Zeolites with Continuously Tuneable Porosity

Zeolites are important materials whose utility in industry depends on the nature of their porous structure. Control over microporosity is therefore a vitally important target. Unfortunately, traditional methods for controlling porosity, in particular the use of organic structure‐directing agents, are relatively coarse and provide almost no opportunity to tune the porosity as required. Here we show how zeolites with a continuously tuneable surface area and micropore volume over a wide range can be prepared. This means that a particular surface area or micropore volume can be precisely tuned. The range of porosity we can target covers the whole range of useful zeolite porosity: from small pores consisting of 8‐rings all the way to extra‐large pores consisting of 14‐rings.     

The removal and kinetic study of Mn,Fe, Ni and Cu ions from wastewater onto activated carbon from coconut shells

Activated carbon from coconut shells (ACCS) was synthesised and used for the removal of metal ions (manganese, iron, nickel and copper) from aqueous solutions. Two different adsorption models were used for analysing the data. Adsorption capacities were determined: copper ions exhibited the greatest adsorption on activated carbon obtained from coconut shells because of their size and pH conditions. Adsorption capacity varied as a function of the pH. Adsorption isotherms from aqueous solutions of heavy metals on ACCS were determined and were found to be consistent with Langmuir’s adsorption model. Adsorbent quantity and immersion enthalpy were studied. The results were compared with other adsorbents used in a prior study.     

Thermal studies on solid 1,4-bis(3-carboxy-3-oxo-prop-1-enyl) benzene of lighter trivalent lanthanides

Solid-state compounds of general formula Ln₂L₃·nH₂O, where L represents 1,4-bis(3-carboxy-3-oxo-prop-1-enyl)benzene and Ln = La, Ce, Pr, Nd, Sm, were synthesized. Complexometric titrations with EDTA, thermogravimetry (TG), differential thermal analysis (DTA), differential scanning calorimetry (DSC), X-ray powder diffractometry, elemental analysis and infrared spectroscopy have been employed to characterize and to study the thermal behavior of these compounds in dynamic air atmosphere. The results led to information about the composition, dehydration, crystallinity, and thermal decomposition of the synthesized compounds.     

Effect of sol-gel preparation method on particle morphology in pure and nanocomposite PZT thin films

Double-scale composite lead zirconate titanate Pb(Zr_0.52Ti_0.48)O₃ (PZT) thin films of 360 nm thickness were prepared by a modified composite sol-gel method. PZT films were deposited from both the pure sol and the composite suspension on Pt/Al₂O₃ substrates by the spin-coating method and were sintered at 650°C. The composite suspension formed after ultrasonic mixing of the PZT nanopowder and PZT sol at the powder/sol mass concentration 0.5 g mL⁻¹. PZT nanopowder (≈ 40–70 nm) was prepared using the conventional sol-gel method and calcination at 500°C. Pure PZT sol was prepared by a modified sol-gel method using a propan-1-ol/propane-1,2-diol mixture as a stabilizing solution. X-ray diffraction (XRD) analysis indicated that the thin films possess a single perovskite phase after their sintering at 650°C. The results of scanning electron microscope (SEM), energy-dispersive X-ray (EDX), atomic force microscopy (AFM), and transmission electron microscopy (TEM) analyses confirmed that the roughness of double-scale composite PZT films (≈ 17 nm) was significantly lower than that of PZT films prepared from pure sol (≈ 40 nm). The composite film consisted of nanosized PZT powder uniformly dispersed in the PZT matrix. In the surface micrograph of the film derived from sol, large round perovskite particles (≈ 100 nm) composed of small spherical individual nanoparticles (≈ 60 nm) were observed. The composite PZT film had a higher crystallinity degree and smoother surface morphology with necklace clusters of nanopowder particles in the sol-gel matrix compared to the pure PZT film. Microstructure of the composite PZT film can be characterized by a bimodal particle size distribution containing spherical perovskite particles from added PZT nanopowder and round perovskite particles from the sol-matrix, (≈ 30–50 nm and ≈ 100–120 nm), respectively. Effect of the PZT film preparation method on the morphology of pure and composite PZT thin films deposited on Pt/Al₂O₃ substrates was evaluated.     

Thermal analysis of hair treated with oxidative hair dye under influence of conditioners agents

This research aimed the effect on Caucasian hair tresses treated with oxidative hair dye, either incorporated or not with conditioners agents, analyzed by Differential Scanning Calorimetry (DSC) and Thermogravimetric analysis (TG). The formulations of hair dyes were emulsions oil-in-water with light blond color containing or not the conditioners agents: silanetriol and panthenol; PEG-12 dimethicone; hydrolyzed silk, hydrolyzed milk protein, and lactose. Each dye (1.5 g) was applied in the hair tress (2.0 g/20.0 cm of length of Caucasian light-brown), previously treated, more 1.5 g of hydrogen peroxide 20 vol during 40 min. Evaluation of mass loss of the different hair sample demonstrates that these chemical hair treatments impair the hair fibers, reduced their moisture content with respect to the untreated hair. The incorporation of conditioners agents (silanetriol and panthenol; PEG-12 dimethicone; hydrolyzed silk, hydrolyzed milk protein, and lactose) in oxidative hair dyes types did not decrease the damage caused on the tresses by the coloring process quantified by TG/DTG. However, the DSC curves demonstrated those conditioners agents (silanetriol and panthenol; PEG-12 dimethicone) dislocated the beginning of the third event in 20 °C and they inhibited the presence of the fourth event, having characterized thermal protection to the hair.     

Sequential spectrofluorimetric determination of free and total glycerol in biodiesel in a multicommuted flow system

A new procedure for spectrofluorimetric determination of free and total glycerol in biodiesel samples is presented. It is based on the oxidation of glycerol by periodate, forming formaldehyde, which reacts with acetylacetone, producing the luminescent 3,5-diacetyl-1,4-dihydrolutidine. A flow system with solenoid micro-pumps is proposed for solution handling. Free glycerol was extracted off-line from biodiesel samples with water, and total glycerol was converted to free glycerol by saponification with sodium ethylate under sonication. For free glycerol, a linear response was observed from 5 to 70 mg L⁻¹ with a detection limit of 0.5 mg L⁻¹, which corresponds to 2 mg kg⁻¹ in biodiesel. The coefficient of variation was 0.9% (20 mg L⁻¹, n = 10). For total glycerol, samples were diluted on-line, and the linear response range was 25 to 300 mg L⁻¹. The detection limit was 1.4 mg L⁻¹ (2.8 mg kg⁻¹ in biodiesel) with a coefficient of variation of 1.4% (200 mg L⁻¹, n = 10). The sampling rate was ca. 35 samples h⁻¹ and the procedure was applied to determination of free and total glycerol in biodiesel samples from soybean, cottonseed, and castor beans.     

Temperature dependent in situ doping of ALD ZnO

This study on ALD grown ZnO layers is aimed at the systematic study of the effect of incorporation of different Al contents on the properties of the layers. An alternate precursor pulse method was used for layer deposition. Optimal doping was achieved at 210 °C at 2 at% Al content. A relationship between crystalline morphology versus temperature and aluminium incorporation was established.     

The relationship between the mercury concentration in fish muscles and scales/fins and its significance

The determination of mercury in fish typically involves analysis of muscles. For predicting the concentration of mercury in fish muscle on the basis of the analysis of fish scales or fins, the relationship between total mercury concentrations in fish muscles and in fish scales and fins was studied. Mercury content in fish muscles, scales and fins was determined by atomic absorption spectrometry with thermal decomposition of the sample in a flow of oxygen. A number of scale treatments were applied in order to remove impurities and to enhance the prediction quality. For scale treatment, 40 min of washing with DI water in an ultrasonic bath is recommended. A coefficient of determination r²= 0.93 for the relationship between Hg concentrations in muscles and scales was achieved for 40 fish among the different fish species tested (European bream, perch, roach) from the Hamry Reservoir, Czech Republic. With respect to fin sampling, the coefficient of determination r² for these fish was 0.86. The analysis of fish scales and caudal fins is a useful screening tool for assessing the relative mercury contamination of monitored fish. The method of sampling scales is not suitable for fish species with small scales such as brown trout.      

Thermal study on electrospun polyvinylpyrrolidone/ammonium metatungstate nanofibers: optimising the annealing conditions for obtaining WO<Subscript>3</Subscript> nanofibers

This article demonstrates how important it is to find the optimal heating conditions when electrospun organic/inorganic composite fibers are annealed to get ceramic nanofibers in appropriate quality (crystal structure, composition, and morphology) and to avoid their disintegration. Polyvinylpyrrolidone [PVP, (C₆H₉NO) _n ] and ammonium metatungstate [AMT, (NH₄)₆[H₂W₁₂O₄₀]·nH₂O] nanofibers were prepared by electrospinning aqueous solutions of PVP and AMT. The as-spun fibers and their annealing were characterized by TG/DTA-MS, XRD, SEM, Raman, and FTIR measurements. The 400–600 nm thick and tens of micrometer long PVP/AMT fibers decomposed thermally in air in four steps, and pure monoclinic WO₃ nanofibers formed between 500 and 600 °C. When a too high heating rate and heating temperature (10 °C min⁻¹, 600 °C) were used, the WO₃ nanofibers completely disintegrated. At lower heating rate but too high temperature (1 °C min⁻¹, 600 °C), the fibers broke into rods. If the heating rate was adequate, but the annealing temperature was too low (1 °C min⁻¹, 500 °C), the nanofiber morphology was excellent, but the sample was less crystalline. When the optimal heating rate and temperature (1 °C min⁻¹, 550 °C) were applied, WO₃ nanofibers with excellent morphology (250 nm thick and tens of micrometer long nanofibers, which consisted of 20–80 nm particles) and crystallinity (monoclinic WO₃) were obtained. The FTIR and Raman measurements confirmed that with these heating parameters the organic matter was effectively removed from the nanofibers and monoclinic WO₃ was present in a highly crystalline and ordered form.