Dechlorination Of Pentachlorophenol Research Articles

Anaerobic mineralization of pentachlorophenol (PCP) by combining PCP‐dechlorinating and phenol‐degrading cultures

The dechlorination and mineralization of pentachlorophenol (PCP) was investigated by simultaneously or sequentially combining two different anaerobic microbial populations, a PCP-dechlorinating culture capable of the reductive dechlorination of PCP to phenol and phenol- degrading cultures able to mineralize phenol under sulfate- or iron-reducing conditions. In the simultaneously combined mixture, PCP (about 35 microM) was mostly dechlorinated to phenol after incubation for 17 days under sulfate-reducing conditions or for 22 days under iron-reducing conditions. Thereafter, the complete removal of phenol occurred within 40 days under both conditions. In the sequentially combined mixture, most of the phenol, the end product of PCP dechlorination, was degraded within 12 days of inoculation with the phenol degrader, without a lag phase, under both sulfate- and iron-reducing conditions. In a radioactivity experiment, [14C-U]-PCP was mineralized to 14CO2 and 14CH4 by the combined anaerobic microbial activities. Analysis of electron donor and acceptor utilization and of the production and consumption of H2, CO2, and CH4 suggested that the dechlorinating and degrading microorganisms compete with other microorganisms to perform PCP dechlorination and part of the phenol degradation in complex anoxic environments in the presence of electron donors and acceptors. The presence of a small amount of autoclaved soil slurry in the medium was possibly another advantageous factor in the successful dechlorination and mineralization of PCP by the combined mixtures. This anaerobic-anaerobic combination technology holds great promise as a cost-effective strategy for complete PCP bioremediation in situ.

Pentachlorophenol dechlorination by an acidogenic sludge

This study reports the feasibility of removing pentachlorophenol (PCP) by an acidogenic process in batch reactors. When the acidogenic sludge was first acclimated with 2,4,6-trichlorophenol (2,4,6-TCP) and developed 2,4,6-TCP dechlorinating activity, PCP could be ortho-dechlorinated to 3,4,5,-trichlorophenol (3,4,5-TCP) via 2,3,4,5-tetrachlorophenol as the intermediary. However, due to PCP's higher hydrophobicity and its higher expected Gibbs free energy yield, it was adsorbed to the sludge and dechlorinated preferentially to 2,4,6-TCP. This resulted in the inhibition of 2,4,6-TCP dechlorination. PCP removal under acidogenic condition was attributed to both reductive dechlorination and adsorption. At low PCP loads of 0.48 μmoles/g MLVSS.d, dechlorination was the dominant removal mechanism (69% of total removal), while at the higher PCP load of 9.3 μmoles/g MLVSS.d, adsorption was the main mechanism (82% of total removal). Attempts to induce meta or para position dechlorination of PCP failed when using meta position chlorophenols such as 2,3,6-TCP, 3,4,5-TCP and 3,5-DCP as the initial substrates. Overall, acidogenic biotreatment was an effective process in reducing PCP loads prior to downstream biological treatment.

Complete dechlorination of pentachlorophenol using palladized bacterial cellulose in a rotating catalyst contact reactor

A rotating catalyst contact reactor (RCCR) was developed which consisted of palladized bacterial cellulose immobilized on acrylic discs for hydrodechlorination of pentachlorophenol (PCP). More than 99% of 40 mg L −1 PCP was dechlorinated to phenol in the presence of hydrogen in batch mode at initial pH values of 5.5 and 6.5 within 2 h of reaction with stoichiometric release of free chloride. The rate of PCP dechlorination was found to be independent of rotational speed of discs. PCP (40 mg L −1) hydrodechlorination experiments were also conducted using RCCR in continuous flow mode at hydraulic retention times of 1 and 2 h. The average outlet PCP concentrations revealed that liquid phase in RCCR closely resembled that of a continuous flow complete mix reactor (CFMR). Approximately 12 and 11 L of 40 mg L −1 PCP (pH 6.5) could be treated in RCCR with 99 and 80% efficiencies in batch and continuous flow modes, respectively without any appreciable loss of the catalytic activity. These results suggested reusability of palladized bacterial cellulose which in turn is expected to substantially reduce the cost of treatment process. Thus RCCR seems to have high potential for treatment of ground water contaminated with chlorinated organic compounds. Dried palladized bacterial cellulose has been used as a material for electrodes in a fuel cell. However, its application as a hydrodechlorination catalyst in a reactor operating under room temperature and atmospheric pressure has not been reported to the best of our knowledge. Scanning electron microscopy, energy dispersive X-ray spectroscopy and X-ray diffraction analyses suggested the irreversible deposition of palladium (Pd 0) particles on the bacterial cellulose fibrils.

Effects of solvent, pH, salts and resin fatty acids on the dechlorination of pentachlorophenol using magnesium–silver and magnesium–palladium bimetallic systems

The effects of pH, organic co-solvent, salts such as sodium chloride, sodium sulfate, and co-pollutants, resin and fatty acids (RFAs) on the dechlorination of pentachlorophenol (PCP) by magnesium/silver (Mg/Ag) and magnesium/palladium (Mg/Pd) systems were examined in the present investigations. Such studies provide relevant information about the applicability of bimetallic systems for remediation of raw wastewaters (such as pulp bleaching effluents) or groundwater. Removal efficiencies of 10 mg L −1 PCP by Mg/Pd and Mg/Ag systems at the end of 1 h reaction were 93% and 78%, respectively, in the presence of acetone (1% v/v). On the other hand, the removal efficiencies were 86% and 70% for reactions conducted in alcoholic solvents (1% v/v) using Mg/Pd and Mg/Ag systems, respectively. The efficiencies of PCP removal by the two bimetallic systems could be correlated to the dipole moments of co-solvents used. The second order reaction rate constant for PCP removal by Mg/Ag system was highest (0.03 L mg −1 min −1) in the absence of any pH-control mechanism. Optimum pH for the dechlorination of PCP by Mg/Pd system was found to be ∼5.5 and >92% of the compound was removed within 15 min of reaction. Presence of chlorinated and non-chlorinated resin fatty acids (RFAs) resulted in substantial reduction in the rate and extent of PCP removal by Mg/Ag system whereas dechlorination by Mg/Pd remained unaffected. Presence of sodium sulfate or sodium chloride in the reaction phase reduced the rate and extent of PCP removal by Mg/Ag system. PCP dechlorination by Mg/Pd system was adversely impacted by the addition of sodium chloride and unaffected by the presence of sodium sulfate.

Dechlorination of chlorophenols using magnesium–palladium bimetallic system

Ninety-four percent removal of 10 mg L −1 of pentachlorophenol (PCP) was achieved by treatment with 154.5 mM Mg 0 and 0.063 mM K 2PdCl 6 in the presence of 175 mM acetic acid in 1 h reaction time. Dechlorination of PCP was found to be sequential and phenol was identified as the end product along with accumulation of trace concentrations of tetra- and trichlorophenols. Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) revealed that palladium in its metallic form (Pd 0) produced by reduction of Pd 4+, was spatially separated from magnesium granules when acid was included in the reaction. These colloidal palladium particles generated active reductive species of hydrogen and dechlorinated chlorophenols. In the absence of acid, the efficiency of dechlorination of PCP by Pd/Mg 0 system was very low and chief mechanism of removal of the compound was through sorption onto solid surfaces. Thus, it was important to include acid in the system to: (a) facilitate corrosion of Mg 0 and reduction of Pd 4+ to Pd 0, (b) provision of protons to produce H 2, (c) retard formation of insoluble oxides and hydroxides that may deposit on the magnesium granules and sorb PCP and its partially dechlorinated products and. Application of 154.5 mM Mg 0/0.063 mM K 2PdCl 6 on PCP, 2,4,5-trichlorophenol (TCP) and 2-chlorophenol (MCP) with organic chloride equivalence showed that the rate and extent of removal increased with decrease in number of chlorine atoms on phenol.

Radiation-initiated dechlorination of pentachlorophenol in aqueous solutions

Radiation-initiated dechlorination of pentachlorophenol in aqueous solutions

Rapid and complete dechlorination of PCP in aqueous solution using Ni–Fe nanoparticles under assistance of ultrasound

The Ni–Fe bimetallic particles have been laboratory prepared using sodium borohydride (NaBH 4) as the reductant to reduce Ni 2+ and Fe 2+ in aqueous solution simultaneously, and characterized by TEM, XRD, BET and XPS. The particles were proved to be nanoscale amorphous alloy with an average diameter of about 30 nm and a BET surface area of 20.9 m 2 g −1. Experiments for dechlorination of pentachlorophenol (PCP) by the Ni–Fe bimetallic nanoscale particles in aqueous solutions were carried out under the enhancement of ultrasound. Major factors that influence the dechlorination efficiency, such as initial pH value, Ni content in the Ni–Fe particles, and output power of ultrasonic irradiation, were investigated. The results indicated that Ni–Fe nanoscale bimetallic particles were very effective for the dechlorination of PCP. Dechlorination efficiency was 46% in 30 min under the optimal condition without assistance of ultrasound, whereas it increased to 96% when ultrasonic irradiation was present. Initial pH value showed apparent effect on the dechlorination. As the pH varied from acidic condition to neutral condition, the dechlorination efficiency decreased dramatically. In addition, the dechlorination efficiency was improved with increased Ni/Fe ratio and ultrasonic output power. Less chlorinated phenols including tetrachlorophenol, trichlorophenol, dichlorophenol, monochlorophenol were formed during the initial reaction, and phenol was determined by GC–MS as sole product in the end of reaction.

Dechlorination of chlorophenols by magnesium–silver bimetallic system

More than 85% of 10 mg L −1 of pentachlorophenol (PCP) was removed by magnesium/silver (206/1.47 mM) bimetal system in the presence of acetic acid. Dechlorination was found to be sequential and phenol was identified as the ultimate hydrocarbon skeleton along with some accumulation of tetra-, tri-, and dichlorophenols. The dechlorination reaction was found to follow second-order kinetics. Lower PCP removal efficiency (35%) was observed when the reaction was carried out in the absence of acid using Mg 0/Ag system. When the reaction was conducted using Mg 0 alone in the presence of acid, substantial sorption of PCP occurred with very low efficiency of PCP dechlorination. Dechlorination studies on 10 mg L −1 initial concentrations of 2,3,4,6-tetrachlorophenol (2,3,4,6-TeCP) and 2,4,5-trichlorophenol (2,4,5-TCP), under identical conditions as to PCP, revealed that dechlorination efficiency and reaction rate constants decrease with decreasing number of chlorine atoms on the target compound. A correlation ( R 2 > 0.9 ) between the dechlorination rate constants and E LUMO for chlorophenols was obtained.

Dechlorination of Chlorophenols Using Magnesium-Palladium Bimetallic System

Abstract Ninety-four percent removal of 10 mg L−1 of pentachlorophenol (PCP) was achieved by treatment with 154.5 mM Mg0 and 0.063 mM K2PdCl6 in the presence of 175 mM acetic acid in 1 h reaction time. Dechlorination of PCP was found to be sequential and phenol was identified as the end product along with accumulation of trace concentrations of tetra- and trichlorophenols. Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) revealed that palladium in its metallic form (Pd0) produced by reduction of Pd4+, was spatially separated from magnesium granules when acid was included in the reaction. These colloidal palladium particles generated active reductive species of hydrogen and dechlorinated chlorophenols. In the absence of acid, the efficiency of dechlorination of PCP by Pd/Mg0 system was very low and chief mechanism of removal of the compound was through sorption onto solid surfaces. Thus, it was important to include acid in the system to: (a) facilitate corrosion of Mg0 and reduction of Pd4+ to Pd0, (b) provision of protons to produce H2, (c) retard formation of insoluble oxides and hydroxides that may deposit on the magnesium granules and sorb PCP and its partially dechlorinated products and. Application of 154.5 mM Mg0/0.063 mM K2PdCl6 on PCP, 2,4,5-trichlorophenol (TCP) and 2-chlorophenol (MCP) with organic chloride equivalence showed that the rate and extent of removal increased with decrease in number of chlorine atoms on phenol.

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.

14C]Pentachlorophenol mineralization in the rice rhizosphere with established oxidized and reduced soil layers

Flooded soils with rooted aquatic macrophytes have adjacent aerobic and anaerobic zones at the soil–water interface and rhizosphere where many common soil constituents undergo sequential oxidation and reduction reactions. To investigate whether pentachlorophenol (PCP) mineralization would also be enhanced under these conditions, a laboratory study was conducted to determine the conversion of [ 14C]PCP to 14CO 2, 14CH 4 and [ 14C]humic substances in soil microcosms with established aerobic–anaerobic zones at the soil–water interface and rice ( Oryza sativa) rhizosphere. Contrary to what was expected, PCP was least rapidly degraded in rhizosphere-soil microcosms that contained the most extensive amounts of aerobic–anaerobic interfaces (63% PCP loss in 82 d) and was most rapidly degraded in soil microcosms that lacked redox interfaces in the soil profile (94% PCP loss in 82 d). Decreased PCP mineralization in the presence of aerobic–anaerobic interfaces was explained by (i) lack of sufficient O 2 for aerobic PCP mineralization, due to the oxidation of other soil constituents in aerobic zones, and (ii) lack of an adequate supply of electron equivalents for reductive dechlorination of PCP, due to the reduction of other alternate electron acceptors in anaerobic zones. It was concluded that PCP mineralization is inhibited in flooded soils that contain extensive amounts of aerobic-anaerobic interfaces, due to redox cycling of other soil constituents that occur in these zones.

Dechlorination ability of municipal waste incineration fly ash for polychlorinated phenols

Pathways of pentachlorophenol dechlorination have been investigated on municipal waste incineration fly ash at 200 °C under nitrogen atmosphere. Thermodynamic calculations have been carried out for these dechlorination conditions using the method of total Gibbs energy minimization for the whole system consisting of gaseous components, i.e., chlorinated phenols, phenol, hydrogen chloride and the Cu 3Cl 3 trimer and of solid Cu 2O and CuCl 2 components. The effects of water, temperature and of the amounts of the reaction components on the thermodynamic equilibrium have been discussed and the experimental results compared with the calculated thermodynamic data.

Growth substrate selection and biodegradation of PCP by New Zealand white-rot fungi

Nine New Zealand native white-rot fungi were studied for their ability to grow and survive on different substrates formulated from bark, wheat straw, sawdust, apple pomace and maize products in order to identify their pentachlorophenol (PCP) biodegradation potential and to select a fungal carrier for bioaugmentation of polluted soils. Isolates were also evaluated to mineralize 14C-PCP in liquid culture and in soil. The American fungus Phanerochaete chrysosporium outgrew the native fungi on the substrates tested, but the high colonisation did not result in superior PCP dechlorination as measured by chloride release. Whilst Trametes versicolor inocula produced on wheat straw and SCS (sawdust–corn meal–starch-mix) gave the highest chloride release, colonization of these two substrates as measured by biological potential was lower compared to the pomace and pomace–sawdust-mix. Neither lignin peroxidase nor manganese peroxidase production were measured for New Zealand white-rot fungi during the experiments. Laccase was the only enzyme detected. In liquid culture, the mineralisation rate was higher for T. versicolor isolates compared to P. chyrysoporium. Very little to no pentachloroanisole (PCA) was captured in the volatile fraction of T. versicolor isolates, whereas 75% of the volatile fraction of P. chrysosporium consisted of PCA. The soil microcosms studies, using contaminated soil from a timber treatment site, clearly showed that the New Zealand T. versicolor isolates mineralized PCP. Degradation of PCP in non-sterile soil was higher in the presence of white-rot fungi than in soil without white-rot fungus. This demonstrates that viable white-rot fungus is necessary for significant PCP degradation and that T. versicolor isolates showed PCP remediation potential. Wheat straw and SCS could be suitable carriers for New Zealand native T. versicolor isolates for bioremediation of PCP polluted soil sites.

Use of an Anaerobic Sludge Digestion Process to Treat Pentachlorophenol-(PCP-) Contaminated Soil

Extensive pentachlorophenol (PCP) contamination and its increasing treatment costs motivate the search for better treatment alternatives. In this study, the feasibility and effectiveness of an anaerobic sludge digestion process was evaluated. Two laboratory-scale digesters mimicking the commonly used anaerobic sludge digester in a municipal wastewater treatment plant were operated to treat PCP. Results showed that up to 0.98 mM of chemical PCP dissolved in acetone and 0.6 mM soil PCP from a contaminated site were treated at nearly 100 and 97.3% efficiencies, respectively. PCP dechlorination followed two major pathways: PCP to 2,3,4,5-TeCP to 2,3,5- or 3,4,5-TCP to 3,5-DCP and PCP to 2,3,5,6-TeCP to 2,3,5-TCP to 3,5-DCP to 3-MCP. The 3-MCP was not present until 26 days after the first addition of PCP, which also concluded the end of the sludge acclimation process to PCP. Microbial acclimation reduced chlorophenol toxicity and enhanced degradation of chlorophenol. Without acclimation the gas production and chlorophenol degradation were both significantly hindered. 95% of the added PCP was transformed to 3-MCP, 4.5% to 3,4-DCP, and 0.5% to 3,5-DCP, and about 20% of the PCP by-products remained in liquid and the rest adsorbed on sludge solids. Results of this study suggested the potential use of an anaerobic sludge digestion process for PCP-contaminated soil remediation.

Influence of humic substances on the removal of pentachlorophenol by a biomimetic catalytic system with a water-soluble iron(III)-porphyrin complex.

To investigate some basic aspects of soil remediation using biomimetic catalysts, the effects of humic substances (HSs) on the removal of xenobiotics, such as pentachlorophenol (PCP), were investigated. The use of a biomimetic catalytic system using tetra(p-sulfophenyl)porphine-iron(III) (Fe(III)-TPPS) and potassium monopersulfate (KHSO5) resulted in the disappearance of PCP, accompanied by dechlorination. In addition, this process was enhanced by the presence of several types of HSs. The degrees of enhancement (% delta(PCP)60) achieved by the presence of HSs from peat and compost soils were larger than those in the presence of other types of HSs (tropical peat, brown forest, and ando soils). In control experiments, no PCP disappearance and dechlorination were observed in the presence of only KHSO5, only Fe(III)-TPPS, or combinations of HSs and either KHSO5 or Fe(III)-TPPS. To better understand the role of added HS in enhancing or inhibiting PCP disappearance, correlations between the chemical parameters of the HSs and % delta(PCP)60 were investigated. The most effective HSs had lower carboxylic acid contents and lower degrees of unsaturation. The carboxylic acid content and degree of unsaturation increase with the extent of humification. Therefore, HSs of a lower degree of humification would be predicted to be more useful in enhancing the disappearance of PCP in an Fe(III)-TPPS/KHSO5 system.

Gamma radiation treatment of pentachlorophenol, 2,4-dichlorophenol and 2-chlorophenol in water

The aim of this work was to investigate γ-irradiation treatment of pentachlorophenol (PCP), 2,4-dichlorophenol (DCP) and 2-chlorophenol (2-CP) in water. The dechlorination of PCP, DCP and 2-CP has been studied by using γ-radiation as well as ozonization. G(Cl −) is always much higher than the corresponding G(-PCP), this means that some primary radiolytic products are unstable during post-irradiation. The COD (Mn) values of irradiated PCP were determined. PCP is much more easily decomposed by irradiation than either DCP or o-CP. Some stable radiolytic intermediates were detected. Preliminary analysis revealed that some chloroquinones were among the final products. Where ozone was used, the results suggest that it enhanced the efficiency of radiation-induced decomposition.

Dechlorination of pentachlorophenol in supercritical carbon dioxide with zero-valent palladium-magnesium bimetallic mixture.

A stream of substrate pentachlorophenol [PCP, 5 mg min(-1) in water-methanol (1 + 4, v/v)] was merged with 1.5 ml min(-1) of supercritical carbon dioxide (scCO2) and delivered to a reactor column (25 cm x 1 cm) of zero-valent palladium-magnesium mixture. The resulting dechlorinations, although very efficient, were not quantitative. For continuous operation at 400 degrees C for 6 h, phenol was the principal product, with lesser quantities of methylated products and only traces of chlorinated products (principally monochlorinated species). PCP deoxygenation was not observed and ring methylation was decreased relative to analogous reactions in hydroxylic organic solvent. With time, the reactor column slowly lost dechlorination activity. Reducing the loading of Pd0 on Mg0 from 2% to 1% (w/w) apparently did not change the course of the reaction; however, the dechlorination capacity was decreased correspondingly. None the less, over 6 h or 5 h of continued operation, the dechlorination efficiency was 0.995 for the 2% (w/w) loading of Pd0 on Mg0 and 0.984 for the 1% (w/w) loading.

Zero-valent metal accelerators for the dechlorination of pentachlorophenol (PCP) in subcritical water

Preliminary trials with 0.5 mg pentachlorophenol (PCP) in the presence/absence of 50 mg of 325-mesh Ag0/Fe0 (2% w/w) granules, demonstrated that the extent of dechlorination increased with both increased reaction time (0.5–2 h) and increased temperature (200–350 °C) but that recoveries of products were incomplete. Whereas reaction (200 °C) in the absence of metal accelerator furnished only unreacted PCP after 2 h and a mixture of tetrachloro species and substrate (∼50%) after 4 h of reaction, timed trials in the presence of Fe0 or 2% (w/w) Ag0/Fe0 bimetallic mixture resulted in more extensive dechlorinations. Only sequential dechlorinations were observed for iron-based accelerators and the dechlorination route was consistent with relief of steric strain as the dominant influence that determined the decomposition products. There was no appreciable difference in the course of the dechlorinations between the Fe0 and the 2% (w/w) Ag0/Fe0 bimetallic mixture but differences in the rates of reaction were evident. Dechlorinations with magnesium-based bimetallic accelerators were more extensive, more rapid and both concerted and stepwise reactions were observed. With 100 mg Pd0/Mg0, 63% of products consisted of phenol plus cyclohexanone and a further 9% was o-chlorophenol yet 13% were tetrachloro species. By contrast, an equal quantity of Mg0 alone mediated only partial dechlorination. The dechlorinations represent a detoxification—the toxiforic chloro substituents of the substrate are reduced to innocuous chloride while the sacrificial Mg metal is oxidised to Mg2+.

Molecular Cloning and Characterization of Pentachlorophenol-Degrading Monooxygenase Genes of Pseudomonas sp. from the Chemostat

Pseudomonas sp. strain IST 103 (PCP103) capable of utilizing pentachlorophenol (PCP) was determined by utilization of a carbon source and release of the hydroxylating enzyme PCP-4 monooxygenase. The metabolites were extracted from the culture medium and analyzed by high-performance liquid chromatography. The enzyme purified to apparent homogeneity from an extract of PCP-grown cells indicated that a fraction of DEAE-cellulose ion exchange chromatography of molecular size of 30,000 kDa determined by gel filtration chromatography and SDS–polyacrylamide gel electrophoresis was responsible for dechlorination of PCP. The plasmid isolated from the bacterium was subjected to Shotgun cloning by restriction digestion by BamHI, HindIII, and SalI, ligated to pUC19 vector, and transformed into Escherichia coli XLBlue1α. The recombinant clones having higher potentiality to degrade PCP were selected by utilization of a carbon source and release of intermediary metabolites during degradation of PCP as the sole source of carbon and energy. The recombinant clones, which contained an insert of 3.0 kb of SalI and HindIII sites, were sequenced and compared with gene sequences deposited in GenBank by BLAST search; this indicated homology with the thdf gene of monooxygenase of thiophene and furan. Southern blot analysis performed by developing gene probes indicated the presence of the PCP monooxygenase gene in plasmids of the bacterium.

Dechlorination of chlorinated phenols by catalyzed and uncatalyzed Fe(0) and Mg(0) particles

Uncatalyzed, and palladium-catalyzed Fe(0) and Mg(0) systems were examined for their efficiencies of dechlorination of 2.86 mM 4-chlorophenol (4-CP), 2.52 mM 2,6-dichlorophenol (2,6-DCP), 3.03 mM 2,4,6-trichlorophenol (2,4,6-TCP), and 2.48 mM pentachlorophenol (PCP) in 50/50 (v/v) 2-propanol/water under room temperature and pressure conditions. Previous investigators have found that PCP is extremely recalcitrant under these conditions. In this investigation, complete dechlorination of 5.0 ml of 2.48 mM PCP was observed for 1.0 g of 2659 ppm Pd/Mg (20 mesh) after 48 h. The only detectable products were cyclohexanol and cyclohexanone at 25% yield. No other chlorinated or otherwise products were observed by mass spectral analysis. It is hypothesized that volatile low molecular weight species were formed from the Pd/Mg dechlorination of PCP. Under conditions of equal surface area (0.0786 m 2), the approximate order of PCP dechlorination power of these systems followed as 2659 ppm Pd/Mg>319 ppm Pd/Mg>Mg≈4856 ppm Pd/Fe>Fe. Degradation of the other chlorinated phenols by all metallic systems was more facile than PCP.