18C6) and dibenzo 30-crown-10 (DB30C10). The obtained materials were characterized by scanning electron microscope (SEM), energy-dispersive X-ray spectroscopy (EDX) and Fourier-transform infrared spectroscopy (FT-IR). The specific surface area (BET) and point of zero charge (PZC) of the two materials were determined. The palladium ions' recovery from synthetic aqueous solutions studies aimed to establish the adsorption mechanism. For this desideratum, the kinetic, equilibrium and thermodynamic studies show that MgSiO3-DB30C10 have a higher adsorption capacity (35.68 mg g-1) compared to MgSiO3-DB18C6 (21.65 mg g-1). Thermodynamic studies highlight that the adsorption of Pd(II) on the two studied materials are spontaneous and endothermic processes. The positive values of the entropy (ΔS0) suggest that the studied adsorption processes show a higher disorder at the liquid/solid interface. Desorption studies were also performed, and it was found that the degree of desorption was 98.3%.

Assessment of the Different Type of Materials Used for Removing Phosphorus from Wastewater.

Reducing the costs associated with water management, improving water quality and the environment are fundamental requirements of sustainable development. Maintaining the optimal level of phosphorus has a direct impact on water quality and the biological system. Current methods used in tertiary wastewater treatment for phosphorus removal present several disadvantages that influence the final water processing cost. Therefore, it is essential for water quality and food safety to develop ecological, cheap and highly efficient materials. This study reported the first comparative assessment of three different types of materials (magnetic, semiconductors and composite) as environmentally friendly, cheap adsorbents for phosphorus removal from wastewater. Several experiments were done to investigate the influence of adsorbent type, dosage and contact time on the efficiency of the processes. The adsorption process was fast and equilibrium was reached within 150 min. We found that the phosphorus adsorption efficiency on of these materials was higher than the chemical method. The obtained results indicated that specific surface area directly influences the performance of the adsorption process. EDS analysis was used to analyze adsorbents composition and analyze the type and content of elements in the substrate before and after reaction with wastewater.

Evaluation of Performance of Functionalized Amberlite XAD7 with Dibenzo-18-Crown Ether-6 for Palladium Recovery.

Due to the increased demand for palladium, as well due to its reduced availability in nature, its recovery from diluted waste solutions becomes a necessity, and perhaps an emergency. As a result of economic and technological development, new materials with improved adsorbent properties that are more efficient for metallic ions' recovery were synthesized and introduced to market. The goal of this study was to obtain a new adsorbent material by functionalizing through impregnation a commercial polymeric support that was both inexpensive and environmentally friendly (Amberlite XAD7) with crown ether (di-benzo-18-crown-6-DB18C6). Crown ethers are known for their ability to form complexes within metallic ions, by including them inside of the ring, regardless of its atomic size. Adsorbent material was prepared by impregnation using the solvent-impregnated resin method (SIR). To highlight the presence of crown ether on the resin surface, a new synthesized material was characterized by scanning electron microscopy (SEM), elemental analysis X-ray energy dispersive spectroscopy (EDX) and Fourier transform infrared spectroscopy (FT-IR). The specific surface of the adsorbent material was also determined by the Brunauer-Emmett-Teller (BET) method. Adsorbent performances of the prepared material were highlighted by kinetic, thermodynamic and equilibrium studies and a possible mechanism was also proposed. The influence of specific parameters for the adsorption process (contact time, temperature, Pd(II) initial concentration) on the maximum adsorption capacity was pursued.

Comparison of Structure and Adsorption Properties of Mesoporous Silica Functionalized with Aminopropyl Groups by the Co-Condensation and the Post Grafting Methods.

The adsorptive potential has been evaluated for the aminopropyl functionalized mesoporous silica materials obtained by co-condensation and post grafting methods. Nitrogen sorption, small angle neutron and X-ray scattering (SANS and SAXS) demonstrated high surface area and well-ordered hexagonal pore structure suitable for applications as adsorbents of metals from waste waters. A comparison of Cr(VI) adsorption properties of the materials prepared by different functionalization methods has been performed. The obtained results demonstrated the adsorption capacity due to the affinity of the chromium ions to the amino groups, and showed that co-condensation of tetraethoxysilane (TEOS) and 3-aminopropyl triethoxysilane (APTES) resulted in higher metal sorption capacity of the materials compared to post-synthesis grafting of aminopropyl groups onto the mesoporous silica particles.

Precious metals recovery from aqueous solutions using a new adsorbent material.

Platinum group metals (PGMs) palladium, platinum, and ruthenium represent the key materials for automotive exhaust gas treatment. Since there are no adequate alternatives, the importance of these metals for the automotive industry is steadily rising. The high value of PGMs in spent catalysts justifies their recycling. Therefore, it is really important to recovery platinum group metals from aqueous solutions. Of the many PGMs recovery procedures, adsorption is a process with a good efficiency, but an important role is played by the adsorbent material used into the process. In order to improve the adsorption properties of materials were developed new methods for chemical modification of the solid supports, through functionalization with different extractants. In present paper a new adsorbent material (Chitosan-DB18C6) was used for PGMs recovery. The new adsorbent material was produced by impregnating Chitosan with dibenzo-18-crown-6-ether using Solvent Impregnated Resin (SIR) method. The crown ethers were chosen as extractant due to their known ability to bind metallic ions, whether they are symmetrically or unsymmetrically substituted. In order to determine the PGMs recovery efficiency for new prepared adsorbent material the equilibrium and kinetic studies were performed. Also, to study the PGMs adsorption mechanism the experimental data were modelled using pseudo-first-order and pseudo-second order kinetic models. Experimental data were fitted with three equilibrium isotherm models: Langmuir, Freundlich and Sips. The results proved that new adsorbent material (Chitosan-DB18C6) is an efficient adsorbent for PGMs recovery from aqueous solutions.

Formulation and Characterization of Alginate-Based Membranes for the Potential Transdermal Delivery of Methotrexate.

The aim of this study is to obtain and characterize of alginate-based membranes, as well as to choose the most suitable membrane type for the transdermal release of methotrexate. The paper presents the synthesis of four types of membranes based on alginate to which are added other copolymers (Carbopol, Tween, and Polyvinylpyrrolidone) as well as other components with different roles. Membranes and binary mixtures made between the components used in membrane synthesis and methotrexate are analyzed by thermogravimetric techniques, FTIR and UV spectroscopic techniques as well as SEM. The analyses aim to establish the type of membrane most indicated in the use of the controlled release of methotrexate, namely those membranes in which there are no interactions that could inactivate the active substance. Following these studies, it was concluded that membranes obtained from alginate/alginate and Tw can be used for methotrexate release. The membrane obtained from alginate and carbopol was excluded from the beginning because it is not homogeneous. Regarding the AGP-MTX membrane, it presents interactions with the active substance, carboxylate group interactions argued by TGA and FTIR studies, and interactions that occur in aqueous medium.

Mesoporous Metal-Organic Framework MIL-101 at High Pressure.

The chromium terephthalate MIL-101 is a mesoporous metal-organic framework (MOF) with unprecedented adsorption capacities due to the presence of giant pores. The application of an external pressure can effectively modify the open structure of MOFs and its interaction with guest molecules. In this work, we study MIL-101 under pressure by synchrotron X-ray diffraction and infrared (IR) spectroscopy with several pressure transmitting media (PTM). Our experimental results clearly show that when a solid medium as NaCl is employed, an irreversible amorphization of the empty structure occurs at about 0.4 GPa. Using a fluid PTM, as Nujol or high-viscosity silicone oil, results in a slight lattice expansion and a strong modification of the peak frequency and shape of the MOF hydroxyl vibration below 0.1 GPa. Moreover, the framework stability is enhanced under pressure with the amorphization onset shifted to about 7 GPa. This coherent set of results points out the insertion of the fluid inside the MIL-101 pores. Above 7 GPa, concomitantly to the nucleation of the amorphous phase, we observe a peculiar medium-dependent lattice expansion. The behavior of the OH stretching vibrations under pressure is profoundly affected by the presence of the guest fluid, showing that OH bonds are sensitive vibrational probes of the host-guest interactions. The present study demonstrates that even a polydimethylsiloxane silicone oil, although highly viscous, can be effectively inserted into the MIL-101 pores at a pressure below 0.2 GPa. High pressure can thus promote the incorporation of large polymers in mesoporous MOFs.