Titanium Dioxide Suspensions Research Articles

Viscosity of aqueous suspensions of titanium dioxide (anatase) nano-particles

Viscosity of aqueous suspensions of titanium dioxide (anatase) nano-particles

Optimization of the color masking and coating unit operations for microencapsulating ferrous fumarate for double fortification of salt

A new coating formulation was developed to eliminate the factor that caused black spots on the iron premix surface, used for making Double Fortified Salt. The formulation is a suspension of titanium dioxide in soy stearin, prepared with ethanol and dichloromethane and applied with a glass sprayer and pan coater. 0–20% w/w titanium dioxide was suspended in 10% w/w soy stearin/hydroxypropyl methylcellulose. Coating with a suspension of 15% w/w TiO2 in 10% w/w soy stearin ensured that all the TiO2 adheres to the premix surface, giving no chance for the recycling of iron contaminated TiO2, which caused the black spot. The new coating formulation ensured that over 90% iodine in Double Fortified Salt was retained after 6 months at 45 °C, 60–70% RH. The whiteness of the premix (L* = 86.4) matched the Double Fortified Salt whiteness (L* = 86.8). Thus, making the new coating method as effective as the previous in desirable characteristics. More so, the new coating method simplifies the existing method by merging the previous color masking, and double coating steps into one step.

A combined model for describing the trans-membrane pressure (P) variation in constant flux dead-end microfiltration (MF) process

In present paper, a constant flux model was established by dividing the trans-membrane pressure (P) into the partial pressure of the membrane layer (Pm) (originating from the pore blocking/shrinking resistance of the membrane and the inherent membrane resistance) and the cake layer (Pc) (originating from the resistance of the deposited cake layer) in constant flux dead-end filtration process with complex fouling mechanism. The pore resistance (Rp) and the available membrane area ratio (A/A0) were determinated by using Hagen-Poiseuille law. In addition, the variations of model parameters (Km, Kp, Kc and K) in the filtration process before and after hydraulic/ultrasonic cleaning process were also discussed. Results showed that the model predictions had good agreements with experimental data at different conditions by using Bovine Serum Albumin (BSA) (R2 =0.99), Humic acid (HA) (R2 = 0.99), Sodium Alginate (SA) solutions (R2 =0.99) and activated sludge (R2 =0.99), kaolin (R2 =0.99) and titanium dioxide suspensions (R2 =0.99). Meanwhile, the available membrane area ratio decreased in the initial stage (pore blocking/shrinking and cake filtration) and keep constant in the following stage (cake filtration). Moreover, the variation of available membrane area ratio before and after hydraulic/ultrasonic cleaning process can be give a guidance to optimize the membrane cleaning process.

Diafiltration of Highly Concentrated Suspensions with Fine Particles by Dynamic Disk Filtration

AbstractA method for washing highly concentrated suspensions with fine particles by using a filter with overlapping disks was studied. For the experiments, alumina and titanium dioxide suspensions were used. It was demonstrated that the used suspensions have non‐Newtonian behavior. The viscosity is influenced by the type of particle system, the solid concentration, and the shear rate. The washing process is operated in a discontinuous and a continuous way. The rotation of the disks and the shear flow across their surface prevents the formation of a filter cake and facilitates the handling of suspensions. The shear stresses at the filter disk and the rheology of the processed suspensions are both influenced by the type of particle system, the solid concentration, and the process parameters.

The Reuse of Industrial By-Products for the Synthesis of Innovative Porous Materials, with the Aim to Improve Urban Air Quality

This works concerns the characterization and the evaluation of adsorption capability of innovative porous materials synthesized by using alginates and different industrial by-products: silica fume and bottom ash. Hydrogen peroxide was used as pore former to generate a porosity able to trap particulate matter (PM). These new materials are compared with the reference recently proposed porous SUNSPACE hybrid material, which was obtained in a similar process, by using silica fume. Structural, morphological, colorimetric and porosimetric analyses were performed to evaluate the differences between the obtained SUNSPACE typologies. The sustainability of the proposed materials was evaluated in terms of the Embodied Energy and Carbon Footprint to quantify the benefits of industrial by-products reuse. Adsorption tests were also performed to compare the ability of samples to trap PM. For this aim, titania suspension, with particles size about 300 nm, was used to simulate PM in the nanoparticle range. The results show that the material realized with bottom ash has the best performance.

Population Balance Application in TiO2 Particle Deagglomeration Process Modeling

The deagglomeration of titanium-dioxide powder in water suspension performed in a stirring tank was investigated. Owing to the widespread applications of the deagglomeration process and titanium dioxide powder, new, more efficient devices and methods of predicting the process result are highly needed. A brief literature review of the application process, the device used, and process mechanism is presented herein. In the experiments, deagglomeration of the titanium dioxide suspension was performed. The change in particle size distribution in time was investigated for different impeller geometries and rotational speeds. The modification of impeller geometry allowed the improvement of the process of solid particle breakage. In the modelling part, numerical simulations of the chosen impeller geometries were performed using computational-fluid-dynamics (CFD) methods whereby the flow field, hydrodynamic stresses, and other useful parameters were calculated. Finally, based on the simulation results, the population-balance with a mechanistic model of suspension flow was developed. Model predictions of the change in particle size showed good agreement with the experimental data. Using the presented method in the process design allowed the prediction of the product size and the comparison of the efficiency of different impeller geometries.

Melia azedarach Activated Carbon and its novel TiO2 Nanocomposite for Chemisorption and Photodecoloration of Reactive Orange 16: Isotherm and Kinetic Modeling

Background: Bulk generated textile wastewater loaded with dyes is posing a stern threat to aquatic health, especially when dumped without prior treatment. Lignocellulosic waste based activated carbon (AC) and Titania (TiO2) suspension can constitute the emerging technological solution. Objectives: Best lignocellulosic precursor biomass, Melia azedarach (Darek sawdust - DSD), was selected for ortho-phosphoric acid impregnated AC production and novel AC-DSD-TiO2 nanocomposite was developed. AC-DSD and AC-DSD-TiO2 nanocomposites were employed for reactive orange 16 (RO16) dye adsorption in batch and decoloration in photocatalytic reactors, respectively. Methods: Materials were characterized by Scanning electron microscope (SEM), energy dispersion X-ray (EDX) spectroscopy and Fourier transform infrared spectroscopy (FTIR). For AC-DSD production, the raw powdered biomass of DSD impregnated (value = 2) with H3PO4 at room temperature and after shaking, was placed in a muffle furnace at 100°C for 12 h in glass tubes and subsequently carbonized at a high temperature of 400°C for 30 min. Batch reactor parameters for the ACDSD- RO16 system were optimized as a function of contact time, adsorbent dose, temperature, initial dye concentration and pH. For AC-DSD-TiO2 nanocomposite synthesis, AC-DSD and TiO2 paste was dried in the furnace at 90°C and calcined at 300°C and stored in a desiccator. Results: AC-DSD exhibited RO16 adsorption capacity of 92.84 mg/g. The experimental data were best described by Langmuir and Dubinin-Radushkevich isotherms with high R2 of 0.9995 and 0.9895 and closeness of predicted adsorption capacities of 94.15 and 88.58 mg/g respectively. This determines the chemisorption nature for RO16 adsorption onto AC-DSD. The experimental data was well explained by the pseudo-second order kinetic model. Thermodynamic parameters also suggest the endothermic, chemisorption and spontaneous adsorption reaction. Photocatalytic studies of novel AC-DSD-TiO2 revealed the higher Kc = 0.1833 value over Kad= 0.0572. Conclusions: Melia azedarach AC-DSD and its novel AC-DSD-TiO2 nanocomposite prove that these materials could provide an optimal solution for treating textile dye solutions effectively as the good adsorbent and photocatalyst.

A novel suspension transport method: Viscoplastic lubrication of high-density fluids

We present proof-of-concept experiments to illustrate the application of viscoplastic lubrication in transport of high-concentration suspensions. The proposed transport method appears robust for a wide range of suspension concentrations. We develop a theoretical description of the flow that incorporates the significant density difference between the suspension and the lubricating fluid. We explore the variation of the pressure gradient and the flow rate ratio with fluid properties and demonstrate that buoyancy effects expand the favorable lubrication regime within the phase space of the problem. We illustrate the possibility of flow reversal in the core fluid and the emergence of a new flow regime, two features not captured when buoyancy stresses are neglected. • Viscoplastic lubrication of suspensions is proposed as a method to enhance transport. • Proof-of-concept experiments show transport of titania suspension with concentration 30–70 wt%. • Theoretical estimates of the flow field are developed to reveal buoyancy effects. • When buoyancy is sufficiently strong, flow reversal is observed in the core fluid. • Buoyancy can augment the favorable lubrication regime.

Box-Wilson design modeling of photocatalytic degradation of industrial dye and wastewater in semi-pilot solar photoreactor

This work focuses on the treatment of a dye solution, C.I. Basic Blue 41 (BB41), and industrial wastewater by UV/TiO2 photocatalytic process using aqueous catalyst suspensions of titanium dioxide (TiO2), Degussa P25. The procedures were carried out in a semi-pilot scale prototype solar photoreactor under solar radiation. Response surface methodology (RSM) based on Box-Wilson design was applied to assess individual effects of the five main independent parameters: initial dye concentration ([BB41]), TiO2 concentration ([TiO2]), flow rate (Q) initial pH and accumulated solar energy (Qvn) on the decolorization efficiency and to optimise the UV/TiO2 process. Photocatalytic mineralisation was carried out at the optimal conditions found by RSM and results were evaluated by total organic carbon (TOC) abatement for BB41 sloution and industrial wastewater. The optimal conditions found by RSM were: 0.4 g/L, 14.04 mg/L, 1,479.6 L/h, 5.52 and 80 KJ/L for TiO2 concentration, initial dye concentration, flow rate, initial pH and accumulated solar energy, respectively. Photocatalytic mineralisation results show that for accumulated visible solar energy equal to 377.714 kJ/L (after 6 hours of irradiation), under these conditions, the percentage of the initial TOC reduction is about 88% and 85.5% for industrial waste and BB41 solution, respectively.

Development of Titanium Dioxide Suspension Utilizing Reversible Dispersion Flocculation Control and its Application to Inkjet

Development of Titanium Dioxide Suspension Utilizing Reversible Dispersion Flocculation Control and its Application to Inkjet

Surface modification of titania nanoparticles by catechol derivative molecules: Preparation of concentrated suspensions

This work focused on the preparation of high solid content suspension from nanosized TiO2 P25 (about 30 nm). Two derivative catechol molecules (Tiron and Dopamine), were used as dispersants to enhance the colloidal stability of the prepared suspensions. Dopamine is a positively charged molecule which was used for the first time as dispersing agent and compared to Tiron, a negatively charged molecule. The effect of the pH and the dispersant percentage on the hydrodynamic size as well as on the surface chemistry of titania was studied in diluted suspension, using dynamic light scattering (DLS) and zeta potential measurements (acoustophoresis). Tiron and Dopamine adsorptions on titania surface were investigated using UV–vis spectrometry and thermogravimetric analyses (TGA). It was illustrated, from the rheological behavior, that Tiron and Dopamine decrease dramatically the viscosity of highly concentrated titania suspensions and allow to reach up to 15 vol% and 20 vol% for dopamine and tiron-modified titania suspensions.

The hydration effect of singly charged ions on the electrosurface properties of titanium dioxide aqueous suspensions

The effect of ordering/disordering degree of water molecules in the vicinity of singly charged cations (Li+, Na+, K+, Rb+, Cs+) and anions (F−, Cl−, Br−, I−) on the electrosurface properties of aqueous suspensions of rutile-type titanium dioxide is discussed. The influence of mentioned ions presence on the position of the isoelectric point, which is one of the integral estimates of the suspensions electrosurface properties was examined. It was accepted that displacement of the isoelectric point is caused by different binding of cations and anions to the titanium dioxide surface. The magnitude of this displacement estimates the relative binding of cations and anions to the surface, which depends on the ordering/disordering degree of water molecules. The dependences were found to have a maximum and a minimum in the case of cations and anions, respectively. The extreme values were determined when the water molecules structure in the vicinity of ions was undisturbed and corresponded to the structure of bulk water. The results obtained are relevant for highly dispersed systems, for which it is important to maintain a stable electrolyte balance and to avoid a significant redistribution of ions between their bulk and surface parts.

Contribution to the Physical Stability Study of Compounded Medications Based on Zinc Oxide, Titanium Dioxide and Precipitated Sulfur Using Emulsified Solid Fats as Vehicles

Background: This investigation evaluated the physical stability of zinc oxide, precipitated sulfur and titanium dioxide suspensions using three solid fats as emulsified vehicles: stearyl alcohol, stearic acid and beeswax. Method: Varying the concentration of solid fat (2%, 4%, 6%) and the agitation speed for the preparation of the emulsified vehicle (250, 500 and 750 rpm). Here 81 suspensions were prepared, 27 for each solid fat used. The apparent viscosity was measured using a Brookfield RVTD rotational viscometer. The selection of revolutions per minute and spindle used in the viscometer was carried out taking into account the need to obtain a reading in the instrument greater than 10.0, in accordance with the recommendation of the equipment manufacturer. The sediment volume was measured using identical graduated bottles. Results: The effects that were studied as indicators of the physical stability of the suspensions were: sediment volume, apparent viscosity and ease of resuspension. This analysis indicated that the selection of the solid fat is a parameter significantly influential, which supports the data obtained through the investigation. Higher sediment volumes were obtained by increasing the concentration of the emulsified fat and increasing the speed of agitation, favoring thixotropic behavior in suspensions. Conclusion: In terms of physical stability and ease of resuspension, the best results were obtained when emulsified stearyl alcohol was used as a vehicle.

One-step, in situ jamming point measurements by immobilization cell rheometry

Dense colloidal suspensions are processed in a wide variety of industries. Challenges for pumping suspensions and slurries at high concentrations include shear thickening and dilation, which can have deleterious consequences. These systems are shear sensitive close to the jamming point, meaning that a significant increase in high shear viscosity can be observed with just a few percent change in volume fractions. Therefore, accurate and rapid determination of the jamming point can greatly aid formulation. Typically, conventional rheometry identifies the jamming point by a time-consuming process, whereby multiple flow curves of suspensions of different volume fraction are measured and extrapolated to the volume fraction where the viscosity diverges. We present an alternative approach for rapid, one-step, experimental determination of the jamming point for aqueous suspensions. The procedure monitors the shear stress under constant shear stress or shear rate as the sample is dewatered using immobilization cell rheometry, until the viscosity diverges. The method is validated by comparing the results of this work with conventional rheometry for a model suspension. Then it is applied to examine the effect of grafting a short-chain polymer to particles, comprising an industrial suspension of silica-coated titania. Polymeric coating of the particles increases the jamming concentration and mitigates shear thickening, qualitatively consistent with predictions from simulations.

Microscale structure designing of nanoparticle-based photocatalyst films for enhanced functionalities and efficient energy utilization

Photocatalysts have increasingly become important materials to utilize renewable solar energy for decomposing pollutants, producing clean water, achieving self-cleaning surface, and so on. Therefore, it is desirable to expand the applications of photocatalysts by enhancing the functionalities and allowing ample design flexibility. Here the potential of nanoparticle-based photocatalyst films with microscale surface structures was investigated in order to enhance their useful functionalities. Photocatalyst films with microscale surface structures were prepared using the suspension of titanium dioxide (TiO2) nanoparticles. The micro-scale structural features of prepared films were evaluated using a scanning electron microscope. Also, an atomic force microscope (AFM) was used. The AFM analysis of a film consisting of nanoparticle spherical aggregates revealed a surface profile of subwavelength surface structure. Then the optical and wetting characteristics were investigated. It was found that the visible-light transmittance increased due to subwavelength surface structures and that the microstructured TiO2 films exhibited the contact angles below 10 degrees, i.e., superhydrophilic behavior, without ultraviolet-light illumination. On the basis of the presented results, it was suggested that the microscale surface structures of photocatalyst film can be designed to achieve enhanced functionalities. It is expected to effectively utilize the energy of sunlight in many applications using functional photocatalyst films with optimized design.

Flocculation of Titanium Dioxide with Functionalized Citrus Pectin

Modified polysaccharides were prepared by the reaction of citrus pectin with a cationic monomer, (1,2-epoxypropyl)triethylammonium chloride, in alkaline medium and under the action of microwave radiation in the reactor system microwave–ultrasonic–UV-induced synthesis. Organic hybrids were prepared by mixing aqueous solutions of natural polysaccharides (pectin and modified pectin with chitosan) under ambient conditions in 1 : 1 ratio. The influence of the concentration of citrus pectin, its modified samples, chitosan, and their organic hybrids on the flocculating properties was studied for a model disperse system, a suspension of titanium dioxide in water and aqueous salt solutions, under the conditions of free (unrestricted) sedimentation. The influence of the ionic strength on the conformational state of polysaccharide macromolecules and on the aggregation of titanium dioxide particles was analyzed.

Study of the Suspension Stability of Titanium Dioxide of Anatase Modification for Self-Purifying Fine Concrete

The suspension stability of the titanium dioxide of anatase modification, obtained by ultrasonic dispersion (USD) at the ultrasound frequency of 35 kHz in the aqueous medium of the stabilizer for self-purifying fine concrete as a finishing material for building envelope, is studied. The extreme dependence of the zeta potential on the ultrasonic dispersion parameters of titanium dioxide in the aqueous medium of the surfactant on the basis of sodium salts of naphthalene sulfonic acid and formaldehyde condensation products is established. Various variants of the sequence of the surfactant introduction into the titanium dioxide suspension are analysed. The ratio between TiO2 and the stabilizer, at which the zeta potential exceeds the threshold value of 30 mV and the suspension stability is maintained during 15 days, is determined. The optimal sequence of the suspension components introduction and the ultrasonic dispersion time are established. The influence mechanism of intermittent surfactant introduction on stabilization of the suspension of titanium dioxide of anatase modification is offered. The dependences of the fine concrete strength on zeta potential of the studied suspensions are obtained.

Photocatalytic degradation of rolling emulsion wastewater over titanium dioxide suspensions

Photocatalytic degradation of rolling emulsion wastewater over titanium dioxide suspensions

The influence of methods of suspension preparation on the redispersion degree of titanium dioxide powder

The redispersion of titanium dioxide powder during the preparation of its aqueous suspensions by mechanical stirring has been considered. The model of the destruction of the spatial structure of powders, which exists in the air, during the preparation of its [titanium dioxide] aqueous suspensions is based on the process of gradual withdrawal of the peripheral particles from the compositional parts most closely associated with it and the establishment of the equilibrium: aggregates <=> primary particles. Following the introduction of air-aggregated powders into the liquid environment, the following physicochemical processes occur, namely: a) the redispersion of the powder particles due to the action of mechanical forces during the stirring of suspensions (destruction of aggregates existing in air); b) the interaction of the components of the liquid medium, in particular hydrogen ions, ions of low molecular weight electrolytes, surfactant molecules with the surface groups of solid particles and the establishment of a new interfacial equilibrium; c) interparticle interaction related to the change in the balance of far-reaching surface forces due to the establishment of a new interphase equilibrium. Five methods for preparing suspensions of titanium dioxide have been used to show that during their preparation, agglomerates of primary particles containing regions of closed air, the size of which depends on the ratio of the intensity of successive processes of fluid flow over the surface of the powder and the formation of areas of closed air and fluid percolation in the formed area of closed air, may occur. The appearance of such agglomerates complicates interparticle interaction and affects the degree of redispersion of powders in liquids. It has been revealed that the presence of surfactants in suspensions causes changes both in the interparticle interaction and in the occurrence of regions of closed air in the intermediate particle agglomerates. Thus, the equilibrium dispersive characteristics of the obtained highly dispersed systems depend on the ratio of the intensity of such processes as the fluid flowing over the surface of the powders and the formation of areas of closed air and subsequent percolation of fluid in the area of closed air. However, it should be borne in mind that the role of these processes depends on the dispersion of the primary particles and their spatial structure in the air, i.e. the whole pre-history of how these powders have been manufactured. Keywords : water suspension, interparticle interaction, powders aggregation, titanium dioxide.

Photocatalytic Degradation of Rolling Emulsion Wastewater over Titanium dioxide Suspensions

Photocatalytic Degradation of Rolling Emulsion Wastewater over Titanium dioxide Suspensions