Removal of some textile dyes from aqueous solutions by poly(N-vinyl-2-pyrrolidone) and poly(N-vinyl-2-pyrrolidone)/K2S2O8 hydrogels

Bioconjugated graphene oxide hydrogel as an effective adsorbent for cationic dyes removal

In this study, graphene oxide - cellulose nanowhiskers nanocomposite hydrogel was easily synthesized through covalent functionalization of cellulose nanowhiskers with graphene oxide via a facile approach. The nitrene chemistry applied for covalent functionalization of graphene oxide sheets. The surface morphology and chemical structure of the nanocomposite hydrogel were characterized by FTIR, TGA, Raman, XRD, elemental analysis and SEM. The UV/Visible absorption spectrum revealed that the obtained porous nanocomposite hydrogel can efficiently remove cationic dyes such as methylene blue (MB) and Rhodamine B (RhB) from wastewater with high absorption power. The adsorption process showed that 100% of MB and 90% of RhB have been removed and the equilibrium state has been reached in 15min for low concentration solutions in accordance with the pseudo-second-order model. Moreover, the sample exhibited stable performance after being used several times. High adsorption capacity and easy recovery are the efficient factors making these materials as good adsorbent for water pollutants and wastewater treatment.

Highly efficient decomposition of Remazol Brilliant Blue R using tubular reactor coated with thin layer of PdO

In this work, we propose a novel approach to dye decomposition under subcritical water conditions using a continuous-flow tubular reactor coated with thin layer of PdO as a catalyst. Remazole Brilliant Blue R was used as an example of synthetic dyes. Hydrogen peroxide was used as an environmental-friendly oxidant as it leaves no residues after treatment. The effect of temperature, pressure and dye concentration on total organic carbon (TOC) removal were studied. 99.9% of TOC removal was achieved at 300 °C and 10 MPa pressure within a short residence time of 3.2 s. This method provided an efficient and rapid process that has a potential for treating a wide range of textile wastewaters.

Sonocatalytic degradation of organic dyes and comparison of catalytic activities of CeO2/TiO2, SnO2/TiO2 and ZrO2/TiO2 composites under ultrasonic irradiation

The CeO(2)/TiO(2), SnO(2)/TiO(2) and ZrO(2)/TiO(2) composites were prepared by dispersing various nano-sized oxides (CeO(2), SnO(2), ZrO(2) and TiO(2)) with ultrasound and mixing TiO(2) with CeO(2), SnO(2) and ZrO(2), respectively, in boiling water in a molar ratio of 4:1, followed by calcining temperature 500 degrees C for 60 min. Then a series of sonocatalytic degradation experiments were carried out under ultrasonic irradiation in the presence of CeO(2)/TiO(2), SnO(2)/TiO(2) and ZrO(2)/TiO(2) composites and nano-sized TiO(2) powder. Also, the influences of heat-treatment temperature and heat-treatment time on the sonocatalytic activities of CeO(2)/TiO(2), SnO(2)/TiO(2) and ZrO(2)/TiO(2) composites, and of irradiation time and solution acidity on the sonocatalytic degradation of Acid Red B were investigated by UV-vis spectra. It was found that the sonocatalytic degradation of Acid Red B shows significant variation in rate and ratio that decreases in order: CeO(2)/TiO(2)>SnO(2)/TiO(2)>TiO(2)>ZrO(2)/TiO(2)>SnO(2)>CeO(2)>ZrO(2), and the corresponding ratios of Acid Red B in aqueous solution are 91.32%, 67.41%, 65.26%, 41.67%, 28.34%, 26.75% and 23.33%, respectively. And that the degradation ratio is only 16.67% under onefold ultrasonic irradiation. Because of the good degradation efficiency, this method may be an advisable choice for the treatment of non- or low-transparent wastewaters in the future.

Sonophotocatalytic degradation of congo red and methyl orange in the presence of TiO2 as a catalyst

A comparative study between the photocatalytic and sonophotocatalytic oxidation process of congo red was carried out using titanium dioxide as a catalyst. The effect of a number of parameters, such as the initial concentration of dye, the presence of oxygen and ultrasound, the TiO(2) crystalline structure and the amount of TiO(2), was studied using an inexpensive reactor. In the second part of this document, the oxidation and reduction processes of methyl orange was studied using the same reactor, but by changing the chemical environment in order to drive either the oxidation or the reduction reaction. The results showed, for all the cases studied, a sinergistic effect between sonolysis and photocatalysis when an ultrasonic bath of 80W was used as a source of ultrasound. On the other hand, the electrochemical experiments showed that the current densities for the oxidation process of the azodyes were higher when a conducting glass electrode covered with a thin film of TiO(2) was used as a working electrode instead of a platinum electrode, showing that the TiO(2) electrode is not passivated by the oxidation reaction.