Volume 13 (2011): Issue 2 (January 2011)

Nano iron oxide particles (Fe₃O₄) were synthesized by coprecipitation of Fe²⁺ and Fe³⁺ by ammonia solution in the aqueous phase. Various instrumentation methods such as X ray Diffractometry (XRD), Transmission Electron Microscopy (TEM), Fourier Transform Infrared (FTIR) spectroscopy, Brunauer-Emmett-Teller (BET) and Vibrating Sample Magnetometery (VSM) were used to characterize the properties of nanoparticles. The size of the nanoparticles was measured and was found to be between 10 to 15 nm. The value of saturation magnetization of the nanoparticles was found to be 55.26 emu/g. The BET surface area of nano iron oxide particles measured to be 86.55 m²/g.

The electron transfer reaction of L-cysteine (RSH) with pyridinium chlorochromate (PCC) has been studied spectrophotometrically over the range 2.0 ≤ 10³ [RSH] ≤ 6.0; 0.01 ≤ [H⁺] ≤ 0.2; 298 ≤ T ≤ 318 K and I = 0.3 mol dm^-3 (NaClO₄). The electron transfer reaction has also been carried out in the presence of anionic, cationic and neutral micelle. The reaction in acid medium is strongly catalyzed by changing [SDS]_T (sodium dodecyl sulfate) up to 3 × 10^-2 mol dm^-3, beyond this concentration of SDS, the rate is retarded. The cationic and neutral micelle has a small effect on the rate. ΔH≠ (kJ mol^-1) and ΔS≠ (JK^-1 mol^-1) values for the k₁ and k₂ paths are 30.20 ± 0.25, -159.65 ± 0.83 and 29.60 ± 0.62, -127.09 ± 2.17, respectively. The negative activation entropy is indicative of the ordered transition state for the electron transfer reaction. Formation of 2-amino-3-(2-amino-2-carboxy-ethyl) disulfanyl-propanoic acid as product is strongly supported by IR spectra.

The Preyssler, Wells-Dowson and Keggin heteropolyacids are efficient and eco-friendly solid acid catalysts for the acylation of electron-rich aromatic compounds with acid anhydrides. The performance of different forms of heteropolyacids was compared. In all the cases, the best results were obtained using the Preyssler heteropolyacid as the catalyst. In the presence of 25 mol% (with respect to H⁺ equivalency) Preyssler catalyst, highly para-selective acetylation of anisole occurs using two equivalents of acetic anhydride, in 15 min at room temperature. The isolated yield of the p-methoxyacetophenone product is 98%.

The paper presents practical utilisation in the construction of a parking lot of compositions based on waste (phosphogypsum) from the wet process of orthophosphoric acid manufacture. The results of strength tests performed after half a year and after one and a half year of parking lot operation confirmed the feasibility, established earlier in laboratory tests, of utilising phosphogypsum mixes with fly ash and stabilising binder.

The purpose of the study is to investigate the optimum conditions for the precipitation of sodium hexafluorosilicate (Na₂SiF₆) from waste hexafluorosilicic acid, an effluent from the phosphoric acid industry. Sodium chloride and sodium hydroxide were used as reactants to produce Na₂SiF₆. The effect of various parameters on the precipitation was investigated and includes; the molar ratio of the reactants, contact time, the temperature and the effect of seeding.

The optimum reaction conditions were found to be as follows; excess sodium chloride or sodium hydroxide to hexafluorosilicic acid of 25%, contact time 40 minutes and a reaction temperature of 40°C.

The reaction of hexafluorosilicic acid with an aqueous solution of sodium chloride at optimum conditions gave a maximum yield of 94.26% Na₂SiF₆ while the reaction of hexafluorosilicic acid with the aqueous solution of sodium hydroxide at optimum conditions gave a maximum yield of 97.3% Na₂SiF₆. The X-Ray diffraction (XRD) analysis reveals that the only crystals present in the precipitate are Na₂SiF₆. Also, Scanning Electron Microscope (SEM) analysis shows that the different morphology of these crystals depend on the precipitation conditions.

Environmental degradability of novel organic-inorganic cellulose acetate butyrate hybrids obtained via solgel process was investigated. The degradation of hybrids was studied under marine exposure conditions in the Baltic Sea for a period of 25 weeks. The influence of characteristic parameters of sea water on the degree of degradation monitored by changes of weight and optical microscopy was discussed. The degraded samples were also examined by FT-IR spectroscopy. It has been established that the CAB/silica hybrids are more susceptible to biodegradation in sea water environment than pure cellulose acetate butyrate.

Batch studies were conducted to investigate the potential of 3-aminopropyltriethoxysilane modified nano zero-valent iron (APS-NZVI) to adsorb two dyes (acid brilliant scarlet GR and reactive brilliant red K-2BP) from aqueous solution. APS-NZVI showed good adsorption performance for two dyes. Under the adsorption conditions of pH 4.5, initial concentration was 100 mg/L, and time=4h, the maximum adsorption capacities of APS-NZVI were 121.06 mg/g for acid brilliant scarlet GR and 191.5 mg/g for reactive brilliant red K-2BP, respectively. The results revealed that the adsorption behavior of the dyes on the nano-particles fitted well with the Langmuir model and the sorption kinetics fits well the pseudo-second-order rate equation.

The new requirements that were placed on STPP, like high bulk density, the proper relation of Form I and Form II and suitable physicochemical properties, resulted in the development of the present production methods. The paper presents the research results on increasing the bulk density of STPP by a chemical method. In the introduced method the solid sodium phosphate from spray drying and sodium orthophosphate solution, after acid neutralization, were rubbed together. Such an operation changes the physicochemical properties of the dried sodium phosphate before calcining, which results in increasing the bulk density of STPP to a level of 0.80 kg/dm3. The dependence of STPP bulk density on process parameters such as: sodium orthophosphate solution to solid sodium phosphate mass ratio, temperature of dosed sodium orthophosphate solution, as well as the calcining temperature of mixtures were analysed.

Experimental tests covering the production of struvite MgNH₄PO₄·6H₂O from water solutions containing 1.0 mass % of phosphate(V) ions using magnesium and ammonium ions in stoichiometric proportions were carried out in a crystallizer of 1.2 dm³ working volume. The process temperature was 298 K. Struvite crystals of mean size L_m from ca. 14 to ca. 38 μm were produced depending on the process environment's pH (9-11) and the mean residence time of suspension in a crystallizer, τ (900-3600 s). In such defined process conditions the linear growth rate of struvite crystals changed from 1.45·10^-8 m/s (pH 9, τ 900 s) to 2.06·10^-9 m/s (pH 11, τ 3600 s) while the nucleation rate from 5.1·10⁷ to 3.2·10⁹ 1/(sm³). Crystal product of the most advantageous granular characteristics was produced at pH 9 and the mean residence time 3600 s. Within this product population the largest sizes reached above 200 μm while the number of crystals smaller than 3 mm was kept below 6%.

A new method to determine the effective diffusion coefficient of sorbate in sorbent granule based on the analytical solution of the shrinking core model (SCM) has been proposed. The experimental data presented by Lewandowski and Roe¹ concerning the sorption of copper ions by alginate granules have been applied to compare the analytical and numerical methods. The results obtained by both methods are very close.

Novel polymeric packaging materials susceptible to environmentally friendly decomposition appeared on the global market. The paper is devoted to an investigation of the impact of degradable polymer packaging on marine life. The chosen polymer was a commercial packaging based on thermoplastic starch (TPS over 85%). The microorganism chosen was Phaeodactylum tricornutum diatom (identified in many aquatic reservoirs, with a tendency to flow with seawater plankton in places of great saline oscillation). The packaging material was incubated both in natural seawater and in the presence of diatom population. The chlorophyll a content was determined as the criterion of diatom growth in the presence of tested polymers. The polymer surface and the colour changes in the diatom culture were recorded photographically. The presence of polymeric samples significantly changed the kinetic of diatom growth in seawater during incubation affecting its biological balance. During the experiment in seawater, diatom adhered to polymer surfaces and the polymer stimulated their growth.

Functionalization of multi-walled carbon nanotubes (MWCNTs) has an effect on the dispersion of MWCNT in the epoxy matrix. Samples based on two kinds of epoxy resin and different weight percentage of MWCNTs (functionalized and non-functionalized) were prepared. Epoxy/carbon nanotubes composites were prepared by different mixing methods (ultrasounds and a combination of ultrasounds and mechanical mixing). CNTs modified with different functional groups were investigated. Surfactants were used to lower the surface tension of the liquid, which enabled easier spreading and reducing the interfacial tension. Solvents were also used to reduce the liquid viscosity. Some of them facilitate homogeneous dispersion of nanotubes in the resin. The properties of epoxy/nanotubes composites strongly depend on a uniform distribution of carbon nanotubes in the epoxy matrix. The type of epoxy resin, solvent, surfactant and mixing method for homogeneous dispersion of CNTs in the epoxy matrix was evaluated. The effect of CNTs functionalization type on their dispersion in the epoxy resins was evaluated on the basis of viscosity and microstructure studies.

A catalytic synthesis of calix[4]pyrroles and N-confused calix[4]pyrroles by reaction of dialkyl or cycloalkyl ketones with pyrrole was performed using Preyssler, sodium30-tungsto pentaphosphate, [NaP₅W₃₀O₁₁₀]^14- and Wells-Dawson heteropolyacids as acidic catalysts. The process occurred under mild, eco-friendly and environmental friendly conditions and as a reusable, green catalyst at room temperature for 6 hours. The results showed that the yield for this synthesis is excellent with the use of Preyssler and Wells-Dawson type tungstophosphoric heteropolyacid, H₆[P₂W₁₈O₆₂], catalysts. The synthesis reaction of calix[4]pyrroles and N-confused calix[4]pyrroles was developed using different solvents and the best yields were obtained in chloroform.