Kinetics of adsorption of oxalic acid on different titanium dioxide samples

FTIR-ATR kinetic studies on the adsorption of oxalic acid on different TiO(2) films were performed. The particulate films were obtained through the evaporation of TiO(2) suspensions. The evolution of the IR bands followed a pseudo-first-order behavior, as previously observed. Systematic studies as a function of the oxalic acid concentration afforded the specific rate constant for adsorption (k(a)) and desorption (k(d)). The influence of physical parameters of the samples, i.e., specific BET area, crystalline domain size, TiO(2) load, film area, and pore size, on the kinetic parameters k(a) and k(d) was analyzed. A mechanism in which the adsorption and desorption processes are controlled by the diffusion through the pores of the films is proposed (intraparticle diffusion). It is concluded that all the samples behave in the same way. Thicker films or those with smaller particle size (higher specific surface area, smaller pores) show the slowest rates of adsorption and desorption. These results are relevant for the design of efficient heterogeneous catalysts and sensors, and for the interpretation of pollutant adsorption.     

Carbon dioxide production in the oscillating Belousov—Zhabotinsky reaction with oxalic acid

A new volumetric method for monitoring the oscillating Belousov—Zhabotinsky reaction with oxalic acid is described. While an oscillatory behavior in the potential of the Pt redox electrode at slow stirring without inert gas bubbling can be observed, a monotonous, nonoscillatory course was found both at the slow and rapid stirring rates for the carbon dioxide evolution. Possible reasons for such observations are discussed.     

Improving titanium dioxide dispersion in water through surface functionalization by a dicarboxylic acid

In this work, we show evidence of improving the dispersion of titanium dioxide particles in water. This is observed in the titanium dioxide-water colloid by the shear-thinning flow behavior in rheological measurements induced by the functionalization of a glutaric acid layer on the surface of titanium dioxide particles. The characterization of the layer was achieved by using infrared spectroscopy and ^13?C nuclear magnetic resonance. Rheological measurements corroborated that functionalization of TiO₂ particles decreases the rheological properties such as viscosity measurements at a constant shear rate in two orders of magnitude compared with the pure TiO₂ in suspensions. We present the results as a novel strategy to limit the formation of agglomerates in these colloidal suspensions, and this will be of great use in applications in the paints field and printing technologies.     

Adsorption of tricarboxylic acid biosurfactant derived from spiculisporic acid on titanium dioxide surface

In the present study, adsorption isotherms of a polycarboxylic-acid-type biosurfantant, the sodium salt of (2-(2-carboxyethyl)-3-decyl maleic anhydride) (DCMA-3Na), on TiO₂, zeta potential, and changes in particle aggregate size as a function of biosurfactant concentration, solid-liquid ratio and pH were systematically investigated. The adsorption of DCMA-3Na on the surface of TiO₂ shows a relatively weak dependence on pH, unlike the adsorption behavior of chemically-synthesized surfactants. Adsorption of DCMA-3Na still occurs at pH above the isoelectric points of TiO₂ due to the buffering capacity, which is due to three carboxylate functional groups in the hydrophilic moiety of DCMA-3Na. Since DCMA-3Na has three anionic head groups, the zeta potential of TiO₂ at pH 3 decreases very steeply from positive to negative values as the surface charges are neutralized by the adsorption of biosurfactants. Trends in zeta potentials as a function of equilibrium DCMA-3Na concentration are quite closely related to the changes in flocculation of individual TiO₂ particles.     

Transesterification of oxalic acid esters

Conclusions Transesterification of some lower oxalate esters with alcohols in the presence of acidic or basic catalysts gave the corresponding higher esters in good yield.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 5, pp. 1102–1105, May, 1968.     

钛白废酸低温除杂浓缩的研究

钛白粉是一种白色颜料,其主要成分为二氧化钛(TiO_2),是一种重要的无机化工产品.其生产工艺有硫酸盐工艺和氯化物工艺两种,硫酸盐法的技术比氯化物法简单,可以用于品位低和比较便宜的矿物~([1]).     

利用盐酸法钛白废液制备铁黄颜料研究

氧化铁黄又称羟基铁,简称铁黄,化学式为α-FeOOH,具有良好的耐光性、耐大气性和耐碱性。较其他黄色颜料的遮盖力高,着色力也强。广泛地用于橡胶制品、油漆、塑料、油墨、药片糖衣等的着色,也是人造大理石、水磨石地面、铺路砖、墙面粉饰等的着色剂[1]。四川省自贡市金红石厂以3     

Adsorption of polymethacrylic acid from aqueous solutions on disperse titanium dioxide

The state of macromolecules of polymethacrylic acid adsorbed on the surface of disperse titanium dioxide was assessed using a combination of the differential concentration approach to the determination of adsorption and methods for determining the size of disperse adsorbents by dynamic light scattering and sedimentation analysis in the field of centrifugal forces. Three sections were found on the isotherm of adsorption: in the first, isolated islands of adsorbed macromolecules formed; in the second, layers of macromolecules with a different degree of deformation were observed; in the third, determining the adsorption of macromolecules is complicated by other accompanying processes, and assessing the state of macromolecules in the adsorption layer becomes difficult.     

Photo-oxidation of alcohols catalysed by platinised titanium dioxide

Irradiation of alcohols in benzene in the presence of platinised titanium dioxide provides a clean and convenient procedure for the synthesis of aldehydes and ketones on preparative scale.     

Enhancement of titanium dioxide photocatalysis by water-soluble fullerenes

Fullerenes are known for their unique electronic properties including high electron affinity. Although use of fullerenes for scavenging photo-generated electrons from titanium dioxide particles has been demonstrated, no attempts have been made to utilize the unique properties of fullerenes to increase the efficacy of photocatalysis. The present study has demonstrated that a mixture of water-soluble polyhydroxy fullerenes (PHF) and titanium dioxide (anatase polymorph) enhances photocatalytic degradation of organic dye. The PHF molecules adsorbed to the surface of titanium dioxide due to electrostatic forces, with adsorption density being higher at lower pH values. The surface coverage of titanium dioxide nanoparticles by PHF molecules determined the extent of enhancement, with an optimum dosed weight ratio of PHF to titanium dioxide at 0.001. Hydroxylation and concomitant solubilization of fullerenes allow their unique electronic properties to be harnessed for photocatalysis.     

Decomposition of oxalic acid with nitric acid

Oxalic acid or oxalate is widely used as a precipitant and a detergent in the field of nuclear energy. The present work aimed at developing a method of decomposing oxalic acid with HNO₃ in the presence of Mn²⁺ ion. The use of Mn²⁺ ion as low as 10^?3 mol/l facilitated the complete decomposition of oxalic acid, and the acidity of the resulting solution became as low as 0.1 eq/1 under the optimum conditions. The decomposition of oxalic acid is a first order reaction and proceeds at temperatures above 80°C; the activation energy of the reaction is 18.6 kcal/mol. This decomposition method is applicable to the dissolution of an oxalate precipitate.     

Visible light absorption by various titanium dioxide specimens

A set of heat-induced and photoinduced absorption spectra of various compositions of Degussa P25 TiO2 and different polymers has been examined. The spectra are described as the sum of overlapping absorption bands (ABs) with maxima at 2.90 eV (427 nm, AB1), 2.55 eV (486 nm, AB2), and 2.05 eV (604 nm, AB3); the spectra correlate entirely with the experimentally observed absorption spectra after the reduction of TiO2. Absorption spectra of visible-light-active TiO2 photocatalysts reported recently in the literature have also been analyzed. Relatively narrow absorption spectra are very similar and independent of the method of photocatalyst preparation. The average absorption spectrum can be described reasonably well by the sum of the two absorption bands AB1 and AB2. It is argued that visible light activation of TiO2 specimens (anion-doped or otherwise) implicates defects associated with oxygen vacancies that give rise to color centers displaying these absorption bands and not to a narrowing of the original band gap of TiO2 (EBG approximately 3.2 eV, anatase) through mixing of dopant and oxygen states, as has been suggested recently in the literature.     

Adsorption of cadmium(II) on humic acid coated titanium dioxide

The rapid increase in nanotechnology has led to growing concerns on environmental effects and health risks of nanoparticles (NPs). Many studies investigated the adsorption of toxic pollutants on NPs; however, the interaction between heavy metals and natural organic matter (NOM) coated metal oxide NPs was scarcely studied. In this study, using humic acid (HA) as model NOM, the adsorption of Cd(II) on humic acid coated titanium dioxide (HA-TiO(2)) NPs was investigated. Solution parameters such as pH and salinity were investigated to exploit the mechanisms. Our results demonstrated that the adsorption isotherms of Cd(II) to both TiO(2) and HA-TiO(2) complied well with Freundlich model. q(e) values increased with pH increase, mainly due to electrostatic attraction, whereas q(e) values increased initially and then decreased at 100 mmol L(-1) with salinity increase, mainly due to complexation and electrostatic effects. It is noteworthy that an overall trend of higher Cd(II) adsorption was observed on HA-TiO(2) compared to that on TiO(2), implying that HA coating might modify bioavailability of heavy metals in aquatic environment. The possible adsorption mechanisms in views of electrostatic interactions and covalent effects were interpreted, and the X-ray photoelectron spectroscopy (XPS) results also verified the possible mechanisms.