Titania Pigment Research Articles

Influence of dispersant functional group architecture on titania pigment particle interactions

Ensuring discrete dispersion of pigment particles is crucial to maintain their separation during processing and storage, and to achieve the desired properties in coatings. To facilitate dispersion and prevent aggregation, the stability of the dispersant along with the chemical interaction between pigment particles and dispersants is critical. This study was conducted to investigate the interaction between robust dispersants containing thermally stable carboxylate and phosphonate functional groups and the titania pigment surface at pH values experienced in pigment manufacturing as well as in application. The study found that the interaction depends on the type of group, the distribution density of the group, and the solution pH. Dispersant adsorption can occur under both alkaline and acidic solution conditions, with the adsorption density increasing when the pH is reduced or the carboxylate group density is increased. At pH 9.5, dispersant adsorption affinity and density is low, and hydrogen bonding occurs in addition to phosphate group chemisorption. At pH 5.5, both the adsorption affinity and density significantly increase due to electrostatic interactions between carboxylate and/or phosphonate groups and the pigment surface, combined with phosphate group driven chemisorption. Linear carboxylate-phosphonate copolymers and carboxylate dispersants present at the pigment surface provide electrostatic stabilisation while branched copolymers provide both electrostatic and steric stabilisation. The synergistic physical and chemical interaction combined with dispersion stability may lead to improved titania pigment suspensions using branched copolymer dispersants.

Effects of Na2CO3 on the carbothermic reduction and magnetic separation of ilmenite concentrate

Ilmenite concentrates are the raw material used for the production of titania pigment and metallic titanium. This work studies the effect of the addition of Na2CO3 in direct carbothermic reduction of ilmenite concentrate to enhance the separation of metallic iron from titanium components. The effects of temperature, Na2CO3 content and C/O molar ratio on the mineral phases, metallization degree of iron, and iron grain size of the reduced product are evaluated. The optimal conditions for the direct reduction of ilmenite concentrate are 1300 °C, a C/O molar ratio of 1.1, and 5 wt% Na2CO3. Under these optimal reduction conditions, the metallization of iron reaches the maximum of 96.8%, and the average iron grain size is 20.1 μm. After grinding and magnetic separation, the direct reduced iron product (magnetic component) contains 93.9 wt% of iron and 4.66 wt% of TiO2, with an iron recovery of 93.9%, while the non-magnetic product contains 69.9 wt% of TiO2 and 7.61 wt% of iron, with a TiO2 recovery of 93.5%. The results show that an appropriate amount of Na2CO3 effectively promotes the reduction of ilmenite. However, excessive Na2CO3 adversely affects ilmenite reduction. The phase transition patterns of Na2CO3 in the direct reduction of ilmenite is investigated.

Development of poly(butyl acrylate‐co‐oleic acid) as biobased polymeric dispersant and its application in preparation of pigment concentrate

AbstractIt is highly desirable to develop bio‐based products using sustainable materials and reduce dependence on petrochemicals. There are various reports on the use of sustainable materials in the synthesis of polymer resins, but research on the use of sustainable materials in development of coating additives such as polymeric dispersant is significantly lacking. Objective of this work is to produce fatty acid‐based polymeric dispersant using oleic acid in combination with butyl acrylate. The performance of the fatty acid‐based polymeric dispersant was benchmarked against commercially available and petrochemical‐based polymeric dispersant. The dispersants produced were characterized using spectroscopies (1H‐NMR and FTIR), thermal analyses (thermogravimetric analysis and differential scanning calorimetry), and molecular weight analysis. Application test was conducted to evaluate the effectiveness of the polymeric dispersant in titania pigment concentrate formulation which was tinted in nitrocellulose clear coating. Properties such as viscosity, fineness, gloss, optical properties, and storage stability were evaluated, and the result obtained shows that fatty acid‐based polymeric dispersant could disperse titania efficiently and produced coatings with good optical properties and excellent gloss retention. The carboxyl group from the incorporated fatty acid served as excellent pigment anchoring group, facilitating good orientation of dispersant on the pigment surface and promote excellent stability.

Stabilization and Dispersion of OSA Starch-Coated Titania Nanoparticles in Kappa-Carrageenan-Based Solution.

Titania is a white pigment used widely in papermaking, paints and cosmetic industries. Dispersion and stabilization of high concentration titania in water-based system remains a great bottleneck in industry nowadays, because aggregation of titania nanoparticles results in severe adverse effects to gloss, opacity, tint strength, color distribution and storage stability of end products. Because kappa-carrageenan (κ-CG) has excellent rheological properties such as emulsification, gelation, stability and so on, it has the ability to form gel and increase the viscosity of aqueous solution. In this work, Octenyl succinic anhydride (OSA) starch was utilized as wall material to encapsulate titania pigments using electrostatic spray drying processing. Transmission electron microscopy (TEM) showed that titania pigments were coated by OSA starch, with a final form of nanoparticle. Accelerating stability test found that around 60% OSA starch–titania particles were stably dispersed in κ-CG-based solution. All materials used in this work were natural ingredient, which would be preferred by cosmetic industry and consumers. The technique used in the present study could potentially be extended to other pigments for similar purpose.

Synthesis and color tuning of titanium oxide inorganic pigment by phase control and mixed-anion co-doping

B and N co-doped anatase, rutile, and brookite TiO2 (abbreviated as BN-Ana, BN-Rut, and BN-Bro) were successfully synthesized. The apparent color of as-obtain BN-Ana, BN-Rut and BN-Bro was red, cyan and yellow-green, respectively. The mechanisms of various coloring were concluded as the different band gap configurations and the formation of covalent B-N bonding. The nitridation time expressed less effect on changing the color. On the contrary, nitridation temperature enabled the distinct color changes by altering the brightness. Lower temperature, fewer doping concentration, and brighter apparent color, vice versa. Through tuning the brightness, a gradient of yellow-orange-red was achieved in the case of BN-Ana, as well the transitions of grey-to-cyan and white-to-pale-yellow were achieved in BN-Rut and BN-Bro, respectively. This research proposed a method for the synthesis of color-full titania pigment without the addition of other toxic transition metal elements.

Beneficiation of fluxed titaniferous slag to a marketable titania product using the modified upgraded slag process

ABSTRACT Smelting production of a limestone-fluxed titaniferous slag with low MgO content for subsequent beneficiation using the modified Upgraded Slag (UGS) process was investigated, with the aim of producing a marketable titania product. Smelting of titaniferous magnetite (titanomagnetite) with a carbon reductant and limestone flux was conducted in a water-cooled copper crucible in an iron-suscepting induction furnace under argon. The resulting titaniferous slag contained high residual iron (from the susceptor and incomplete iron reduction in the titanomagnetite), which caused crystallization of an ulvospinel. The slag was beneficiated using the modified UGS process, an industrial roast–leach process used for beneficiation of low-titania slag to a feedstock suitable for production of titania pigment. The upgraded product contained 90.5 mass% TiO2, with a recovery of 83%. Although the TiO2 grade met the feedstock specification for pigment production via the chloride route, SiO2, Al2O3, CaO, and Cr2O3 concentrations exceeded the specification and the particle size distribution was too fine.

Dispersion state of TiO2 pigment particles studied by ultra-small-angle X-ray scattering revealing dependence on dispersant but limited change during drying of paint coating

The dispersion state of titania (TiO2) pigment particles in coatings is crucial to obtain optimal optical properties while minimizing the consumption of pigment, and thereby the cost and environmental impact of the product. By having the particles well-dispersed, with limited aggregation, the best opacity can be obtained with the smallest amount of pigment. The aggregation of titania particles is typically investigated using various microscopy techniques on the dry coating. In this work, Small-Angle X-ray Scattering was applied as a non-invasive tool to probe the distribution of titania during the coating drying process. The titania pigment particles were dispersed by using either a polymeric surfactant or nanosized silica particles as dispersant. The use of silica nanoparticles resulted in the highest degree of dispersion, both in dilute suspension, and in acrylic and alkyd-based coating formulations. Only minor changes in the aggregate structure was observed during drying of the coatings, indicating that the optical performance is to a large extent determined already before drying, in the wet paint. For the formulations containing nanosilica dispersant, the drying time was increased by diluting the paint or by adding less dryer catalyst. The former resulted in a reduced pigment dispersion, whereas the latter seems to increase the degree of dispersion. In both cases, however, the change of dispersion during the drying phase remained minor.

Desilication of Highly Acidic Titanyl Chloride Solution for the Production of High-Purity Titania Pigment from a Spent Selective Catalytic Reduction Catalyst

Desilication of Highly Acidic Titanyl Chloride Solution for the Production of High-Purity Titania Pigment from a Spent Selective Catalytic Reduction Catalyst

Processing anatase ores for pigment production

Compared with processing high-TiO2 concentrates such as ilmenite ores, processing an anatase ore to achieve impurity levels acceptable for pigment production is more difficult because of the extensive number of accessory minerals present, the significant intergrowths between minerals and the fact that impurity elements may be distributed in several different minerals. In this paper, conditions applicable to processing anatase ores are reviewed with an aim of identifying conditions that may produce a suitable feedstock for processing to titania pigment by either the sulphate or chloride routes.Anatase ores containing 25–35 wt% TiO2 currently are processed using mineral dressing techniques of crushing and grinding, classification, magnetic separation and flotation to produce a concentrate with around 65 wt% TiO2. This concentrate is then typically upgraded to over 90 wt% TiO2 using combinations of heating and leaching treatments, often with the addition of a fluxing reagent to assist in impurity removal. The suitability of these products as a feedstock for the sulphate and chloride routes to pigment is discussed.

A spectroscopic method for quick evaluation of tint strength and tint tone of titania (rutile) pigment and factors affecting them

AbstractTitanium dioxide (TiO2) manufacturing industries measure optical properties such as brightness, colour, tint strength, tint tone, gloss, scatter coefficient, and others to ensure the quality of the product. Product characterization and process control generally focus on the optical properties, which determine its quality. In this work, titania rutile pigment with varying tint strength and tint tone is analyzed and a correlation is established between particle size and the optical properties such as tint strength and tint tone. It is observed that optical properties of titania pigment depends on the particle size as well as particle size distribution. A relatively faster evaluation of tint strength and tint tone can be made using the reflectance and particle size measurements. Analytical samples were prepared by ultrasonic dispersion of pigment in water containing calgon as dispersing agent. To verify the accuracy of the method, pigment tint strength and tint tone obtained from this study are compared with those resulting from traditional analysis. The results showed that the new method is viable.

Combined production of synthetic rutile in the sulfate TiO2 process

Abstract This paper describes a novel process for preparation of synthetic rutile using an intermediate, sulfated ilmenite from the sulfate TiO 2 process as the feedstock. The synthetic rutile can be obtained by selective thermal decomposition of the sulfated ilmenite, followed by targeted leaching for removal of various impurities. The results of the decomposition unit showed that almost all the TiOSO 4 in the sulfated ilmenite decomposed to TiO 2 , while the iron component mainly existed in the form of sulfates in the optimal thermal decomposition conditions, i.e., a roasting temperature of 540 ° C and a roasting time of 120 min under air flow or in stagnant air or a roasting temperature of 510 ° C and a roasting time of 120 min under nitrogen flow. The thermal decomposition can be divided into three stages. The sulfates of titanium and iron in the sulfated ilmenite were first decomposed to TiO 2 and water-insoluble FeOHSO 4 , respectively, at a temperature less than 500 ° C. The FeOHSO 4 was further converted into water-soluble Fe 2 O(SO 4 ) 2 at 500–560 ° C. Finally, the Fe 2 O(SO 4 ) 2 was decomposed to Fe 2 (SO 4 ) 3 and Fe 2 O 3 at a temperature above 560 ° C. The water-soluble metal sulfates, the water-insoluble FeOHSO 4 /Fe 2 O 3 and the SiO 2 in the TiO 2 -containing slag can be removed through leaching by using water, dilute sulfuric acid and sodium hydroxide, respectively. The results showed that 70–85% of the iron, as well as a majority of the magnesium, calcium, etc. impurities, could be leached by water, and up to 92% of the total iron could be removed after the subsequent acid leaching in a 15 wt% H 2 SO 4 solution, while the silicon removal reached 65% in a 5 wt% NaOH solution. A synthetic rutile with a TiO 2 content over 90 wt% and total MgO + CaO less than 1 wt% was obtained under the optimal conditions listed above. The present process can be integrated with the sulfate TiO 2 process, producing titania pigment and synthetic rutile simultaneously. The advantages of the TiO 2 beneficiation process include the moderate reaction conditions, the capability of recycling the H 2 SO 4 completely and the recovery of a large part of the iron, as well as comprehensive utilization of the waste sulfuric acid discharged from the sulfate TiO 2 production process.

Vacuum Carbothermic Reduction of Panzhihua Ilmenite Concentrate: A Thermodynamic Study

ABSTRACTElectric arc furnace is mainly used in the production of high titania slag; however, since impurities cannot be eliminated, this causes difficulty in the production of titania pigment with chlorination process. Consequently, removing impurities is the crucial way to deal with low-grade ilmenite, especially for the Panzhihua ilmenite concentrate in China. This article studied the theoretical calculation of vacuum carbothermic reduction of Panzhihua ilmenite concentrate. Thus, when the temperature was higher than 1600°C and the carbon amount was greater than 12%, all of the Fe almost entered into the gas phase. When the temperature was higher than 1300°C and the carbon amount was greater than 14%, magnesium also entered the gas phase. When the temperature was higher than 1100°C, most of the element manganese was volatilized in the gas phase. The TiO2 grade increased with the increase in carbon amount (14%). When the temperature was higher than 1600°C and the carbon amount was less than 14%, the TiO2 grade in the slag phase could reach the maximum value, which can be used for the chlorination process to prepare titanium dioxide.

Comprehensive utilization of Panzhihua ilmenite concentrate by vacuum carbothermic reduction

An electric arc furnace is mainly employed to produce high titania slag, although impurities could not be removed through this process, making the production of titania pigment through chlorination difficult. Removal of impurities is crucial to fully utilize low-grade ilmenite, especially the Panzhihua ilmenite concentrate obtained in China. This work proposes a new process to maximize Panzhihua titanium resources. Panzhihua ilmenite concentrate was reduced in a vacuum furnace, and residual slag and condensations were subsequently obtained. When the temperature exceeded 1500 °C and the carbon content exceeded 12%, Mg and Si impurities were removed, entered the gas phase, and formed ferrosilicon alloy. Finally, high-grade titania slag was obtained.

Use of Ultrasound in the Washing Process of Titania Pigment Production: Water Saving and Process Optimization

Washing of metatitanic acid (H2TiO3) consumes a large amount of water during the production of titanium dioxide (TiO2) by the sulfate process. In this work, ultrasound technology is used for the pretreatment of a metatitanic acid slurry before washing. The water consumptions of washing process are compared in the absence and presence of ultrasound treatment. The effects of wash liquor properties, ultrasound time, and ultrasound power on removal of iron impurities are investigated. The washed product was characterized by X-ray diffraction, scanning electron microscopy, and particle size distribution. The effects of ultrasound on the crystal structure of TiO2 and the mechanism of water saving are discussed. The results show that better removal of iron impurities from metatitanic acid is achieved using ultrasound. The saving wash liquor when using ultrasound was 93 mL for washing a 100 mL metatitanic acid slurry when using a pH 2 wash liquor, ultrasonic time of 30 min, and 185 W ultrasonic power. The average particle size was reduced from 2.11 to 1.02 µm, which improves washing performance. The crystal lattice parameters of TiO2 exhibited no effect on rutile type or quality of product.

Influence of the seed layer on photoactivity inhibition of mica–titania pigments

The influence of the seed layer on the phase composition and photoactivity inhibition of mica–titania pigments was investigated. The prior deposition of MnO2 or SnO2 as a seed layer resulted in a complete rutile TiO2 coating without calcinations, while the prior deposition of ZnO led to a mixture of anatase and rutile. The rutile promoting effect of MnO2 and SnO2 could be ascribed to the small lattice mismatch (＜5%) between the seed layer and the rutile TiO2. Moreover, the seed layer had a great influence on the photoactivity inhibition of mica–titania pigments. A seed layer of MnO2 inhibited the photoactivity of the pigments, whereas a seed layer of SnO2 or ZnO enhanced the photoactivity of the pigments. The degradation rate constant of mica–MnO2–TiO2 was approximately 72.7% that of mica–TiO2, while the degradation rate constant of mica–SnO2–TiO2 was approximately 4.5 times as high as that of mica–TiO2. The influence of the seed layer on the photoactivity of mica–titania pigments depended on the transfer process of electron–hole pairs between the seed layer and TiO2.

Multiphase simulation of mine waters and aqueous leaching processes

Managing of large amounts of water in mining and mineral processing sites remains a concern in both actively operated and closed mining areas. When the mining site with its metal or concentrate producing units is operational, the challenge is to find either ways for economical processing with maximum yields, while minimizing the environmental impact of the water usage and waste salt treatments. For safe closure of the site, the environmental control of possible drainage will be needed. For both challenges, the present-day multiphase process simulations tools can be used to provide improved accuracy and better economy in controlling the smooth and environmentally sound operation of the plant. One of the pioneering studies in using the multiphase thermodynamic software in simulation of hydrometallurgical processes was that of Koukkari et al. [1]. The study covered the use of Solgasmix equilibrium software for a number of practical acid digesters. The models were made for sulfuric acid treatments in titania pigment production and in NPK fertilizer manufacturing. During the past two decades the extensive data assessment has taken place particularly in geochemistry and a new versions of geochemical multiphase equilibrium software has been developed. On the other hand, there has been some progress in development of the process simulation software in all the aforementioned fields. Thus, the thermodynamic simulation has become a tool of great importance in development of hydrometallurgical processes. The presentation will cover three example cases of either true pilot or industrial systems including a South African acid mine water drainage treatment, hydrometallurgical extraction of rare earths from uranium leachate in Russia and a multistage process simulation of a Finnish heap leaching mine with its subsequent water treatment system.

Diffusion process of an ink drop in core–shell silica–titania pigment particles

Recording coatings have been successfully prepared by the core–shell structural silica–titanium dioxide particles, which were synthesized using sol–gel methods and fabricated as a close-packed colloidal crystalline array. The size of the nano-silica particles (50–100nm) was controlled via varying the concentration of ammonium hydroxide. The silica spheres coated with titania (core–shell structure) were prepared by a self-assembly coating deposition process. Transmission electron microscopy and scanning electron microscopy were used to analyze the microstructure of the core/shell composite particles. X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy were used to analyze the molecular structure of the composite particles and the formation of the chemical bonds (Ti–O and Ti–O–Si) on the shell surface. The prepared composite pigment particles were applied in recording materials. The diffusion process of the ink drop on the surface of the recording materials was studied by the edge detection method. We also investigated the role of the ink drop in the diffusion process of the different composite pigment particle.

The fate of chromium impurities during acid sulphate digestion of ilmenite concentrates

Ilmenite concentrates from the Murray Basin region of southeastern Australia are contaminated with chromium impurities that must be removed for the ilmenite to become a satisfactory feedstock for the sulphate route to titania pigment production. The chromia is present primarily as discrete, compositionally variable, chrome-rich spinel grains with a smaller amount as intra-grain chromia distributed as coatings in fractures and pores of weathered ilmenite grains. Characterisation of chromia deportment through a simulated acid sulphate digestion process showed a small but non-negligible solubility of the spinels. Most spinels were resistant to dissolution with the exception of those containing high Fe(Al,Cr)2O4 and magnetite (Fe3O4) components. Intra grain chromia was highly soluble. Processing to achieve low bulk chromia using a magnetising roast procedure must ensure that well crystallised rutile is not produced because of its insolubility in the sulphate process. It is also important that the roast conditions do not substantially increase the magnetite content of the spinels making them more susceptible to dissolution. This work highlights the importance of characterising all spinel composition types within ilmenite concentrates in addition to the level of intra-grain chromia associated with the ilmenite when considering the suitability of Murray Basin primary ilmenites as a feedstock to sulphate route titania pigment plants.

Solar spectral optical properties of rutile TiO2 coated mica–titania pigments

Different shaped rutile TiO2 coated mica–titania pigments were prepared by hydrolysis of TiCl4 ethanolic solution at 70 °C. SnO2 as a rutile promoting additive was deposited onto mica prior to TiO2. The use of TiCl4 played a crucial role in controlling the morphology of rutile TiO2 coatings. Monodisperse nanoneedles were assembled into nanoflowers with an increasing particle size as the TiO2 loading increased. A possible crystal growth mechanism of rutile TiO2 with rich nanostructures was proposed. The obtained rutile samples showed stronger ultraviolet shielding ability and higher near-infrared reflectance property than that of anatase sample. What's more, the rutile TiO2 coating with smaller particle size possessed higher reflectance in the region of 1300–2500 nm in accordance with the Kubelka–Munk theory. The near-infrared solar reflectance of the rutile TiO2 coated mica–titania pigment was as high as 97%, making them good candidates for solar reflective pigments.

Stability of sodium polyphosphate dispersants in mineral processing applications

Polyphosphates are commonly used industrially to provide electrostatic stabilisation to mineral and material suspensions. Polyphosphate solutions however have shown instability under processing conditions such as high temperature and acidic pH which may lead to a reduction in dispersion properties when added to mineral or material suspensions.In this study the influence of pH, temperature and divalent cation concentration pre-treatment on polyphosphate dispersion properties is reported. Dispersion properties are determined using rheological suspension analysis. The suspensions investigated are material-based model systems of titania pigment and high purity boehmite. Infrared spectroscopy studies of polyphosphate solutions were undertaken to directly investigate the polyphosphate structure after pre-treatment. The rheological measurements show reduced polyphosphate dispersion properties with reduced pH, increased temperature and at high calcium concentrations which correlate with directly measured and reported changes in the polyphosphate structure. When pH, temperature and high divalent cation concentrations are combined, the synergistic effect on reduced polyphosphate dispersion performance is particularly prominent.