Investigation on adsorption capacity of TiO2-P25 nanoparticles in the removal of a mono-azo dye from aqueous solution: A comprehensive isotherm analysis

In this work TiO2-P25 nanoparticles with high surface area have been used as adsorbent for the removal of C.I Acid Red 27 (AR27), as an organic contaminant from aqueous solution. Characteristics of phases and crystallite size of TiO2-P25 nanoparticles were achieved from XRD and the surface area and pore size distribution were obtained from BET and BJH techniques. TiO2-P25 nanoparticles with almost 80% anatase and 20% rutile phases, the average crystallite size of 18 nm, have specific surface area of 56.82 m2 g-1. The effect of various parameters like initial AR27 concentration, pH, contact time and adsorbent dosage has been carried out in order to find desired adsorption conditions. The desired pH for adsorption of AR27 onto TiO2-P25 nanoparticles was 3. The equilibrium data were analyzed with various 2-, 3- and 4-parameter isotherm models. Equilibrium data fitted very well by the 4-parameter Fritz-Schluender model. Results of adsorption kinetics study indicated that the pseudo-second order kinetics provided the best fit with correlation coefficients close to unity

Combination of Design Equation and Kinetic Modeling for a Batch-Recirculated Photoreactor at Photooxidative Removal of C.I. Acid Red 17

In this work, a design equation has been presented for a reactor composed of an annular photoreactor and a continuous stirred tank reactor (CSTR) with a batch-recirculated current. In this reactor the removal of a contaminant namely C.I. Acid Red 17 (AR17) that is a monoazo acidic dye by means of UV/H2O2 process has been investigated. AR17 kinetics in all cases follows pseudo-first-order kinetics. The effects of the operational parameters such as liquid volume inside the CSTR, volumetric flow rate and initial concentration of H2O2 in the removal efficiency have been surveyed. The results indicate that the increase in volumetric liquid rate increases the removal rate; also, the increase in the experimental liquid volume inside the CSTR decreases the removal efficiency. H2O2 concentration has a critical effect in the removal efficiency. A rate equation for removal of AR17 was achieved by kinetic modeling. Resulted equation was combined with mole balance equation for achieving final equation. The presented final design equation is thoroughly able to predict the reaction rate constant (kap1) under various conditions so that calculated and experimental results are in good agreement.</jats:p

Characterization and photocatalytic activity of SiO₂-TiO₂ mixed oxide nanoparticles prepared by sol-gel method

1593-1600SiO2-TiO2 mixed oxides have been prepared by sol-gel technique from titanium tetraisopropoxide and tetraethylorthosilicate. The prepared materials were characterized by X-ray diffraction, FT-IR spectroscopy, scanning electron microscopy, nitrogen physisorption and UV-vis diffuse reflectance spectroscopy. The results indicate that compared to pure TiO2, the SiO2-TiO2 mixed oxides show higher thermal stability, larger surface area, greater band gap energy and smaller crystallite size. The higher thermal stability of SiO2-TiO2 nanoparticles allows calcination of SiO2-TiO2 nanoparticles at higher temperatures without the accompanying phase transformations from anatase to rutile. The photocatalytic activity of the prepared materials has been compared in the photodegradation of new fuchsin (C.I. 42520) and amaranth (C.I. 16185). Effects of SiO2 concentration and calcination temperature on the photocatalytic activity of SiO2-TiO2 nanoparticles have been investigated. The photodegradation rate of new fuchsin in the presence of 40% SiO2-TiO2 nanoparticles calcined at 600 ºC was higher than that observed with pure TiO2 and Degussa P25 TiO2 by 7.9 and 3.27 times, respectively