Kinetics of Solvent Blue and Reactive Yellow removal using microwave radiation in combination with nanoscale zero-valent iron

We investigated the efficiency and kinetics of the degradation of soluble dyes over the p H range 5.0–9.0 using a method employing microwave radiation in combination with nanoscale zero-valent iron（MW–n ZVI）. The n ZVI particles（40–70 nm in diameter） were prepared by a liquid-phase chemical reduction method employing starch as a dispersant.Compared to the removal of Solvent Blue 36 and Reactive Yellow K-RN using only n ZVI,more rapid and efficient dye removal and total organic carbon removal were achieved using MW–n ZVI. The dye removal efficiency increased significantly with decreasing p H, but was negligibly affected by variation in the microwave power. The kinetics of dye removal by MW–n ZVI followed both an empirical equation and the pseudo first-order model, while the kinetics of dye removal using n ZVI could only be described by an empirical equation. It was also concluded that microwave heating of the dye solutions as well as acceleration of corrosion of n ZVI and consumption of Fe（II） were possible reasons behind the enhanced dye degradation.

Photocatalytic parameters and kinetic study for degradation of dichlorophenol-indophenol (DCPIP) dye using highly active mesoporous TiO_2 nanoparticles

Highly active mesoporous TiO_2 of about 6 nm crystal size and 280.7 m^2/g specific surface areas has been successfully synthesized via controlled hydrolysis of titanium butoxide at acidic medium. It was characterized by means of XRD（X-ray diffraction）, SEM（scanning electron microscopy）, TEM（transmission electron microscopy）, FT-IR（Fourier transform infrared spectroscopy）, TGA（thermogravimetric analysis）, DSC（differential scanning calorimetry） and BET（Brunauer–Emmett–Teller） surface area. The degradation of dichlorophenol-indophenol（DCPIP） under ultraviolet（UV） light was studied to evaluate the photocatalytic activity of samples. The effects of different parameters and kinetics were investigated. Accordingly, a complete degradation of DCPIP dye was achieved by applying the optimal operational conditions of 1 g/L of catalyst, 10 mg/L of DCPIP, pH of 3 and the temperature at 25 ± 3°C after 3 min under UV irradiation. Meanwhile, the Langmuir–Hinshelwood kinetic model described the variations in pure photocatalytic branch in consistent with a first order power law model.The results proved that the prepared TiO_2 nanoparticle has a photocatalytic activity significantly better than Degussa P-25.

Photocatalytic degradation of methyl orange by polyoxometalates supported on yttrium-doped TiO_2

A series of novel photocatalysts, H3PW12O40-Y-TiO2 nanocomposites with different H3PW12O40 loading levels （10%-40%） were prepared by impregnation method. And the Y-TiO2 support, doped with yttrium, was synthesized via sol-gel technique. The prepared catalysts were characterized by Fourier transform infrared spectroscopy （FT-IR）, powder X-ray diffraction （XRD）, nitrogen adsorption-desorption analysis and scanning electron microscopy （SEM）. The processes allowed obtaining Keggin structure and crystallized anatase with large BET surface area as well as uniform distribution. The effects of H3PW12O40 loadings, catalyst dose, initial pH and concentration of dye solution on the degradation kinetics of methyl orange under UV light （λ≥365 nm） were discussed. Kinetics studies showed that the photocatalytic degradation of methyl orange fitted the apparent first-order reaction. Methyl orange was totally degraded in 21 min under optimum conditions： 20% loading, 0.03 g dose and pH 1.0. The catalyst was stable and easily to be separated from reaction system for recovery.

Synthesis of malachite@clay nanocomposite for rapid scavenging of cationic and anionic dyes from synthetic wastewater

Synthesis of malachite@clay nanocomposite was successfully carried out for the removal of cationic（Methylene Blue,MB） and anionic dyes（Congo Red,CR） from synthetic wastewater.Nanocomposite was characterized by TEM,SEM,FT-IR,EDS analysis and zeta potential.TEM analysis indicated that the particle diameter of nanocomposite was in the range of 14 to23 nm.Various important parameters viz.contact time,concentration of dyes,nanocomposite dosage,temperature and solution pH were optimized to achieve maximum adsorption capacity.In the case of MB,removal decreased from 99.82%to 93.67%while for CR,removal decreased from 88.55%to 75.69%on increasing dye concentration from 100 to 450 mg/L.pH study confirmed the higher removal of CR in acidic range while MB removal was higher in alkaline range.Kinetic study revealed the applicability of pseudo-second-order model for the adsorption of both dyes.Negative values of AG0 for both systems suggested the feasibility of dye removal and support for spontaneous adsorption of CR and MB on nanocomposite.Nanocomposite showed 277.77 and 238.09 mg/g Langmuir adsorption capacity for MB and CR respectively.Desorption of dyes from the dye loaded nanocomposite was easily carried out with acetone.The results indicate that the prepared malachite@clay nanocomposite is an efficient adsorbent with high adsorption capacity for the aforementioned dyes.