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PubMed2001

Separation of chlorophenoxyacetic acids and chlorophenols by using capillary zone electrophoresis.

In this study, the choice of electrolyte systems for the separation and detection of a range of chlorophenoxyacetic acids and chlorophenols by means of capillary zone electrophoresis (CZE) is discussed. A series of acetate buffers over the buffering capacity pH range 4.03-5.5 were initially chosen for the separation. It was found that chlorophenoxyacetic acids could be separated at pH 4.03 and 4.5 but the most satisfactory separation of chlorophenols was obtained at pH 5.5. The factors affecting separation selectivity, including the addition of organic modifiers, was also studied. The use of 25% 2-butanol, 5% ethylene glycol and 10% acetonitrile as organic solvents resulted in the total separation of both classes of these compounds but poor peak shape of chlorophenols resulted and a number of chlorophenoxyacetic acids were not well separated. A borate-phosphate buffer gave improved peak shape of chlorophenols. Further improved separation of the components of the mixture was obtained by the addition of 2 mM fully methylated-beta-cyclodextrin to the 35 mM borate- 60 mM phosphate buffer at pH 6.5, maintaining good peak shape. In this case, separation of the two compound classes, chlorophenoxyacetic acids and chlorophenols, is achieved, with complete resolution of individual compounds in less than 5 min with high efficiency (of the order of 150,000 plates for the ca. 40 cm column). The method is applied to a commercial 2,4-dichlorophenoxyacetic acid (2,4-D) herbicide mixture.

2,4-Dichlorophenoxyacetic Acid↗

PubMed1982

Epidemiological study of nasal and nasopharyngeal cancer and their relation to phenoxy acid or chlorophenol exposure.

Soft tissue sarcoma and malignant lymphoma have been related to exposure to chlorinated phenoxy acids or chlorophenols as well as exposure to organic solvents and malignant lymphoma. However, colon cancer studied by the same case-referent design did not show any such associations, which helps to rule out alleged systematical bias of the study approach. Further considerations about exposure routes for phenoxy acids and chlorophenols suggested that nasal and nasopharyngeal cancers should be studied. Forty-four cases with nasal cancer and 27 cases with nasopharyngeal cancer were eligible for study during 1970-1979 together with 541 referents, as utilized also in the aforementioned studies. Exposure to phenoxy acids gave formally a doubled but insignificant risk for the studied cancer types. Exposure to chlorophenols, as present particularly in woodwork, was related to an about sevenfold and significant increase in the risk for both cancer types. In woodworkers without exposure to chlorophenols there was an approximate normal risk, but cabinet makers, even without exposure to chlorophenols, had nearly doubled (but insignificant) risk of nasal cancer.

Adenocarcinoma↗

PubMed2001

Two distinct enzyme systems are responsible for tetrachloroethene and chlorophenol reductive dehalogenation in Desulfitobacterium strain PCE1.

Desulfitobacterium strain PCE1 is able to use tetrachloroethene and chloroaromatics as terminal electron acceptors for growth. Cell extracts of Desulfitobacterium strain PCE1 grown with tetrachloroethene as electron acceptor showed no dehalogenase activity with 3-chloro-4-hydroxyphenylacetate (Cl-OH-phenylacetate) and other ortho-chlorophenolic compounds in an in vitro assay. Extracts of cells that were grown with Cl-OH-phenylacetate as electron acceptor dechlorinated tetrachloroethene at 10% of the dechlorination rate of Cl-OH-phenylacetate. In both cell extracts dechlorination was inhibited by the addition of 1-iodopropane and dinitrogen oxide, inhibitors of cobalamin-containing enzymes. The enzymes responsible for tetrachloroethene and Cl-OH-phenylacetate dechlorination were partially purified. A 100-fold enriched fraction of chlorophenol reductive dehalogenase was obtained that mainly contained a protein with a subunit size of 48 kDa. The characteristics of this enzyme are similar to that of the chlorophenol reductive dehalogenase of D. dehalogenans. After partial purification of the tetrachloroethene reductive dehalogenase, a fraction was obtained that also contained a 48-kDa protein, but the N-terminal sequence showed no similarity with that of the chlorophenol reductive dehalogenase sequence or with the N-terminal amino acid sequence of tetra- and trichloroethene reductive dehalogenase of Desulfitobacterium strain TCE1. These results provide strong evidence that two different enzymes are responsible for tetrachloroethene and chlorophenol dechlorination in Desulfitobacterium strain PCE1. Furthermore, the characterization of partially purified tetrachloroethene reductive dehalogenase indicated that this enzyme is a novel type of reductive dehalogenase.

Amino Acid Sequence↗

PubMed1988

Toxicity and bioaccumulation of chlorophenols in earthworms, in relation to bioavailability in soil.

The acute toxicity of five chlorophenols for two earthworm species was determined in two sandy soils differing in organic matter content and the results were compared with adsorption data. Adsorption increased with increasing organic matter content of the soils, but for tetra- and pentachlorophenol was also influenced by soil pH. Earthworm toxicity was significantly higher in the soil with a low level of organic matter. This difference disappeared when LC50 values were recalculated to concentrations in soil solution using adsorption data. Eisenia fetida andrei showed LC50 values lower than those of Lumbricus rubellus although bioaccumulation was generally higher in the latter species. Toxicity and bioaccumulation based on soil solution concentrations increased with increasing lipophilicity of the chlorophenols. The present results indicate that the toxicity and bioaccumulation and therefore the bioavailability of chlorophenols in soil to earthworms are dependent on the concentration in soil solution and can be predicted on the basis of adsorption data. Both the toxicity of and bioaccumulation data on chlorophenols in earthworms demonstrated surprisingly good agreement with those on chlorophenols in fish.

Adsorption↗

PubMed1989

The excretion of chlorophenylmercapturic acid, chlorophenols and a guanine adduct in the urine of chlorobenzene-treated rats after phenobarbital pretreatment.

Chlorobenzene (CB) was administered to male Wistar rats. Twenty-four-hour urine samples were collected over a period of 7 days. p-Chlorophenylmercapturic acid, chlorophenols and a guanine adduct were determined by chromatographic methods. The excretion pattern of p-chlorophenyl-mercapturic acid did not seem to be significantly affected by phenobarbital. To analyze for the chlorophenols and guanine adducts, diluted urine was subjected to cation exchange chromatography using UV-detection. Fractions were found containing chlorophenols and a compound showing chromatographic properties similar to those of the synthetic N7-phenylguanine. The results of the HPLC analyses suggested the presence of a guanine adduct excreted on days 1 and 2 and between days 4 and 6 post-administration. There were no compounds detected which were identical with p-, m- or o-isomers of N7-chlorophenylguanine. The excretion of p- and m-chlorophenols by phenobarbital-pretreated animals was twice as high as that in untreated rats. A 4-fold increase was detected for o-chlorophenol. It is assumed that it is mainly direct hydroxylation that can be induced by phenobarbital. Dehalogenated phenolic metabolites may be capable of covalent binding to DNA.

Acetylcysteine↗

PubMed2004

Biodegradation of p-chlorophenol by a microalgae consortium.

An aquatic community was recovered from a waste discharge container fed with several aromatic pollutants. After 3 months of selective enrichment with p-chlorophenol and p-nitrophenol, two microalgae species, Chlorella vulgaris and Coenochloris pyrenoidosa, were recovered from the microbial consortium. As an axenic culture, this microalgae consortium was able to remove p-chlorophenol under different photo-regimes. Cultures grown under a 24h light regime were capable of biodegrading 50mg l(-1) of p-chlorophenol within 5 days. Addition of zeolite, an adsorbing material, did not improve the p-chlorophenol removal. However, when p-chlorophenol at 150mgl(-1) was fed to the culture supplemented with zeolite, the growth rate of the consortium improved, but the lag phase was longer (16 against 14 days in the absence of zeolite).

Adsorption↗

PubMed2002

The enhancement of 2-chlorophenol degradation by a mixed microbial community when augmented with Pseudomonas putida CP1.

The effect of the introduction of Pseudomonas putida CP1 to a commercial mixed microbial community for the degradation of 1.56mM 2-chlorophenol was investigated. Degradation of 2-chlorophenol by the commercial mixture was via a meta-cleavage pathway leading to incomplete degradation, while P. putida CPI was shown to be capable of the complete degradation of 2-chlorophenol via an ortho-cleavage pathway. Augmentation of the commercial mixed culture with P. putida CP1 resulted in complete degradation of 2-chlorophenol via an ortho-cleavage pathway. The augmented mixed culture displayed increased degradative capabilities, with times of degradation reduced when compared to those achieved by P. putida CP1 in isolation. The ability of P. putida CP1 to degrade 2-chlorophenol was increased with the addition of increasing concentrations of the mixed culture. Increasing the mixed culture inoculum size added to P. putida CP1 decreased lag periods and increased rates of degradation, resulting in decreased times of degradation.

Biodegradation, Environmental↗

PubMed2000

Oxidation of chlorophenols with hydrogen peroxide in the presence of goethite.

The use of goethite (alpha-FeOOH) and hydrogen peroxide was recently found that they could effectively oxidize organic compounds. The study was to investigate the effect of goethite particle size, goethite concentration, Fe2+ and Fe3+ on the 2-chlorophenol oxidation. Results indicated that 2-chlorophenol can be decomposed with hydrogen peroxide catalyzed by goethite and the oxidation rate increased with decreasing goethite particle size. 2-Chlorophenol degradation was almost retarded with 0.8 g/l of goethite because ferrous ions could not be produced at this condition. Addition of Fe2+ and Fe3+ can enhance the catalytic oxidation rate of 2-chlorophenol very efficiently. In conclusion, the main mechanism of goethite catalyzing hydrogen peroxide to oxidize 2-chlorophenol may be due to the catalysis of ferrous ions and goethite surface.

Chlorophenols↗

PubMed2002

Photocatalytic degradation of aqueous 4-chlorophenol by silica-immobilized polyoxometalates.

The degradation of 4-chlorophenol with near-UV light by silica-immobilized polyoxometalate (POM-in-SiO2) catalysts has been studied. The silica-immobilized Na6W7O24 (SW7), H4W1032 (SW10), H3PW12O40 (SPW12), and H6P2W18O62 (SP2W18) were prepared by means of the sol-gel hydrothermal technique through the hydrolysis of tetraethoxysilane in aqueous solution of the corresponding polyoxometalate, respectively. The degradation of 4-chlorophenol was monitored by measuring Cl- and CO2 concentrations and analyzing reaction intermediates by GC/MS analysis. During irradiation, 4-chlorophenol first dechlorinated to form hydroquinone and p-benzoquinone, and then these intermediates further mineralized to form CO2 and H2O. The degree to which 4-chlorophenol was mineralized by photocatalytic oxidation was investigated. Results indicate less than 15% for SW7 but nearly complete mineralization for SW10 after 60 min of photoirradiation. The present studies suggest that POM-in-SiO2 catalysts may be a novel type of photocatalyts for the purification of the environmentally chlorophenol-contaminated water.

Catalysis↗

PubMed2005

An infrared and X-ray spectroscopic study of the reactions of 2-chlorophenol, 1,2-dichlorobenzene, and chlorobenzene with model cuO/silica fly ash surfaces.

The surface-mediated reactions of 2-chlorophenol, 1,2-dichlorobenzene, and chlorobenzene were studied using CuO/ SiO2 as a fly ash surrogate. These compounds served as model precursors that have been implicated in the formation of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs). With FTIR, we determined that reactions of the model precursors with a substrate composed of CuO dispersed on silica result in the formation of a mixture of surface-bound phenolate and carboxylate partial oxidation products from 200 to 500 degrees C. Chemisorption of 2-chlorophenol and 1,2-dichlorobenzene resulted in the formation of identical surface-bound species. Using X-ray absorption near-edge structure spectroscopy, we measured the time- and temperature-dependent reduction of Cu(II) in a fly ash surrogate during reaction with each precursor. It was demonstrated that CuI2O is the major reduction product in each case. The rate of Cu(II) reduction could be described using pseudo-first-order reaction kinetics with Arrhenius activation energies for reduction of Cu(II) of 112, 101, and 88 kJ mol(-1) for 2-chlorophenol, 1,2-dichlorobenzene, and chlorobenzene, respectively. We demonstrate that chlorinated phenol and chlorinated benzene both chemisorb to form chlorophenolate. Although chlorinated phenols chemisorb at a faster rate, chlorinated benzenes are found at much higher concentrations in incinerator effluents. The implication is that chlorinated benzenes may form 10 times more chlorophenolate precursors to PCDD/Fs than chlorinated phenols in combustion systems.

Adsorption↗

PubMed1999

Degradation of mono-chlorophenols by a mixed microbial community via a meta- cleavage pathway.

A mixed microbial community, specially designed to degrade a wide range of substituted aromatic compounds, was examined for its ability to degrade mono-chlorophenols as sole carbon source in aerobic batch cultures. The mixed culture degraded 2-, 3-, and 4-chlorophenol (1.56 mM) via a meta- cleavage pathway. During the degradation of 2- and 3-chlorophenol by the mixed culture, 3-chlorocatechol production was observed. Further metabolism was toxic to cells as it led to inactivation of the catechol 2,3-dioxygenase enzyme upon meta- cleavage of 3-chlorocatechol resulting in incomplete degradation. Inactivation of the meta- cleavage enzyme led to an accumulation of brown coloured polymers, which interfered with the measurement of cell growth using optical density. Degradation of 4-chlorophenol by the mixed culture led to an accumulation of 5-chloro-2-hydroxymuconic semialdehyde, the meta- cleavage product of 4-chlorocatechol. The accumulation of this compound did not interfere with the measurement of cell growth using optical density. 5-chloro-2-hydroxymuconic semialdehyde was further metabolized by the mixed culture with a stoichiometric release of chloride, indicating complete degradation of 4-chlorophenol by the mixed culture via a meta- cleavage pathway.

Actinomycetales↗

PubMed1996

Isolation and characterization of Desulfitobacterium frappieri sp. nov., an anaerobic bacterium which reductively dechlorinates pentachlorophenol to 3-chlorophenol.

An anaerobic bacterium, strain PCP-1T (T = type strain), which dechlorinates pentachlorophenol (PCP) to 3-chlorophenol, was isolated from a methanogenic consortium. This organism is a spore-forming rod-shaped bacterium that is nonmotile, asaccharolytic, and Gram stain negative but Gram type positive as determined by electron microscopic observations. Inorganic electron acceptors, such as sulfite, thiosulfate, and nitrate (but not sulfate), stimulate growth in the presence of pyruvate and yeast extract. The optimum pH and optimum temperature for growth are 7.5 and 38 degrees C, respectively. The dechlorination pathway is: PCP-->2,3,4,5-tetrachlorophenol -->3,4,5-trichlorophenol-->3,5-dichlorophenol-->3-chlorophenol. This bacterium dechlorinates several different chlorophenols at ortho, meta, and para positions; exceptions to this are 2,3-dichlorophenol, 2,5-dichlorophenol, 3,4-dichlorophenol, and the monochlorophenols. The time course of PCP dechlorination suggests that two enzyme systems are involved in dehalogenation in strain PCP-1T. One system is inducible for ortho dechlorination, and the second system is inducible for meta and para dechlorinations. A 16S rRNA analysis revealed that strain PCP-1T exhibits 95% homology with Desulfitobacterium dehalogenans JW/IU-DC1, an anaerobic bacterium which can dehalogenate chlorophenols only in ortho positions. These results suggest that strain PCP-1T is a member of a new species and belongs to the recently proposed genus Desulfitobacterium. Strain PCP-1T differs from D. dehalogenans JW/IU-DC1 by its broader range of chlorophenol dechlorination. Strain PCP-1 is the type strain of the new species, Desulfitobacterium frappieri.

Bacteria, Anaerobic↗

PubMed1992

Reductive dehalogenation of chlorophenols by Desulfomonile tiedjei DCB-1.

Reductive dehalogenation of chlorophenols has been reported in undefined anaerobic cultures but never before in an anaerobic pure culture. We found that the sulfate-reducing bacterium Desulfomonile tiedjei DCB-1 reductively dehalogenates pentachlorophenol (PCP) and other chlorophenols. The maximum rate of PCP dechlorination observed was 54 mu mol of Cl- h-1 g of protein-1. 3-Chlorobenzoate appeared to serve as a required inducer for PCP dehalogenation; however, neither PCP nor 3-chlorophenol induced dehalogenation. Dehalogenation was catalyzed by living cells, and formate served as a required electron donor. D. tiedjei dehalogenated meta-chlorine substituents of chlorophenols (i.e., PCP was degraded to 2,4,6-trichlorophenol). Generally, more highly chlorinated phenol congeners were more readily dechlorinated, and 3-chlorophenol was not dehalogenated. Growing cultures dehalogenated PCP, but greater than 10 microM PCP (approximately 1.7 mmol g of protein-1) reversibly inhibited growth.

Bacteria, Anaerobic↗

PubMed2004

Degradation of chlorophenol by in-situ electrochemically generated oxidant.

A novel in-situ electrochemical oxidation method was applied to the degradation of wastewater containing chlorophenol. Under oxygen sparging, the strong oxidant, hydrogen dioxide, could be in-situ generated through the reduction of oxygen on the surface of the cathode. The removal rate of chlorophenol could be increased 149% when oxygen was induced in the electrochemical cell. The promotion factor was estimated to be about 82.63% according to the pseudo-first-order reaction rate constant (min(-1)). Important operating parameters such as current density, sparged oxygen rate investigated. Higher sparged oxygen rate could improve the degradation of chlorophenol. To make full use of oxygen, however, sparged oxygen rate of 0.05 m(3)/h was adopted in this work. Oxidation-reduction potential could remarkably affect the generation of hydrogen peroxide. It was found that the removal rate of chlorophenol was not in direct proportion to the applied current density. The optimum current density was 3.5 mA/cm(2) when initial chlorophenol concentration was 100 mg/L and sparged oxygen rate was 0.05 m(3)/h.

Catalysis↗

PubMed2005

Study on US/O3 mechanism in p-chlorophenol decomposition.

Study on the effects of sonolysis, ozonolysis and US/O3 system on the decomposition of p-chlorophenol in aqueous solutions indicated that in the cases of US/O3 system, individual ozonolysis and sonolysis, the decomposition rate of p-chlorophenol reached 78.78%, 56.20%, 2.79% after a 16-min reaction while its CODcr (chemical oxygen demand) removal rate was 97.02%, 62.17%, 3.67% after a 120-min reaction. The decomposition reaction of p-chlorophenol follows pseudo-first-order kinetics. The enhancement factors of p-chlorophenol and its COD(cr) under US/O3 system reached 63% and 237% respectively. The main intermediates during the decomposition include catechol, hydroquinone, p-benzoquinone, phenol, fumaric acid, maleic acid, oxalic acid and formic acid. The decomposition mechanism of p-chlorophenol was also discussed.

Chlorophenols↗

PubMed2005

Fe salts as catalyst for the wet oxidation of o-chlorophenol.

Catalytic wet air oxidation (CWAO) of o-chlorophenol in wastewater was studied in a stainless steel autoclave using four different Fe catalysts in the temperature range of 100-200 degrees C. Experimental results showed that high rate of o-chlorophenol and COD(Cr) (Chemical Oxygen Demand, mg/L) removal by CWAO was obtained at relatively low temperature and pressure. The catalysts Fe2(SO4)3, FeSO4, Fe2O3 and FeCl3 all exhibited high catalytic activity. More than 93.7% of the initial COD(Cr) and nearly 100% of o-chlorophenol were removed at 150 degrees C after 150 min with FeSO4 as catalyst. The CWAO of o-chlorophenol was found to be pseudo-first order reaction with respect to o-chlorophenol, with activation energy of 75.56 kJ/mol in the temperature range of 100-175 degrees C.

Catalysis↗

PubMed2004

Biodegradation of 2-chlorophenol in forest soil: effect of inoculation with aerobic sewage sludge.

Decontamination of 2-monochlorophenol-containing forest soil was studied in laboratory experiments. We found that in sterile soil, sorption of chlorophenol can occur. Chlorophenol disappearance of approximately 55% was observed in native soil; both soil sorption and degradation by indigenous soil populations caused this disappearance. In native soil, however, the rate of chlorophenol disappearance was enhanced up to slightly more than 90% by inoculation with a sludge taken from the aeration tank of a municipal wastewater treatment plant. In this sludge, the presence of Alcaligenes and Pseudomonas spp. was observed. In other experiments, addition to the soil of a laboratory culture preacclimated to 2-monochlorophenol did not lead to a greater increase in chlorophenol disappearance. In contrast to native soil, inoculation of sterile soil had no effect on disappearance of the chlorophenol. A possible explanation for the lack of cometabolic degradation is that autoclaving of the soil destroys the organic substances within it.

Absorption↗

PubMed1996

[Distribution of chlorophenols in a water environment].

The purpose of this study was to establish the distribution of the selected chlorophenols of point (2,4-DCF, 2,6-DCF, 2,4,5-TCF and 2,3,6-TCF) and nonpoint origin (2,4,6-TCF,2,3,4,6-TeCF and PCF) under conditions simulating the environment of river and distilled water and laboratory water ecosystem. The distribution process developed in accordance with the kinetic equation of 1st order, the average degradation half-time at 20 degrees C amounted: model of river -23, 58-76, 92 days, and model of distilled water-36, 53-47, 25 days. The rate degradation in river and distilled water indicates that the river water microorganisms have no influence on the degradation of determined compounds. When the microflora had been adapted to the presence of chlorophenols the process of degradation was as rule more rapid both investigated temperatures (20 degrees C and 7 degrees C). This process was slowed down by temperature fall to about 7 degrees C. The mixture of chlorophenols at concentration of 10 and 50 micrograms/l when exposed for 20 days to water ecosystem under dynamic conditions, was found to be reduced up 13%. Chlorophenols were not absorbed by Elodea canadensis and Physa fortinalis and weakly by Lebistes reticulatus (cumulation coefficients -0.42-30.27). In the case residual DCP and TCP -weakly (4.71-46.23 micrograms/kg). The investigated concentrations of chlorophenols didn't exert positive effect on the aquatic biocenosis (except Lebistes reticulatus), settled in the ecosystem.

Absorption↗