Degradation Of P-cresol Research Articles

Loading Effect in Copper(II) Oxide Cluster-Surface-Modified Titanium(IV) Oxide on Visible- and UV-Light Activities

Cu(acac)2 is chemisorbed on TiO2 particles [P-25 (anatase/rutile = 4/1 w/w), Degussa] via coordination by surface Ti–OH groups without elimination of the acac ligand. Post-heating of the Cu(acac)2-adsorbed TiO2 at 773 K yields molecular scale copper(II) oxide clusters on the surface (CuO/TiO2). The copper loading amount (Γ/Cu ions nm–2) is controlled in a wide range by the Cu(acac)2 concentration and the chemisorption–calcination cycle number. Valence band (VB) X-ray photoelectron and photoluminescence spectroscopy indicated that the VB maximum of TiO2 rises up with increasing Γ, while vacant midgap levels are generated. The surface modification gives rise to visible-light activity and concomitant significant increase in UV-light activity for the degradation of 2-naphthol and p-cresol. Prolonging irradiation time leads to the decomposition to CO2, which increases in proportion to irradiation time. The photocatalytic activity strongly depends on the loading, Γ, with an optimum value of Γ for the photocatalytic activity. Electrochemical measurements suggest that the surface CuO clusters promote the reduction of adsorbed O2. First principles density functional theory simulations clearly show that, at Γ < 1, unoccupied Cu 3d levels are generated in the midgap region, and at Γ > 1, the VB maximum rises and the unoccupied Cu 3d levels move to the conduction band minimum of TiO2. These results suggest that visible-light excitation of CuO/TiO2 causes the bulk-to-surface interfacial electron transfer at low coverage and the surface-to-bulk interfacial electron transfer at high coverage. We conclude that the surface CuO clusters enhance the separation of photogenerated charge carriers by the interfacial electron transfer and the subsequent reduction of adsorbed O2 to achieve the compatibility of high levels of visible and UV-light activities.

Soil remediation using soil washing followed by Fenton oxidation

Soil washing was applied to a contaminated soil with p-Cresol by using a nonionic surfactant (Tween 80). A mathematical model has also been proposed to describe both the pollutant desorption and the surfactant adsorption, taking place simultaneously. The effect of temperature (20–40°C) and surfactant concentration (0.1–10gL−1) have been analyzed on both kinetic rates. The kinetic desorption rate of p-Cresol increases as the initial solubilizer concentration. Desorption of p-Cresol was slightly greater with increasing temperature. The obtained kinetic model represents quite well the experimental results.Soil washing wastewater (20mgL−1 of p-Cresol and 0.86gL−1 of Tween 80) has been treated with Fenton Reagent to remove the pollutant extracted (p-Cresol) and to recover the surfactant solution. The pH of the soil washing wastewater was about 6.5 and did not change significantly during the Fenton Reagent treatment. Total conversions of p-Cresol were observed, at very short times, at the conditions tested for the Fenton reaction (100mgL−1 of H2O2 and 10mgL−1 of Fe2+). The hydrogen peroxide was not totally exhausted, showing conversions near 60% at 120min. Besides, the removal of Tween 80 during the Fenton’s reaction was lower than 10%, which suggests that the reaction is mainly selective to p-Cresol degradation. The toxicity of the liquids, measured by Microtox bioassay, was significantly reduced after the oxidation reaction, suggesting the negligible formation of degradation intermediates with higher toxicity than p-Cresol.

Biodegradation of p-cresol by aerobic granules in sequencing batch reactor

The cultivation of aerobic granules in sequencing batch reactor for the biodegradation of p-cresol was studied. The reactor was started with 100 mg/L of p-cresol. Aerobic granules first appeared within one month of start up. The granules were large and strong and had a compact structure. The diameter of stable granules was in the range of 1–5 mm. The integrity coefficient and granules density was found to be 96% and 1046 kg/m3, respectively. The settling velocity of granules was found to be in the range of 2×10−2–6×10−2 m/sec. The aerobic granules were able to degrade p-cresol upto 800 mg/L at a removal efficiency of 88%. Specific p-cresol degradation rate in aerobic granules followed Haldane model for substrate inhibition. High specific p-cresol degradation rate up to 0.96 g p-cresol/(g VSS·day) were sustained upto p-cresol concentration of 400 mg/L. Higher removal efficiency, good settling characteristics of aerobic granules, makes sequencing batch reactor suitable for enhancing the microorganism potential for biodegradation of inhibitory compounds.

Photocatalytic degradation of p-cresol on Pt/γAl2O3–TiO2 mixed oxides: Effect of oxidizing and reducing pre-treatments

Abstract Pt/γAl 2 O 3 –TiO 2 photocatalysts were prepared by wet impregnation and tested in the photodegradation of p-cresol. The γAl 2 O 3 –TiO 2 (5, 10 and 20 wt% TiO 2 ) mixed oxides were prepared by simultaneous hydrolysis of boehmite and titanium alkoxide. The solids were characterized by nitrogen adsorption (BET surface area), XRD, UV–vis, FTIR-CO spectroscopy and TOC determinations. The mixed oxides showed higher specific surface areas than those obtained with the TiO 2 bare semiconductor. On the Pt/γAl 2 O 3 –TiO 2 photocatalysts, it was observed that the anatase phase was stabilized and the E g band was shifted to the blue region. In the p-cresol photodegradation the reduced-Pt/γAl 2 O 3 –TiO 2 solids were more active than the calcined-Pt/γAl 2 O 3 –TiO 2 photocatalysts. The formation of reduced Pt 0 leads to a highest photoactivity for the p-cresol photodegradation by enhancing the electron–hole separation.

Biodegradation of P-Cresol by Mixed Culture in Batch Reactor – Effect of the Three Nitrogen Sources Used

Phenols are distributed either as nature or artificial mono-aromatic compounds in various environmental sites as major pollutants. Their existence in wastes from industrial processes such as oil refineries, coking plants, wastewater treatment plants, petroleum-based processing, phenols resin industry manufacturing and plants, has been well established. Many processes have been used for the remediation of Phenolic compounds. Conventional methods of treatment have been largely chemical or physical, but these processes have led to secondary effluent problems and costly. Biological treatment is an effective method that is used where many micro-organisms can be growing on Phenolic compounds as the sole source of carbon.The temperature (30°C), the stirring velocity (200 r/min), NaH2PO4 concentration (3g. L-1), MgSO4 concentration (0.1g. L-1), initial concentration of p-cersol (100mg. L-1) and KH2PO4 concentration (3g. L-1) for (NH4)2SO4, (3g. L-1) for NH4NO3, (3g. L-1) for NH4Cl; while the initial concentration of nitrogen sources ((NH4)2SO4, NH4NO3, NH4Cl) was varied in the following range, 0 – 2g. L-1. All experiments were carried out at a given initial bacterial concentration, 0.08g.L-1 (based on optical density determination, 0.079).Irrespective of the culture conditions, total p-cresol degradation (100 m g. L-1) was recorded for culture time ranging from 32.5 to 49h. the optimal concentration were therefore, 1g. L-1 for all nitrogen sources, leading to a specific growth rate of 0.3 h-1. Higher maximum specific growth rate values were recorded during this work, if compared to those reported in the available literature, even those dealing with mixed culture. This result showed the relevance of the specific microbial consortium used.Two mathematical models were used to describe the length of lag phase versus initial nitrogen concentration; the growth length of lag phase was fitted using polynomial models, the correlation coefficient was varied in the following range, 0.99 – 1.

Photocatalytic Degradation of p-Cresol by Zinc Oxide under UV Irradiation

Photocatalytic degradation of p-cresol was carried out using ZnO under UV irradiation. The amount of photocatalyst, concentration of p-cresol and pH were studied as variables. The residual concentration and mineralization of p-cresol was monitored using a UV-visible spectrophotometer and total organic carbon (TOC) analyzer, respectively. The intermediates were detected by ultra high pressure liquid chromatography (UPLC). The highest photodegradation of p-cresol was observed at 2.5 g/L of ZnO and 100 ppm of p-cresol. P-cresol photocatalytic degradation was favorable in the pH range of 6–9. The detected intermediates were 4-hydroxy-benzaldehyde and 4-methyl-1,2-benzodiol. TOC studies show that 93% of total organic carbon was removed from solution during irradiation time. Reusability shows no significant reduction in photocatalytic performance in photodegrading p-cresol.

Identification of a p-Cresol Degradation Pathway by a GFP-Based Transposon in Pseudomonas and Its Dominant Expression in Colonies

In this study, the chromosome-encoded pcuRCAXB genes that are required for p-cresol degradation have been identified by using a newly constructed green fluorescent protein (GFP)-based promoter probe transposon in the long-chain alkylphenol degrader Pseudomonas alkylphenolia. The deduced amino acid sequences of the genes showed the highest identities at the levels of 65-93% compared with those in the databases. The transposon was identified to be inserted in the pcuA gene, with the promoterless gfp gene being under the control of the pcu catabolic gene promoter. The expression of GFP was positively induced by p-cresol and was about 10 times higher by cells grown on agar than those in liquid culture. In addition, phydroxybenzoic acid was detected during p-cresol degradation. These results indicate that P. alkylphenolia additionally possesses a protocatechuate ortho-cleavage route for pcresol degradation that is dominantly expressed in colonies.

Advanced Oxidation of Trace Organics in Water by Hydrogen Peroxide Solar Photolysis

Solar-UV/H2O2 advanced oxidation for destruction of trace organics was investigated under a variety of operating conditions in homogeneous, laboratory-scale batch reactor experiments. Fluorescein and p-cresol were selected as representative targets in the experiments. Half times for degradation of p-cresol ranged between 500 min with 2 mM H2O2 and 20 min with 50 mM H2O2 during high-solar irradiance experiments (around noon on July 15th). A kinetic model, previously developed for monochromatic light, was adapted for use with solar UV irradiance, using (i) calculated ground-level solar spectral irradiance for the date and time of the experiments and (ii) wavelength-dependent light attenuation in the reaction mixture. The model accurately represents experimental data without adjustable parameters. Model output included the time-dependent pH arising from complete mineralization of the targets. Observed radical scavenging effects were correctly predicted by the kinetic model. Contaminant transformation was also measured in a municipal secondary wastewater effluent matrix. Here, 2-D fluorescence spectroscopy was used as a measure of the time-dependent bulk organic characteristics in treated wastewater. Results indicated that solar-UV/H2O2 advanced oxidation is capable of eliminating or drastically reducing the concentrations of organic constituents that remain in conventionally treated municipal wastewater effluent.

Kinetics studies of p-cresol biodegradation by using Pseudomonas putida in batch reactor and in continuous bioreactor packed with calcium alginate beads

Present study deals with the biodegradation of p-cresol by using Pseudomonas putida in a batch reactor and a continuous bioreactor packed with calcium alginate beads. The maximum specific growth rate of 0.8121 h(-1) was obtained at 200 mg L(-1) concentration of p-cresol in batch reactor. The maximum p-cresol degradation rate was obtained 6.598 mg L(-1) h(-1) at S(o)=200 mg L(-1) and 62.8 mg L(-1) h(-1) at S(o)=500 mg L(-1) for batch reactor and a continuous bioreactor, respectively. The p-cresol degradation rate of continuous bioreactor was 9 to 10-fold higher than those of the batch reactor. It shows that the continuous bioreactor could tolerate a higher concentration of p-cresol. A Haldane model was also used for p-cresol inhibition in batch reactor and a modified equation similar to Haldane model for continuous bioreactor. The Haldane parameters were obtained as µ(max) 0.3398 h(-1), K(s) 110.9574 mg L(-1), and K(I) 497.6169 mg L(-1) in batch reactor. The parameters used in continuous bioreactor were obtained as D(max) 91.801 mg L(-1) h(-1), K(s) 131.292 mg L(-1), and K(I) 1217.7 mg L(-1). The value K(I) of continuous bioreactor is approximately 2.5 times higher than the batch reactor. Higher K(I) value of continuous bioreactor indicates P. putida can grow at high range of p-cresol concentration. The ability of tolerance of higher p-cresol concentrations may be one reason for biofilm attachment on the packed bed in the continuous operation.

Photoassisted Degradation of 4-Chlorophenol and p-Cresol Using MgAl Hydrotalcites

MgAl hydrotalcites, or layered double hydroxides (LDHs), with different Mg/Al molar ratios were synthesized by the coprecipitation method. The structure of the solids was collapsed by thermal treatment at 723 K obtaining MgAl mixed oxides with high specific surface areas (264-318 m 2 /g). When these oxides were put in contact with aqueous solutions containing 4-chlorophenol and para-cresol (80 ppm:0.62 and 0.73 mmol, respectively) the layered structure was recovered by rehydration of the material showing the named memory effect of LDH materials. Mg/Al LDHs were active for chlorophenol and p-cresol degradation under UV irradiation, being more active and selective to the mineralization of the pollutants than TiO 2 P-25 photocatalysts. Since Mg/Al hydrotalcites are not semiconductors their high photoassisted activity was surprising; this activity was explained by a photo excitation which produces mobility of charges in the lamellar structure, inducing the formation of photoactive defects.

Cresols utilization by Trametes versicolor and substrate interactions in the mixture with phenol

The ability of the white rot fungus Trametes versicolor strain 1 to degrade and utilize methylated phenols (cresols) was established for the first time in a medium not containing any other carbon components. The data obtained demonstrated the better potential of the strain to assimilate p-cresol instead of o- or m- cresol. The 0.5 g/l p-cresol provided was degraded in full after 96 h. The effect of a dual substrate mixture (0.3 g/l phenol + 0.2 g/l p-cresol) on the growth behavior and degradation capacity of the investigated strain was examined. The cell-free supernatants were analyzed by HPLC. It was established that the presence of p-cresol had not prevented complete phenol degradation but had a significant delaying effect on the phenol degradation dynamics. Phenol hydroxylase, catechol 1.2-dioxygenase and cis,cis-muconate cyclase activities were obtained in conditions of single and mixed substrates cultivation. The influence of different phenolic substrates on phenol hydroxylase activity in Trametes versicolor 1 was established. The mathematical models describing the dynamics of single substrates' utilization as well as the mutual influence of phenol and p-cresol in the mixture were developed on the bases of Haldane kinetics. The estimated interaction coefficients (I(ph/cr) = 4.72, I(cr/ph) = 7.46) demonstrated the significant inhibition of p-cresol on phenol biodegradation and comparatively low level of influence of phenol presence on the p-cresol degradation. Molecular 18S RNA gene taxonomy of the investigated strain was performed.

Selectivity in photocatalysis by particulate semiconductors

AbstractTiO2, Fe2O3, CuO, ZnO, ZnS, Nb2O5, MoO3, CdO, CdS, Sb2O3, CeO2, HgO, Pb2O3, PbO2 and Bi2O3 microparticles exhibit band gap excitation with UV-A light but they are selective to photodegrade phenols. While TiO2 anatase and ZnO photocatalyze the degradation of phenol, o-aminophenol, m-aminophenol, p-aminophenol, o-chlorophenol, m-chlorophenol, p-chlorophenol, o-nitrophenol, p-nitrophenol, o-cresol, m-cresol, p-cresol, catechol, resorcinol and quinol, MoO3 does not photodegrade any of the fifteen phenols. Fe2O3, CuO, ZnS, Nb2O5, CdO, CdS, Sb2O3, CeO2, HgO, Pb2O3, PbO2 and Bi2O3 are selective in photodegrading the fifteen phenols; however, the phenols get adsorbed over all sixteen particulate semiconductors.

Sequential degradation of p-cresol by photochemical and biological methods

Sequential photo- and biodegradation of p-cresol was studied using a mercury lamp, as well as KrCl and XeCl excilamps. Preirradiation of p-cresol at a concentration of 10(-4) M did not affect the rate of its subsequent biodegradation. An increase in the concentration of p-cresol to 10(-3) M and in the duration preliminary UV irradiation inhibited subsequent biodegradation. Biodegradation of p-cresol was accompanied by the formation of a product with a fluorescence maximum at 365 nm (lambdaex 280 nm), and photodegradation yielded a compound fluorescing at 400 nm (lambdaex 330 nm). Sequential UV and biodegradation led to the appearance of bands in the fluorescence spectra that were ascribed to p-cresol and its photolysis products. It was shown that sequential use of biological and photochemical degradation results in degradation of not only the initial toxicant but also the metabolites formed during its biodegradation.

Biodegradation of p-cresol by immobilized cells of Bacillus sp. strain PHN 1

The Bacillus sp. strain PHN 1 capable of degrading p-cresol was immobilized in various matrices namely, polyurethane foam (PUF), polyacrylamide, alginate and agar. The degradation rates of 20 and 40 mM p-cresol by the freely suspended cells and immobilized cells in batches and semi-continuous with shaken cultures were compared. The PUF-immobilized cells achieved higher degradation of 20 and 40 mM p-cresol than freely suspended cells and the cells immobilized in polyacrylamide, alginate and agar. The PUF- immobilized cells could be reused for more than 35 cycles, without losing any degradation capacity and showed more tolerance to pH and temperature changes than free cells. These results revealed that the immobilized cell systems are more efficient than freely suspended cells for degradation of p-cresol.

Biodegradation kinetic studies for the removal of p-cresol from wastewater using Gliomastix indicus MTCC 3869

Biodegradation of p-cresol by a pure culture of new filamentous fungal strain Gliomastix indicus was studied. The fungus strain was acclimatized to the higher concentration of 700 mg/l of p-cresol in modified czapeck medium over a period of two months. The lag period was 24 h. The shake flask batch experiments were carried out at temperature of 28 °C and pH of 6 over a wide range of initial p-cresol concentration (10–700 mg/l) keeping initial biomass concentration constant at 18.72 mg/l. Experimentally it was observed that p-cresol was inhibitory type substrate and the inhibition effect of p-cresol became predominant above a concentration of 50 mg/l. The kinetics of cell growth and p-cresol degradation were investigated. Six kinetic models (Haldane, Andrews, Webb, Yano, Aiba, and Teissier) were fitted to the experimental growth kinetic data. Models by Haldane, Andrews, Webb and Yano (correlation coefficient R 2 > 0.99) were found to be most suitable models. In addition, the variation of observed yield coefficient Y X with specific growth rate μ g was investigated. The maintenance energy coefficient and true growth yield coefficient, were found to be 0.0227 h −1 and 1.0708 (mg/mg), respectively. The specific substrate utilization rate was represented in terms of specific biomass growth rate. The decay coefficient was found to be 0.0055 h −1. The effect of pH and nitrogen source of medium on biodegradation of p-cresol was investigated as well.

Intradiol pathway of para‐cresol conversion by Rhodococcus opacus 1CP

The growth of Rhodococcus opacus 1CP in medium with different concentrations of p-cresol as the sole source of carbon and energy was studied. It was shown that the optimal concentration of p-cresol was 600 mg/L. The ability of this strain to transform practically all amounts of p-cresol to 4-methylcatechol followed by its utilization through ortho-pathway was shown. New enzymes (4-methylcatechol 1,2-dioxygenase, catechol 1,2-dioxygenase, and methylmuconate cycloisomerase) were purified to homogeneity and characterized. Based on the data obtained on p-cresol degradation, formation of intermediates, and the enzymes participating in this pathway, we suggest an ortho-pathway of p-cresol degradation by R. opacus 1CP through 4-methylcatechol and 3-methyl-cis, cis-muconate.

Anaerobic biodegradation of 4-alkylphenols in a paddy soil microcosm supplemented with nitrate

Anaerobic degradation of phenol, p-cresol, 4- n-propylphenol ( n-PP), 4- i-propylphenol ( i-PP), 4- n-butylphenol ( n-BP) and 4- sec-butylphenol ( sec-BP) was observed in a paddy soil supplemented with nitrate. We detected the metabolites 4′-hydroxypropiophenone (HPP) from n-PP, 4- i-propenylphenol from i-PP, and 4-(1-butenyl)phenol and 4′-hydroxybutyrophenone (HBP) from n-BP. Compared with the original soils, Betaproteobacteria became predominant in the microcosm during the degradation of phenol and p-cresol whereas no remarkable change was observed in the community degrading propylphenols and butylphenols. The microcosm, however, did not degrade 4- t-butylphenol ( t-BP), 4- t-octylphenol ( t-OP) and 4- n-octylphenol ( n-OP). Paddy soil supplemented with sulfate or iron (III) as electron acceptors did not degrade phenol and 4-alkylphenols with the exception of the degradation of p-cresol in sulfate-reducing conditions. It was demonstrated for the first time that anaerobic microbial degradation of alkylphenols, in a paddy soil supplemented with nitrate as an electron acceptor, occurred via oxidation of the alpha carbon in the alkyl chain.

Genomic and microarray analysis of aromatics degradation in Geobacter metallireducens and comparison to a Geobacter isolate from a contaminated field site

BackgroundGroundwater and subsurface environments contaminated with aromatic compounds can be remediated in situ by Geobacter species that couple oxidation of these compounds to reduction of Fe(III)-oxides. Geobacter metallireducens metabolizes many aromatic compounds, but the enzymes involved are not well known.ResultsThe complete G. metallireducens genome contained a 300 kb island predicted to encode enzymes for the degradation of phenol, p-cresol, 4-hydroxybenzaldehyde, 4-hydroxybenzoate, benzyl alcohol, benzaldehyde, and benzoate. Toluene degradation genes were encoded in a separate region. None of these genes was found in closely related species that cannot degrade aromatic compounds. Abundant transposons and phage-like genes in the island suggest mobility, but nucleotide composition and lack of synteny with other species do not suggest a recent transfer. The inferred degradation pathways are similar to those in species that anaerobically oxidize aromatic compounds with nitrate as an electron acceptor. In these pathways the aromatic compounds are converted to benzoyl-CoA and then to 3-hydroxypimelyl-CoA. However, in G. metallireducens there were no genes for the energetically-expensive dearomatizing enzyme. Whole-genome changes in transcript levels were identified in cells oxidizing benzoate. These supported the predicted pathway, identified induced fatty-acid oxidation genes, and identified an apparent shift in the TCA cycle to a putative ATP-yielding succinyl-CoA synthase. Paralogs to several genes in the pathway were also induced, as were several putative molybdo-proteins. Comparison of the aromatics degradation pathway genes to the genome of an isolate from a contaminated field site showed very similar content, and suggested this strain degrades many of the same compounds. This strain also lacked a classical dearomatizing enzyme, but contained two copies of an eight-gene cluster encoding redox proteins that was 30-fold induced during benzoate oxidation.ConclusionG. metallireducens appears to convert aromatic compounds to benzoyl-CoA, then to acetyl-CoA via fatty acid oxidation, and then to carbon dioxide via the TCA cycle. The enzyme responsible for dearomatizing the aromatic ring may be novel, and energetic investments at this step may be offset by a change in succinate metabolism. Analysis of a field isolate suggests that the pathways inferred for G. metallireducens may be applicable to modeling in situ bioremediation.

Fluorescence and bioluminescence analysis of sequential UV‐biological degradation of p‐cresol in water

The photolysis and Penicillium tardum H-2 degradation of p-cresol in water containing humic acids was investigated by fluorescence and bioluminescence methods. Humic acids extracted from peat (the Vasuygan bog, Tomsk region of Russia) induce the phototransformation of p-cresol. The influence of humic acids on the phototransformation of p-cresol under different irradiation conditions was investigated. Comparison of the data on the KrCl* (lambda = 222 nm) and XeCl* (lambda = 308 nm) excilamps light showed that the most effective p-cresol degradation was observed with mercury lamp irradiation in the presence of humic acids.

Transient Accumulation of Metabolic Intermediates of p-Cresol in the Culture Medium by a Pseudomonas sp. Strain A Isolated from a Sewage Treatment Plant

Activated sludge from a sewage treatment plant in Kanpur, India, was screened for bacterial strains metabolizing p-cresol exclusively under aerobic conditions. One such isolate was identified to be belonging to the genus Pseudomonas based on morphological and physiological criteria as well as 16S ribosomal RNA gene sequence analysis. Two intermediates were identified from the culture medium during the growth phase of Pseudomonas sp. strain A that indicated that the strain degraded p-cresol via the protocatechuate (PCA) pathway. p-Cresol was rapidly converted into p-hydroxybenzaldehyde (PHB) during early growth phase, which was later utilized after p-cresol depletion. p-Hydroxybenzoate (PHBA) accumulation was observed during the later stages of exponential growth phase. Kinetic constants for the degradation of p-cresol were determined using Haldane’s model. High μmax and inhibitory constant (K I) values along with the observed accumulation of significant amounts of PHB in culture filtrates seem to indicate that the isolated Pseudomonas sp. strain A may be of potential use in biotransformations.