Regeneration of natural zeolite polluted by lead and zinc in wastewater treatment systems

The aim of this work was to investigate the potential regeneration of natural zeolite which had been contaminated with lead and zinc contained in aqueous solutions, treated secondary effluent and primary treated wastewater. Several desorbing solutions were examined for the removal of Pb(II) and Zn(II) from zeolite and the highest desorption efficiency was obtained for 3M KCl and 1M KCl, respectively. The desorption process depended on the type and concentration of the desorbing solution, the metal being desorbed, the mineral selectivity towards the metal and the composition of the liquid medium where the adsorption process had taken place. Successive regeneration cycles resulted in the reduction of desorption efficiency by more than 50% after 9 and 4 cycles for lead and zinc, respectively. Kinetics examination showed that desorption was slower than adsorption, while metal ions which had been easily adsorbed were difficult to be desorbed. Adsorption was characterized by a three-stage diffusion process, while desorption followed a two-stage diffusion process.     

Microbial synthesis of semiconductor lead sulfide nanoparticles using immobilized Rhodobacter sphaeroides

A reliable and eco-friendly process for the synthesis of nanoparticles such as using biological systems has been developed. In this study, we synthesized PbS nanoparticles with the average particle size ca. 10.5 ± 0.15 nm using immobilized Rhodobacter sphaeroides. The PbS nanoparticles were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), energy dispersive analyses of X-rays (EDX) and Uv–vis optical absorption. Culture time, as an important physiological parameter for R. sphaeroides growth, could significantly control the size of the biosynthesized lead sulfide nanoparticles. Extracellular synthesis of nanoparticles by immobilized mass could be highly advantageous from the point of view of synthesis in large quantities and easy downstream processing.     

Optical properties of the gold nanorods tuned by lead sulfide

In this paper, the optical properties of gold nanorods (GNRs) tuned by lead sulfide (PbS) were studied. GNRs used in this work were synthesized by seed-mediated methods. Using electrostatic self-assembly methods, GNRs were modified by repetition of adsorbing oppositely charged polyelectrolyte. Then GNR-PbS nanostructure was fabricated by alternatively adsorbing Pb(2+) and S(2-) ions on the surface of polyelectrolyte-modified-GNRs. The formation of PbS nanocrystals on GNRs can effectively regulate their optical properties, including longitudinal surface plasmon resonance (LSPR) and fluorescence.     

A study on fabrication, morphological and optical properties of lead sulfide nanocrystals

To investigate the properties of lead sulfide (PbS) nanocrystals, we have prepared PbS nanocrystals on/in the porous alumina membrane with a pore diameter 20 nm. Utilizing the reaction of Pb wires and the hydrogen sulfide (H2S) gas, PbS nanocrystals produced and grew as the reaction time increased. The composition identification of the nanocrystals was performed by the XPS and EDS analyses. More structure characteristics of the PbS nanocrystals obtained from the TEM analysis. As indicated in the PL spectra, an orange-red emission band appeared and the emission intensities were obviously related to the defects in the nanocrytals. A significant quantum confinement effect made the energy gap of PbS nanocrystals produce a blue shift from 0.41 eV to 1.89 eV. Furthermore, the growth mechanism of the PbS nanocrystals was also discussed.     

Microstructure and properties of lead sulfide films deposited from solutions containing ammonium halides

Data are presented on the structure and photoelectric properties of lead sulfide films chemically deposited from aqueous solutions containing ammonium halides. The concentration of ammonium halides in the solution has a crucial effect on the microstructure and texture of the films. The photosensitivity and spectral response of the films are shown to correlate with their microstructure.     

Structure and optical properties of silica-supported Ag-Au nanoparticles

Bimetallic Ag-Au nanoparticles are synthesized by sequential deposition of Au and Ag on amorphous silica by Radio Frequency (RF)-sputtering under mild conditions. Specimens are thoroughly characterized by a multi-technique approach, aimed at investigating the system properties as a function of the Ag/Au content, as well as the evolution induced by ex-situ annealing under inert (N2) or reducing (4% H2/N2) atmospheres. The obtained results demonstrate the possibility to obtain Ag-Au alloyed nanoparticles with controllable size, shape, structure, and dispersion under mild conditions, so that the optical properties can be finely tuned as a function of the synthesis and thermal treatment conditions.     

Effect of zeolite nanoparticles on the optical properties of diacetone acrylamide-based photopolymer

The effect of zeolite nanoparticles with BEA type framework structure on the optical properties of a diacetone acrylamide (DA)-based holographic photopolymer has been investigated. Both types of zeolite nanocrystals, as synthesized (BEA) and silver containing (BEA-Ag), are used for doping the DA photopolymer. Doping of the DA photopolymer with BEA zeolites results in an 11% decrease of the average refractive index of the nanocomposite layer, while the inclusion of BEA-Ag nanoparticles decreases the average refractive index by 3% only. This observation is in good agreement with the fact that the contrast in refractive index between the host photopolymer and nanoparticles is expected to be much lower for the BEA nanoparticles containing Ag in their pores. Doping of the DA photopolymer with pure BEA zeolite nanoparticles results in a significant increase in refractive index modulation due to holographic recording, Δn, of up to 91% at a concentration of 2 wt.% compared to un-doped layers. For the BEA-Ag zeolites, a maximum increase in Δn of up to 17% at a concentration of 0.5 wt.% is observed. The increase in Δn is attributed to the difference in n between the host photopolymer and nanoparticles and the redistribution of the nanoparticles during holographic recording. It is demonstrated that the DA photopolymer is compatible as a host material for the porous BEA nanoparticles. This is due to the large size of the DA monomer molecules, which restricts monomer migration into the zeolite pores and thus the pores of the Ag-free BEA nanoparticles remain empty, making them suitable for application in holographic sensors.     

Optical and surface morphological properties of triethylamine passivated lead sulphide nanoparticles

The triethylamine capped lead sulphide (PbS) nanoparticles were successfully synthesized by simple wet chemical method. The synthesized product has been characterized by powder X-ray diffraction (XRD), UV–vis spectrophotometry, FTIR spectroscopy, atomic force microscopy (AFM), transmission electron microscopy (TEM) and photoluminescence studies. The size of the PbS nanoparticles was determined from AFM, TEM, XRD and from these studies it is found that the size of the particles of the order of 10–15 nm. Significant “blue shift” from bulk material was observed on the PbS nanoparticles using UV–vis and photoluminescence spectrum.     

Structure and properties of natural and artificial leathers

The Scanning Electron Microscope (SEM) has been used to determine the structure and to study the mechanical and chemical stability of natural and artificial leathers in wear and after testing in the laboratory. Artificial leathers, such as impermeable coated fabrics and poromerics which are permeable to water vapour, have been used more frequently in the last decade for clothing and footwear.The mechanical flex cracking of leather and poromerics is discussed and the SEM studies have enabled the type of failure of the material in laboratory tests to be compared with that found in worn footwear.Recent work has demonstrated that chemical degradation of poromerics is due to hydrolysis of the Polyurethane used in the microporous layer and these results have been confirmed by SEM studies. Reasonably good correlation between laboratory hydrolysis tests and chemical deterioration of the poromerics in wear has also been found.Paper presented to Institute of Physics and Physical Society Conference Scanning Electron Microscopy in Materials Science. Newcastle, 7–9 July, 1970.     

Comparative and competitive adsorption of cadmium, copper, nickel, and lead ions by Iranian natural zeolite

The competitive adsorption behavior of cadmium (Cd²⁺), copper (Cu²⁺), nickel (Ni²⁺), and lead (Pb²⁺) ions using Iranian natural zeolite has been studied in order to determine its applicability in treating industrial wastewater. Tests to determine both the rate of adsorption and the uptake at equilibrium were performed under batch conditions from single- and multi-component solutions. The optimum conditions for the treatment process were investigated by observing the influence of pH levels, the presence of competing ions, varying the mass of zeolite and different contact time. Adsorption kinetics of the zeolite followed first-order kinetics, showing about 100 % of Pb²⁺ removal within 40 min and reaching an equilibrium state within 24 h for Cd²⁺, Cu²⁺, and Ni²⁺. The results indicated that removal of metals from single- and multi-component solutions is best described by a Freundlich isotherm, in which the distribution coefficient was in the following order: Pb²⁺ > Cu²⁺ > Cd²⁺ > Ni²⁺. In the multi-component solutions, metals exhibit competitive adsorption on the zeolite. The adsorption is reduced to 90, 53, 30, and 22 % of single component of Cu²⁺, Ni²⁺, Cd²⁺, and Pb²⁺, respectively. However, the total adsorption was higher than single component. Finally, soil solution saturation indices and speciation of metals was assessed using Visual MINTEQ 2.6 software, and probability of precipitation of minerals supported by scanning electron microscopy. The research indicates that Cd²⁺ and Ni²⁺ retention by zeolite can be viewed as the result of ion exchange reaction, but Pb²⁺ and Cu²⁺ retention is both due to ion exchange and precipitation. These results show that Iranian natural zeolite particularly effective in removing cationic heavy metal species from industrial wastewater.     

Synthesis of hollow lead sulfide microspheres

Lead sulfide (PbS) uniform hollow spheres have been successfully synthesized by γ-irradiating PMMA–CS₂–ethanol aqueous solution that contains Pb(CH₃COO)₂·3H₂O at room temperature. X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), transmission electron micrograph (TEM), and high-resolution transmission electron micrograph (HRTEM) experimental results show that the diameter of PbS hollow spheres, the thickness of sphere shell, and the size of these crystallites are about 500, 20, and 10 nm, respectively. Room temperature UV–vis absorption spectrum of the PbS hollow spheres gives its peak centered at around 238 nm and a weak shoulder peak centered at about 322 nm. The obvious blue shift of the absorption peak may be attributed to the small dimension of the PbS bricks of the spheres wall. A possible growth mechanism of PbS hollow sphere is also presented. The successful preparation of PbS hollow spheres in large scale under mild conditions could be of interest for both applications and fundamental studies.     

Optical properties of manganese-doped zinc sulfide nanoparticles classified by size using poor solvent

To elucidate the dependence of the optical properties of semiconductor nanoparticles (NPs) on their size, it is of requisite importance to control or narrow the size distribution of NPs. In this paper, we demonstrated how to attain such controlled states by classifying manganese-doped zinc sulfide (ZnS:Mn) NPs. The classification method proposed was the gradual stage-wise flocculation of NPs relying on interparticle interaction forces between NPs, which were controlled by the addition of a poor solvent, 2-propanol. The mean diameter of ZnS:Mn NPs was evaluated from X-ray diffraction pattern and UV–vis absorption spectrum with the tight-binding approximation. As the number of classification cycles increased, smaller-sized particles were collected. The first-collected sample, which comprised a group of the largest-sized NPs, showed the highest photoluminescence intensity.     

Structure and properties of polylactide/natural rubber blends

Polylactide, PLA, is a biodegradable thermoplastic polyester derived from biomass that has restricted packaging applications due to its high brittleness and poor crystallisation behaviour. Here, new formulations based on natural rubber–PLA blends have been developed. The processing windows, temperature, time, and rotor rate, and the rubber content have been optimised in order to obtain a blend with useful properties. The rubber phase was uniformly dispersed in the continuous PLA matrix with a droplet size range from 1.1 to 2.0 μm. The ductility of PLA has been significantly improved by blending with natural rubber, NR. The elongation at break improved from 5% for neat PLA to 200% by adding 10 wt% NR. In addition, the incorporation of NR not only increased the crystallisation rate but also enhanced the crystallisation ability of PLA. These materials are, therefore, very promising for industrial applications.     

Thermooptical properties of composites based on cadmium sulfide nanoparticles stabilized in a low-density polyethylene matrix

The thermooptical properties of composites based on a low-density polyethylene matrix containing stabilized cadmium sulfide nanoparticles have been studied. The optical absorption coefficient and refractive index have been measured in the samples with various concentrations of nanoparticles dispersed in the polymer matrix. It is established that, upon reaching a certain temperature, the subsequent heating and cooling of a sample are accompanied by hysteresis in the optical properties.     

Utilization of natural zeolite in aerated concrete production

In this study, natural zeolite (clinoptilolite) was used as an aggregate and bubble-generating agent in autoclaved aerated concrete (AAC) production. The crushed and grinded samples were classified into two different particle sizes: 100 μm (fine-ZF) and 0.5–1 mm (coarse-ZC) before using in AAC mixtures. The effects of particle size, replacement amount (25%, 50%, 75% and 100% against quartz) and curing time on the AAC properties were experimentally investigated. It was found that usage of natural zeolite, especially with a coarser particle size, has beneficial effect on the physical and mechanical properties of AAC. The optimum replacement amount was determined as 50% and at this rate the compressive strength, unit weight and thermal conductivity of AAC were measured as 3.25 MPa, 0.553 kg/dm³ and 0.1913 W/mK, respectively. Scanning electron microscopy analysis also confirmed the above findings. Denser C–S–H structures were obtained up to a replacement amount of 50%. Finally, the test results demonstrated that calcined zeolite acts as both an aggregate and a bubble-generating agent, and that AAC with a compressive strength of 4.6 MPa and unit weight of 0.930 kg/dm³ can be produced without aluminum powder usage.     

Remediation of arsenic and lead with nanocrystalline zinc sulfide

Nanocrystalline (1.7 ± 0.3 nm) zinc sulfide with a specific surface area up to 360 m(2) g(-1) was prepared from the thermal decomposition of a single-source precursor, zinc ethylxanthate. Zinc ethylxanthate decomposes to cubic zinc sulfide upon exposure to temperatures greater than or equal to 125 °C. The resulting zinc sulfide was tested as a water impurity extractant. The target impurities used in this study were As(5+), As(3+), and Pb(2+). The reaction of the nanocrystalline ZnS with Pb(2+) proceeds as a replacement reaction where solid PbS is formed and Zn(2+) is released into the aqueous system. Removal of lead to a level of less than two parts per billion is achievable. The results of a detailed kinetics experiment between the ZnS and Pb(2+) are included in this study. Unlike the instance of lead, both As(5+) and As(3+) adsorb on the surface of the ZnS extractant as opposed to an ion-exchange process. An uptake capacity of > 25 mg g(-1) for the removal of As(5+) is possible. The uptake of As(3+) appears to proceed by a slower process than that of the As(5+) with a capacity of nearly 20 mg g(-1). The nanocrystalline zinc sulfide was extremely successful for the removal of arsenic and lead from simulated oil sand tailing pond water.     

Structure and magnetic properties of iron based nanoparticles with oxide shells

Oxide-coated iron nanoparticles with average dimensions from 6 to 75 nm have been synthesized by chemical vapor condensation. The structure of particles and their size distribution have been determined. These data are used to interpret the results of measurements of the magnetic hysteresis characteristics.     

Microwave absorption properties of double-layer absorbers based on spindle magnetite nanoparticles and flower-like copper sulfide microspheres

In this work, the spindle magnetite nanoparticles (SMNPs) and flower-like copper sulfide microspheres (FCSMSs) were synthesized via hydrothermal method. The structures, chemical composition and morphologies of samples were analyzed and characterized in detail. The microwave absorption properties of single-layer and double-layer absorbers were investigated based on the electromagnetic transmission line theory in the frequency range from 2 to 18 GHz. The results show that the double-layer absorbers consisting of FCSMSs as matching layer and SMNPs as absorbing layer display superior microwave absorbing performance compared to the single-layer ones due to the proper combination of magnetic loss of SMNPs and dielectric loss of FCSMSs, and the improved impedance matching characteristics. When the thicknesses of the absorbing layer and the matching layer are 1.6 and 0.4 mm, respectively, the minimum reflection loss reaches ??74.3 dB at 10.9 GHz, and the efficient absorption bandwidth is up to 5.34 GHz (8.46–13.8 GHz). The optimal SMNPs/FCSMSs double-layer absorbers can become a novel microwave absorption material with strong-absorption and broad-band.     

The effect of interfacial interactions on the mechanical properties of polypropylene/natural zeolite composites

The effect of interfacial interactions on the mechanical properties of polypropylene (PP)/natural zeolite composites was investigated under dry and wet conditions. Interfacial interactions were modified to improve filler compatibility and mechanical properties of the composites by surface treatment of natural zeolite with a non-ionic surface modifier; 3 wt% polyethylene glycol (PEG) and three different types of silane coupling agents; 3-aminopropyltriethoxysilane (AMPTES), methyltriethoxysilane (MTES) and 3-mercaptopropyltrimethoxysilane (MPTMS), at four different concentrations (0.5–2 wt%). PP composites containing (2–6 wt%) zeolite were prepared by an extrusion technique. The tensile properties of the composites determined as a function of the filler loading and the concentration of the coupling agents were found to vary with surface treatment of zeolite. Silane treatment indicated significant improvements in the mechanical properties of the composites. According to the dry and wet tensile test results, the maximum improvement in the mechanical properties was obtained for the PP composites containing 1 wt% AMPTES treated zeolite. The improvement in the interfacial interaction was confirmed using a semi-empirical equation developed by Pukanszky. Good agreement was obtained between experimental data and the Pukanszky model prediction. Scanning electron microscopy studies also revealed better dispersion of silane treated filler particles in the PP matrix.