Low-cost zeolite-based sorbents prepared from industrial perlite by-product material for Zn2+ and Ni2+ removal from aqueous solutions: synthesis, properties and sorption efficiency.

The conversion of waste/by-product materials into efficient sorbents is at the forefront of innovative remediation techniques. In the present study, the relationships among the synthesis conditions, physicochemical properties of synthesized sorbents and Zn2+ and Ni2+ removal efficiencies were studied in detail. Zeolite X, zeolite P, phillipsite, analcime, sodalite and cancrinite were synthesized from industrial perlite by-product material. The zeolite content in the synthesized sorbents and zeolite framework topology (dimensions, numbers and spatial configuration of channels) were the key factors affecting the removal of Zn2+ and Ni2+ from aqueous solutions. Zeolite X-based sorbent exhibited the best sorption performance mainly due to the large zeolite channel dimensions, low Si/Al ratio, high cation exchange capacity and high specific surface area. Nevertheless, the efficiency and stability of this sorbent need to be tested under field conditions prior to its application for remediation technologies.

Modified Polymer Surfaces: Thin Films of Silicate Composites via Polycaprolactone Melt Fusion.

Polymer/layered silicate composites have gained huge attention in terms of research and industrial applications. Traditional nanocomposites contain particles regularly dispersed in a polymer matrix. In this work, a strategy for the formation of a composite thin film on the surface of a polycaprolactone (PCL) matrix was developed. In addition to the polymer, the composite layer was composed of the particles of saponite (Sap) modified with alkylammonium cations and functionalized with methylene blue. The connection between the phases of modified Sap and polymer was achieved by fusing the chains of molten polymer into the Sap film. The thickness of the film of several µm was confirmed using electron microscopy and X-ray tomography. Surfaces of precursors and composite materials were analyzed in terms of structure, composition, and surface properties. The penetration of polymer chains into the silicate, thus joining the phases, was confirmed by chemometric analysis of spectral data and changes in some properties upon PCL melting. Ultimately, this study was devoted to the spectral properties and photoactivity of methylene blue present in the ternary composite films. The results provide directions for future research aimed at the development of composite materials with photosensitizing, photodisinfection, and antimicrobial surfaces.

Effect of Corrosive Media on the Chemical and Mechanical Resistance of IPS e.max® CAD Based Li2Si2O5 Glass-Ceramics.

The influence of 4% acetic acid (pH~2.4) and an alkaline solution of NaOH (pH~10) on the corrosion resistance and micromechanical properties of disilicate crystals containing glass-ceramics (LS2-GC's) is studied. Partially crystallized lithium metasilicate crystal containing glass-ceramics (LS-GC's) are annealed to fully LS2-GC's using a one stage and a two-stage heating to induce nucleation. Materials with various chemical and wear resistance are prepared. The content of the crystalline phase in the material annealed in the two-stage process A is 60.0% and increases to 72.2% for the material heated in the one-stage process B. The main elements leached in the acidic medium are lithium and phosphorus, while lithium, silicon, and phosphorus leached into the alkaline environment. Material B exhibits better chemical resistance to the corrosive influence of 4% acetic acid under quasi-dynamic conditions. In the alkaline corrosion medium, silicon is leached from material A faster compared to the material B. After prolonged exposure to acidic or basic environments, both materials show evidence of surface structural changes. A decrease of the sliding wear resistance is observed after corrosion in the acidic environment under dynamic conditions. In both materials, the wear rate increases after corrosion.

Surface Characterization and Anti-Biofilm Effectiveness of Hybrid Films of Polyurethane Functionalized with Saponite and Phloxine B.

The main objective of this work was to synthesize composites of polyurethane (PU) with organoclays (OC) exhibiting antimicrobial properties. Layered silicate (saponite) was modified with octadecyltrimethylammonium cations (ODTMA) and functionalized with phloxine B (PhB) and used as a filler in the composites. A unique property of composite materials is the increased concentration of modifier particles on the surface of the composite membranes. Materials of different compositions were tested and investigated using physico-chemical methods, such as infrared spectroscopy, X-ray diffraction, contact angle measurements, absorption, and fluorescence spectroscopy in the visible region. The composition of an optimal material was as follows: nODTMA/mSap = 0.8 mmol g-1 and nPhB/mSap = 0.1 mmol g-1. Only about 1.5% of present PhB was released in a cultivation medium for bacteria within 24 h, which proved good stability of the composite. Anti-biofilm properties of the composite membranes were proven in experiments with resistant Staphylococcus aureus. The composites without PhB reduced the biofilm growth 100-fold compared to the control sample (non-modified PU). The composite containing PhB in combination with the photodynamic inactivation (PDI) reduced cell growth by about 10,000-fold, thus proving the significant photosensitizing effect of the membranes. Cell damage was confirmed by scanning electron microscopy. A new method of the synthesis of composite materials presented in this work opens up new possibilities for targeted modification of polymers by focusing on their surfaces. Such composite materials retain the properties of the unmodified polymer inside the matrix and only the surface of the material is changed. Although these unique materials presented in this work are based on PU, the method of surface modification can also be applied to other polymers. Such modified polymers could be useful for various applications in which special surface properties are required, for example, for materials used in medical practice.

Optical Characterization of Few-Layer PtSe2 Nanosheet Films.

Thin films of transition-metal dichalcogenides are potential materials for optoelectronic applications. However, the application of these materials in practice requires knowledge of their fundamental optical properties. Many existing methods determine optical constants using predefined models. Here, a different approach was used. We determine the sheet conductance and absorption coefficient of few-layer PtSe2 in the infrared and UV-vis ranges without recourse to any particular model for the optical constants. PtSe2 samples with a thickness of about 3-4 layers were prepared by selenization of 0.5 nm thick platinum films on sapphire substrates at different temperatures. Differential reflectance was extracted from transmittance and reflectance measurements from the front and back of the sample. The film thickness, limited to a few atomic layers, allowed a thin-film approximation to calculate the optical conductance and absorption coefficient. The former has a very different energy dependence in the infrared, near-infrared, and visible ranges. The absorption coefficient exhibits a strong power-law dependence on energy with an exponent larger than three in the mid-infrared and near-infrared regions. We have not observed any evidence for a band gap in PtSe2 thin layers down to an energy of 0.4 eV from our optical measurements.

Determination of water content in raw perlites: Combination of NIR spectroscopy and thermoanalytical methods.

A new approach to determination of water content in raw perlites, an industrially important material, and obsidian was proposed, utilizing diffuse reflectance spectroscopy in the near-IR region. The phase composition of the perlite of the perlite samples was over 94% rhyolitic volcanic glass, with only small admixture of other components. The observed volatile species contents detected from both thermogravimetric analysis (TG) and the loss of ignition method (LOI) varied from 3 to 7%. The samples with the highest content of volatiles released over the temperature interval 30-250 °C (based on thermogravimetric analysis) displayed sharp signals in the 1H MAS NMR spectra, with chemical shifts of 4.6-4.7 ppm attributed to water molecules of high mobility. Using IR spectra taken in the near-infrared region, the water content of perlites was evaluated using the combination mode (ν + δ)H2O near 5240 cm-1. The band area depended on the H2O content, with the highest value found for the sample which displayed the highest mass loss in the thermoanalytical experiments. The samples showed variations in properties depending on the location in the deposit they were taken from. The relationship between water content determined gravimetrically and calculated band areas showed a correlation coefficient of 0.78 and 0.74 for TG and LOI respectively. The correlation was significantly improved by adding internal standards, hexadecyltrimethylammonium bromide salt (HDTMA) or layered hydrosilicate talc, to the perlite samples, and then normalizing the spectra of the mixtures to selected bands of those standards (R2 = 0.89 and 0.88 respectively for TG methods). A better correlation between infrared and TG/LOI results was obtained for HDTMA-Br than for talc. The proposed method using standards could be a reliable way of estimating water content in raw perlites in processing plants.

PDDA-Montmorillonite Composites Loaded with Ru Nanoparticles: Synthesis, Characterization, and Catalytic Properties in Hydrogenation of 2-Butanone.

The effect of synthesis parameters on the physicochemical properties of clay/ polydiallyldimethylammonium (PDDA)/Ru composites and their applicability in hydrogenation of 2-butanone under very mild conditions (room temperature, atmospheric pressure, and aqueous solution) was studied. Three synthetic procedures were employed, differing in the order of addition of components and the stage at which metallic Ru species were generated. The materials were characterized with XRD (X-ray diffraction), XRF (X-ray fluorescence), EDS (energy-dispersive spectroscopy), AFM (atomic force microscopy), TEM/HRTEM (transmission electron microscopy/high resolution transmission electron microscopy), and TG/DSC (thermal gravimetry/differential scanning microscopy techniques. The study revealed that the method of composite preparation affects its structural and thermal properties, and controls the distribution and size of Ru particles. All catalysts are active in hydrogenation of 2-butanone. For best catalytic performance (100% conversion within 30 min) both the size of Ru particles and the load of polymer had to be optimized. Superior catalytic properties were obtained over the composite with intermediate crystal size and intermediate PDDA load, prepared by generation of metallic Ru species in the polymer solution prior to intercalation. This method offers an easy way of controlling the crystal size by modification of Ru/PDDA ratio.

Spectroscopic study of water adsorption on Li(+), TMA(+) and HDTMA(+) exchanged montmorillonite.

The potential of IR and NMR spectroscopy in characterization the interaction of water with natural and organically modified montmorillonites was introduced. Organoclays were prepared from Li-saturated montmorillonite (Li-S) and tetramethylammonium (TMA) or hexadecyltrimethylammonium (HDTMA) salts. The influence of organic cation size on the water vapour uptake was examined and a comparative study with natural clay mineral was provided. The near-IR spectra confirmed the reduced water content in TMA-S and HDTMA-S. After exposure of the samples to water vapour under various relative humidities (RH) the H2O content was determined. According to the adsorption isotherms the amount of water decreased in order Li-S>TMA-S>HDTMA-S. The intensities of the 2νOH and [Formula: see text] bands, corresponding to the vibrations of H2O, gradually increased in hydrated samples. The (13)C MAS NMR and near-IR of hydrated organoclays confirmed the presence of H2O close to the cation's headgroup. NMR signals of inner -CH2- groups in HDTMA-S were also affected by hydration: the intensity of disordered gauche conformers (31.1 ppm) overtook the intensity of ordered all-trans conformers (33.0 ppm).

The effect of acid treatment on the structure and surface acidity of tetraalkylammonium-montmorillonites.

The effect of tetrabutylammonium (Bu4N+) and tetrapentylammonium (Pe4N+) cations on the modification of the organo-montmorillonite structure upon acid-treatment was investigated. Samples were treated with HCl for various times (2-12 h). Structural changes were followed by MAS NMR spectroscopy. The 29Si MAS NMR spectra of initial Na-saturated form (Na-SAz) showed gradual decrease of the intensity of the resonance assigned to SiO4 cross-linked in the tetrahedral sheets Q3(0Al) while signals arising from the reaction product Q31OH and Q4(0Al) became more pronounced upon acid treatment. The Q3(0Al) signal almost completely disappeared for Na-SAz treated for 8 h on contrary to Bu4N-SAz and Pe4N-SAz showing signal of relatively high intensity even after 12 h. The 27Al MAS NMR measurement proved that more than one half of Al remained in the reaction product of Bu4N-SAz and Pe4N-SAz after 8 h treatment, while Al content dropped below 5% for Na-SAz. Formation of acid sites was investigated via pyridine adsorption. Only physically adsorbed and H-bonded pyridine was detected for acid-untreated samples. In contrast, the IR spectra of the samples partially decomposed in HCl revealed bands of pyridine adsorbed on Brønsted acid sites. Strongly bonded pyridine was able to bear up heating even at 230°C.

Alterations of the surface and morphology of tetraalkyl-ammonium modified montmorillonites upon acid treatment.

The effect of short alkyl chain cations on the modification of the structure, surface and textural properties of organo-montmorillonites upon their acid treatment was investigated. Samples prepared from Ca-SAz montmorillonite and tetramethylammonium (Me(4)N(+)-), tetraethylammonium (Et(4)N(+)-), tetrapropylammonium (Pr(4)N(+)-) and tetrabutylammonium (Bu(4)N(+)-) salts were treated in 6 M HCl at 80 °C for 2-8 h and analyzed by different methods. Acid treatment of organo-montmorillonites caused gradual release of Al and Mg from the octahedral sheets and destruction of their layered structure. The extent of the changes depended significantly on the size of organo-cation. While large plate-like particles of Ca-SAz and Me(4)N-SAz were disintegrated during acid treatment and smaller fine grains were created, the morphology of Bu(4)N-SAz was modified only slightly. Pore size analysis showed generation of pore network upon organo-montmorillonites dissolution. After longer acid attack, pore volume increased and pore size distribution curves were shifted to pores with diameter above 25 Å. The surface area of acid-treated samples increased due to destruction of the montmorillonite layers and formation of the SiO(2)-rich reaction product. The highest value 475 m(2)/g was observed for Me(4)N-SAz treated 4 h. Surface area of Et(4)N-SAz, Pr(4)-SAz and Bu(4)N-SAz was 441, 419 and 293 m(2)/g, respectively, after 8 h treatment. Similar decomposition level was observed for Ca-SAz and Me(4)N-SAz, and less destruction was found for Et(4)N-SAz, Pr(4)-SAz and very low for Bu(4)N-SAz. Though Bu(4)N(+) is short alkyl chain cation, its size is large enough to cover the inner and outer surfaces of montmorillonite and thus to protect the clay layers from acid attack.