A systematic study for the removal of anionic dyes by sepiolites modified with a homologous series of trimethylammonium-surfactants from single and binary component solutions

Trimethylammonium surfactants have been extensively used for modification of sepiolite to improve its sorption ability for anionic dye removal. Here, a detailed systematic sorption study is presented to choose the best surfactant for modification having the highest removal efficiency for different types of anionic dyes belonging to anthraquinone (Lanaset-Green-B), azo (Lanaset-Red-2B) and complex (Lanaset-Red-G) subclasses. Adsorption kinetics and equilibria of the dyes onto the pristine and decyl-, dodecyl-, teradecyl- and hexadecyl-tetramethylammonium sepiolites were investigated in single and binary component systems. Multilayered arrangements have been proposed for surfactants on the sepiolite based on x-ray diffraction and diffuse-reflectance-Fourier-transform spectroscopy analyses. The arrangements and the size of the surfactants comparing to dyes play important role in the adsorption process. The proposed dye-surfactant interactions are consistent with all kinetics and equilibrium results. The tetradecylammonium modified sepiolite has the best capacity for all dyes (similar to 0.32 mmol/g) at the first-stage of isotherms and is independent of the molecular structure of dyes. This correlated to the numbers of free head groups of surfactant oriented upward. The highest capacity is 0.50 mmol/g for Lanaset-Red-2B at the second stage of the isotherms on the dodecylammonium modified sepiolite which is attributed to dye-dye interactions

A comparison of anionic and cationic dye removal efficiency of industrial bauxite waste red-mud

Sorption characteristics of the acid-activated bauxite waste red-mud for Nylomine-Blue and Methylene-Blue were investigated to predict its potential removal ability for anionic-di-anthraquinone and cationic-thiazine-dyes, respectively. Surface characteristics of the red-mud were examined using atomic-force-microscopy, diffuse-reflectance-Fourier-transform, and X-ray-diffraction spectroscopy techniques. Kinetic data obtained at four different temperatures fit well to the pseudo-second-order and homogeneous-surface-diffusion models. The experimental Nylomine-Blue sorption capacity (0.020 mmol/g) is higher than that of Methylene-Blue (0.012 mmol/g) at 288 K but they change oppositely with the temperature and attain 0.013 and 0.043 mmol/g at 318 K, respectively. Experimental equilibrium data for Methylene-Blue and Nylomine-Blue are well predicted by the Freundlich, Langmuir, and Dubinin-Radushkevich isotherm equations. The mean-sorption-energies fall into the ion-exchange range for Methylene-Blue but electrostatic-attraction-forces play a more important role in Nylomine-Blue sorption. These mechanisms were correlated to the pH changes in the sorption process and the differences in the diffuse-reflectance-Fourier-transform spectra of dye-loaded sorbents. The atomic-force-microscopy topography and phase images revealed that the hematite and sodalite appear as hills on the red-mud surface but gibbsite and calcite minerals cover the valleys. The Methylene-Blue molecules are sorbed by ion-exchange in the positively-charged-valleys in dilute solutions but Nylomine-Blue is sorbed specifically on overall surface in whole concentration range

Capacitive performance of electrochemically deposited Co/Ni oxides/hydroxides on polythiophene-coated carbon-cloth

Cobalt, nickel, and their mixed hydroxides were electrochemically deposited on polythiophene-coated carbon-cloth substrate to develop new pseudo-capacitive electrodes for energy storage devices. Thiophene was electro-polymerized on carbon-cloth by the potentiodynamic method in acetonitrile containing 1-butyl-2,3-dimethylimidazolium hexafluorophosphate ionic-liquid as supporting electrolyte. The scanning-electron-microscopy images imply that flower-like Co(OH)(2) microstructures deposited on bamboo-like polythiophene coatings on carbon-fibers but they are covered by net curtain like thin Ni(OH)(2) layer. The Co-Ni layered-double-hydroxide deposited from their equimolar sulfate solutions is composed of large aggregates. The electron-dispersive-spectrum exhibits that Co/Ni ratio equals unity in the layered-double-hydroxide. The capacitances of Co, Ni, and Co-Ni hydroxide-coated PTh electrodes are 100, 569, and 221 F/g at 5 mA/cm(2) in 1 M KOH solution, respectively. Their corresponding oxides obtained by calcination at 450 degrees C in de-aerated medium possess higher capacitance up to 911, 643, and 696 F/g at 2 A/cm(2). The shape of cyclic-voltammetry and galvanostatic-charge-discharge curves, as well as the Nyquist plots derived from electrochemical-impedance-spectroscopy measurements, reveal that hydroxide coatings on the polythiophene-coated carbon-cloth are more promising electrode materials for supercapacitor applications. The mixed hydroxide-coated electrode shows good cyclic stability of 100% after 400 cycles at 5 mA/cm(2)

Photocatalytic efficiency of titania nonylphenol ethoxylate composite thin films under solar irradiation

Photocatalytic efficiency of titania thin-films on ITO synthesized in the presence of nonylphenol-surfactants containing different numbers of ethoxylate-units was investigated under solar-irradiation. A colorless transparent titania-gel formed in the non-aqueous medium in the presence of nonylphenol-10-ethoxylates while milky white opaque gel was observed with nonylphenol-35-ethoxylates. They were coated on ITO plate by dipping method and calcined at 350, 500 and 700 degrees C. The XRD, IRRAS, EDS, SEM and AFM analyses revealed that different composite nanostructures are formed by calcinations of Ti-nonylphenol-35-ethoxylates at 350 and 500 degrees C. The photocatalytic-efficiencies of the composite films are better than the other titania nanostructures. Transparency and band-gap energy evaluated from transmittance measurements demonstrated that visible-light responsive Ti-nonylphenol-35-ethoxylates composites are more efficient catalysts than UV-absorbable Ti-nonylphenol-b0-ethoxylates films. The photocatalytic degradation rate of the methylene-blue on the catalysts was calculated using the Langmuir-Hinshelwood equation and its modified form derived in this study by considering intensity changes in solar light. The dye degradation efficiency of the Ti-nonylphenol-ethoxylate films changes in the 58-74% range after 2 h of irradiation in 0.02 mM MB solution. The solution completely decolorized after 8 h of irradiation on the TiNP-35 catalysts calcined at 350 degrees C