Pentachlorophenol In Water Research Articles

Adsorption and electrocatalytic dechlorination of pentachlorophenol on palladium-loaded activated carbon fibers

The palladium-loaded activated carbon fiber (Pd/ACF) adsorption/electroreduction process was employed for electrocatalytic dechlorination of pentachlorophenol (PCP) solution. PCP in water was adsorbed onto Pd (4.2 wt.%)/ACF first and then the PCP was degraded at a constant current. At 25 mA/cm 2, the degradation of PCP was 94.8% after electrolysis of 200 min and phenol was the main product with a yield of 86.1% and a current efficiency of 17.4%. After being reused three times, the Pd (4.2 wt.%)/ACF cathode still had acceptable electrocatalytic activity.

Cyclodextrin-enhanced solubilization of pentachlorophenol in water

The solubilization of pentachlorophenol (PCP) by β-cyclodextrin (β-CD) and three of its most used derivatives, methyl-β-cyclodextrin (MCD), hydroxypropyl-β-cyclodextrin (HPCD) and carboxymethyl-β-cyclodextrin (CMCD), has been investigated. The formation of soluble inclusion complexes between PCP and cyclodextrin (CDs) increases the aqueous solubility of PCP. Due to the ionizable nature of PCP, the effects of pH and ionic strength on the equilibrium complexation were evaluated. All CDs were found to form 1:1 inclusion complexes. Equilibrium constants calculated from solubility enhancement experiments revealed that the stability of the complexes was dependent on the polarity of the compound, on the ionic strength and on the cyclodextrin type. In general, weaker equilibrium constants were observed for PCP with β-CD than with MCD or CMCD. For all CDs, the complexation or the solubilization efficiency of PCP (weak acid) depended on pH and ionic strength. Moreover, we observed that the solubility of the β-CD/PCP complex was lower than that of the β-CD molecule and dependent on the ionic strength of the solution. Although the equilibrium constant of PCP/CD complex was found to be higher at pH 3 than at pH 7 in water, extraction of PCP from porous media by a CD solution at neutral pH would be achievable due to the higher PCP aqueous solubility in neutral/basic media.

Temperature measurement of GAC and decomposition of PCP loaded on GAC and GAC-supported copper catalyst in microwave irradiation

A sheltered type-K thermocouple was applied to record the temperature rising courses of granular activated carbon (GAC) in a microwave irradiation field under various conditions. The results showed that GAC could absorb microwave energy effectively and its temperature rose up to 1100 °C in a few minutes. This interaction of GAC and microwave was utilized to the preparation of GAC-supported copper catalyst. The catalyst was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), iodine number and adsorption isotherm. It was found that elemental copper distributed uniformly on the surface of GAC, and after loading copper, the adsorption capacity of GAC decreased due to occupation of adsorption sites by copper. Decomposition of a typical chlorinated organic chemical, pentachlorophenol (PCP), on virgin GAC and copper-loaded GAC was assisted by microwave irradiation. Firstly, PCP in water was adsorbed onto GAC, then PCP-loaded GAC irradiated by microwave in a quartz reactor. The results indicated that most of PCP adsorbed on virgin GAC was decomposed or bound irreversibly to GAC under 850 w microwave irradiation for 10 min, and less than 2% was transformed into intermediates. A more rapid decomposition rate of PCP was observed on copper-loaded GAC with larger amount of intermediates formed. Identification of intermediates was accomplished by gas chromatography/mass spectrometry (GC/MS) analysis.

Simultaneous pentachlorophenol decomposition and granular activated carbon regeneration assisted by microwave irradiation

This paper describes an integrated granular activated carbon (GAC) adsorption/microwave (MW) irradiation process used for the treatment of high concentration pentachlorophenol (PCP) wastewater. Firstly, PCP in water was adsorbed onto GAC, then the PCP was decomposed and GAC regenerated by MW irradiation. The liquid and gas produced during irradiation were collected through condensing, and absorbed by a 0.1 mol l −1 NaOH solution, respectively. The determination of the PCP concentrations in the distillate, absorption solution and GAC was accomplished by a HPLC. The results suggested that when irradiated with 850 W MW for 10 min, most of the PCP adsorbed by GAC and whatever fragments formed were decomposed to CO 2, H 2O and HCl or tightly bound to GAC, and less than 2% of PCP was transformed into intermediates in the distillate. Some dechlorination and dehydroxylation products were identified by the GC/MS analysis, and the degradation mechanism was proposed. It was also confirmed that GAC could be reused after several adsorption/MW regeneration cycles and its adsorption capacity could maintain a relatively high level, even higher than that of virgin GAC, as indicated by BET results, iodine values and PCP adsorption isotherms.

Application of LPME/GC-ECD for determination of PCP in water

Liquid-phase microextraction (LPME) followed by gas chromatography (GC) coupled with an electron capture detector (ECD) was applied for the analysis of pentachlorophenol (PCP) in aqueous samples. After alkalization with Na2CO3 solution, PCP was acetylated with acetic anhydride. The pentachlorophenyl acetate derivative was then extracted with n-hexane by LPME. 1.5 μL organic drop exposed to the aqueous sample solution at 15°C for 5 min, stirring rate at 100 r/min was chosen as the optimum extraction condition. Under this condition, LPME provided a very simple, fast and solvent-less procedure to collect PCP from aqueous sample for GC determination. The linearity of LPME/GC-ECD for PCP in distilled water was investigated at the range of 2–200 μg/L with a coefficient of correlation 0.998. The repeatability of this method was determined at the level of 50 μg/L with the average of relative standard deviations (RSDs) 7%. Detection limit was obtained at less than 0.5 μg/L levels. When LPME/GC-ECD was applied to the determination of PCP in municipal sewage, the average of relative recoveries and RSDs were 70% and 6.5%, respectively.

Electrochemical Hydrodehalogenation of Chlorinated Phenols in Aqueous Solutions : II. Effect of Operating Parameters

The effect of operating parameters on chloride ion release, current efficiencies, and energy consumptions of the electrochemical hydrodehalogenation (HDH) of dilute aqueous solutions of pentachlorophenol (PCP) and 2, 4-dichlorophenol (DCP) is reported. The parameters include the concentrations of PCP and DCP, applied current density, controlled cathode potential, temperature, and flow rate. Relatively high concentrations, high-temperature, and moderate current density (e.g., 10 mA cm−2) have the most beneficial effect on the HDH process. For example, the HDH of 20 mM DCP in an H-cell at 70°C gave current efficiencies up to 70% and an energy consumption of 2.6 kWh/kg DCP. Good results were also achieved in a solid polymer electrolyte zero gap flow cell, e.g., a current efficiency of 35% and an energy consumption of 4.5 kWh/kg. Encouragingly, the energy consumed for the HDH of 50 ppm PCP in water at ambient temperature is in a range of 28 and 80 kWh/kg PCP, which is much lower than previously reported. © 2002 The Electrochemical Society. All rights reserved.

PVC membrane ion selective electrode for the determination of pentachlorophenol in water, wood and soil using tetrazolium pentachlorophenolate

A novel PVC membrane electrode selective for the determination of pentachlorophenolate (PCP) ion based on 2,3,5-triphenyl-2H-tetrazolium (TPT) pentachlorophenolate ion pair as an electroactive material is described. The electrode shows a linear response for PCP ion over the concentration range of 6×10 −5 to 1×10 −2 M with lower detection limit of 4×10 −5 M at 25 °C. The electrode posses a Nernstian slope of −55.0±1.0 mV/decade and a fast potential response of 45 s, which is almost constant over a pH range of 5.5–10.5. Selectivity coefficient data for some common ions show negligible interference, however, 2,4,6-trichlorophenolate and cetylpyridinium ions interfere. An average recovery of 96.2% with relative standard deviation of 2.3% has been achieved for the determination of 75.0 ppm PCP in wastewater samples. The determination of PCP in soil and wood samples gave results that compare favorably with those obtained by gas chromatography. The electrode has been utilized as an end point indicator electrode for the determination of PCP using potentiometric titration.

Identification of Photolytical Transformation Products of Pentachlorophenol in Water

The photodegradation of pentachlorophenol in water was examined with a high-pressure mercury lamp. A number of photodegradation products of pentachlorophenol, such as less-chlorinated phenols through reductive dechlorination, and catechol and trihydroxylated products via the addition of hydroxyl radicals, were observed as major products. Moreover, polychlorinated biphenylethers, hydroxylated polychlorobiphenylethers and polychlorinated dibenzo-p-dioxins as minor products were also formed by dimerization process during the photolysis of pentachlorophenol. These compounds were identified by gas chromatography-mass spectrometry. The degradation rate of PCP in water was measured against the UV-irradiation time. After the irradiation for 15 min, 75% of PCP was converted into a number of products through reductive dechlorination and oxidation. On the basis of the identified products, the photodegradation pathways of PCP under UV irradiation were proposed.

Liquid−Liquid and Liquid−Solid Equilibria of Systems Containing Water and Selected Chlorophenols

The solubilities of phenol, 4-chlorophenol, 2,4-dichlorophenol, 2,4,6-trichlorophenol, and pentachlorophenol in water were determined in the temperature range between 270 K and 423 K. Dynamic thermal analysis and a visual static method were used to establish the phase diagrams. Results obtained over a wide temperature and concentration range were used to model the liquid−liquid coexistence curve of the systems studied.

Degradation and detoxification of the wood preservatives creosote and pentachlorophenol in water by the photo-Fenton reaction

Pentachlorophenol (PCP) and the organic compounds in creosote often contaminate groundwater at wood preserving facilities. Since many of these compounds are toxic, effective water treatment technologies must be identified. In laboratory scale experiments saturated aqueous solutions of creosote and PCP were treated by the photo-assisted Fenton reaction, Fe 3+/H 2O 2/UV ([Fe 3+]=1 mM, [H 2O 2]=10 mM, 1.4×10 −3 M h ν min −1 black lamp ultraviolet light (UV), pH=2.75 and 25°C). The disappearance of 37 polycyclic aromatic hydrocarbons (PAHs), O, N and S-heterocyclic aromatic compounds and phenolic compounds and their mineralization products were monitored during a 180 min reaction period. Substantial (>90%) transformation of all compounds except a few 4- and 5-ring PAHs was achieved in 5 min, with more extensive transformation occurring thereafter. The reactivity followed the order: 2 ring PAHs>heterocyclics>phenolics>3 ring PAHs>4–5 ring PAHs. Complete dechlorination of PCP required only 10–20 min. Within 180 min the total organic carbon concentration declined by about 80% and added 9- 14C-phenanthrene or 4,5,9,10- 14C-pyrene were mineralized by 93% and 35%, respectively. About 33% of the organic nitrogen was converted to a 2:1 mole ratio of NH 4 + and HNO 3 and trace amounts of HNO 2. An undetermined yield of sulfate was also generated. The acute toxicity of the treated solution to fathead minnows ( Pimephales promelas) was nearly eliminated and the acute toxicity to daphnia ( Daphnia pulex) was reduced. These results demonstrate the efficacy of Fe 3+/H 2O 2/UV for removing creosote and PCP in water.

An investigation of the electrochemical reduction of pentachlorophenol with analysis by HPLC

A study has been made of the electrochemical reduction of pentachlorophenol (PCP) on a lead electrode in both water and propylene carbonate. A combination of voltammetric measurements and analysis of reaction products by high performance liquid chromatography (HPLC) have established that the reduction of PCP in propylene carbonate occurs by two different pathways, depending upon the electrode potential. At -1.9V vs SCE, reduction is mediated by adsorbed hydrogen, whereas at -2.3V vs SCE direct reduction of PCP also occurs. A similar approach has established that the reduction of PCP in water follows only one reaction pathway, namely, direct electron transfer from lead to PCP.

Study of the release in water of a chemical used for preservation of wood. Effect of the dimensions of the wood

Various chemicals are used for protecting wood samples against fungi, and some of them are released in water, leading to pollution of the water. The kinetics of release of pentachlorophenol in water has here been studied, by considering the diffusion through the wood along the three principal axes of diffusion. The experiments and the modelling of the process is successfully coupled. The numerical model takes the three principal diffusivities, the partition factor, the volumes of wood and water into account. The effect of the length of the wood sample taken along the longitudinal axis of diffusion is especially studied, as the longitudinal diffusivity is much higher than the other two principal diffusivities. The effect of the relative volumes of wood and water is also of considerable interest not only for the concentration of the chemical in water but also for the rate of release.

Photosensitized dechlorination of polychlorinated phenols 2. Photoinduced by poly(sodium styrenesulphonate-co- N-vinylcarbazole) dechlorination of pentachlorophenol in water

The photodechlorination of pentachlorophenol (PCP) solubilized in an aqueous solution of poly(sodium styrenesulphonate-co- N-vinyl-carbazole) (PSSS-VCz) copolymer was studied. The reaction was found to be photoinduced by the polymeric carbazole chromophores. The products were identified using gas chromatography-mass spectrometry (GC-MS) analysis. It was found that the ultimate reaction product was unsubstituted phenol.

Determination of Pentachlorophenol in Water and Soil by a Magnetic Particle-Based Enzyme Immunoassay

A competitive enzyme immunoassay using specific pentachlorophenol (PCP) antiserum covalently coupled to a magnetic particle solid phase has been developed for the detection of PCP in water and soil. The immunoassay allows the quantification of PCP from 100 ppt(parts per trillion, ng/L) in water and 100 ppb (parts per billion, mg/L) in soil. Spike recovery from water samples with no sample pretreatment and from various soil types following a simple extraction technique averaged 105% and 94%, respectively. The method compares favorably with GC/MS and HPLC measurements in water (r=0.980) and soil (r=0.996) samples.

Modelling the process of release of a chemical from wood in finite volumes of water in succession

Chemicals used for protection of wood against fungi may be released in water when the sample comes into contact with water. The process of release of pentachlorophenol in water was studied in this paper, when the presaturated wood specimen is immersed in a finite volume of water up to a time at which equilibrium is not attained. The wood sample is then dried and immersed again in water. This process is continued many times. Moreover a finite coefficient of matter transfer at the wood surface is observed. A numerical model with finite differences was successfully tested by comparing the kinetics of release obtained either by experiments and calculation. The process was simplified in the sense that only the transfer of the chemical through the water located in the wood was considered. The model is thus able to provide the kinetics of release and the profiles of concentration.

Effect of pH on the accumulation kinetics of pentachlorophenol in goldfish

The kinetics of accumulation of pentachlorophenol (PCP) at various pH values were investigated to explore how pH-dependent accumulation might influence PCP toxicity. Goldfish (Carassius auratus) were exposed to 5 micrograms PCP/L in a static system buffered with 7.5 mM bicine or N,N-bis(2-hydroxyethyl)-2-aminoethane sulfonic acid (BES) at pH 7.0, 8.0, or 9.0. The amount of PCP in the fish, concentration of PCP in water, and the total amount of metabolites in the system were measured after exposure of fish from 1 to 96 hr. Equations for these variables based on a two compartment pharmacokinetic model were fitted simultaneously to the data using NONLIN, which uses an iterative nonlinear least squares technique. Uptake clearance, metabolic clearance, and apparent volume of distribution of PCP decreased as pH increased. The decrease in PCP accumulation with increased pH was not due solely to a pH-induced decrease in uptake. In addition, the distribution of PCP within the fish was altered by changes in the external pH. The pH-associated changes in distribution may have altered access of PCP to sites of metabolism, thereby altering the metabolic clearance. The pH-related changes in the pharmacokinetics of PCP resulted in a decrease in its bioconcentration factor with an increase in pH and account both for the decreased capacity of the fish to accumulate PCP and for its reduced LC50.

Photochemistry of halogenated benzene derivatives. Part VIII. Photoformation of 2-methyl-4,5,6,7-tetrachlorobenzoxazole from pentachlorophenol in water–acetonitrile

Photolysis of a solution of pentachlorophenol (1) in H2O–CH3CN (2:3 v/v) was conducted on a synthetic scale using wavelengths ≥290 nm. After changing the pH of the photolyzate of 1 to ≥12, the photoproduct 2-methyl-4,5,6,7-tetrachloro-benzoxazole (2) was extracted with n-hexane. The product 2 was crystallized from methanolic solution. Ultraviolet, IR, FT-1H-NMR, proton-decoupled normal FT-13C-NMR, and proton-decoupled DEPT (distortionless enhancement by polarization transfer) sequence FT-13C-NMR spectroscopy were used to identify photoproduct 2 as 2-methyl-4,5,6,7-tetrachlorobenzoxazole. A mechanism for the photoformation of benzoxazole 2 from 1 is proposed. 3,4,5,6-Tetrachlorocyclohexa-3,5-diene-1,2-ketocarbene formed from 2-hydroxy-3,4,5,6-tetrachlorophenyl radical is suggested as key intermediate involved in the generation of oxazole 2 from phenol 1. The chemical yield of 2 on the basis of 1 was ca. 1%. A mechanism is proposed to explain the mass spectral fragmentation of 2 via the losses of Ċl,:C=O, Cl—Ċ=O, CH3—Ċ=O, CH3CN, and C3H3ClNO species from the parent molecular ion.

Analysis of pentachlorophenol in water and urine by enrichment with lipidex ® 5000

A method using the lipophilic gel Lipidex ® 5000 for sorption of pentachlorophenol (PCP) from water and urine is described. The procedure for water gives a simultaneous clean-up from lipophilic contaminants and also offers the possibility for determination of less polar compounds, such as 1,1-bis(4-chlorophenyl)-2,2,2-trichloroethane ( p,p′-DDT) and 2,3,7,8-tetrachlorodibenzo- p-dioxin (TCDD), collected in a separate fraction. The extracted PCP is derivatized to pentachlorophenyl acetate, which is determined by electron-capture gas chromatography. The average recovery of 0.01–0.15 ng PCP per ml water was 96% and of labelled p,p′-DDT (ca. 5 ng/ml) and TCDD (ca. 0.001 ng/ml) 95 and 92%, respectively. A similar method for enrichment of PCP was applied to acidified urine and to urine hydrolysed with hydrochloric acid or with digestive juice from Helix pomatia. Recoveries of 0.1–2.5 ng PCP per ml non-hydrolysed urine were on an average 92% and of 2.5–10 ng PCP per ml hydrolysed urine 96%. The analyses indicate that PCP in urine from non-occupationally exposed persons is originally conjugated and to some extent liberated when stored. The contamination of organic solvents and laboratory environments with PCP is discussed.

Pentachlorophenol: health and environmental effects profile.

Pentachlorophenol is used as an industrial wood preservative for utility poles, crossarms, fence posts, and other purposes (79%);for NaPCP (12%); and miscellaneous, including mill uses, consumer wood preserving formulations and herbicide intermediate (9%) (CMR, 1980). As a wood preservative, pentachlorophenol acts as both a fungicide and insecticide (Freiter, 1978). The miscellaneous mill uses primarily involve the application of pentachlorophenol as a slime reducer in paper and pulp milling and may constitute ∼6% of the total annual consumption of pentachlorophenol (Crosby et al., 1981). Sodium pentachlorophenate (NaPCP) is also used as an antifungal and antibacterial agent (Freiter, 1978). Pentachlorophenol also is used as a general herbicide (Martin and Worthing, 1977).Photolysis and microbial degradation are the important chemical removal mechanisms for pentachlorophenol in water. In surface waters, pentachlorophenol photolyzes rapidly (ECETOC, 1984; Wong and Crosby. 1981; Zepp et al., 1984); however,...

A simple spectrophotometric technique for the determination of pentachlorophenol in water

Pentacnlorophenol (PCP) and i t s sodium sa l t are the second most widely used biocides in the United States (CIRRELLI 1979) with the annual world production exceeding 20,000 tons (RAPPE & NILSSON 1972). The inevitable contamination of aquatic and marine environments resul t ing from agr icu l tura l and industr ia l usage of PCP has prompted a number of investigations concerning the fate and effects of th is chlorophenol in animals and the environment (RAO 1978).