Volume 10 (2008): Issue 2 (January 2008)

Single-wall carbon nanotubes (SWCNT) have proved to be very special materials due to their unique electronic properties. Over the last years many scientists have dedicated their research to the study of the these materials as an electronic system. Amphoteric doping effects (n-type and p-type), which can be reversed, became a very popular way of manipulating the optic and electronic properties of carbon nanotubes. In the particular case of SWCNT, the most common and widely used procedure, which changes their properties, is acid treatment applied as a purification procedure. The effect of the addition of this kind of the dopant has been widely studied but not fully understood so far. Here, we present a study, of two kinds of SWCNT, produced within different techniques: (i) chemical vapors deposition and (ii) laser ablation. The main difference between the two types is the diameter distribution of the obtained materials, which is broad in the first technique and narrow in the second. After the acid treatment it is possible to observe a diameter sensitive doping effect on both samples. Resonance Raman spectroscopy, optical absorption spectroscopy (OAS) in UV/Vis/NIR and the Fourier transform middle-infrared (FTIR) spectroscopy have been applied for the characterization of the samples.

This paper shows the results of using the modified kaolin by silane coupling agents in HDPE composite and the effect of surface modifications of fillers on the properties of polyethylene composites. In the first stage pure and modified kaolin was subjected to a number of tests in order to determine the backfill density, water and paraffin oil absorbability, the surface area and pore volume, the morphology of their grains, thermal analysis and the FT-IR spectroscopy.

In the second stage the composites, which were moulded into the samples that could be subjected to further tests, were produced. The samples were characterised by the determination of the hardness according to Shore, the elasticity modulus, the tensile strength and tearing strength.

The modification of the kaolin surface has resulted in a substantial improvement of the strength parameters of the obtained polyethylene composites.

The preparation method and the activity of the TiO₂-P25/N doped photocatalyst based on commercial titanium dioxide (TiO₂ Aeroxide® P-25 Degussa, Germany) are presented. For the TiO₂-P25/N preparation TiO₂-P25 and gaseous ammonia were kept in a pressure reactor (10 bars) for 4 hours at the temperature of 200°C. This modification process changed the chemical structure of the TiO₂ surface. The formation of NH₄⁺ groups was confirmed by the FTIR measurements. Two bands in the range of ca. 1430 - 1440 cm^-1 attributed to bending vibrations of NH₄⁺ could be observed on the FTIR spectra of the catalysts modified with ammonia and the band attributed to the hydroxyl groups at 3300 - 3500 cm^-1, which were not reduced after N-doping. The photocatalytic activity of the photocatalysts was checked through the decomposition of two dyes under visible light irradiation. The modified TiO₂ thus prepared samples were more active than TiO₂-P25 for the decomposition of dyes under visible light irradiation.

A highly sensitive indirect spectrophotometric redox method for the determination of osmium is reported on. The method is based on the oxidation of iodide by osmium (VI) and the spectrophotometric detection of the liberated iodine in the form of complex anion associate with 2-(4-diethylaminostyryl)-1,3,3-trimethyl-5-thiocyanato-3H-indolium chloride reagent. The appropriate reaction conditions have been established. The molar absorptivity is (0.2-1.2)·10⁵ dm³/mol·cm at 589.5 nm wavelength. The absorbance of the coloured extracts obeys the Beer's law in the range to 7.6 mg/dm³ of Os(VI).

The methane to methanol conversion via esterification is an interesting method which makes it possible to eliminate the otherwise necessary phase of obtaining synthesis gas. On the basis of laboratory investigations mass balances for this process were determined. Preliminary assessment of the way of conducting the process and possibilities of practical applications of this technology was also made. It was pointed out that regardless of any possible modifications of methane to methanol conversion via esterification redundant sulfuric acid will always be produced during ester hydrolysis. Production of methanol from methane using this method can only be done when it is combined with producing other substances, which needs using H₂SO₄.

Membrane distillation (MD) was applied for the concentration of solutions containing hydrochloric acid and potassium chloride. The studies of the concentration and separation of HCl through the hydrophobic membrane were performed. In the investigations plate and frame or capillary modules, equipped with membranes from polytetrafluoroethylene and polypropylene were applied, respectively. The feed temperature amounted to 333 K or 343 K and permeate 293 K at the inlet of the module. Under the MD operation conditions the transfer of water vapour and hydrogen chloride from potassium chloride and hydrochloric acid solutions through the hydrophobic membranes took place, whereas the potassium chloride as a nonvolatile component underwent concentration in the feed. The influence of acid concentration and salt presence in the feed on the HCl molar flux through the membrane was systematically studied. The increase of the temperature and salt concentration in the feed caused higher partial pressure volatile of HCl and the resultant HCl Flux through a membrane was higher.

During MD for the initial concentration in the feed equal 50 g KCl/dm³ and 40g HCl/dm³, at the feed temperature 343K, the permeate flux decreased from 353 dm³/m²d to 289 dm³/m²d, whereas the HCl flux increased to 6 mol/m²d for the capillary module. At higher KCl concentration in the feed, amounting to 100g KCl/dm³ and under the same operation conditions, the permeate flux decreased to 285 dm³/m²d, but the molar flux HCl increased to 18 mol/m²d. The results were compared with the data obtained for the plate and frame module.

Chicken feathers generated in large quantities by the poultry industry are hazardous for the natural environment because of their poor digestibility and their potential as a source of microbiological pathogens. Currently, the main method of feather waste management is the production of feather meal by steam pressure cooking. This technology requires a high energy input. The high costs of hydrothermal degradation of these wastes are conducive to finding other alternative possibilities of poultry wastes management. This paper describes the feather-utilization method with calcium oxide treatment in a rotational reactor, which leads to the production of organic-mineral fertilizers. The effectiveness of this method has been tested in chemical and microbiological analyses. The results of the study confirm the possibility of the environmental usage of utilization-products.

The permanently rising costs of food industry waste management create a real necessity for searching for new economical and environmentally friendly technologies with which such waste can be utilized. The purpose of this study was an evaluation of waste composting using rotational reactor technology with further use of the resultant product as a fertilizer. In order to conduct the research, a rotational reactor was designed and constructed. For the composting process, such waste materials as meat and bone pulp, past its sell-by date dairy and bakery products, sawdust, poultry and cattle manure, were used. The composition of the composted masses was chosen so that their approximate C:N:P proportions and consistency were appropriate for the growth of biodegradating micro-organisms. The efficiency of the presented technology was evaluated based on the inactivation of selected strains of bacteria and the eggs of invasive parasites. The products obtained were tested by the Institute of Soil Science and Plant Cultivation in Puławy with regard to its possible environmental usage.

The potential of burned water hyacinth (BWH) for phenol adsorption from aqueous solution was studied. Batch kinetic and isotherm studies were carried out under varying experimental conditions of contact time, phenol concentration, adsorbent dosage and pH. The pH at the point of zero charge (pH_PZC) of the adsorbent was determined by the titration method and the value of 8.8 ± 0.2 was obtained. The FTIR of the adsorbent was carried out in order to find the potential adsorption sites for the interaction with phenol molecules. The Freundlich and Langmuir adsorption models were used for the mathematical description of adsorption equilibrium and it was found that the experimental data fitted very well to the Langmuir model. Maximum adsorption capacity of the adsorbent was found to be 30.49 mg/g. Batch adsorption models, based on the assumption of the pseudo-first-order and pseudo-second-order models, were applied to examine the kinetics of the adsorption. The results showed that kinetic data closely followed the pseudo-second-order model.