Solvent-Free Synthesized Monolithic Ultraporous Aluminas for Highly Efficient Removal of Remazol Brilliant Blue R: Equilibrium, Kinetic, and Thermodynamic Studies.

In this study, ultraporous aluminas (UPA) were synthesized as new effective adsorbents for Remazol Brilliant Blue R (RBBR) removal from aqueous solutions. The UPA monoliths were grown via facile oxidation process, followed by isochronous annealing treatment in air at different temperatures, through which γ, θ, and α phase polycrystalline fibrous grains of UPA can be accordingly obtained. The experimental factors that affect the material adsorption performances including initial pH, contact time, and temperature were comprehensively studied by batch experiments. The RBBR adsorption isotherms of UPA(γ) and UPA(θ) powders were found almost identical, while UPA(α) powders showed low effectiveness. To obtain the desirable mechanical stability of the UPA monolith with considerable RBBR adsorption capacity, UPA(θ) powders were further studied. The UPA(θ) powders exhibited maximum RBBR adsorption at pH 2 due to the positively charged surface under acidic conditions. Compared with the Lagergren pseudo-first-order model, the pseudo-second-order model was found to explain the adsorption kinetics better. Despite the film diffusion dominating the adsorption process, the contributions of the intraparticle diffusion and chemical reactions were also found significant. The adsorption equilibrium data at different temperatures were fitted by the Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich (D-R) isotherm models. The Langmuir model was found the most effective in the description of equilibrium data, and the maximum RBBR adsorption capacity retained by UPA(θ) powders was 122.55 mg·g-1 at 295 K. Thermodynamic parameters (ΔG0, ΔH0, and ΔS0) indicated the adsorption process was spontaneous and exothermic in nature.

Spray plasma device, a new method to process nanostructured layers. application to deposit ZnO thin layers.

The aim of this paper is to present a new plasma spray device to deposit nanostructured films. In this process, aqueous droplets of a starting material, in this case, a nitrate salt, of small and uniform size produced in an aerosol generator are injected into a low pressure plasma reactor. Droplets are then submitted to the reactivity of plasma and projected against a substrate where they form the final film. The reactor is designed to reduce the turbulence that results in coalescence of the particles and affects the uniformity of the deposited films. The plasma is produced by an inductive RF generator that avoids the contamination of the layers by electrodes. The control of plasma gas composition, i.e., argon and oxygen, permits adjustment of the concentration of reactive species leading to control the stoichiometry of the deposited layers. The ability of this process to produce nano scale zinc oxide films by the use of an aqueous solution containing Zn(NO3)2 is demonstrated. The films obtained under defined experimental conditions are smooth, colorless and transparent. SEM and AFM photographs show the formation of uniform layers with 20 to 60 nm in thickness. XRD patterns of deposited films showed that preferential c-axis orientation of crystallites depends highly on the concentration of Zn(NO3)2 in the starting solution. Willamson-Hall method in accordance with AFM photographs showed that the size of crystallites ranges between 24 and 34 nm.