Multifunctional Oxide-Based Materials: From Synthesis to Application

The book deals with novel aspects and perspectives in metal oxide and hybrid material fabrication

Effect of exogenously added rhamnolipids on citric acid production yield

The influence of a biosurfactant (rhamnolipids) on the effectiveness of citric acid production by Yarrowia lipolytica from sunflower oil was studied. The surfactant-mediated solubilization of the hydrophobic substrate was assessed by particle size distribution characteristics with and without the presence of sunflower oil hydrolization products. The presence of rhamnolipids contributed to a decrease of the oil droplet size, most notably for samples containing sunflower oil and its hydrolization products. The citric acid yield for cultures not supplemented with rhamnolipids was at 82.9 g/l, with a 1:0.04 citric acid to isocitric acid ratio (CA:ICA). The addition of rhamnolipids at 1 g/l resulted in a 5% increased citric acid yield (87.1 g/l), however a decrease (79.0 g/l) was observed for samples containing 5 g/l of rhamnolipids. The rhamnolipids-induced emulsification of sunflower oil did not seem to influence the citric acid production efficiency. Additional research revealed that the biosurfactant was degraded by yeast cells during the bioconversion process. The possible explanations of this phenomenon include the utilization of rhamnolipids as an alternative carbon source or microbial destabilization of micelles formed by this biosurfactant due to potential bioavailability issues.Keywords: Yarrowia lipolytica, citric acid, rhamnolipids, sunflower oilAfrican Journal of Biotechnology Vol. 12(21), pp. 3313-332

Removal of nickel(II) and lead(II) ions from aqueous solution using peat as a low-cost adsorbent: A kinetic and equilibrium study

AbstractAnalysis was carried out to determine the physicochemical characteristics – morphological and structural, electrokinetic properties, elemental composition and functional groups – of peat, with a view to its use as a potential adsorbent of heavy metal ions from aqueous solutions. A significant part of the study comprised tests of adsorption of nickel(II) and lead(II) ions from model solutions. It was determined how the parameters of the adsorption process (time, pH, quantity of sorbent) influence the effectiveness of removal of nickel(II) and lead(II) ions. The adsorption kinetics are also described, using a pseudo-first-order model and pseudo-second-order models of types 1–4. The results show strong correspondence to a pseudo-second-order kinetics model of type 1 (r2=0.999 for all initial concentrations). Another key part of the analysis was the use of the Langmuir and Freundlich models to determine the adsorption isotherms. The experimental data were in strong correspondence with Langmuir’s isotherm model. The sorption capacities of peat with respect to nickel(II) and lead(II) ions were 61.27mg(Ni2+)/g and 82.31mg(Pb2+)/g. Desorption tests confirmed the possibility of reusing peat as an effective sorbent of environmentally harmful metals. A mechanism is also proposed for the adsorption of Ni2+ and Pb2+ ions on adsorbent

Removal of Hazardous Oxyanions from the Environment Using Metal-Oxide-Based Materials

Scientific development has increased the awareness of water pollutant forms and has reawakened the need for its effective purification. Oxyanions are created by a variety of redox-sensitive metals and metalloids. These species are harmful to living matter due to their toxicity, nondegradibility, and mobility in aquatic environments. Among a variety of water treatment techniques, adsorption is one of the simplest, cheapest, and most effective. Since metal-oxide-based adsorbents poses a variety of functional groups onto their surface, they were widely applied in ions sorption. In this paper adsorption of harmful oxyanions by metal oxide-based materials according to literature survey was studied. Characteristic of oxyanions originating from As, V, B, W and Mo, their probable adsorption mechanisms and comparison of their sorption affinity for metal-oxide-based materials such as iron oxides, aluminum oxides, titanium dioxide, manganium dioxide, and various oxide minerals and their combinations are presented in this paper

Synthesis of vanadium-enriched oxide materials via modified sol-gel route with the use of waste solutions contaminated with vanadium ions

In this study, the synthesis of zirconia as well as zirconia enriched with vanadium by modified sol-gel method was presented. The modification of the method was based on the replacement of the traditional basic promoter of hydrolysis, which is ammonia, with sodium hydroxide solution. The most favorable conditions for the synthesis of zirconium with a new hydrolysis promoter were selected. A comparative analysis of $ZrO_2$ obtained using various hydrolysis promoters was performed. Both materials exhibited almost the same physicochemical properties, which proves that in this case the nature of the hydrolysis promoter used in sol-gel route does not significantly affect the properties of the $ZrO_2$. Then, synthesis of $ZrO_2$/V systems was carried out using model and real solutions containing vanadium ions as hydrolysis promoters. The solutions formed after vanadium catalyst leaching were used as real solutions. The effect of vanadium concentration and the presence of impurities on the final physicochemical properties of the obtained hybrid materials were investigated via scanning electron microscopy (SEM), dynamic light scattering (DLS), energy-dispersive X-ray microanalysis (EDS), Fourier transform infrared spectroscopy (FT-IR), low-temperature nitrogen sorption (BET), thermogravimetric analysis (TGA). The analysis of the obtained results allows to state that the developed technique for the synthesis of $ZrO_2$ and $ZrO_2$/V systems, using a modified sol-gel method, enabled the production of attractive materials

Preparation and Physicochemical Properties of Functionalized Silica/Octamethacryl-Silsesquioxane Hybrid Systems

Alkoxysilane-grafted silica/polyhedral oligomeric silsesquioxane with methacryl substituents (SiO2/silane/POSS) hybrid material was synthesized according to hydrolyzation and condensation reactions in the so-called “bifunctionalization process.” It is a new attractive system because of its physicochemical, especially thermal and structural, properties. This innovative method of preparation as well as specific physicochemical and useful properties determine the potential applications of such products in many industries. The structure and physicochemical parameters of obtained hybrid systems were characterized using infrared spectroscopy (FTIR), 13C and 29Si solid-state nuclear magnetic resonance (CP MAS NMR), and thermal analysis. The mechanism of bifunctionalization reaction was proposed. The chemical immobilization of silane coupling agent and Methacryl POSS onto silica support surface was noted during the study. Those changes caused a significant increase in the hydrophobic character of fillers obtained. Moreover, changes in thermal stability of SiO2/silane/POSS hybrid systems in comparison to pure POSS modifier were also observed

Influence of Selected Alkoxysilanes on Dispersive Properties and Surface Chemistry of Titanium Dioxide and TiO2–SiO2 Composite Material

The paper reports on characterisation of titanium dioxide and coprecipitated TiO2–SiO2 composite material functionalised with selected alkoxysilanes. Synthetic composite material was obtained by an emulsion method with cyclohexane as the organic phase, titanium sulfate as titanium precursor, and sodium silicate solution as precipitating agent were applied. Structures of titania and composite material samples were studied by the wide angle X-ray scattering method. The chemical composition of TiO2–SiO2 composite material precipitated was evaluated based on the energy dispersive X-ray spectroscopy technique. The functionalised TiO2 and TiO2–SiO2 composite material were thoroughly characterised to determine the yield of functionalisation with silanes. The characterisation included determination of dispersion and morphology of the systems (particle size distribution, scanning electron microscope images), adsorption properties (nitrogen adsorption isotherms), and electrokinetic properties (zeta potential)

Effect of sedimentation time on the granulometric composition of suspended solids in the backwash water from biological activated carbon filters

The paper presents the results of analyzes of the granulometric composition of suspended solids in backwash water from biological activated carbon (BAC) filters and its changes during sedimentation. Backwash water samples were taken during backwashing of two pilot filters after different filtration time. It was found that regardless of the concentration of suspended solids in the collected backwash water, particle sizes vs. their percentage volume contributions for all samples were similar. Particle sizes were in the range of 2–100 μm. However, the two-hour sedimentation for most of the samples proved to be effective (total suspended solids removal up to 93%), which is caused by self-coagulation of the sample