Optimizing reaction conditions and experimental studies of selective catalytic reduction of NO by CO over supported SBA-15 catalyst.

Selective catalytic reduction of NO with CO (CO-SCR) was investigated based on optimizing the operating conditions by response surface methodology (RSM) and by appropriately choosing the supported SBA-15 catalysts. The effects of the CO-SCR reaction parameters such as NO:CO molar ratios and oxygen concentrations on the catalytic performance were determined by RSM to evaluate the NO conversion using a first-order polynomial model. The CuO/SBA-15 and Fe2O3/SBA-15 catalysts were synthesized by a hydrothermal method and characterized by X-ray diffraction (XRD), atomic absorption spectroscopy (AAS), N2 adsorption-desorption (BET), scanning electron microscopy coupled to energy dispersive X-Ray spectroscopy (SEM-EDS), and Fourier transform infrared spectroscopy (FTIR) to investigate the physicochemical properties of the solids. The RSM showed a very good agreement between predicted values and experimental results with the Pareto analysis confirming the accuracy and reliability of the model. The optimized results indicated the maximum NO conversion at 500 °C with using the NO to CO molar ratio of 1:2 (500:1000 ppm) in the absence of oxygen. Under these conditions, CuO/SBA-15 catalyst achieved 99.7% of NO conversion, whereas Fe2O3/SBA-15 had 98.1% of the catalytic parameter. Catalytic tests in CO-SCR reaction were performed on both catalysts at optimum operating conditions with CuO/SBA-15 exhibiting better performance compared to that of Fe2O3/SBA-15. The results revealed that CuO/SBA-15 was a promising catalyst for CO-SCR of NO due to the well-dispersed CuO phase on SBA-15 surface that allows the solid being more tolerant to the presence of oxygen.

Acid Red 66 Dye Removal from Aqueous Solution by Fe/C-based Composites: Adsorption, Kinetics and Thermodynamic Studies.

The presence of synthetic dyes in water causes serious environmental issues owing to the low water quality, toxicity to environment and human carcinogenic effects. Adsorption has emerged as simple and environmental benign processes for wastewater treatment. This work reports the use of porous Fe-based composites as adsorbents for Acid Red 66 dye removal in an aqueous solution. The porous FeC and Fe/FeC solids were prepared by hydrothermal methods using iron sulfates and sucrose as precursors. The physicochemical properties of the solids were evaluated through X-ray diffraction (XRD), Scanning electron microscopy coupled with Energy dispersive spectroscopy (SEM-EDS), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared s (FTIR), Raman and Mössbauer spectroscopies, nitrogen adsorption-desorption isotherms, Electron Paramagnetic Resonance (EPR) and magnetic saturation techniques. Results indicated that the Fe species holds magnetic properties and formed well dispersed Fe3O4 nanoparticles on a carbon layer in FeC nanocomposite. Adding iron to the previous solid resulted in the formation of γ-Fe2O3 coating on the FeC type structure as in Fe/FeC composite. The highest dye adsorption capacity was 15.5 mg·g-1 for FeC nanocomposite at 25 °C with the isotherms fitting well with the Langmuir model. The removal efficiency of 98.4% was obtained with a pristine Fe sample under similar experimental conditions.

Flow injection analysis of ethyl xanthate by in-line dialysis and UV spectrophotometric detection.

A simple and sensitive spectrophotometric flow method for determination of low concentrations of the flotation collector O-ethyldithiocarbonate (ethyl xanthate, CH(3)CH(2)-O-CS(2)(-)) in solutions is described. The method is based on ethyl xanthate detection at 301nm in medium of NaOH 50mmolL(-1). By injection of 200muL of sample, the analytical method shows linear response for the ethyl xanthate concentration from 0.5 up to 500mumolL(-1). Successive injections of 4mumolL(-1) ethyl xanthate (n=23) show a coefficient of variation lower than 0.6%, denoting high repeatability. The detection limit is 0.3mumolL(-1). At a flow rate of 2.0mLmin(-1), a frequency of 120injections/h of ethyl xanthate can be attained. By introduction of a tangential dialysis cell in the FIA system, the manual sample filtration step with 0.22mum filter was eliminated and the residual interference of suspended material, was completely overcome even for unfiltered sludge suspension samples, an important advantage that compensates for the frequency reduction to 25injections/h elevation and detection limit elevation to 2mumolL(-1), still outreaching for many applications. Potential applications of the method embrace the at line determination of ethyl xanthate in the ore processing industry, control of the concentration at its optimal level during the flotation process, as well as monitoring of residues in the effluents.