Aydin Hassani

Sonocatalytic removal of an organic dye using TiO2/Montmorillonite nanocomposite

The sonocatalytic performance of the synthesized TiO2/Montmorillonite K10 (TiO2/MMT) nanocomposite was studied in removal of Basic Blue 3 (BB3) from water. The TiO2/MMT nanocomposite was prepared by hydrothermal method. Scanning electron microscope, X-ray diffraction and Fourier transform infrared were used to characterize the synthesized nanocomposite. The average size of TiO2 nanoparticles decreased from 60-80nm to 40-60nm through the immobilization of this semiconductor on the surface of MMT. The obtained results indicated that the sonocatalytic activity of TiO2/MMT nanocomposite was higher than that of pure TiO2 nanoparticles and MMT particles. Furthermore, the main influence factors on the sonocatalytic activity such as the BB3 concentration, pH of solution, TiO2/MMT dose, power of ultrasonic generator, and inorganic salts were studied. The intermediates of BB3 degradation during the sonocatalytic process in the presence of the TiO2/MMT nanocomposite have been monitored by gas chromatography-mass spectrometry.

Sonocatalytic degradation of ciprofloxacin using synthesized TiO2 nanoparticles on montmorillonite

TiO2/Montmorillonite (TiO2/MMT) nanocomposite as sonocatalyst was produced by immobilizing synthesized TiO2 on the surface of montmorillonite. The characteristics of produced nanocomposite were investigated using XRD, XRF, FTIR, TEM, SEM, EDX, UV-vis DRS and nitrogen adsorption-desorption analyses. The synthesized TiO2 and TiO2/MMT samples were applied as catalysts for sonocatalytic degradation of ciprofloxacin (CIP). The performance of the TiO2/MMT was greater than pure TiO2 sample in treatment of CIP solution. The degradation efficiency of the CIP by sonocatalytic process was affected by solution pH, catalyst dosage, initial CIP concentrations and ultrasonic power. Degradation efficiency of 65.01% was obtained at the pH of 6, catalyst dosage of 0.2gL-1, initial CIP concentration of 10mgL-1 and ultrasonic power of 650WL-1. It was observed that the presence of inorganic and organic scavengers suppressed the performance of sonocatalytic process. The stability of the nanocomposite was studied in several successive experiments, and the degradation efficiency declined only 61.48% after 4 repeated experiments. The main degradation by-products were recognized by GC-MS method to propose the possible sonocatalytic mechanism for the degradation of CIP.

Ultrasound-assisted adsorption of textile dyes using modified nanoclay: Central composite design optimization

The removal of two anionic dyes, C.I. Acid Orange 7 (AO7) and C.I. Acid Red 17 (AR17), by ultrasound-assisted adsorption on the modified nanoclay in aqueous solutions was studied. The modified nanoclay was characterized by SEM/EDX, BET, XRD and FT-IR techniques. The average crystal size for the interlayer spacing of the modified nanoclay was about 14.3 nm. Central composite design (CCD) was used for the optimization of the operational parameters, including the initial dye concentration, sonication time, adsorbent dosage and temperature. The results demonstrated a good agreement between the predicted values obtained by the model and the experimental values for both AO7 (R2= 0.959) and AR17 (R2=0.971).

Heterogeneous sono-Fenton-like process using magnetic cobalt ferrite-reduced graphene oxide (CoFe2O4-rGO) nanocomposite for the removal of organic dyes from aqueous solution

We report herein the synthesis of monodisperse cobalt ferrite (CoFe2O4) nanoparticles (NPs) via a surfactant-assisted high temperature thermal decomposition method and then their assembly on reduced graphene oxide (rGO) to yield CoFe2O4-rGO nanocomposites, which displayed outstanding sonocatalytic activity for the removal of organic dyes from aqueous solutions under ultrasonic irradiation. As-prepared CoFe2O4-rGO nanocomposites were characterized by using transmission electron microscopy (TEM), high-resolution scanning electron microscopy (HR-SEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), Micro-Raman spectroscopy, Vibrating sample magnetometer (VSM) and inductively couple plasma mass spectrometer (ICP-MS). To evaluate the sonocatalytic activity of the CoFe2O4-rGO nanocomposites, the sonocatalytic removal of several organic dyes (AO7, AR17, BR46 and BY28) was studied. The reaction conditions were optimized by studying the effects of various key operating parameters such as pH, catalyst dosage, H2O2 initial concentration, initial dye concentration, ultrasonic power and reaction time on the removal of AO7 dye. The maximum removal efficiency of 90.5% was achieved at pH 3 using 0.08gL-1 catalyst, 3mM H2O2 and 10mgL-1 AO7 dye under 350W ultrasonic power in 120min of reaction time span. Experimental results revealed that the kinetic of the removal process could be described using Langmuir-Hinshelwood (L-H) kinetic model. The trapping experiments showed that O2·- radicals constitute the major reactive oxygen species (ROS) in the AO7 dye removal process. The reusability of the nanocomposites revealed about 22% drop in the removal efficiency within five consecutive runs. A possible sonocatalytic mechanism for the removal of organic dyes was also proposed. The intermediate by-products of the dye formed in the removal process were characterized by using the GC-MS technique.

Heterogeneous photocatalytic ozonation of ciprofloxacin using synthesized titanium dioxide nanoparticles on a montmorillonite support: parametric studies, mechanistic analysis and intermediates identification

A titanium dioxide/montmorillonite (TiO2/MMT) nanocomposite was prepared as a photocatalyst by a hydrothermal method. The physicochemical properties of the prepared sample were comprehensively characterized using scanning electron microscopy (SEM), electron dispersive X-ray spectroscopy (EDX), high resolution transmission electron microscopy (HRTEM), Fourier transform infrared spectroscopy (FTIR), X-ray fluorescence (XRF), N2 adsorption–desorption, ultraviolet-visible diffuse reflectance spectroscopy (UV-vis DRS), and the pH of the zero point of charge (pHzpc) analysis. The photocatalytic ozonation of ciprofloxacin (CIP) was studied in the presence of the TiO2/MMT nanocomposite under different experimental conditions. Comparison of the main processes such as photocatalysis, ozonation and photocatalytic ozonation revealed that photocatalytic ozonation resulted in the highest degradation efficiency (90.00% at 30 min) of the pollutant under the optimum conditions ([CIP]0 = 20 mg L−1, [catalyst]0 = 0.04 g L−1, ozone gas flow rate = 2 L h−1 and pH = 5). This increase was due to a synergistic effect between photocatalysis and ozonation triggered by TiO2/MMT. The mechanism of the photocatalytic ozonation process was investigated in the presence of various organic and inorganic reactive oxygen species (ROS) scavengers. Accordingly, among the radical scavengers, the iodide ions and benzoquinone showed the highest inhibitory effect on the degradation efficiency of CIP. The photocatalytic ozonation mechanism of the TiO2/MMT nanocomposite for the degradation of CIP was thoroughly investigated. The performance of the photocatalytic ozonation process in a real water matrix was evaluated using well and ground water samples. In addition, the reusability of the TiO2/MMT nanocomposite in the photocatalytic ozonation process was examined. The result showed that the degradation efficiency of CIP declines by only about 7% after four consecutive runs. The main degradation intermediates of CIP produced in the photocatalytic ozonation process were identified by gas chromatography coupled to mass spectrometry (GC-MS) analysis.

Surfactant-modified montmorillonite as a nanosized adsorbent for removal of an insecticide: Kinetic and isotherm studies

Surfactant-modified montmorillonites (MMT) were prepared using trimethyloctylammonium bromide (TMOAB) and employed as a nanosized adsorbent to remove diazinon from aqueous solutions. The prepared adsorbent was characterized using Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive X-ray (EDX). The dependence of removal efficiency on initial diazinon concentration, amount of adsorbent, pH of the solution and ionic strength was investigated. The affinity sequence for ion adsorption on TMOAB/MMT was in the order: without anion> sodium carbonate> sodium bicarbonate> sodium sulphate> sodium chloride. The adsorption kinetic and isotherm were best fit by a pseudo-second-order kinetic and Langmuir isotherm models, respectively.