2-chlorophenol In Aqueous Solution Research Articles

Degradation of 2-Chlorophenol in Aqueous Solutions Using Persulfate Activated by Biochar Supported Sulfide-Modified Nanoscale Zero-Valent Iron: Performance and Mechanisms

In this work, soybean biochar-supported sulfide-modified nanoscale zero-valent iron (BC@S-nZVI) was synthesized and used to activate persulfate (PS) to degrade 2-chlorophenol (2-CP) in aqueous solutions. Batch experiments were carried out to investigate the degradation effects under different conditions, including initial mass ratios among 2-CP, PS, and BC@S-nZVI, initial pH values, temperature, and anions. The results showed that the mass ratio of PS to 2-CP equal to 70 and the mass ratio of BC@S-nZVI to PS equal to 0.4 were the optimum mass ratios in the degradation system. The degradation efficiency of 2-CP was higher under acidic and alkaline conditions than the neutral condition, and the effect was best at a pH of 3; meanwhile, it increased with the increase in temperature. Moreover, the degradation rate was restrained with the addition of Cl−, promoted with the addition of NO3− and CO32−. Both free radical and material functions played leading roles in the degradation of 2-CP, and the stability of BC@S-nZVI was better than nZVI and S-nZVI. The experimental results showed that it was promising to remove 2-CP and other organic pollutants from groundwater by PS activated with BC@S-nZVI.

ZnO-Based Catalyst for Photodegradation of 2-Chlorophenol in Aqueous Solution Under Simulated Solar Light Using a Continuous Flow Method

ZnO nanoparticles, stacked on the bottom of a glass dish, were used as a catalyst for the photodegradation of aqueous 2-chlorophenol (2-CP) contaminant. Solutions of 2-CP at different concentrations and pH values were passed over the ZnO film under simulated solar light. The effect of the light intensity on the contaminant photodegradation rate was investigated. The photodegradation efficiency was evaluated based on the percentage degradation, turnover number, turnover frequency, and quantum yield. The reaction efficiency parameters showed no significant variation when changing the pH across moderate values (neutral, slightly basic, and slightly acidic). Complete mineralization of the contaminant to CO2, H2O, and other minerals was confirmed by various analytical methods including high-performance liquid chromatography, ultraviolet–visible (UV–Vis) spectroscopy, and total organic carbon measurements. The continuous flow method applied in this work showed promising results in terms of safe removal of 2-CP from water at laboratory scale. More study of this method is needed to enable its use at larger, pilot plant scale.

Adsorption of 2-chlorophenol onto the surface of underutilized seed of Adenopus breviflorus: A potential means of treating waste water

Seed of Adenopus breviflorus was prepared as an adsorbent and its adsorption capacities for 2-chlorophenol in aqueous solutions was studied. Fourier Infrared spectroscopy (FTIR), X-ray Diffraction analysis (XRD), particle size distribution, zeta potential, thermogravimetric (TG) analysis and Scanning Electron Microscopy (SEM) measurements were used to characterize the A. breviflorus seed adsorbent. The kinetics studies showed that the adsorption of 2-chlorophenol onto the adsorbent followed the pseudo-second order model while adsorption isotherm plots yielded good results for Temkin, Langmuir and Freundlich models. The adsorption capacity of 2-chlorophenol onto A. breviflorus seed increased with a decrease in pH of 2-chlorophenol solution. From the study, seed of A. breviflorus exhibited properties which suggested its potential application as adsorbent for the removal of 2-chlorophenol from polluted or waste water.

Ozonation of 2-Chlorophenol in Aqueous Solution in a Novel Rotating Packed Contactor

AbstractA modified rotating packed contactor was designed and evaluated for the mass transfer of ozone and the ozonation efficiency of 2-chlorophenol under various operational conditions. The rotating packed contactor was composed of an immobilized disc and a rotating packed disc. Both the overall ozone transfer coefficient and decomposition rate of 2-chlorophenol by ozonation process in the modified rotating packed bed were enhanced with increasing rotor speed or decreasing gas/liquid flow rate ratio. The decomposition rate of 2-chlorophenol was accelerated by increasing H

Visible light photocatalytic activity of Fe3+-doped ZnO nanoparticle prepared via sol–gel technique

The optical properties of a ZnO photocatalyst were enhanced with various dopant concentrations of Fe3+. Doped ZnO nanoparticles were synthesized via a sol–gel method without the use of capping agents or surfactants and was then characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and ultraviolet–visible (UV–Vis) spectroscopy. The results showed that ZnO has a wurtzite, hexagonal structure and that the Fe3+ ions were well incorporated into the ZnO crystal lattice. As the Fe3+ concentration increased from 0.25wt.% to 1wt.%, the crystal size decreased in comparison with the undoped ZnO. The spectral absorption shifts of the visible light region (red shift) and the band gap decreases for each Fe–ZnO sample were investigated. The photocatalytic activities of the ZnO and Fe–ZnO samples were evaluated based on the degradation of 2-chlorophenol in aqueous solution under solar radiation. The samples with a small concentration of Fe3+ ions showed enhanced photocatalytic activity with an optimal maximum performance at 0.5wt.%. The results indicated that toxicity removal of 2-chlorophenol at same line of degradation efficiency. Small crystallite size and low band gap were attributed to high activities of Fe–ZnO samples under various concentrations of Fe3+ ions compared to undoped ZnO.

Gallium- and iodine-co-doped titanium dioxide for photocatalytic degradation of 2-chlorophenol in aqueous solution: Role of gallium

Visible-light-driven TiO2-based catalysts for the degradation of pollutants have become the focus of attention. In the present work, iodine-doped titania photocatalysts (I-TiO2) were improved by doping with gallium (Ga,I-TiO2) and the resulting physicochemical properties and photocatalytic activity were investigated. The structural properties of the catalysts were determined by X-ray diffraction, UV–vis diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy, Brunauer–Emmett–Teller analysis and transmission electron microscopy. We found that Ga probably enters the TiO2 framework for doping levels <0.5mol%. A further increase in Ga content probably leads to dispersal of excess Ga on the TiO2 surface. The photocatalytic activity of Ga,I-TiO2 catalysts was evaluated using 2-chlorophenol (2-CP) as a model compound under visible and UV–vis light irradiation. The results indicate that 0.5mol% Ga loading and calcination at 400°C represent optimal conditions in the calcining temperature range 400–600°C and with doping levels from 0.1% to 1mol%. The effective enhancement of 2-CP degradation might be attributed to the formation of oxygen vacancies by Ga doping, which could decrease the recombination of electron–hole pairs.

Dopant Effects on the Photocatalytic Activity of Colloidal Zinc Sulfide Semiconductor Nanocrystals for the Oxidation of 2-Chlorophenol

In this work, colloidal zinc sulfide nanocrystals, prepared with selected concentrations of manganese(II) ions in the range of 0−2% and stabilized with a polymeric capping agent, were used in the photocatalytic degradation of 2-chlorophenol in aqueous solutions. Particle sizes for the synthesized nanocrystals were determined using UV−vis absorbance spectroscopy and X-ray diffraction (XRD). UV−vis spectra for all of the synthesized nanocrystals display an excitonic peak at around 290 nm, which corresponds to a particle size of approximately 3 nm, in agreement with the XRD analysis. Photoluminescence emission spectra recorded for undoped ZnS nanocrystals exhibit an emission peak at 460 nm in the spectrum, whereas peaks corresponding to the dopant ion are red-shifted to 590 nm. With increasing addition of the dopant ion, the area of the peak at 460 nm first increases and then decreases for higher dopant concentrations, whereas the area of the peak at 590 nm increases. This finding clearly indicates that the ...

Catalytic wet air oxidation of substituted phenols: Temperature and pressure effect on the pollutant removal, the catalyst preservation and the biodegradability enhancement

The influence of temperature (140 and 160 ◦ C) and oxygen partial pressure (2 and 9 bar) on the continuous catalytic wet air oxidation (CWAO) over activated carbon (AC) has been investigated for the removal of phenol, o-cresol and 2-chlorophenol in aqueous solutions. Seventy-twohour tests were performed in a fixed bed reactor in trickle flow regime. A commercial AC was employed as catalyst. The pollutant elimination effectiveness, the distribution of major reaction products and the AC behaviour were studied for each compound. Also, respirometric screening tests were completed to the effluents before and after each CWAO experiment to assess the biodegradability enhancement. The results show that pollutant disappearance, chemical oxygen demand (COD) removal, total organic carbon (TOC) abatement and biodegradability enhancement (fraction of COD readily biodegradable, %CODRB) were very sensitive to temperature but rather independent of the oxygen partial pressure (PO2 ). On the contrary, AC catalyst preservation was strongly influenced by both temperature and pressure. For instance, for phenol CWAO at 2 bar of PO2 ,a s temperature increased from 140 to 160 ◦ C, phenol conversion increased from 45% to 78%, COD removal from 33% to 65%, TOC abatement from 21% to 62% and %CODRB from 4% to 36%. Similar behaviour was found for the other model compounds tested, although the level of refractoriness was rather different. © 2007 Elsevier B.V. All rights reserved.

Ozonation of 2-Chlorophenol in Aqueous Solutions with a Packed Contactor

The dissolution of ozone and the decomposition of 2-chlorophenol were noticeably enhanced for experiments conducted in the fixed packed contactor than those conducted in a bubble column. The rate of ozone transfer was increased with the increasing amount of Pall rings contained in the packed contactor and the decreasing gas/liquid ratio (G∕L) because the gas–liquid interface may be renewed effectively. The decomposition of 2-chlorophenol by ozonation was found to be faster for experiments conducted in alkaline solutions while the decomposition of total organic carbon only slightly enhanced. However, the decomposition of total organic carbon only slightly increased for experiments conducted in alkaline solutions.

Kinetics of the degradation of 2-chlorophenol by ozonation at pH 3

Prediction of byproduct distribution during ozonation is of importance to the design of treatment process. In this study, degradation products in direct ozonation of 2-chlorophenol in aqueous solution were identified by employing the chemical derivatization technique, specifically, silylation. Transient distribution of degradation products, in a semi-batch reactor under three ozone dosages were identified and determined by HPLC analysis. An empirical degradation pathway was proposed to describe the ozonation reaction. A mathematical protocol consisting of 11 equations and 12 rate constants was developed to solve and optimize the kinetic parameters. Modeling results revealed that the empirical pathway was capable of predicting the ozonation reaction at the beginning phase under a higher ozone dosage (e.g., greater than 6 mg/L g). The degree of agreement between predicted and experimental data decreased as the ozone dosage decreased to 1.2 mg/L g. Results suggested that there was a dosage-dependent pathway in the direct ozonation of 2-chlorophenol.

Photocatalytic decomposition of 2-chlorophenol in aqueous solution by UV/TiO 2 process with applied external bias voltage

The decomposition of 2-chlorophenol by UV/TiO 2 process with the application of external bias voltage was examined in this study. Experiments were conducted in a batch reactor using TiO 2-coated titanium sheet as anode and platinum sheet as cathode. The anode photocatalysis of 2-chlorophenol was totally inhibited for experiments conducted with the application of external anodic bias voltage lower than the flat band potential of TiO 2. The decomposition rate of 2-chlorophenol was then increased with increasing external anodic bias voltage applied up to 0.0 V (versus SCE). The application of external bias voltage higher than 1.0 V did not markedly promote the photocatalysis of 2-chlorophenol possibly because the photocurrent induced was constant. Experimental results indicated that the decomposition of 2-chlorophenol was more effective for experiments conducted in acidic solutions due to the lower flat band potential of TiO 2 and the higher photocurrent induced. The presence of electron scavengers in aqueous solution, such as oxygen molecules, may increase the decomposition rate of 2-chlorophenol. However, the effect of dissolved oxygen was diminished for experiments conducted with applied external bias voltage. The photocatalytic decomposition rate of 2-chlorophenol was enhanced linearly with the increasing UV light intensity when the external bias voltage was applied.

Decomposition of 2-Chlorophenol in Aqueous Solutions by Ozone and UV/Ozone Processes in the Presence of t-Butanol

The decomposition of 2-chlorophenol in aqueous solutions by ozone and UV/ozone process was studied with the presence of t-butanol. The addition of t-butanol decreased the surface tension of aqueous solutions and subsequently increased the gas-liquid contact area. The presence of t-butanol did not affect the steady-state dissolved ozone concentration in aqueous solution; however, the ozone transfer rate between gas-liquid interface was noticeably enhanced and the time required to reach the steady state was reduced. The presence of t-butanol was found to promote the decomposition of 2-chlorophenol for both ozone and UV/ozone processes. Nonetheless, the presence of excessive dosages of t-butanol might decrease the reaction rates for experiments conducted in alkaline solutions probably because t-butanol also served as the scavenger for hydroxyl free radicals.

Adsorption/ion-exchange behavior between a water-insoluble cationic starch and 2-chlorophenol in aqueous solutions

Adsorption/ion-exchange behavior between a water-insoluble cationic starch and 2-chlorophenol in aqueous solutions

Ultrasonic destruction of 2-chlorophenol in aqueous solution

The decomposition of 2-chlorophenol in aqueous solution by ultrasonic waves was studied under various process variables including solution pH level, dissolved oxygen value and solution temperature to investigate the temporal behavior of this reaction. The phases of reaction, gaseous in the cavitation bubble and aqueous in the film, are found to be determined by the solution pH. The presence of dissolved oxygen in aqueous solution plays a major role on the mechanisms involved, pyrolysis or free radical attack, for the decomposition of 2-chlorophenol by sonolysis. The decomposition rate of 2-chlorophenol was found to be slightly reduced at higher solution temperature. A two-phase reaction scheme was proposed to explain the effect of process variables on the 2-chlorophenol decomposition by sonication.

Decomposition of 2-chlorophenol in aqueous solution by UV irradiation with the presence of titanium dioxide

The decomposition of 2-chlorophenol in aqueous solution by UV TiO 2 oxidation process was studied under various solution pH values, light intensities and types of TiO 2. The removal of 2-chlorophenol and organic intermediates was found to be more effective for acidic solutions. The decomposition of 2-chlorophenol can be fitted well by a pseudo first-order kinetics. Experimental results indicated that the distribution of non-chlorinated and chlorinated intermediates on the photocatalytic decomposition rate of 2-chlorophenol were highly dependent on solution pH. At the same light intensity, the adequate dosage of TiO 2 was found to be less for alkaline solutions than that for acidic solutions. Increasing the light intensity would significantly increase the decomposition rate of 2-chlorophenol at pH 3, but not at pH 11. Both rutile and anatase forms of TiO 2 were used in this study. The destruction rate of 2-chlorophenol of unit weight of rutile was less than that of anatase. However, the decomposition rates of 2-chlorophenol of unit surface area for both were almost the same in this research. Thus, the difference of the decomposition rates of 2-chlorophenol might be attributed to the difference of the surface area of various forms of TiO 2, not to the difference of the crystal properties.

Decomposition of 2-chlorophenol in aqueous solution by ultrasound/H2O2 process

Several authors have indicated that ultrasound is effective in oxidizing organic contaminants in water and in wastewater either as the sole means of treatment or in combination with ozonation and UV irradiation. In this work we decomposed 2-chlorophenol (2-cp) in aqueous solution with ultrasound and H2O2. The experiment was conducted with a sonicator (Microson XL-2020) operated at 20 kHz. The double amplitude at the tip of the standard horn (12.7 mm) was adjusted to 0, 72 and 120 μm, corresponding to power input 0, 125 and 160 W. The initial concentration of aqueous 2-cp solution was 100 mg/l, treated in the system with 0, 100, 200 and 500 mg/l H2O2 individually. The volume of solution was 1 l in a mixing flask, and was circulated to the sonication cell at the rate 500 mL/min. Oxygen was continuously purged into the flask. The temperature of solution was kept constant at 25°C and pH was controlled at 3, 5, 7, 9 and 11. The results showed the decomposition of 2-cp was effective at increased amplitude of ultrasound and concentration of H2O2, and smaller pH. At reaction duration 360 min, 2-cp decomposition with 500 mg/l H2O2 was found with 57% improvement over the control, i.e. without H2O2 addition. The pH, controlled below the pKa of 2-cp (8.49 at 25°C), had significantly better decomposition of 2-cp than at greater values. The decomposition rate of 100 mg/l 2-cp was 99% at 120 μm double amplitude with H2O2 (200 mg/L) and pH 3, after 360 min of reaction. The removal of total organic carbon was found to be only 63%. From analysis of the experimental results, the data on 2-cp decomposition appeared to follow pseudo-first-order reaction kinetics. The squared correlation coefficient, R2, of the model was greater than 0.9 for various pH values.

Decomposition of 2-chlorophenol in aqueous solution by ultrasound/H2O2 process

Several authors have indicated that ultrasound is effective in oxidizing organic contaminants in water and in wastewater either as the sole means of treatment or in combination with ozonation and UV irradiation. In this work we decomposed 2-chiorophenol (2-cp) in aqueous solution with ultrasound and H2O2. The experiment was conducted with a sonicator (Microson XL-2020) operated at 20 kHz. The double amplitude at the tip of the standard horn (12.7 mm) was adjusted to 0, 72 and 120 εm, corresponding to power input 0, 125 and 160 W. The initial concentration of aqueous 2-cp solution was 100 mg/l, treated in the system with 0, 100, 200 and 500 mg/H2O2 individually. The volume of solution was 1 1 in a mixing flask, and was circulated to the sonication cell at the rate 500 mL/min. Oxygen was continuously purged into the flask. The temperature of solution was kept constant at 25±C and pH was controlled at 3, 5, 7, 9 and 11. The results showed the decomposition of 2-cp was effective at increased amplitude of ultrasound and concentration of H2O2 and smaller pH. At reaction duration 360 mi 2-cp decomposition with 500 mg/l H2O2 was found with 57% improvement over the control, i.e. without H2O2 addition. The pH, controlled below the pKa of 2-ep (8.49 at 25±C), had significantly better decomposition of 2-cp than at greater values. The decomposition rate of 100 mg/l 2-cp was 99% at 120 µm double amplitude with H2O2 (200 mg/L) and pH 3, after 360 mm of reaction. The removal of total organic carbon was found to be only 63%. From analysis of the experimental results, the data on 2-cp decomposition appeared to follow pseudo-first-order reaction kinetics. The squared correlation coefficient, R2, of the model was greater than 0.9 for various pH values.