Degradation Of 2,4-dichlorophenol Research Articles

Loading nano-rod cobalt phthalocyanine onto nitrogen-doped graphene and its application in photodegradation reaction under visible-light

The preparation of nanostructure cobalt phthalocyanine/nitrogen-doped graphene (CoPc/NG) composite is described in this contribution. The products were characterized by X-ray diffraction (XRD), FT-IR, Raman spectrometer, X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS and Map). The photocatalytic activity of the final product was tested for degradation of 2,4-dichlorophenol (DCP), as a probe contaminant under visible-light irradiation. The result shows that the DCP degradation efficiency is increased with a hybrid of CoPc and nitrogen-doped graphene (NG). This composite could eliminate about 80% of DCP (50 mL, 40 mg L-1) within 135 min. The study of kinetic models showed that the DCP degradation process follows pseudo first-order kinetics. The prepared CoPc/NG composite containing an appropriate dose of nitrogen exhibited the highest reaction rate constant in comparison with other catalysts.

Surfactant-assisted removal of 2,4-dichlorophenol from soil by zero-valent Fe/Cu activated persulfate

The organic compounds contaminated soil substantially threatens the growth of plants and food safety. In this study, we synthesis zero-valent bimetallic Fe/Cu catalysts for the degradation of 2,4-dichlorophenol (DCP) in soils with persulfate (PS) in combination of organic surfactants and exploring the main environmental impact factors. The kinetic experiments show that the 5% (mass) dosage of Fe/Cu exhibits a higher degradation efficiency (86%) of DCP in soils, and the degradation efficiency of DCP increases with the increase of the initial PS concentration. Acidic conditions are favorable for the DCP degradation in soils. More importantly, the addition of Tween-80, and Triton-100 can obviously desorb DCP from the soil surface, which enhances the degradation efficiency of DCP in soils by Fe/Cu and PS reaction system. Furthermore, the Quenching experiments demonstrate that S O 4 - · and OH are the predominant radicals for the degradation of DCP during the Fe/Cu and PS reaction system as well as non-radical also exist. The findings of this work provide an effective method for remediating DCP from soils.

Synthesis of an efficient photocatalyst by incorporation of phthalocyanine into KIT-6

The three dimensional KIT-6 with interconnected channels was synthesized and was used for uploading sulphonated copper phthalocyanine (CuPcS). Grafting of CuPcS to the walls of KIT-6 was performed by anchorage of 3-(aminopropyl)-triethoxysilane onto KIT-6 via post-synthesis method. Exploitation of dimethyl sulfoxide as solvent caused a high amount of CuPcS to be loaded onto KIT-6. The CuPcS/NH2-KIT-6 was comprehensively characterized using small-angle X-ray diffraction, nitrogen BET and BJH physisorption, diffuse reflectance spectroscopy, FTIR, scanning electron microscopy, energy-dispersive X-ray and transmission electron microscopy methods. The photocatalyst was tested for degradation of 2,4-dichlorophenol (DCP) in aqueous solutions under visible and UV-A light irradiation. The results obtained reveal that a very low amount of the photocatalyst can progressively and efficiently proceed degradation of DCP. The decomposition process is completed within about 3 h using a dose of 0.2 g/L of the catalyst under visible light. The reusability of the catalyst is fine and there is not any obvious reduction in its activity following four cycles of repeated use. The kinetics of photodegradation and the intermediates products were studied and the mechanism of the photocatalyst was clarified upon the obtained results.

Synthesis, characterization and photocatalytic studies of MCM-41 mesoporous silica core-shells doped with selenium oxide and lanthanum ions

Abstract A synthesis method was developed to produce uniform micro-size spheres of silica coated with MCM-41 mesoporous shell for preparation of SiO2@MCM-41 core-shell. Lanthanum ion and selenium dioxide, were introduced separately and together into this core-shell structure. The SiO2@MCM-41, SiO2@SeO2-MCM-41, La–SiO2@MCM-41 and La–SiO2@SeO2-MCM-41core-shells were prepared. A range of reliable instruments and methods including X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), Barrett-Joyner-Halenda (BJH), DLS (dynamic light scattering) and energy-dispersive X-ray spectroscopy (EDS) were employed for characterization of the fabricated core-shells. It was found that presence of La in the core and SeO2 in the mesoporous shell, generate very efficient photocatalytic activity of the materials. The prepared photocatalysts were used for degradation of 2,4-dichlorophenol (DCP) as a model compound. The obtained results showed the photocatalytic efficiency was increased in the order of SiO2@MCM-41 (5%)

Degradation kinetics of 2,4-dichlorophenol by gamma ray irradiation in the presence of ozone

Gamma ray-induced degradation of 2,4-dichlorophenol (DCP) in the presence of ozone has been investigated. The results show that ozone can remarkably increase the degradation rate of 2,4-DCP in aqueous solution. The degradation kinetics of 2,4-DCP can be described by the first-order reaction model, and the rate constant was 0.443, 0.490 and 1.247 h−1, respectively, for γ-ray irradiation only, γ-ray irradiation + 13 mg/L O3 and γ-ray irradiation + 30 mg/L O3. High-performance liquid chromatography analysis shows that the dechlorinated products are 4-chlorophenol, 2-chlorophenol and phenol; and the oxidation products are hydroquinone, benzoquinone, maleic, fumaric, acrylic, malonic, oxalic, acetic and formic acids. The possible pathways for 2,4-DCP degradation involving all these oxidation products are tentatively proposed. Combining γ-ray irradiation with ozonation is a promising technology for removing toxic pollutants from water and wastewater.

Study on Photocatalytic Degradation of 2,4-Dichlorophenol by ZnS Microsphere.

The self-supported ZnS microsphere composed of interwoven nanosheets was synthesized by hydrothermal method. The as-prepared ZnS powders were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The photocatalytic activity of the fabricated ZnS powders was evaluated by the degradation of 2,4-dichlorophenol (DCP) under UV light. Effects of DCP initial concentration, ZnS dosage, solution pH, light source, and dissolved oxygen on DCP photocatalytic degradation efficiency were investigated and optimized systematically. Results demonstrated that 53% of DCP could be effectively degraded under the optimal experimental conditions. Finally, high-performance liquid chromatography (HPLC) and gas chromatography-mass spectrometry (GC-MS) were used to analyze the degradation products. Based on the experimental results obtained, a prob- able degradation pathway was proposed.

Nonmetal species in the carbon modified TiO2 and its visible light photocatalytic activity

A carbon modified TiO2 (CT) was synthesized by hydrolyzing titanium tetrachloride with diethylamine and calcination at 400°C. CT was then handled with a NaOH aqueous solution elution and a subsequent re-assembling treatment. X-ray diffraction (XRD), transmission electron microscopy (TEM), nitrogen adsorption–desorption analysis, X-ray photoelectron spectroscopy (XPS), thermogravimetric and differential thermal analysis (TG-DTA), chemical oxygen demand (COD) and UV-vis diffuse reflectance spectroscopy (DRS) were then used to assess the changes of CT during the whole process. It is revealed that carbon in the CT should mostly be presented as surface deposited organic matters but not likely doped into the TiO2 lattice. CT exhibits obvious visible absorption and high photocatalytic activity for the degradation of 2,4-dichlorophenol (DCP) under visible light irradiation. Meanwhile, CT photocatalyst possesses excellent stability and reusability. NaOH solution elution washes off a large amount of surface deposited organics and worsens the visible absorbance and photocatalytic activity of CT, which can be well recovered by the re-assembling treatment. The re-assembled photocatalyst, CTSL, exhibits exhibits a very similar photocataytic activity with CT for degradation of DCP under the visible light irradiation, but is much higher than that of CTS.

Photocatalytic degradation of 2, 4-dichlorophenol using granular activated carbon supported TiO 2

Photocatalytic degradation of 2, 4-dichlorophenol (DCP) using granular activated carbon (GAC) supported TiO 2 (Ti–GAC, using sol–gel method) is investigated. Operation parameters including annealing temperature, catalyst loading, air flow rate, initial pH and DCP concentration are optimized. The results show that DCP removal increases with the increase of Ti–GAC while decreases with the increase of initial DCP concentration. DCP is removed much faster in neutral conditions than in acidic or alkaline conditions. Comprehensive comparison among adsorption, photolysis and photocatalysis in DCP removal is conducted to reveal the synergistic effect in the photocatalysis process, and the results indicate that the DCP is removed by the joint effect of adsorption and HO∙ oxidation. In addition, the photocatalysis is applied in a continuous form to treat DCP polluted real raw water for drinking water production, and it is found to have potentially advantageous on dissolved pollutants in drinking water, and would have great potential for a wide range of practical applications.

ZnO activation by using activated carbon as a support: Characterisation and photoreactivity

The effect of the mixing ZnO with different portions of activated carbon (AC) has been studied. The resulting catalysts were characterised and evaluated in the photocatalytic decomposition of aqueous pollutants. Changes in the catalyst colour and in the FTIR vibration bands of the surface hydroxyl groups were recorded. νOH vibrations were shifted to lower wavenumbers as AC loading increased, demonstrating modification of the acid-base character of the catalysts. Laser scattering studies showed that AC loading leads to smaller ZnO particles. BET surface area measurements and scanning electron micrograph (SEM) analysis showed agglomeration of ZnO particle pores in the AC structure. Results showed that in addition to a synergistic effect of the AC-ZnO combination, AC content modifies the ZnO particle properties and consequently photocatalytic behaviour. This was evident in phenol degradation experiments where changes in the concentration profiles of the catechol and hydroquinone degradation intermediates, were observed. However, the AC-ZnO catalysts were less efficient than pure ZnO in the degradation of 2,4-dichlorophenol (DCP). This seems to be due to the strong adsorption of the DCP molecule on AC, resulting in lower diffusion to the catalytic ZnO and thus a lower rate of photocatalysis.

Visible-light-driven boron/ferrum/cerium/titania photocatalyst

A boron/ferrum/cerium/titania photocatalyst with visible-light-induced performance was prepared by the conventional sol–gel method, in which tetrabutyl titanate (Ti(O- nC 4H 9) 4) was used as the precursor and boric acid (H 3BO 3), ferric nitrate enneahydrate (Fe(NO 3) 3·9H 2O), and cerium nitrate hexahydrate (Ce(NO 3) 3·6H 2O) were the sources of boron, ferrum, and cerium, respectively. The microstructure and optical property of the photocatalyst were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), N 2 adsorption–desorption isotherm, and UV–vis diffusive reflectance spectroscopy (DRS). It was found that the as-prepared photocatalyst composed of anatase and that the presence of impurities could retard phase transformation of TiO 2 from anatase to rutile at elevated temperatures and could prohibit growth of polycrystalline, which favored forming photocatalyst with large surface area. Degradation of 2,4-dichlorophenol (DCP) under visible light illumination was used to evaluate the photocatalytic activity. Comparative investigations showed that photocatalytic performance of the boron/ferrum/cerium/titania photocatalyst was the highest among the all test samples. It was testified that boron doping led to the band gap narrow and the response to visible light, and that ferrum and cerium impurities, which presented in the forms of FeO/Fe 2O 3 and Ce 2O 3/CeO 2, dispersed on the surface of TiO 2, suppressed the electron and hole recombination, and resulted in the enhancement of catalytic performance. The results exhibited that the synergistic effects of boron, ferrum and cerium played an important role in the band gap narrow and the increase of photoactivity.

Higher intrinsic photocatalytic efficiency of 2,4,6-triphenylpyrylium-based photocatalysts compared to TiO 2 P-25 for the degradation of 2,4-dichlorophenol using solar simulated light

The photocatalytic efficiency of two 2,4,6-triphenylpyrylium (TP +) based photocatalysts (supported on silica or incorporated inside zeolite Beta, 3 wt%) for the degradation of 2,4-dichlorophenol (DCP) in aqueous media has been compared with TiO 2 (Degussa P-25). It was found that the efficiency of the degradation depends on the photocatalytic setup, recirculation through a tubular reactor being highly unfavorable for the TP +-based photocatalysts due to the deposition of the silica or zeolite particles. In contrast, high efficiency in DCP disappearance (up to 87%) and in the total organic content decrease (up to 62%) were obtained using a discontinuous batch reactor in which the TP + photocatalysts were uniformly suspended. Kinetic studies were also made and DCP degradation follows a first order kinetics. The obtained kinetic constants when corrected to account for the influence of the fraction of light absorbed and the amount of active sites shows that the intrinsic activity of TP + adsorbed on silica or incorporated inside zeolite Beta was over one order of magnitude higher than TiO 2 activity.

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.

Comparative Study of 2,4-Dichlorophenol Degradation With Different Advanced Oxidation Processes

Chlorophenols (CPs) are toxic nonbiodegradable pollutants. In recent decades, several alternative processes for the treatment of these compounds have been investigated. Advanced Oxidation Processes (AOPs) are some of the most promising technologies. Among them, the UV-based AOPs [O3+Fe(II)+UV, photo-Fenton, UV+Fe(III), UV+H2O2, photocatalysis and photolysis] have previously been studied for the degradation of 2,4-dichlorophenol (DCP) in an aqueous solution at laboratory scale. In this paper, these techniques are compared and kinetic constants and pseudoquantum yields are estimated. O3−+Fe(II)+UV and photo-Fenton seem to be the most effective. To study scale-up of these processes from the laboratory to a pilot plant operating with sunlight, equivalent photocatalytic experiments were carried out in such installations. The results are promising and show trends similar to those obtained in the laboratory with lamps. The data obtained have been used to calculate some scale-up factors, which have been employed to make a rough estimation of the amount of waste water that can be treated by the solar AOPs studied. The results obtained are encouraging and prove the feasibility of this type of technology.

Kinetics of 2,4-dichlorophenol degradation by Pseudomonas putida CP1 in batch culture

Abstract Biological degradation of 2,4-dichlorophenol (DCP) by Pseudomonas putida CP1 was investigated in batch shake flask-cultures. Experiments were carried out at initial DCP concentrations between 50 and 750 mg l - 1 and the rate and extent of DCP degradation were quantified. With increasing initial DCP concentrations in shake-flask cultures, percentage removal of DCP decreased and residual DCP concentrations increased proportionally. The rate of DCP degradation increased with increasing initial DCP concentration up to 577 mg DCP l - 1 . Further increases in DCP concentration caused decreases in the rate of degradation because of substrate inhibition. A kinetic model based on substrate inhibition was proposed. Rate and inhibition constants were determined using the experimental data.

Photocatalysis by titanium dioxide and polyoxometalate/TiO2 cocatalysts. Intermediates and mechanistic study.

A representative polyoxometalate, alpha-12-tungstophosphatic acid (PW12(3-), POM), is loaded on the surface of TiO2 particles used as a cocatalyst to gain further insights into the underlying reaction mechanism and to estimate the feasibility of using the new POM/TiO2 cocatalyst in the photocatalytic degradation of 2,4-dichlorophenol (DCP) in aqueous media. Loading the PW12(3-) species on the surface of TiO2 enhances charge separation in the UV-illuminated TiO2, thereby accelerating the hydroxylation of the initial DCP substrate but not the mineralization of DCP, which is somewhat suppressed in the presence of the polyoxometalate. An increase in the load of POM increases the concentration of aromatic intermediates, and more toxic intermediates, such as 2,6-dichlorodibenzo-p-dioxin, 2,4,6-trichlorophenol, are detected in the PW12(3-)/TiO2 system. By contrast, cleavage of the whole conjugated structure of DCP predominates in TiO2 only dispersions. Strong ESR signals for the superoxide radical anionic species, O2*- (HO2* radicals in acidic media; pH < 5), are detected in TiO2 only dispersions; signals of O2*- are much weaker in the TiO2/ POM composite system under otherwise identical conditions. Experimental results infers that enhancement of charge separation in TiO2 photocatalysis does not always result in improvement of the efficiency of mineralization of organic substrates, and the reaction between organic radical cations and the formed superoxide radical anions may be responsible forthe mineralization of the chlorophenol.

Degradation of various chlorophenols under alkaline conditions by gram-negative bacteria closely related to Ochrobactrum anthropi.

From concrete debris of a demolished herbicide production plant several Gram-negative bacterial strains were isolated, which exhibit metabolic capabilities for the degradation of 2,4-dichlorophenol (DCP)l), 4-chloro-2-methylphenol (MCP) and 4-chlorophenol (4-CP), while 2-chlorophenol (2-CP) was degraded at a slower rate. Degradative activity was inducible and was impeded by adding of 100 mg/l of chloramphenicol to growing cultures. The strains displayed alkaliphilic properties with optimum DCP/MCP degradation at pH values around 8.5-9.5; activity was observed up to pH values of 11. Degradation was most likely complete according to chlorine balances; formation of intermediary products was observed with MCP some time. Specific activity of up to 380 mumol/h.g dry mass was found within the concentration range of 10-20 mg/l DCP; higher concentrations retarded the activity with complete inhibition at 200-400 mg/l. Some of the strains carry plasmids whose presence was not unambiguously correlated to the degradative properties. Ribotyping revealed a high degree of relationship between the strains. Preliminary taxonomic investigations showed close relationship to Ochrobactrum anthropi.

Photochemistry of semiconductor particles. Part 4.—Effects of surface condition on the photodegradation of 2,4-dichlorophenol catalysed by TiO2suspensions

The photocatalysed degradation of 2,4-dichlorophenol (DCP) has been investigated in aqueous suspensions of TiO2. A possible reaction scheme has been proposed for the degradation, in which chlorobenzoquinone (CBQ) was detected as a predominant intermediate present in the reaction solution. Kinetic details for the degradation steps have been analysed based on the experimental results. The essential role of oxygen was considered to be the capturing of the photogenerated electron to form the oxidizing species, such as H2O2, HO˙2 and OH˙. In anaerobic conditions, the photodegradation rate was quite low even with the adsorbed Cu2+ ion on the TiO2 powder as an alternative electron scavenger. This is due to the rapid indirect recombination of the photogenerated electron and hole, which is mediated by the short-circuiting reaction of Cu2+. However, in aerobic conditions, oxygen takes up the photogenerated electron trapped at the adsorbed Cu2+ ion to prevent it from recombining with the photogenerated hole. As a result, the hole has sufficient opportunity to participate in the oxidizing reactions. The degradation rate was dependent to some extent on the surface charge of the TiO2 particles. Positive charge always promotes the photodegradation, whereas negative change is detrimental. This was attributed to the effects of surface charge on the migration of electrons from the interior of the TiO2 particles to the surface.

Some ecological factors in the degradation of 2,4-dichlorophenol in waters from aquatic environments.

The relationships between the degradation of 2, 4-dichlorophenol (DCP) and the changes in the density of DCP-degraders were examined in water samples from aquatic enviroments. In most of the water samples, the rapid degradation of 1 μg DCP-C·ml-1 or 0.1, μg DCP-C·ml-1 was observed, after a lag period lasting for more than a week, when DCP-degraders had increased to 104-105 cells·ml-1 or 103-104 cells·ml-1, respectively. However, in the water sample from the spring Masugata-no-ike, the degradation of 0.1 μg DCP-C·ml-1 was not observed for 42 day incubation, although DCP-degraders had increased to 104 cells·ml-1 at 35-day incubation. When both nitrogen and phosphorus were added to the water sample, the rapid degradation of DCP was observed. These results suggested that the sufficient increase in the density of DCP-degraders was a prerequisite condition for the degradation of DCP, but ecological factors such as mineral nutrients might limit the expression of the ability of DCP-degraders even when their densities were high.

Possible reasons for the failure of natural microbial community to degrade low concentration of 2,4-dichlorophenol.

The rapid microbial degradation of 2, 4-dichlorophenol (DCP) at 1.0μg DCP-C/ml in a groundwater was observed when the density of responsible degraders, estimated by the most probable number (MPN) method, had increased to 105 cells/ml. However, no degradation of 0.1 or 0.03μg DCP-C/ml was observed even when the density of degraders had increased to 104-105 cells/ml. Rapid degradation of 0.1μg DCP-C/ml occured within a day in the qroundwater in which 1.0μg DCP-C/ml was degraded beforehand, but not in the groundwater which had been precultured with 0.1μg DCP-C/ml. Addition of mineral nutrients enhanced the degradation of 0.1μg DCP-C/ml, but not the growth of degraders. These results suggest that in the groundwater the failure of DCP degradation at low concentration may be attributable to the failure of degraders to express their DCP-degrading activity, such as induction of responsible enzyme(s), and not to the failure to grow or to increase their density.