Abstract: Ce-modified mesoporous silica materials MCM-41 and SBA-15, namely 32 wt % Ce–Si–MCM-41, 16 wt % Ce–H–MCM-41 and 20 wt % Ce–Si–SBA-15, were prepared, characterized and studied in the selective preparation of trans-carveol by α-pinene oxide isomerization. The characterizations of these catalysts were performed using scanning electron microscopy, X-ray photoelectron spectroscopy, nitrogen adsorption and FTIR pyridine adsorption. Selective preparation of trans-carveol was carried out in the liquid phase in a batch reactor. The activity and the selectivity of catalyst were observed to be influenced by their acidity, basicity and morphology of the mesoporous materials. The formation of trans-carveol is moreover strongly influenced by the basicity of the used solvent and in order to achieve high yields of this desired alcohol it is necessary to use polar basic solvent.
Abstract: Alumina-zirconia (AZ) composites are attractive structural materials, which combine the high hardness and Young’s modulus of the alumina matrix with additional toughening effects, due to the zirconia dispersion. In this study, AZ composites containing different amounts of zirconia (in the range 5–20 vol %) were prepared by a wet chemical method, consisting on the surface coating of alumina powders by mixing them with zirconium salt aqueous solutions. After spray-drying, powders were calcined at 600 °C for 1 h. Green bodies were then prepared by two methods: uniaxial pressing of spray-dried granules and slip casting of slurries, obtained by re-dispersing the spray dried granulates. After pressureless sintering at 1500 °C for 1 h, the slip cast samples gave rise to fully dense materials, characterized by a quite homogeneous distribution of ZrO2 grains in the alumina matrix. The microstructure, phase composition, tetragonal to monoclinic transformation behavior and mechanical properties were investigated and are here discussed as a function of the ZrO2 content. The material containing 10 vol % ZrO2 presented a relevant hardness and exhibited the maximum value of KI0, mainly imputable to the t → m transformation at the crack tip.
Abstract: South African fly ash has been shown to be a useful feedstock for the synthesis of some zeolites. The present study focuses on the effect of impeller design and agitation rates on the synthesis of zeolite Na-P1 which are critical to the commercialization of this product. The effects of three impeller designs (4-flat blade, Anchor and Archimedes screw impellers) and three agitation speeds (150, 200 and 300 rpm) were investigated using a modified previously reported synthesis conditions; 48 hours of ageing at 47 °C and static hydrothermal treatment at 140 °C for 48 hours. The experimental results demonstrated that the phase purity of zeolite Na-P1 was strongly affected by the agitation rate and the type of impeller used during the ageing step of the synthesis process. Although zeolite Na-P1 was synthesized with a space time yield (STY) of 15 ± 0.4 kg d−1m−3and a product yield of 0.98±0.05 g zeolites/g fly ash for each impeller at different agitation speeds, zeolite formation was assessed to be fairly unsuccessful in some cases due the occurrence of undissolved mullite and/or the formation of impurities such as hydroxysodalite with the zeolitic product. This study also showed that a high crystalline zeolite Na-P1 can be synthesized from South African coal fly ash using a 4-flat blade impeller at an agitation rate of 200 rpm during the ageing step at 47 °C for 48 hours followed by static hydrothermal treatment at 140 °C for 48 hours.
Abstract: e effects of biological pretreatment on the rubberwood (Hevea brasiliensis), was evaluated after cultivation of white rot fungi Ceriporiopsis subvermispora, Trametes versicolor, and a mixed culture of C. subvermispora and T. versicolor. The analysis of chemical compositions indicated that C. subvermispora had greater selectivity for lignin degradation with the highest lignin and hemicellulose loss at 45.06% and 42.08%, respectively, and lowest cellulose loss (9.50%) after 90 days among the tested samples. X-ray analysis showed that pretreated samples had a higher crystallinity than untreated samples. The sample pretreated by C. subvermispora presented the highest crystallinity of all the samples which might be caused by the selective degradation of amorphous components. Fourier transform infrared (FT-IR) spectroscopy demonstrated that the content of lignin and hemicellulose decreased during the biological pretreatment process. A study on hydrolysis of rubberwood treated with C. subvermispora, T. versicolor, and mixed culture for 90 days resulted in an increased sugar yield of about 27.67%, 16.23%, and 14.20%, respectively, as compared with untreated rubberwood (2.88%). The results obtained demonstrate that rubberwood is a potential raw material for industrial applications and white rot fungus C. subevermispora provides an effective method for improving the enzymatic hydrolysis of rubberwood.
Abstract: High-grade cellulose (97% α-cellulose content) of 48% crystallinity index was extracted from the renewable marine biomasswaste Posidonia oceanica using H2O2 and organic peracids following an environmentally friendly and chlorine-free process. This cellulose appeared as a new high-grade cellulose of waste origin quite similar to the high-grade cellulose extracted from more noble starting materials like wood and cotton linters. The benefits of α-cellulose recovery from P. oceanica were enhanced by its transformation into cellulose acetate CA and cellulose derivative GMA-C.Fully acetylated CA was prepared by conventional acetylation method and easily transformed into a transparent film. GMA-C with a molar substitution (MS) of 0.72 was produced by quenching Fenton’s reagent (H2O2/FeSO4) generated cellulose radicals with GMA. GMA grafting endowed high-grade cellulose from Posidonia with adsorption capability. GMA-C removes β-naphthol from water with an efficiency of 47%, as measured by UV-Vis spectroscopy. After hydrolysis of the glycidyl group to glycerol group, the modified GMA-C was able to remove p-nitrophenol from water with an efficiency of 92%, as measured by UV-Vis spectroscopy. α-cellulose and GMA-Cs from Posidonia waste can be considered as new materials of potential industrial and environmental interest.
Abstract: Doxorubicin hydrochloride (DOX) is an effective anticancer agent for leukemia chemotherapy, although its clinical use has been limited because of its side effects such as cardiotoxicity, alopecia, vomiting, and leucopenia. Attention has been focussed on developing new drug carriers with high adsorption capacity and rapid adsorption rate in order to minimize the side effects of DOX. Graphene oxide (GO), a new type of nanomaterial in the carbon family, was prepared by Hummers method and used as adsorbent for DOX from aqueous solution. The physico-chemical properties of GO were characterized by transmission electron microscope (TEM), Fourier transform infrared spectroscopy (FTIR), zeta potential, and element analysis. The adsorption properties of DOX on GO were studied as a function of contact time, adsorbent dosage, temperature and pH value. The results showed that GO had a maximum adsorption capacity of 1428.57 mg/g and the adsorption isotherm data fitted the Langmuir model. The kinetics of adsorption fits a pseudo-second-order model. The thermodynamic studies indicate that the adsorption of DOX on GO is spontaneous and endothermic in nature.