Synthesis and Characterisation of Ag/SnO2/Clay Nanocomposites with Potential Application as Photocatalysts

This work reported a novel synthesis and characterization of Ag/SnO2/clay nanocomposites. The obtained materials were characterized using techniques such as X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy, particles size distribution, BET analyses and Scanning Electron Microscopy. The Ag/SnO2/clay nanocomposites have been used as efficient and environmentally benign photocatalysts. The protocols developed using this kind of material is advantageous in terms of simple experimentation, reusable catalyst, excellent yields of the products, short reaction time and preclusion of toxic solvents. The synthesized nanosized AgSnO2/clay nanocomposites have been used as photocatalysts for degradation and discoloration of synthetic wastewater containing Eosin Y dye, xanthene fluorescent dye, under solar radiation

A Comparative Approach of Degradative Potential of Two Different Nanophotocatalysts onto a Model Textile Dye

Motivations and objectives. It is quite a difficult issue to treat, decolorize and mineralize textile dye waste containing dyes by conventional chemical methods (primary: adsorption, flocculation and secondary: chlorination, ozonization. It has been demonstrated that semiconductor photocatalytic oxidation of organic substances can be an alternative to conventional methods of removal of organic pollutants from water [1]. Advanced oxidation processes (AOPs) employing heterogeneous catalysis have emerged as a potentially destructive technology leading to the total mineralization of most of organic pollutants. An additional advantage of the photocatalytic process is its mild operating conditions and the fact the semiconductor can be activated by sunlight (near UV), thus reducing significantly the electric power requirement and hence the operating cost [2]. The main result and characterizing aspect of the research consist of the effectiveness of a semiconductor photocatalytic treatment of synthetic wastewater. Nanophotocatalysts ZnO have been successfully grown by hydrothermal method, onto some fibrous supports previously functionalized (grafted with MCT (monochlorotriazinyl-β-cyclodextrin, MCT-β-CD). The synthesis is reported elsewhere. The hydrothermal synthesis was performed using two types of surfactants widely used in nanoparticles preparation: Pluronic P123(triblock copolymer) and CTAB (cetyltrimethylammonium bromide). The novelty of the study consists in using these two different surfactants in growning of ZnO onto the fibrous supports. For degradation of Erionyl Roth dye, batch experiments were performed by irradiating the aqueous solution of model textile dye, containing ZnO nanocoated fibrous supports as semiconductor, in the presence of UV light. The photocatalytic process occurs under the illumination of an UV lamp, emitting light at wavelength 365 nm. The rate of decolorization was estimated spectrophotometrically from residual concentrations. Results and discussion. The enhancement of the photocatalytic activity is attributed to the CTAB. The performance of the photocatalytic system indicated that the photodegradation of the Erionyl Roth, in the presence of CTAB, occured with a 20 % reduction of time, compared to P123.The study has demonstrated that using the semiconductor performed by CTAB on the ZnO nano-oxides synthesized onto previously MCT grafted fibrous supports is effective in degradation of dyes as well as in the treatment of textile dye waste

Chromium(VI) Ion Removal from Aqueous Solutions Using a Zn–Al-Type Layered Double Hydroxide

This paper deals with the structural and adsorptive characterisation of a Zn–Al-type layered double hydroxide to be used for the retention of chromate ions from aqueous media. Structural characterisation by X-ray diffraction and FT-IR spectroscopy showed that the material was a layered double hydroxide with carbonate in the interlayer; however, certain impurities were also identified. Thermogravimetric analysis allowed appropriate calcination temperatures to be chosen for the sorption studies. The equilibrium adsorption of the Cr(VI) ion was best described by the Langmuir–Freundlich equation. Calcining the material at 500 °C led to a product containing mostly stable zinc oxide with low adsorptive properties. The kinetics of Cr(VI) ion retention on the uncalcined layered double hydroxide obeyed the pseudo-first-order model as described by the Lagergren equation. Structural analysis of the product obtained after Cr(VI) ion sorption onto Zn–Al–CO 3 showed that the carbonate anion was not replaced in the interlayer and that the Cr(VI) ion was adsorbed within cavities formed by three adjacent metal hydroxide octahedra situated at the edge of the brucite-like layer

Sorption of phosphates and thiocyanates on isomorphic substituted Mg/Zn–Al-type hydrotalcites

The sorption equilibriums of phosphate and thiocyanate anions on isomorphic substituted Mg/Zn–Al-type hydrotalcites were investigated in this study. Langmuir and Freundlich isotherms were used to interpret the equilibrium data for phosphate. The sorption equilibriums of phosphate on Mg3Al, Mg2ZnAl and Mg1.5Zn1.5Al hydrotalcites were well described by the Langmuir isotherm. The highest maximum sorption capacities for these adsorbents were as follows: 111, 101 and 95 mg g-1. The equilibrium constant and standard Gibbs energy changes were also calculated from the sorption data. Standard Gibbs energy changes of about –20 kJ mol-1 indicated that the process might be considered as physical adsorption. The sorption equilibriums of phosphate on isomorphic substituted samples of MgZn2Al and Zn3Al were well described by the Freundlich isotherm. Thiocyanate showed a relative low affinity for the studied materials, as indicated by both the “S”-shaped isotherms and low sorption capacities. The sorption of phosphate and thiocyanate on the investigated hydrotalcites showed a continuous decrease of the sorption capacity in the following order: Mg3Al > Mg2ZnAl > Mg1.5Zn1.5Al > MgZn2Al > Zn3Al