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PubMed1998

Uptake of moderately hydrophobic chlorophenols from water by semipermeable membrane devices (SPMDs) and by goldfish (Crassius auratus).

Semipermeable membrane devices (SPMDs) filled with triolein and goldfish (Crassius auratus) were simultaneously exposed to nine moderately hydrophobic chlorophenols in a laboratory continuous-flow experiment. The results showed that the test compounds were concentrated in the device to an extent very closed to that in fish. The overall uptake rate constants (Ku) and average pollutant sampling rates (Rs) were similar for both SPMDs and goldfish. We conclude that the SPMDs can be used to estimate the levels of moderately hydrophobic chlorophenols in field water as an environmental monitor.

Animals↗
PubMed2000

Chemical kinetic modelling of PCDD formation from chlorophenol catalysed by incinerator fly ash.

A kinetic model is developed for PCDD formation from chlorophenol catalysed by incinerator fly ash. The key step in the model is a Langmuir-Hinshelwood type elementary step for the coupling of two adsorbed chlorophenol species to PCDD. Kinetic expression is derived which can relate PCDD formation rates with process variables including temperature, precursor concentration, fly ash loading and number of active sites in fly ash. Calculated PCDD formation rates based on this kinetic model are in good agreement with laboratory measurements reported in the literature. When the model is applied to industrial incinerator conditions, at maximum a PCDD yield of 10(-3) microg/N m3 is calculated.

Air Pollution↗
PubMed2002

Impact of protein binding on the availability and cytotoxic potency of organochlorine pesticides and chlorophenols in vitro.

In vitro toxicity data are generally based on nominal concentrations and thus depend on both activity and availability of a compound. The aims of the present study were to examine the influence of protein binding on the cytotoxicity of selected organochlorine pesticides and chlorophenols in Balb/c 3T3 cell cultures and to determine parameters of protein binding which can be used to estimate protein bound fractions and to model distribution in vitro. EC(50)-values derived from concentration-effect relationships determined in the presence of various concentrations of bovine serum albumin (BSA) were linearly correlated to BSA concentration. Increasing the BSA concentration from about 1.2 to 40 mg/ml increased the EC(50)-values by factors between 3.4 and 34.4. Molar ratios of substance bound to albumin ranged from 0.11 to 2.42. Calculated fractions bound to albumin in the normal growth medium were 0.075-0.17 (p,p'-DDT, p,p'-DDE, dieldrin, lindane), 0.09-0.1 (4-mono- and 2,4-dichlorophenol), 0.68 (2,4,5-trichlorphenol) and almost 1.0 (pentachlorophenol). At 40 mg/ml BSA any compound was largely bound to albumin (fractions bound > or = 0.74). Distribution modelling revealed that the availability of the highly hydrophobic organochlorines additionally was significantly reduced by partitioning into lipids. The results clearly demonstrate that nominal and relative toxic potencies of organochlorine pesticides and chlorophenols determined in vitro are substantially influenced by effects of protein binding on availability.

3T3 Cells↗
PubMed2000

Anodic destruction of 4-chlorophenol solution.

The electrochemical oxidation of 4-chlorophenol solutions was studied using a dimensional stable anode (DSA), made of pure titanium sheet mesh coated with Ti/TiO(2) and RuO(2) film. An electrochemical cell with one working electrode and two counter-electrodes was designed. A gas collecting system to collect the electrolysis gaseous products was also designed. The influence of current density (6.51-21.58 mA/cm(2)), pH (2.0-12.6) and initial 4-chlorophenol concentration (25-100 mg/l) on the destruction was investigated. Complete elimination was successfully achieved within 2 h for most investigated conditions. Highest rates of elimination were achieved at a pH of 12.6.A new approach to calculate the current efficiency (CE) of the cell was proposed. The volumes of the gases produced at the anode and at the cathode were the basis for the new CE calculations. It was observed that the worst CE was approximately 20% and the best CE was approximately 89%. The most efficient pH was at 12.6 and the most efficient current density was at 11.39 mA/cm(2).

Chlorophenols↗
PubMed2003

Photocatalytic degradation of 2-chlorophenol: a study of kinetics, intermediates and biodegradability.

The kinetics of photocatalytic (TiO(2)/UV) degradation of 2-chlorophenol (2-CP), characterization of intermediates and induction of biodegradability in treated chlorophenol solutions is reported. Approximately 95% of the 2-CP is removed in approximately 2h at pH 5 and 0.2g TiO(2)l(-1) when the 2-CP concentration is < or =100mgl(-1); the pseudo-first-order rate constant (k) is estimated to be 0.0183 min(-1). GC-MS analyses detected phenol, catechol, hydroxyhydroquinone (HHQ), and chlorohydroquinone (CHQ) intermediates during the short irradiation time (<1h); however two other higher carbon intermediates 2-hydroxy-benzaldehyde (HB) and [1.1'-biphenyl]-2,2'-diol (BPD) are found as major intermediates over longer irradiation times. The biochemical oxygen demand (BOD) of treated 2-CP solutions improved substantially. A tentative mechanistic pathway to explain formation of higher carbon intermediates is presented.

Biodegradation, Environmental↗
PubMed2001

Photochemical oxidation of p-chlorophenol by UV/H2O2 and photo-Fenton process. A comparative study.

In this study, photochemical advanced oxidation processes (AOPs) utilizing the combinations of UV/H2O2 and the photo-Fenton reaction (UV + classical Fenton reaction) were investigated in lab-scale experiments for the degradation of p-chlorophenol. The study showed that the photo-Fenton process, (a mixture of hydrogen peroxide and ferrous or ferric ion), was the most effective treatment process under acidic conditions and produced a higher rate of degradation of p-chlorophenol at a very short radiation time. It accelerated the oxidation rate by 5-9 times the rate for the UV/H2O2 process. The reaction was found to follow the first order, the reaction was influenced by the pH, the input concentration of H2O2 and the amount of the iron catalyst and the type of iron salt. The experimental results showed that the optimum conditions were obtained at a pH value of 3, with 0.03 mol/l H2O2, and 1 mmol/l Fe(II) for the UV/H2O2/Fe(II) system and 0.01 mol/l H2O2 and, 0.4 mmol/l Fe(III) for the UV/H2O2/Fe(III) system. The reactions were accompanied by the generation of Cl- which reached its maximum value at a short reaction time when using the photo-Fenton process. Finally a rough comparison of the specific energy consumption shows that photo-Fenton process reduced the energy consumption by at least 73 to 83% compared with the UV/H2O2 process.

Chlorophenols↗
PubMed2002

Adsorption of phenol and m-chlorophenol on organobentonites and repeated thermal regeneration.

Experimental investigations were conducted on the adsorption characteristics of phenol and m-chlorophenol by organobentonites. The organobentonites were prepared by modifying natural bentonite with various quaternary ammonium salts including tetramethylammonium bromide, hexadecyltrimethylammonium bromide, benzyl-triethylammonium bromide, tetraethylammonium bromide and cetylpyridinium bromide. The adsorption characteristics of phenol and chlorophenol by these organobentonites were examined in detail. The empirical Freundlich isotherm was found to describe well the equilibrium adsorption data. Thermal regeneration of spent organobentonites was also investigated and operating conditions of 200 degrees C and 2 h heating were found to yield very good results.

Adsorption↗
PubMed2004

Sonochemistry of degrading p-chlorophenol in water by high frequency ultrasound.

The degradation process and mechanism of p-chlorophenol in water using high frequency ultrasound (1.7 mHz) was investigated in this paper. The p-chlorophenol was degraded successfully in the high frequency ultrasonic device with low consumption of energy. The degradation effect was improved by increasing the solution concentration. No products or intermediate products were detected in the reaction mixture by the analytic methods of MS and 1H-NMR after ultrasonic irradiation. The dominant degradation mechanism is high temperature pyrolysis in ultrasonic cavities rather than free radical oxidation, and the experimental results can be explained completely according to pyrolysis mechanism.

Chlorophenols↗
PubMed2002

Electrochemical oxidation of chlorophenols at a boron-doped diamond electrode and their determination by high-performance liquid chromatography with amperometric detection.

Anodically pretreated diamond electrodes have been used for the detection of chlorophenols (CPs) in environmental water samples after high-performance liquid chromatographic (HPLC) separation. The anodization of as-deposited boron-doped polycrystalline diamond thin-film electrodes has enabled the stable determination of phenols over a wide concentration range. Prior to the HPLC analysis, a comparative study with ordinary glassy carbon, as-deposited diamond, and anodized diamond was made to examine the oxidative behavior of phenols by cyclic voltammety and flow injection analysis with amperometric detection. At anodized diamond electrodes, reproducible, well-defined cyclic voltammograms were obtained even at high CP concentration (5 mM), due to a low proclivity for adsorption of the oxidation products on the surface. In addition, after prolonged use, the partially deactivated diamond could be reactivated on line by applying a highly anodic potential (2.64 Vvs SCE) for 4 min, which enabled the destruction of the electrodeposited polymer deposits. Hydroxyl radicals produced by the high applied potential, in which oxygen evolution occurs, are believed to be responsible for the oxidation of the passivating layer on the surface. When coupled with flow injection analysis (FIA), anodized diamond exhibited excellent stability, with a response variability of 2.3% (n = 100), for the oxidation of a high concentration (5 mM) of chlorophenol. In contrast, glassy carbon exhibited a response variability of 39.1%. After 100 injections, the relative peak intensity, for diamond decreased by 10%, while a drastic decrease of 70% was observed for glassy carbon. The detection limit obtained in the FIA mode for 2,4-dichlorophenol was found to be 20 nM (S/N = 3), with a linear dynamic range up to 100 microM. By coupling with the column-switching technique, which enabled on-line preconcentration (50 times), the detection limit was lowered to 0.4 nM (S/N = 3). By use of this technique, anodized diamond electrodes were demonstrated for the analysis of CPs in drainwater that was condensed from the flue gas of waste incinerators.

Boron↗
PubMed2003

X-ray spectroscopic studies of the high temperature reduction of Cu(II)O by 2-chlorophenol on a simulated fly ash surface.

The reaction of 2-chlorophenol on Cu(II)O at 375 degrees C is studied using X-ray absorption near edge structure (XANES) spectroscopy. A mixture of copper(II) oxide and silica is prepared to serve as a surrogate for fly ash in combustion systems. 2-Chlorophenol is utilized as a model precursor for formation of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/F). The Cu K-edge spectra shiftto lower binding energy, reflecting the reduction of the copper. The substrate is found to form a mixture of Cu(II), Cu(I), and Cu(O), with the dominant species being Cu(I). The data are fitted well with a first-order reaction scheme, with a time constant at 375 degrees C of 76 s. This is the first application of XANES spectroscopy for studying the kinetics and mechanism of heterogeneous reactions relevant to combustion processes, and the results demonstrate the utility and desirability of such X-ray spectroscopic studies.

Air Pollutants↗
PubMed2001

Electrochemical oxidation of ochratoxin A: correlation with 4-chlorophenol.

Ochratoxin A (OTA, 1A) is a mycotoxin implicated in human kidney carcinogenesis, in which oxidative activation is believed to play a key role. To gain an understanding of the oxidative behavior of the toxin, we have carried out an electrochemical study and have observed a direct correlation between the electrochemistry of OTA and 4-chlorophenol (4-ClPhOH). Cyclic voltammetry (CV) of OTA in acetonitrile (MeCN) showed that the toxin exhibits an irreversible oxidative half-peak potential (E(p/2)) of 1.81 V vs saturated calomel electrode (SCE); the corresponding value for 4-ClPhOH is 1.59 V. For both compounds, subsequent scans revealed the appearance of the respective hydroquinone/benzoquinone couple, which formed from the oxidation of the parent para-chlorophenol moiety. The hydroquinone of OTA (OTHQ, 2) exhibited E(p/2) = 1.21 V in MeCN. Deprotonation of OTA to form the phenolate (OTA(-)) lowered the potential to E(p/2) = 1.0 V in MeCN. However, from the oxidation of OTA(-), no evidence for the OTHQ(2)/OTQ(3) redox couple was found. In aqueous phosphate buffer (pH 6-8), the electrochemical behavior of OTA mimicked that observed for OTA(-) in MeCN; E(p/2) was approximately 0.8 V vs SCE and subsequent scans did not generate the OTHQ/OTQ redox couple. From capillary electrophoresis (CE), a diffusion coefficient (D) of 0.48 x 10(-5) cm(2) s(-1) was determined for OTA in phosphate buffer, pH 7.0. Combining this value with electrochemical data suggested that OTA undergoes a 1H(+)/1e oxidation in aqueous media. The biological implications of these findings with respect to the oxidative metabolism of OTA, and other chlorinated phenols, are discussed.

Carcinogens↗
PubMed2001

Enzymes of a new modified ortho-pathway utilizing 2-chlorophenol in Rhodococcus opacus 1CP.

Chlorocatechol 1,2-dioxygenase (CC 1,2-DO), chloromuconate cycloisomerase (CMCI), chloromuconolactone isomerase (CMLI), and dienolactone hydrolase (DELH), the key enzymes of a new modified ortho-pathway in Rhodococcus opacus 1CP cells utilizing 2-chlorophenol via a 3-chlorocatechol branch of a modified ortho-pathway, were isolated and characterized. CC 1,2-DO showed the maximum activity with 3-chlorocatechol; its activity with catechol and 4-chlorocatechol was 93 and 50%, respectively. The enzyme of the studied pathway had physicochemical properties intermediate between the pyrocatechase of ordinary and chlorocatechase of modified pathways described earlier for this strain. In contrast to the enzymes investigated earlier, CMCI of the new pathway exhibited high substrate specificity. The enzyme had Km for 2-chloromuconate of 142.86 microM, Vmax = 71.43 U/mg, pH optimum around 6.0, and temperature optimum at 65 degrees C. CMCI converted 2-chloromuconate into 5-chloromuconolactone. CMLI converted 5-chloromuconolactone into cis-dienolactone used as a substrate by DELH; this enzyme did not convert trans-dienolactone. DELH had Km for cis-dienolactone of 200 microM, Vmax = 167 U/mg, pH optimum of 8.6, and temperature optimum of 40 degrees C. These results confirm the existence of a new modified ortho-pathway for utilization of 2-chlorophenol by R. opacus 1CP.

Bacterial Proteins↗
PubMed1979

Case-control study: soft-tissue sarcomas and exposure to phenoxyacetic acids or chlorophenols.

In 1977 a number of patients with soft-tissue sarcomas and previous exposure to phenoxyacetic acids were described. Following from these observations a matched case-control study was made. Exposure to chlorophenols was also included in this study. The results showed that exposure to phenoxyacetic acids or chlorophenols gave an approximately 6-fold increase in the risk for this type of tumour. It was not possible to determine, however, whether the carcinogenic effect was exerted by these compounds or by impurities such as chlorinated dibenzodioxins and dibenzofurans that in almost all cases were part of the commercial preparations.

2,4,5-Trichlorophenoxyacetic Acid↗
PubMed1981

Malignant lymphoma and exposure to chemicals, especially organic solvents, chlorophenols and phenoxy acids: a case-control study.

A number of men with malignant lymphoma of the histiocytic type and previous exposure to phenoxy acids or chlorophenols were observed and reported in 1979. A matched case-control study has therefore been performed with cases of malignant lymphoma (Hodgkin's disease and non-Hodgkin lymphoma). This study included 169 cases and 338 controls. The results indicate that exposure to phenoxy acids, chlorophenols, and organic solvents may be a causative factor in malignant lymphoma. Combined exposure of these chemicals seemed to increase the risk. Exposure to various other agents was not obviously different in cases and in controls.

2,4,5-Trichlorophenoxyacetic Acid↗
PubMed2002

Evaluation of interactive toxicity of chlorophenols in water and soil using lux-marked biosensors.

An assessment of the toxicity of three chlorophenol compounds (2,4-dichlorophenol (2,4-DCP), 2,4,6-trichlorophenol (2,4,6-TCP) and pentachlorophenol (PCP)), individually and in combinations, was made in deionised water, soil extracts and soils using the lux-marked microbial biosensors: Escherichia coli HB101 pUCD607 and Pseudomonas fluorescens 10586r pUCD607. These biosensors responded to the bioavailable fraction of pollutants enabling a rapid and ecologically relevant toxicity test. Toxicity interaction responses of pollutant mixtures were predicted after individual compounds were assessed. Synergistic interactions were observed in the response of P. fluorescens to all combinations of chlorophenols tested, while the toxicity response of E. coli varied with the matrices tested. Soil characteristics influenced the toxicity response when compared with aqueous solutions. These results highlight the significance of interactive factors and physicochemical parameters when evaluating toxicity. To develop an understanding of pollution derived hazard assessment in soils we need to integrate a wide spectrum of parameters.

Anthelmintics↗
PubMed2003

Photooxidation of 4-chlorophenol sensitised by iron meso-tetrakis(2,6-dichloro-3-sulfophenyl)porphyrin in aqueous solution.

The photosensitised degradation of 4-chlorophenol (4-CP) by iron meso-tetrakis(2,6-dichloro-3-sulfophenyl)porphyrin (FeTDCPPS) has been studied in aerated aqueous solution, and is shown to lead to formation of p-benzoquinone (BQ) and p-hydroquinone (HQ) as main photoproducts. In deaerated solution no p-benzoquinone was formed. The photolysis products were identified by high performance liquid chromatography (HPLC) and UV-visible spectroscopy. The photodegradation in aerated solution was also carried out in the presence of sodium azide (NaN(3)) as a singlet oxygen [(1)O(2)((1)[capital Delta](g))] quencher, and showed a significant decrease in the rate of photolysis, suggesting under these conditions, that Type II sensitisation is one of the dominant mechanisms of 4-CP degradation. Support for this comes from laser flash photolysis and time-resolved singlet oxygen phosphorescence measurements. However, these also show direct reaction between the excited porphyrin and 4-CP, indicating that there are two mechanisms involved in the chlorophenol photodegradation.

Benzoquinones↗
PubMedDate not supplied

Identification of 4-bromo-2-chlorophenol as a contaminant responsible for organoleptic taint in melons.

An off-odour, described by the growers as similar to profenofos, occurred in melons in which this pesticide had been used in crop treatment. However, profenofos, O-(4-bromo-2-chlorophenyl) O-ethyl S-propyl phosphorothioate, could not be detected in the melons using GC/MS although a component with a shorter retention time was found. Concentration of melon volatiles by steam distillation yielded a product identical to that obtained by hydrolysis of profenofos, identified as 4-bromo-2-chlorophenol. A solution of this compound in water had similar organoleptic properties to that of the contaminated fruits. It was concluded that 4-bromo-2-chlorophenol was responsible for the taint detected in melons.

Chlorophenols↗
PubMed2007

Gas chromatographic methods for monitoring of wastewater chlorophenol degradation in anaerobic reactors.

Wastewater samples from an anaerobic reactor were extracted with hexane and derivatized with diazomethane (method 1) and with acetic anidride (method 2). Gas chromatography with electron-capture detection (ECD) was employed for separating the parent compound and intermediates trichlorophenols (TCP) and dichlorophenols (DCP) which originated from the penta chlorophenol (PCP) degradation process. The relations between concentrations of PCP, TCP and DCP areas were linear in the range of concentrations of 0.2 to 8 mg/L and 0.025 mg/L to 5 mg/L for methods 1 and 2, respectively. The repeatability of the extraction methods was satisfactory, with variation coefficients lower than 11%. For method 1, at the fortification level of 0.2 mg/L, recovery of PCP, TCP, and DCP was 112%, 74% and 45%, respectively. For method 2, the corresponding recovery values at the fortification level of 0.1 mg/L were 91%, 93% and 103%, respectively. Storage of the frozen samples did not alter their PCP determination properties. The chromatographic methods adapted for chlorophenol determination in wastewater were suitable with relatively simple manipulation techniques. The obtained results were reproducible and allowed identification of intermediates formed during the PCP degradation process.

Acetic Anhydrides↗