Degradation of 2,4-dichlorophenol in aqueous solution by sono-Fenton method

This study presents the results of the Sono-Fenton process for the degradation of 2,4-dichlorophenol (DCP). The influential parameters such as H₂O₂, Fe²⁺ and pH for the Sono-Fenton process were investigated. Sono-Fenton method was found to be the best one for degradation efficiency of DCP when compared with that of the Fenton process. The optimum concentrations for the degradation of DCP using conventional Fenton’s method were found to be 20 mg/L of Fe²⁺ and 580 mg/L of H₂O₂ at pH 2.5. In the case of Sono-Fenton, the optimal concentrations were found to be 10 mg/L of Fe²⁺ and 400 mg/L of H₂O₂ at pH 2.5. Sono-Fenton method resulted in the reduction of required Fe²⁺ concentration (50%) and H₂O₂ concentration (31%). In addition, this method could be applicable even at pH 5.0 and a degradation efficiency of DCP was 77.6%. Kinetic studies for the degradation of DCP proved that the degradation of DCP tends to follow pseudo first order reaction and the rate constant was found to be 7 × 10⁻⁴ min⁻¹.     

UV/H2O2 treatment of Rhodamine B in aqueous solution: Influence of operational parameters and kinetic modeling

The decolorization and degradation of Rhodamine B (RB) were investigated using UV radiation in the presence of H₂O₂ in a batch photoreactor at different light intensities. H₂O₂ and UV light have a negligible effect when they were used on their own. Removal efficiency of RB was sensitive to the operational parameters such as initial concentrations of H₂O₂ and RB, initial pH and light intensity. The results indicated that efficiency of process decreased with addition of inorganic ions and alcohols to the dye solution as hydroxyl radical scavengers. The semilogarithmic graphs of the concentrations of RB versus time were linear, suggesting pseudo-first order reaction for decolorization and degradation processes. A simple kinetic model is proposed which confirms pseudo-first-order reaction. The electrical energy per order (EE/O) values for decolorization and degradation of RB solution were calculated. Results shows that applying an optimum hydrogen peroxide concentration can reduce the EE/O.     

Application of Ni-doped ZnO rods for the degradation of an azo dye from aqueous solutions

Ni-doped ZnO rods were applied as a photocatalyst for the degradation of an azo dye (Reactive Black 5). Effects of solution pH, catalyst dosage, initial RB5 concentration, H₂O₂ concentration, different purging gases, and type of organic compounds on the removal efficiency of RB5 were studied. Ni-doped ZnO rods were synthesized by co-precipitation method. Neutral pH was selected as an optimal pH condition due to a photo-corrosion of ZnO in acidic and basic conditions. Photocatalytic degradation efficiency of RB5 was increased as the catalyst dosage increased up to 1 g/L, while it was decreased by increasing initial RB5 concentration. Pseudo-first-order rate constant (k _obs ) decreased from 0.122 to 0.0051 min^-1 and electrical energy per order (E _Eo ) increased from 39.34 to 941.18 (kWh/m³) by increasing RB5 concentration from 5 to 100mg/L, respectively. Photocatalytic degradation efficiency of RB5 increased by increasing H₂O₂ concentration, but this trend was not observed above 10 mM. Photocatalytic degradation efficiency of RB5 increased in the presence of folic acid and citric acid while interference was observed in the presence of humic acid, EDTA, oxalic acid, and phenol. Photocatalytic activity was maintained even after five successive cycles.     

Titanium (IV)-Improved H2O2/O3 Process for Acetic Acid Degradation under Acid Conditions

The effect of Ti(IV) on the degradation efficiency of acetic acid by O₃/H₂O₂ was investigated. The removal rate of acetic acid by O₃/H₂O₂ increased from 8.0% to 62.9% after 30 min when Ti(IV) was added to acetic acid solution at pH 2.8. The optimized parameters were as follows: the pH of acetic acid solution less than 5.0; the mass concentration ratios of H₂O₂ to Ti(IV), and to acetic acid about 40:1, and 3:50, respectively. The analysis of the kinetics of acetic acid degradation using the relative method showed that Ti(IV)/H₂O₂/O₃ produced more hydroxyl radicals than did H₂O₂/O₃.     

Photocatalytic activity of copper ferrite graphene oxide particles for an efficient catalytic degradation of Reactive Black 5 in water

The photocatalytic performance of copper ferrite graphene oxide catalyst, CFXGO (CF: Copper ferrite, CuFe₂O₄; GO: Graphene oxide; X: GO weight percentage) was tested for photo Fenton-like oxidation of Reactive Black 5 by using UV light irradiation. The effect of the graphene oxide content in the catalyst structure on dye removal efficiency was tested by comparing the performances of the catalysts with different weight ratios of graphene oxide varying between 5 and 90%. The catalysts were characterized by Scanning Electron Microscopy, X-Ray Diffraction, Brunauer–Emmett–Teller method, and, Vibrating Sample Magnetometer. The influences of catalyst loading, initial pH, and, the H₂O₂ concentration were investigated in the presence of CF90GO catalyst, which has 90% graphene oxide content. According to the parametric studies, 98.2% decolorization and 82.8% TOC removal efficiencies were achieved in 2 h for the treatment of 50 mg/L RB5 solutions when the catalyst loading, the initial pH, and, the initial hydrogen peroxide concentration were 0.275 g/L, 7, and, 5.5 mM, respectively.     

Study of photochemical and sonochemical processes efficiency for degradation of dyes in aqueous solution

The degradation of two commercially available dyestuffs (C.I. Reactive Black 5 and C.I. Disperse Orange 25) by ultraviolet radiation (UV), ultrasonic irradiation (US), UV/H₂O₂ and US/H₂O₂ processes was investigated in a laboratory-scale batch photoreactor equipped with a 55 W immersed-type low-pressure mercury vapor lamp and a sonoreactor with low frequency (42 kHz) plate type transducer at 170 W of acoustic power. The toxicity was also evaluated in acute toxicity studies using Daphnia magna. Results showed that color removal efficiencies by US and US/H₂O₂ processes were negligible for both dyes. Almost complete disappearance of Reactive Black 5 (97.9%) in UV/H₂O₂ process was possible after 5 min of irradiation. The maximum color removal efficiency of Disperse Orange 25 after 10 min of irradiation, however, was only 9.2% and reached a maximum value of 41% after 120 min of irradiation. Pseudo-first order kinetics with respect to dyestuffs concentrations was found to fit all the experimental data. The results clearly showed that both dyes examined were toxic to D. magna and resulted in quite low LC₅₀ values.     

Microwave-assisted extractive catalytic-oxidative desulfurization of diesel fuel via a VO(acac)2/ionic liquid system with H2O2 and H2SO4 as oxidizing agents

The removal of sulfur compounds from transportation fuel is an important aspect for protecting environment and for fuel cell applications. On the other hand, an innovative way to remove the sulfur is necessary because clean low-sulfur diesel is more widely used in the world today. In this work, we studied the effect of microwave irradiation power and time on the extractive catalytic oxidative desulfurization (ECODS) process of diesel fuel model (40 mL with initial S-content of 450 ppm), using vanadyl acetylacetonate (VO(acac)₂) as a catalyst and N-carboxymethylpyridine hydrosulphate ionic liquid ([CH₂COOHPy][HSO₄] IL) as an extractant, and hydrogen peroxide (H₂O₂) as an oxidant agent. The optimal microwave-assisted extractive catalytic – oxidative desulfurization (MECODS) experimental conditions were as follows: microwave irradiation power?=?500?W, microwave irradiation time?=?90?s, IL/diesel volume ratio?=?1:10, VO(acaca)₂/diesel mass ratio?=?0.5?wt%, and H₂O₂ volume?=?1 mL. Under these conditions, the sulfur content in commercial diesel fuel was reduced from 450 to 60?ppm (sulfur removal efficiency of 86.67%), which was superior to that of the simple oxidation with no IL (22.6%) or oxidation with not including catalyst (11.3%), and without affecting the physicochemical properties of diesel fuel. The catalytic system VO(acac)₂/IL can be recycled 5 times with merely a negligible loss in activity. Based on these experimental results, a MECODS mechanism was proposed. Ultra-deep desulfurization with 99.1% of sulfur removal efficiency was reached, using MECODS reaction under optimum conditions by adding 3?mL of H₂SO₄ (0.1?N) to the main reaction. This highest sulfur removal efficiency can be attributed to the synergetic effect between microwave activation heating energy and the additional protonation, which multiplied the sulfones’ (BTO₂s and DBTO₂s) formation pathways and thus accelerated the desulfurization reactions.     

Degradation of C.I. Acid Orange 7 by heterogeneous Fenton oxidation in combination with ultrasonic irradiation

BACKGROUND: A mesoporous alumina supported nanosized Fe₂O₃ was prepared through an original synthesis procedure and used as a heterogeneous catalyst for the Fenton process degradation of the model azo dye C.I. Acid Orange 7 enhanced by ultrasound irradiation (US/Fe₂O₃‐Al₂O₃‐meso/H₂O₂ system). The effect of various operating conditions was investigated, namely hydrogen peroxide concentration, initial pH, ultrasonic power and catalyst loading. RESULTS: The results indicated that the degradation of C.I. Acid Orange 7 followed a pseudo‐first‐order kinetic model. There exists an optimal hydrogen peroxide concentration, initial pH, ultrasonic power and catalyst loading for decolorization. The aggregate size of the spent catalyst was reduced after dispersion in water by ultrasonic irradiation. A very low level of iron leaching was observed ranging from < 0.1 to 0.23 mg L^?1. The intermediate products of C.I. Acid Orange 7 degradation were identified using gas chromatography–mass spectrometry (GC‐MS). CONCLUSION: The optimal conditions for efficient C.I. Acid Orange 7 degradation were pH close to 3, hydrogen peroxide concentration 4 mmol L^?1, catalyst loading 0.3 g L^?1, and ultrasonic power 80 W. Copyright © 2011 Society of Chemical Industry     

Comparative Study of Reactive Dyes Oxidation by H2O2/UV,H2O2/UV/Fe2+ and H2O2/UV/Fe° Processes

The decolorization and mineralization of two reactive dyes C.I. Reactive Blue 4 (RB 4) and C.I. Reactive Blue 268 (RB 268) were studied using various advanced oxidation processes (AOPs) such as H₂O₂/UV, H₂O₂/UV/Fe²⁺, and the H₂O₂/UV/Fe°. All processes were performed within a laboratory-scale photo-reactor setup. The experimental results were assessed in terms of absorbance (A) and total organic carbon (TOC) reduction. The main degradation products were identified by high resolution gas chromatography/high resolution mass spectrometry analyses. The results of our study demonstrated that the additions of moderate concentrations of H₂O₂ and Fe catalyst during the AOPs evidently increased the decolorization efficiencies within the first few minutes of the processing time (5–10 min) for both tested dyes, and prolonged irradiation does not necessarily significantly improve decolorization. On contrary, TOC removal rate increased with the processing time and with the addition of the catalyst from 40–50% up to 70–80% at defined experimental conditions. All the tested AOPs were very successful methods for RB 268 decolorization, having very complex structure and much higher molecular weight compared to the dye RB 4. This is important from both economic and ecological points of view.     

New aspects of heterogeneous photocatalysts for water decomposition

Several new photocatalysts for overall water splitting are described. Under UV light irradiation (270 nm), La-doped NaTaO₃ modified with NiO decomposed water into H₂ and O₂ with extremely high quantum efficiency. Under an optimized condition, the apparent quantum efficiency, which was estimated with numbers of irradiated photons and evolved H₂ molecules, reached 56%. New stable photocatalytic materials containing elements with d¹⁰ electronic configuration such as In³⁺ Sn⁴⁺ and Sb⁵⁺ were developed for overall water splitting. Some mesoporous oxides were proved to be effective photocatalysts. (Oxy)nitrides of some early transition metals, i.e., Ta, Nb and Ti, were found to be stable materials having potentials for H₂ and O₂ evolutions under visible light irradiation (⪯600 nm). The electronic structures of these photocatalysts are also discussed based on DFT calculation.     

The sonochemical decolorisation of textile azo dye CI Reactive Orange 127

In the present study, Fenton and sono‐Fenton processes were applied to the oxidative decolorisation of synthetic textile wastewater including CI Reactive Orange 127 and polyvinyl alcohol. Process optimisation [pH, ferrous ion (Fe²⁺) and hydrogen peroxide (H₂O₂)], kinetic studies and their comparison were carried out for both of the processes. The sono‐Fenton process was performed by indirect sonication in an ultrasonic water bath, which was operated at a fixed 35‐kHz frequency and 80 W power. The optimum conditions were determined as [Fe²⁺] = 20 mg l^?1, [H₂O₂] = 15 mg l^?1 and pH = 3 for the Fenton process and [Fe²⁺] = 25 mg l^?1, [H₂O₂] = 5 mg l^?1 and pH = 3 for the sono‐Fenton process. The colour removals were 89.9% and 91.8% by the Fenton and sono‐Fenton processes, respectively. The highest decolorisation was achieved by the sono‐Fenton process because of the production of some oxidising agents as a result of sonication. Consequently, ultrasonic irradiation in the sono‐Fenton process slightly increased the colour removal to 91.8%, while decreasing the hydrogen peroxide dosage to one‐third of that of the Fenton process.     

Characterization of blue CoAl2O4 nano-pigment synthesized by ultrasonic hydrothermal method

Nano-sized CoAl₂O₄ pigments, which have received significant attention as a coloring agent in glaze and bulk tile compositions, were successfully synthesized by substituting mechanical stirring during hydrothermal process with ultrasonic irradiation. Difference in physicochemical and optical properties of the CoAl₂O₄ pigments prepared by an ultrasonic-assisted-hydrothermal method was characterized using simultaneous thermo-gravimetric and differential thermal analysis (TG–DTA), X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), diffuse reflectance spectroscopy, CIELAB colorimetric analysis, and testing in ceramic glazes and bodies. The ultrasonic-assisted CoAl₂O₄ pigments present a narrow particle size distribution with vivid blue color, and better thermal stability, allowing their use for ceramic inks processed at high temperature. Application of ultrasonic irradiation during the hydrothermal process produces nano-sized powders with better physicochemical and optical properties.     

Preparation of poly(butyl methacrylate)/γ‐Al2O3 nanocomposites via ultrasonic irradiation

A new technique (ultrasonic irradiation) has been employed to prepare poly(n‐butyl methacrylate) PBMA/γ‐Al₂O₃ nanocomposites, taking advantages of the multiple effects of ultrasonic irradiation, such as dispersion, pulverization and activation. When subjected to ultrasonic irradiation, n‐butyl methacrylate (BMA) is polymerized to form poly(n‐butyl methacrylate) (PBMA) latex without any chemical initiators, and the monomer conversion reaches 72.5% in 25 min. At an appropriate pH, surfactant bilayers are formed through electrostatic interactions between γ‐Al₂O₃ nanoparticles and the anionic surfactant sodium dodecyl sulfate (SDS), which adsorb BMA. After ultrasonic induced polymerization of BMA in the presence of nanoparticles of γ‐Al₂O₃, the γ‐Al₂O₃ nanoparticles are encapsulated by PBMA shells formed. The influence of factors such as pH, surfactant concentration and the nanoparticle content is investigated. The FTIR spectra show that there are still polymers tightly adsorbed by nanoparticles even after extraction by acetone for 72 h. The difference observed in the XPS spectra of nanocomposite residues and the pure γ‐Al₂O₃ nanoparticles may indicate some interactions between γ‐Al₂O₃ nanoparticles and the PBMA matrix. Furthermore, the feasibility of SDS bilayer formation and encapsulating polymerization is proven by XPS characterization. © 2001 Society of Chemical Industry     

Effect of the sonication and coating time on the photocatalytic degradation of TiO2, TiO2-Ag,and TiO2-ZnO thin film photocatalysts

Abstract

Today, the ultrasound utilizing for material synthesis has been extensively investigated. The unusual acoustic cavitation phenomenon caused by ultrasonic waves has created a new world for the production of high efficiency photocatalysts with new structures. In this study, TiO₂, TiO₂-Ag, and TiO₂-ZnO thin film photocatalysts were prepared using titanium isopropoxide Ti[OCH(CH₃)₂]₄, zinc acetate dehydrates (CH₃COO)₂Zn·2H₂O, and silver nitrate AgNO₃ by a sol–gel method under the ultrasonic irradiation. The prepared photocatalysts were characterized by UV–vis diffuse reflectance spectroscopy, X-ray diffraction, scanning electron microscopy (SEM), and energy dispersive spectroscopy. The SEM images showed that the Ag and ZnO particles were evenly dispersed in the photocatalysts due to the ultrasonic irradiation, and Ag particles were approximately 90?nm, which is relatively small compared to the photocatalysts which is not treated with ultrasonic irradiation. The catalytic activity of the photocatalysts was determined using Acid Red 27 dye. The most excellent catalytic degradation was obtained with TiO₂-ZnO thin film photocatalyst. In comparison to the conventional photocatalyst, the efficiency of photocatalytic activity of the photocatalyst produced under ultrasonication has been increased due to the reduced size of Ag and ZnO and its uniform dispersion.     

A comparative study on the performance of different advanced oxidation processes (UV/O3/H2O2) treating linear alkyl benzene (LAB) production plant's wastewater

A detailed investigation on photooxidation of linear alkyl benzene (LAB) industrial wastewater is presented in this study. The process analysis was performed by varying four significant independent variables including two numerical factors (initial pH (3–11) and initial H₂O₂ concentration (0–20 mM)) and two categorical factors (UV irradiation and ozonation). The experiments were conducted based on a central composite design (CCD) and analyzed using response surface methodology (RSM). To assess the process performance, two parameters viz. TCOD removal efficiency and BOD₅/COD were measured throughout the experiments. A maximum reduction in TCOD was 58, 53, 51, and 49%, respectively for UV/H₂O₂/O₃, H₂O₂/O₃, UV/O₃ and UV/H₂O₂ processes at the optimum conditions (initial pH of 7, initial H₂O₂ concentration of 100 mM, and reaction time of 180 min). A considerable increase in BOD₅/COD ratio was obtained in the combined processes (0.46, 0.51, 0.53, and 0.55 for UV/H₂O₂, UV/O₃, H₂O₂/O₃ and UV/H₂O₂/O₃, respectively) compared to the single oxidant process (0.35). The results showed that mineralization of the LAB industrial wastewater in neutral pH is more favored than in acidic and basic pH. Gas chromatography–mass spectrometry (GC–MS) was applied to show the fate of organic compounds. In conclusion, the photooxidation process (UV/H₂O₂/O₃, H₂O₂/O₃, UV/O₃ and UV/H₂O₂) could be an appropriate pretreatment method prior to a biological treatment process.     

Degradation of C.I. Basic Red 29 solution by combined ultrasound and Co-H2O2 system

Ultrasonic degradation of Basic Red 29 (BR29) textile dye in the presence of Co²⁺-H₂O₂ system was investigated in this study. The effects of presence of ultrasonic power, concentrations of cobalt (II) acetate (Co(II)Act) and H₂O₂, temperature and initial pH on the BR29 degradation were examined. Initial dye concentration of 20 mg/L BR29 was used in the study as a model solution. In sonication experiments, an ultrasonic bath at a frequency of 40 kHz was employed. Best experimental conditions were also obtained in the studies as follows: 1000 mg/L Co(II)Act, 1000 mg/L H₂O₂, 40 °C and original pH of 6.70.According to the results, after 30 min of sonication in the presence of Co²⁺-H₂O₂ dye removal efficiency of practically 100% was achieved. It was also found that US enhanced the degradation rate of BR29.     

Decolourisation and detoxifying of Remazol Red dye and its mixture using Fenton's reagent

A systematic approach was followed to optimise pH, temperature and the doses of FeSO₄ and H₂O₂ for Feton's reagent (FR) to decolourize and detoxify the solutions containing of Remazol Red 120 (RR) dye and its mixture with Remazol Brillant Blue (RB) and Remazol Yellow 84 (RY) reactive dyes. The acute toxicity of each dye composition was measured using D. magna. Optimum pH for RR singly used and for the dye mixture was found 3.5 while optimum temperature was determined 50°C, 40°C and 30°C for 100 mg/l of RR, 200 mg/l of RR and the dye mixture, respectively. More than 98% of colour and 92% of COD removal were obtained for the dye solutions. For obtaining high colour and COD removal H₂O₂ concentration had to be increased 3 times when RR concentration was doubled whereas FeSO₄ was to be increased 2.5 times for the dye mixture. The results obtained indicate that FR can be assurely used for complete toxicity removal and obtaining high colour and COD efficiency with no toxic effluent on D. magna for the dye solutions studied. Acute toxicity test with H₂O₂ was useful to evaluate the complete oxidation resulting in practically no residual H₂O₂ (<3 mg/l) in the solution.     

Comparison of Ozone and Hydroxyl Radical-Induced Oxidation of Chlorinated Hydrocarbons in Water

The efficiency of ozonation and advanced oxidation processes such as ozone/UV, ozone/H₂O₂ and H₂O₂/UV was assessed for chlorinated hydrocarbons using a closed batch-type system. 1,1-Dichloropropene (DCPE), trichloroethylene (TCE), 1-chloropentane (CPA), and 1,2-dichloroethane (DCA) were used as model compounds.

The direct reaction between substrates and ozone predominated at lower pH, which resulted in the efficient oxidation of the olefin, DCPE. At higher pH, ozonation resulted in more efficient oxidation of the chlorinated alkanes, with a corresponding decrease in the efficiency of DCPE oxidation. Consistent results were observed for ozone/H₂O₂ and ozone/UV treatment. Due to slow UV-induced decomposition of H₂O₂, the process using H₂O₂/UV (254 nm) resulted in very slow oxidation of all four compounds.

The total ozone requirement to achieve a given degree of elimination (to 37% of the original concentration), δ0.37, was used to assess the combined effects of the direct and indirect reactions for different types of waters.     

Visible light induced photocatalytic overall water splitting over micro-SiC driven by the Z-scheme system

We present the micro-sized SiC powder applying to overall water splitting under visible light irradiation without adding any sacrificial compounds. The stoichiometric amounts of H₂ and O₂ in 2:1 were obtained when using WO₃ nanoparticle and Pt-loaded micro-SiC grains as the O₂ and H₂ evolution photocatalysts, respectively. The relatively low efficiency step for splitting water reaction is the H⁺ reduction in the solution. Under optimal condition, the apparent quantum efficiency reaches up to 0.021% at 420 nm. Our results provide a method to enhance the photocatalytic activity of micro-sized SiC powder for overall water splitting using solar energy.     

Effect of Inorganic Ions on the Oxidative Efficiency of Ti(IV)-Catalyzed H2O2/O3 Process in the pH Range of 1.0 to 6.0

The oxidative efficiency of Ti(IV)-catalyzed H₂O₂/O₃ (Ti(IV)/H₂O₂/O₃) for acetic acid (HAc) degradation was investigated in the initial pH range of 1.0 to 6.0, and the effects of some common inorganic ions were also discussed in detail. The results showed that the effects of SO₄ ^2? and NO₃ ^? on the efficiency of Ti(IV)/H₂O₂/O₃ were negligible. However, adding Br^? greatly reduced the removal rate of HAc. The presence of Cl^? also reduced the efficiency of Ti(IV)/H₂O₂/O₃, but its negative effect became negligible in the initial pH range of 4.5 to 5.5. The presence of H₂PO₄ ^? could improve the removal rate of HAc, and addition of sodium carbonate had no influence on the efficiency of Ti(IV)/H₂O₂/O₃ in the initial pH range of 4.5 to 5.5.