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PubMedDate not supplied

Development of the infrared hollow waveguide sampler for the detection of chlorophenols in aqueous solutions.

A method based on the infrared hollow waveguide sampler was developed for sensing chlorophenols in aqueous solutions. This sampler was constructed by coating a suitable hydrophobic film onto the inner surface of an infrared hollow waveguide. By passing the aqueous solution through the hollow waveguide sampler, analytes can be absorbed into the hydrophobic layer. The adsorbed analytes can be sensed later by using Fourier transform infrared spectrometry. Six hydrophobic polymers were investigated for their performance in conjunction with the infrared hollow waveguide sampler for the detection of chlorophenols. Results indicated that poly(acrylonitrile-co-butadiene) was a most suitable hydrophobic material for absorption of chlorophenols in aqueous solutions. To further increase the detection sensitivity, factors such as sampling flow rate, sampling time, and thickness of the hydrophobic film were also investigated. Results indicated that the infrared signals were similar in the examined flow rates (2-30 mL/min), but that a higher flow rate tended to produce a higher analytical signal. Fast detection speed was an advantage of this method for the detection of chlorophenols, and the sampling/detection time can be <10 min. In addition, analytical signals were nearly proportional to the thickness of the hydrophobic film coating the inside of the hollow waveguide. With the optimal conditions found in this work, detection limits based on 3 times the peak-to-peak noise level were around 300 ppb for the chlorophenols examined. A high degree of linearity in the standard curves was also observed for this method in the concentration range of 10-100 ppm. The typical regression coefficients were >0.994 for the chlorophenols examined.

Algorithms↗

PubMed2004

Chlorophenols identification in water using an electronic nose and ANNs (artificial neural networks) classification.

Electronic artificial noses are being developed as systems for the automated detection and classification of odours, vapors and gases. In the food industry, such devices are used as aids for quality control or process-monitoring tools. An electronic nose (EN) is generally composed of a chemical sensing system and a pattern recognition system (e.g. artificial neural network). An EN based on a non-specific conducting polymer array was used to monitor chlorophenols in water samples. Operational parameters for the EN were optimized by a Plackett-Burman factorial design. The experimental parameters studied were: sample volume, platen temperature, sample equilibration time, loop fill time, sample pressurization time and injection time. Optimal experimental conditions were applied to chlorophenols determination and differentiation in ultrapure water samples spiked with the EPA listed chlorophenols. Data analysis was carried out using principal component analysis (PCA) and artificial neural networks (ANNs) to predict the chlorophenols presence in water samples. The obtained results showed that it was possible to differentiate the five chlorophenol groups: monochlorophenol, dichlorophenol, trichlorophenol, tetrachlorophenol and pentachlorophenol. Differentiation of chlorophenol groups was based on Mahalanobis distance between the formed clusters. This Mahalanobis distance is designated by the Quality Factor, a value >2 for this quality factor means a good differentiation between the clusters.

Automation↗

PubMed1989

Effects of commercial chlorophenolate, 2,3,7,8-TCDD, and pure phenoxyacetic acids on hepatic peroxisome proliferation, xenobiotic metabolism and sister chromatid exchange in the rat.

The induction of hepatic peroxisome proliferation and drug metabolizing enzymes and of sister chromatid exchange (SCE) in lymphocytes was studied in male Han/Wistar rats after exposing them for 2 weeks to a commercial chlorophenolate formulation (Ky-5) (100 mg/kg/day), to 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD; 0.05-5 micrograms/kg/wk) and to the pure phenoxyacetic acids, 2,4-dichlorophenoxyacetic acid (2,4-D; 100 mg/kg/day) and 2-chloro-4-methylphenoxyacetic acid (MCPA; 100 mg/kg/day). The chlorophenolate formulation and pure 2,4-D and MCPA caused significant increases in the number of peroxisomes in liver cells, although the average size of peroxisomes was not affected, whereas the effect of even the highest dose of 2,3,7,8-TCDD remained small. This finding indicates that dioxin impurities do not account for the peroxisome proliferation induced by chlorophenolate. The relative weight of the liver increased significantly in rats treated with the chlorophenolate formulation and with 2,3,7,8-TCDD (5.0 and 0.5 micrograms/kg). The pattern of induction of xenobiotic metabolizing enzymes showed some differences between chlorophenolate treatment and 2,3,7,8-TCDD treatment. Furthermore, the effects of pure phenoxyacetic acids were different from that seen with chlorophenolate and 2,3,7,8-TCDD. The highest dose of 2,3,7,8-TCDD increased the frequency of SCE in circulating lymphocytes slightly, but significantly.

Animals↗

PubMed1998

Investigating the potential impacts of chlorophenols on the lake baikal (Siberia, russia) food web by employing daphnia grazing bioassays and a chlorella growth bioassay

A grazing bioassay was employed to assess the impacts of chlorophenols on Daphnia magna and Daphnia pulex. The effects of two chlorophenols, pentachlorophenol (PCP) and 4-chlorophenol, were investigated at concentrations of 0.001, 0.01, and 0.1 mg . L-1 over a 96-h period. All tests were conducted in water from the southern basin of Lake Baikal (Siberia). For D. magna, grazing rates were significantly depressed after exposure to 0.001 mg . L-1 of PCP for 48 h or to 0.01 mg . L-1 of 4-chlorophenol for 96 h. However, neither chemical continued to depress filtering rates as either dose or time increased, thus effective concentrations (EC50s) could not be determined. This prevents the use of this bioassay as a tool for assessing exposure to chlorophenols, but it is still useful in that it provides insight into potential ecological effects. In the case of D. pulex, depressed rates were also found at 0.001 mg . L-1 of PCP after 48 h; due to problems with the control, no conclusions were drawn for the effect of 4-chlorophenol on this species. The growth rates of Daphnia's prey, Chlorella vulgaris, were also investigated in the presence of these chemicals; no observable effects were found at any concentration during the 96-h period, implying that ecosystem effects may be limited to higher trophic levels.

Journal Article↗

PubMed1995

NTP Initiation/Promotion Study of o-Benzyl-p-Chlorophenol (CAS No. 120-32-1) in Swiss (CD-1(R)) Mice (Mouse Skin Study).

o-Benzyl-p-chlorophenol (BCP), an aryl halide, is a broad spectrum germicide used in disinfectant solutions and soap formulations in United States hospitals and households. Human exposure to BCP occurs by absorption through the skin and mucous membranes and by ingestion. BCP was studied because of the widespread human exposure and because BCP is an irritant and certain phenolic compounds are weak promoters of skin neoplasia. Groups of Swiss (CD-1(R)) mice were used to study BCP in a 1-year mouse skin initiation/promotion protocol. Genetic toxicology studies were conducted in Salmonella typhimurium and cultured Chinese hamster ovary cells. 1-YEAR INITIATION/PROMOTION STUDY: Groups of 50 male and 50 female Swiss (CD-1(R)) mice were topically exposed to BCP to study its effect as an initiator, promoter, and complete carcinogen. A number of control groups were included in these studies as a reference for the responses of the mouse skin to o -benzyl- p -chlorophenol (see following table). See report abstract or full report for Dose Regimen for Reference Controls in the 1-Year Initiation/Promotion Study of o -Benzyl- p - Chlorophenol. BCP in acetone was tested as an initiator with the promoter 12- O -tetradecanoylphorbol-13-acetate (TPA). The potential of BCP as an initiator was studied by applying a single 100 mL dose of BCP in acetone at a concentration of 10 mg/mL to the dorsal interscapular region of the backs of mice during week 1 of the study. Following the initial BCP application, mice were administered promoting doses of 5 mg TPA three times per week in 100 mL acetone for the first 6 months of the study and once weekly for the final 6 months of the study. BCP in acetone was tested as a promoter with the initiator 7,12-dimethylbenz(a)anthracene (DMBA). Mice were administered a single initiating dose of 50 mL DMBA in 100 mL acetone. Beginning on the second week of the study, mice received 100 mL applications of 0.1, 1.0, or 3.0 mg BCP in acetone three times weekly for up to 51 weeks. Comparative control groups used during the study of BCP as a promoter included: vehicle control (acetone/acetone); promoter control (TPA/TPA); and initiator control (DMBA/acetone). The potential for BCP to act as a complete carcinogen was studied by applying a single initiating dose of 10 mg BCP in 100 mL of acetone, followed by tri-weekly 100 mL applications of 0.1, 1.0, or 3.0 mg BCP to 50 male and 50 female Swiss (CD-1(R)) mice for 52 weeks. The responses of these groups were compared to vehicle control (acetone/acetone) and complete carcinogen control (acetone/DMBA) groups. The following table shows the various groups with BCP as a promoter, an initiator, and as a complete carcinogen. See full report or abstract for Dose Regimen in the 1-Year Initiation/Promotion Study of o - Benzyl- p -Chlorophenol. Results in the Study of BCP as a Complete Carcinogen: BCP acted as an irritant when tested as a complete carcinogen using a single initiating dose of 10 mg BCP followed by repetitive applications of 0.1, 1.0, or 3.0 mg BCP for up to 52 weeks, and many of the mice developed cutaneous lesions of scaling/crusts and ulceration. During the course of the study, a single papilloma was first observed after 12 weeks in one 0.1 mg BCP male mouse. One 3.0 mg BCP female was observed with a papilloma at week 10, and three 0.1 mg BCP females were observed with papillomas between weeks 22 and 27. No mice administered BCP/BCP had papillomas at the end of the study, and no malignant cutaneous epithelial tumors were observed at the application sites on any BCP/BCP mice. Thus, in the present study, BCP was not a complete carcinogen. Results in the Study of BCP as an Initiator: One vehicle control (acetone/acetone) male mouse had developed crusts at the site of application at necropsy, but no male or female vehicle controls had developed papillomas. Mice administered BCP/TPA developed application site lesions including scaling/crusts, ulceration, and irritation; the incidences of these lesions were similar to those in the initiator/promoter control (DMBA/TPA) /TPA) groups. After 22 weeks papillomas were observed in 12/50 male mice administered BCP/TPA. After 12 weeks papillomas were observed in 7/50 female mice administered BCP/TPA. However, the incidences of papillomas in mice administered BCP/TPA were lower than those in mice administered TPA/TPA (males, 16/50; females, 16/50) and were much lower than those in DMBA/TPA mice (males, 40/50; females, 48/50). Although the incidences of papillomas in mice administered BCP as an initiator were significantly greater than those in the vehicle controls, the incidences were not significantly different from those in TPA/TPA mice. Thus, in the present study, BCP did not demonstrate initiating potential. Results in the Study of BCP as a Promoter: During the course of the study, incidences of scaling and/or crusts, ulceration, and irritation were observed at the site of application in DMBA/BCP male and female mice, and the incidences were dose-related. Incidences of scaling and/or crusts, ulceration, and irritation in 3.0 mg BCP mice were similar to the incidences of these lesions in initiator/promoter control (DMBA/TPA) group, but much higher than the incidences of these lesions in the initiator control (DMBA/acetone) group. A dose-related increased incidence of papillomas was observed in males (DMBA/acetone, 8/50; DMBA/0.1 mg BCP, 3/50;DMBA/1.0 mg BCP, 5/50; and DMBA/3.0 mg BCP, 14/50) and females (2/50, 6/50, 6/50, and 18/50). The incidence of papillomas in DMBA/3.0 mg BCP females was significantly greater (P<0.001) than that in DMBA/acetone females; the incidence of papillomas in DMBA/3.0 mg BCP males was marginally increased (P=0.077). No acetone/acetone mice developed papillomas. Although a higher percentage of DMBA/3.0 mg BCP mice developed papillomas over the course of the study than did DMBA/acetone controls, the time it took for half of the number of responding animals to develop papillomas was similar between DMBA/acetone groups and DMBA/3.0 mg BCP groups (DMBA/acetone males, week 38; DMBA/acetone females, week 34; DMBA/3.0 mg BCP males, week 36; DMBA/3.0 mg BCP females, week 37). However, the time to appearance of the first papilloma was shorter in DMBA/3.0 mg BCP mice (males, week 18; females, week 10) than in DMBA/acetone mice (males, week 26; females, week 27). BCP was considered to have promotion potential because the incidences of papillomas in mice treated with DMBA/3.0 mg BCP were greater than those in DMBA/acetone (initiator control) mice and because topical exposure to BCP alone caused no significant increased incidence of papillomas. However, the incidences of papillomas in DMBA/3.0 mg BCP mice (males, 14/50; females, 18/50) were much less than the incidences in DMBA/TPA (promoter control) mice (males, 40/50; females, 48/50); thus, BCP was classified as a weak promoter. GENETIC TOXICOLOGY: o -Benzyl- p -chlorophenol did not induce gene mutations in Salmonella typhimurium strains TA98, TA100, TA1535, or TA1537, and it did not induce sister chromatid exchanges or chromosomal aberrations in cultured Chinese hamster ovary cells. All tests were performed with and without S9 activation. CONCLUSIONS: Under the conditions of this 1-year mouse skin initiation/promotion study in Swiss (CD-1®) mice, o -benzyl- p -chlorophenol was a cutaneous irritant and a weak skin tumor promoter relative to strong promoters such as TPA. BCP had no activity as an initiator or as a complete carcinogen.

Journal Article↗

PubMed1999

Determination of chlorophenols in human urine based on the integration of on-line automated clean-up and preconcentration unit with micellar electrokinetic chromatography.

A new method was developed and validated for the determination of chlorophenols in human urine by using micellar electrokinetic chromatography (MEKC) coupled via a mechanic arm to an on-line automatic clean-up and preconcentration unit for urine samples. Separation is accomplished by using a selective buffer consisting of 15 mM borate, 25 mM phosphate and 100 mM sodium dodecyl sulfate (SDS) at pH 9.1 in addition to a positive power supply of 25 kV at 18 degrees C. The proposed capillary electrophoresis (CE) method allows the separation of 11 chlorophenols within 7 min with a reproducibility as relative standard deviation (RSD) between 2.6% and 7.2%, and limits of detection (LODs) between 0.08 and 0.46 microg/mL for all chlorophenols. Urine samples were previously hydrolyzed with 37% HCl at 80 degrees C for 60 min and then cleaned on a C-18 mini-column. Recoveries ranged from 58% to 103%. The preconcentration treatment affords limits of determination between 4 and 12 ng/mL for all chlorophenols except pentachlorophenol and 4-chlorophenol, which could not be determined. The overall analysis time, including on-line clean-up, preconcentration and electrophoretic separation is 20 min per sample.

Chlorophenols↗

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↗

PubMed2006

Modeling chlorophenols degradation in sequencing batch reactors with instantaneous feed-effect of 2,4-DCP presence on 4-CP degradation kinetics.

Two instantaneously fed sequencing batch reactors (SBRs), one receiving 4-chlorophenol (4-CP) (SBR4) only and one receiving mixture of 4-CP and 2,4-dichlorophenol (2,4-DCP) (SBRM), were operated with increasing chlorophenols concentrations in the feed. Complete degradation of chlorophenols and high-Chemical oxygen demand (COD) removal efficiencies were observed throughout the reactors operation. Only a fraction of biomass (competent biomass) was thought to be responsible for the degradation of chlorophenols due to required unique metabolic pathways. Haldane model developed based on competent biomass concentration fitted reasonably well to the experimental data at different feed chlorophenols concentrations. The presence of 2,4-DCP competitively inhibited 4-CP degradation and its degradation began only after complete removal of 2,4-DCP. Based on the experimental results, the 4-CP degrader's fraction in SBRM was estimated to be higher than that in SBR4 since 2,4-DCP degraders were also capable of degrading 4-CP due to similarity in the degradation pathways of both compounds.

Chlorophenols↗

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↗

PubMed2006

Removal of chlorophenols in sequential anaerobic-aerobic reactors.

Combination of upflow anaerobic sludge blanket (UASB) and aerobic rotating biological contactor (RBC) reactors having higher biomass concentration and higher sludge retention time (SRT) was applied for the sequential treatment of priority pollutant chlorophenol containing wastewater. Target compounds 2-chlorophenol (2-CP) and 2,4-dichlorophenol (2,4-DCP) present in two simulated wastewaters at a concentration of 30 mg/l each individually were sequentially treated in continuous mode by combined UASB-I, RBC-I and combined UASB-II, RBC-II reactors, respectively after the acclimation of their biomass with the corresponding chlorophenol. Reactor combinations took 190 and 215 days for acclimation with 30 mg/l of 2-CP and 2,4-DCP respectively. Hydraulic retention time (HRT) studies showed that 12h HRT of UASB-I and 23 h HRT of RBC-I as well as 12h HRT of UASB-II and 28.8h HRT of RBC-II were the optimum combinations for the treatment of simulated wastewater containing 2-CP and 2,4-DCP respectively. Optimum HRT combinations produced 2-CP and 2,4-DCP effluent having corresponding chlorophenol concentration of below detectable limit (BDL) and 0.1 mg/l respectively. Half velocity coefficients (Ks) for 2-CP and 2,4-DCP biodegradation in UASB reactors were determined to be 5.07 mg 2-CP/l and 6.49 mg 2,4-DCP/l. Optimum ratio of substrate (chlorophenol): co-substrate (sodium acetate) was 1:100.

Aerobiosis↗

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↗