Phenol Degradation Process Research Articles

Harnessing self-supported Au nanoparticles on layered double hydroxides comprising Zn and Al for enhanced phenol decomposition under solar light

Gold nanoparticles (AuNPs) self-coupled on semiconductors have attracted extensive attentions in the field of catalysis, however, the progress in understanding and optimizing their photocatalytic performance in response to solar light irradiation is limited. In this paper, a series of AuNPs with Zn2Al-layered double hydroxide (LDH) as support was fabricated via self-assembly routes at room temperature and the tuned oxidation state of AuNPs (as Au0, Au3+ as well as mixed Au0/Au3+) was revealed to have a crucial effect on establishing their photocatalytic efficiency for the degradation of phenol from aqueous solution under solar irradiation. X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) analyses permitted to characterize the specific interactions of Zn2Al-LDH with AuNPs and to verify that the state of Au0/Au3+NPs appears due to the electron transfer from Zn2Al-LDH to AuNPs when Zn2Al-LDH reconstruction in the aqueous solution of Au(O2CCH3)3 was achieved under solar irradiation. On the basis of these AuNPs–Zn2Al-LDH systems, the possible roles of Au0, Au3+ or Au0/Au3+ in establishing synergetic effects with Zn2Al-LDHs supports for enhancing the photocatalytic response induced by the irradiation with solar light, for manipulating the mechanism, and the catalyst stability in phenol degradation process, are critically discussed.

Research on degradation product and reaction kinetics of membrane electro-bioreactor (MEBR) with catalytic electrodes for high concentration phenol wastewater treatment

The membrane electro-bioreactor (MEBR) is a novel technology, it treats wastewater by combining membrane filtration, electrokinetic phenomena, and biological processes in one reactor. This paper aims to deal with hard biodegradation and high concentration phenol wastewater. Investigating the influence factors such as initial concentration, voltage, pH value, temperature and mixed liquor suspended solids (MLSS) toward phenol degradation process in electrocatalytic process and membrane bioreactor (MBR), and then apply the optimum conditions in the MEBR system. Results of continuous flow experiments demonstrated that MEBR increased the quality of the treated wastewater than conventional MBR. The above technics followed the zero-order reaction kinetics. The removal efficiency of MEBR was about 11.1% higher for phenol than the sum of the two individual processes. With the help of gas chromatography/mass spectrometry (GC-MS), this qualitative analysis looks at the degradation products of phenol generated in MEBR, through which 2,6-di-tert-butyl-p-benzoquinone was confirmed as the main degradation product.

Comparative proteomic analysis of phenol degradation process by Arthrobacter

Phenol is a widespread environmental pollutant due to their broad usage and applications, and presence in many industrial effluents. To date, bacterial degradation of phenol remains to be the preferred method for its removal and remediation. Although the degradation pathway has been extensively studied, the variations in the level of expression of the key enzymes during catabolism are still not quantitatively understood. An explicit quantitative expression helps us know the degradation process in detail. It is important and valuable for us to further understand mechanisms underlying phenol degradation. In this study, we used iTRAQ-based comparative proteomics analysis approach to determine variations in expression and regulation of key enzymes in Arthrobacter during phenol degradation. We propose that the phenol biodegradation pathway is mainly determined by 5 pivotal enzymes, which belonged to 3-oxoadipate pathway and tricarboxylic acid cycle. Arthrobacter mainly degrades phenol through 3-oxoadipate pathway, which makes the pathway of this strain for degrading the toxic compound clearer. These findings provide new insights into phenol biodegradation process and would help us understand the step by step stages of this metabolic pathway.

The Effect of Fe-Loading and Calcination Temperature on the Activity of Fe/TiO2 in Phenol Degradation

In this research work, iron modified titanium dioxide photocatalyst was synthesized by the sol-gel method. The catalyst is characterized by FT-IR, XRF, and TGA techniques. Since the activity of Fe/TiO2 is highly affected by the loading of Fe, our major purpose of this work was focused on the role of this factor. Moreover, the effect of calcination temperature, which was also of high importance, was studied in this work. FT-IR results indicated the existence of a peak in the range of 1100-1200corresponding to Ti-O-Fe bonds. The intensity of this peak is proportional to the amount of iron, which is incorporated into the TiO2 lattice. Optimum Fe-loading was specified by FT-IR and it was measured by XRF. In order to evaluate the catalytic activity of Fe/TiO2, a synthetic wastewater of phenol was irradiated by the UV lamp (757.38 mW/cm3), Fe/TiO2 with the dosage of 0.5 g/L was applied as the catalyst and H2O2 (12.5 mL, 30% wt. /wt.) was added as an oxidizing agent.Experimental results proved, the optimum condition for phenol degradation process over Fe/TiO2 is as follows: Fe loading in the TiO2 lattice: Fe2O3/TiO2 is 0.27%, calcination temperature: 600°C, and irradiation time of 600 min. Under this circumstance, 98.26% of the phenol in water was decomposed.

Coupling of Photoactive TiO2 and Impressed Magnetic Field for Phenol Highly Efficient Degradation

Synergistic effect of nanosized TiO2 and impressed magnetic field (MF) was studied by investigating the photocatalytic degradation of phenol at room temperature. The introducing of MF with relatively high intensity (>0.082 T) has obvious promotion effects on phenol degradation rate (C/C 0), while negative influences of MF on C/C 0 can be observed under low-intensity MF (<0.044 T). The yield of hydroxyl radicals (·OH) in reaction processes increases with the raising of MF intensity initially and reaches the maximum concentration when the magnetic intensity is 0.082 T. The photoinduced carriers initially decrease until the MF intensity reaches at 0.024 T, and then increase with the increasing of MF intensity. The effects of MF on photoinduced carriers can be explained in terms of the Δg mechanism together with the hyperfine coupling mechanism. Low-intensity MF accelerates the recombination of electrons and holes and suppresses the generation of photoinduced carriers, which further restricts the degradation of phenol. In contrast, the presence of high-intensity MF retards the recombination of hydroxyl radicals and thus enhances the production of ·OH radicals. The generation of hydroxyl radicals is the primary factor in determining the phenol degradation process in the high-intensity MF region.

Phenol degradation in heterogeneous system generating singlet oxygen employing light activated electropolymerized phenothiazines

Five selected amine-derivatives of phenothiazine were electropolymerized on an ITO/glass substrate and then used in the daylight-activated process to produce in situ singlet oxygen which degrades phenol in a solution. The phenothiazines were immobilized in a simple electrochemical procedure in an acidic solution which led to the formation of an ultrathin transparent polymeric film. All films obtained on the ITO substrate including azure A (AA), azure C (AC), methylene blue (MB), toluidine blue (TBO), and thionine (Th) had a comparable surface coverage at the level of picomoles/cm2. The activity of these materials was then compared and presented in terms of an efficiency of the phenol degradation process in an aqueous solution by photogenerated singlet oxygen. That efficiency was determined by the UV–vis spectroscopy employing a phenol/4-aminoantipyrine complex. All the phenothiazine ultrathin polymeric films were capable of generating the singlet oxygen in the aqueous solution under daylight activation, which was used in the consecutive process of phenol degradation. The highest efficiency at a level of 51.4% and 45.4% was found for the AC/ITO and MB/ITO layers, respectively.

High-Throughput Screening for a Moderately Halophilic Phenol-Degrading Strain and Its Salt Tolerance Response

A high-throughput screening system for moderately halophilic phenol-degrading bacteria from various habitats was developed to replace the conventional strain screening owing to its high efficiency. Bacterial enrichments were cultivated in 48 deep well microplates instead of shake flasks or tubes. Measurement of phenol concentrations was performed in 96-well microplates instead of using the conventional spectrophotometric method or high-performance liquid chromatography (HPLC). The high-throughput screening system was used to cultivate forty-three bacterial enrichments and gained a halophilic bacterial community E3 with the best phenol-degrading capability. Halomonas sp. strain 4-5 was isolated from the E3 community. Strain 4-5 was able to degrade more than 94% of the phenol (500 mg·L−1 starting concentration) over a range of 3%–10% NaCl. Additionally, the strain accumulated the compatible solute, ectoine, with increasing salt concentrations. PCR detection of the functional genes suggested that the largest subunit of multicomponent phenol hydroxylase (LmPH) and catechol 1,2-dioxygenase (C12O) were active in the phenol degradation process.

Preparation and Degradation Phenol Characterization of Ti/SnO2–Sb–Mo Electrode Doped with Different Contents of Molybdenum

The Ti/SnO 2 –Sb–Mo electrodes doped with different molar ratios of molybdenum (Mo) were prepared by sol–gel method in order to investigate the effect of Mo on the characterization of Ti/SnO 2 –Sb–Mo electrodes. X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), energy dispersive spectrometry (EDS), and linear scanning voltammetry (LSV) were used to scrutinize the coating material and the electrochemical activity. The concentration of phenol, the value of total organic carbon (TOC), the mineralization current efficiency (MCE) and the ultraviolet–visible spectroscopy (UV–Vis) spectrum of phenol solution were measured over the electrochemical degradation process of phenol to confirm the phenol degradation characterization of Ti/SnO 2 –Sb–Mo electrodes. Results showed that the electrode at the Mo content of 1 at.% provided optimal catalytic activity for phenol degradation and the longest life time. The removal percentage of phenol and TOC were 99.62% and 82.67%, respectively. The Ti/SnO 2 –Sb–Mo electrode with 1 at.% of Mo reached maximum MCE of phenol oxidation. The kinetic investigation of phenol and TOC degradation displayed the pseudo-first order reaction model. The Ti/SnO 2 –Sb–Mo electrode coating with 7 at.% Mo presented the highest oxygen evolution overpotential, indicating the diverse effects for different Mo molar ratio doping.

Switching Oxygen Reduction Pathway by Exfoliating Graphitic Carbon Nitride for Enhanced Photocatalytic Phenol Degradation.

The selectivity of molecular oxygen activation on the exfoliated graphitic carbon nitride (g-C3N4) and its influence on the photocatalytic phenol degradation process were demonstrated. Compared with bulk g-C3N4, the exfoliated nanosheet yielded a 3-fold enhancement in photocatalytic phenol degradation. ROS trapping experiments demonstrated that although the direct hole oxidation was mainly responsible for phenol photodegradation on both g-C3N4 catalysts, molecular oxygen activation processes on their surface greatly influenced the whole phenol degradation efficiency. Reactive oxygen species and Raman spectroscopy measurements revealed that oxygen was preferentially reduced to ·O2(-) by one-electron transfer on bulk g-C3N4, while on g-C3N4 nanosheet the production of H2O2 via a two-electron transfer process was favored due to the rapid formation of surface-stabilized 1,4-endoperoxide. The latter process not only promotes the separation of photogenerated electron-hole pairs but also greatly facilitates reactive oxygen species formation and subsequently enhances phenol degradation.

Preparation and Photocatalytic Activity of Mixed Phase Anatase/rutile TiO2 Nanoparticles for Phenol Degradation

The evolution of desirable physico-chemical properties in high performance photocatalyst materials involves steps that must be carefully designed, controlled, and optimized. This study investigated the role of key parameter in the preparation and photocatalytic activity analysis of the mixed phase of anatase/rutile TiO2 nanoparticles, prepared via sol-gel method containing titanium-n-butoxide Ti(OBu)4 as a precursor material, nitric acid as catalyst, and isopropanol as solvent. The prepared TiO2 nanoparticles were characterized by means of XRD, SEM, and BET analyses, and UV-Vis-NIR spectroscopy. The results indicated that the calcination temperature play an important role in the physico-chemical properties and photocatalytic activity of the resulting TiO2 nanoparticles. Different calcination temperatures would result in different composition of anatase and rutile. The photocatalytic activity of the prepared mixed phase of anatase/rutile TiO2 nanoparticles was measured by photodegradation of 50 ppm phenol in an aqueous solution. The commercial anatase from Sigma-Aldrich and Degussa P25 were used for comparison purpose. The mixed phase of anatase/rutile TiO2 nanoparticles (consists of 38.3% anatase and 61.7% rutile) that was prepared at 400°C exhibited the highest photocatalytic activity of 84.88% degradation of phenol. The result was comparable with photocatalytic activity demonstrated by Degussa P25 by 1.54% difference in phenol degradation. The results also suggested that the mixed phase of anatase/rutile TiO2 nanoparticles is a promising candidate for the phenol degradation process. The high performance of photocatalyst materials may be obtained by adopting a judicious combination of anatase/rutile and optimized calcination conditions.

Kinetic modeling for phenol degradation using photo-impinging streams reactor

In the present study, a novel kinetic model has been proposed for photocatalytic degradation of wastewater. In the first step, statistical experimental designs have been used to optimize the process of phenol degradation in a photo-impinging streams reactor. The crucial parameters, namely phenol concentration, catalyst loading, pH, and slurry flow rate, were selected for process optimization, applying central composite design. The analysis results indicated that interactions between catalyst loading and pH significantly affect phenol degradation. The predicted data showed that the maximum removal efficiency of phenol (99 %) could be obtained under the optimum operating conditions (phenol concentration = 50 mg l−1, catalyst loading = 2.1 g l−1, pH 6.2, and slurry flow rate = 550 ml min−1). These predicted values were then verified by certain validating experiments. Residence time distribution (RTD) of the slurry phase within the reactor was then measured using the impulse tracer method. A number of different assumptions were made, i.e., continuous stirred tank reactors (CSTRs) in series model and gamma distribution model with bypass (GDB). A comparison made between the sum of the square errors for experimental and predicted RTD values in case of each flow model revealed that both CSTRs in series model and GDB were proper descriptions for reactor behavior. The CSTRs in series model and RTD data were applied in conjunction with the phenol degradation kinetic model to predict the coefficients of the reaction rate.

Treatment of high salinity phenol-laden wastewater using a sequencing batch reactor containing halophilic bacterial community

Sequencing batch reactors (SBRs) were used to degrade phenol compounds efficiently; however, most investigations on such reactors have focused on fresh rather than saline wastewaters, even though saline effluents containing phenolic compounds are generated by many industries. This study assessed the performance of the aerobic SBR process in the removal of phenol as the sole substrate under conditions of high salinity. A flexible concentration of phenol could be completely degraded in SBR process, varied from 400 mg l−1 to 1200 mg l−1 at the existing of 80 g l−1 NaCl. The value of specific oxygen uptake rate (SOUR) suggested that the exiting bacteria could adapt to the phenol and salt conditions well at each stage. Cloning and sequencing of the 16S rRNA showed that the acclimated active sludge included two dominant genera: Pseudomonas and Alcaligenes. PCR detection of the functional genes suggested that phenol hydroxylase (Lph), catechol 1,2-dioxygenase (C12O), and catechol 2,3-dioxygenase (C23O) were active in the phenol-degradation process. Real-time PCR showed that the phenol-degrading bacteria comprised 63.3% of the total bacterial community.

Almond shell activated carbon: adsorbent and catalytic support in the phenol degradation

In this work, two technologies are studied for the removal of phenol from aqueous solution: dynamic adsorption onto activated carbon and photocatalysis. Almond shell activated carbon (ASAC) was used as adsorbent and catalytic support in the phenol degradation process. The prepared catalyst by deposition of anatase TiO2 on the surface of activated carbon was characterized by scanning electron microscopy, sorption of nitrogen, X-ray diffraction, Fourier transform infrared (FT-IR) spectroscopy, and pHZPC point of zero charge. In the continuous adsorption experiments, the effects of flow rate, bed height, and solution temperature on the breakthrough curves have been studied. The breakthrough curves were favorably described by the Yoon-Nelson model. The photocatalytic degradation of phenol has been investigated at room temperature using TiO2-coated activated carbon as photocatalyst (TiO2/ASAC). The degradation reaction was optimized with respect to the phenol concentration and catalyst amount. The kinetics of disappearance of the organic pollutant followed an apparent first-order rate. The findings demonstrated the applicability of ASAC for the adsorptive and catalytic treatment of phenol.

Catalytic Ozonization of Phenol with the Use of Alternative Catalysts

Phenol and its derivatives constitutes one of the most dangerous groups of organic chemicals which can cause many environmental and health risks. Therefore removal and degradation of phenol from aqueous solutions is one of the great industrial importance. Ozone is considered to be one of the most effective oxidizing agent for phenol degradation.. The objectives of this study are to examine the roles of added catalyst to rapid the process of phenol degradation by ozone.

Mechanism of phenol degradation processes induced by direct-current atmospheric-pressure discharge in air

The phenol degradation kinetics and the buildup kinetics of the products hydroxyphenols, nitrophenols, carboxylic acids, and formaldehyde in electrolytic-cathode direct-current discharge have been studied, as well as the formation of nitric acid. On the basis of the results, a scheme of the processes has been proposed; calculations according to this scheme describe well the experimental data on the degradation kinetics of phenol and the formation/decay kinetics of its transformation products.

Examination of benzoquinone electrooxidation pathway as crucial step of phenol degradation process

The electrochemical oxidation of benzoquinone on expanded graphite (EG) electrode was conducted. Electrochemical process was realized by cyclic voltammetry technique in alkaline solution. The main part of this work was devoted to examination of benzoquinone oxidation proceeding through the opening of aromatic ring accompanied by the formation of carboxylic acids. Water samples containing benzoquinone and short chain mono- and dicarboxylic acids were analyzed qualitatively and quantitatively with high performance liquid chromatography (HPLC). The validation of chromatographic method was determined for benzoquinone, oxalic acid, malonic acid, acetic acid, maleic acid, succinic acid and fumaric acid.

A comprehensive study on wastewater treatment using photo-impinging streams reactor: Continuous treatment

The degradation of phenol was investigated in a continuous flow impinging streams system. In the first step, statistical experimental designs were used to optimize the process of phenol degradation in a photo-impinging streams reactor. The more important factors affecting phenol degradation (p<0.05) were screened by a two-level Plackett-Burman design. Four of the latter parameters, namely phenol concentration, catalyst loading, pH and slurry flow rate, were selected for final process optimization, applying central composite design (CCD). The predicted data showed that the maximum removal efficiency of phenol (99%) could be obtained under the optimum operating conditions (phenol concentration=50 mg l−1, catalyst loading=2.1 g l−1, pH 6.2 and slurry flow rate=550ml min−1). These predicted values were then verified by certain validating experiments. A good correlation was observed between the predicted data and those determined by the experimental study. This may confirm the validity of the statistical optimum strategy. Finally, continuous degradation of phenol was performed, and the results indicated a higher efficiency and an increased performance capability of the present reactor in comparison with the conventional processes.

Phenol degradation kinetic property in coking wastewater with pulse corona

The degradation kinetics of phenol in coking wastewater and the effect of electrode parameters on phenol’s removal ratio in pulse corona discharge were investigated with experiments and theoretical analysis. The result showed that Chemical Oxygen Demand (COD) and Biochemical Oxygen Demand after five days (BOD 5 ) in the wastewater increased in the initial step, and decreased later. Conductivity rose, and pH of the wastewater decreased with the increase of action time. The phenol degradation process was a one order reaction, and the rate constant ( k ) was positively related to discharge frequency and voltage. Phenol’s removal ratio and degradation rate in weak acidity were larger than those in weak alkalinity and neutral wastewater. The removal ratio reached its maximum when the electrode distance was set at 3.6 cm. This achievement is beneficial to the application of pulse corona discharge technology in coking wastewater disposal.

The simultaneous photocatalytic degradation of phenol and reduction of Cr(VI) by TiO 2/CNTs

The main objective of this paper is to verify the potential of TiO 2/CNTs in the simultaneous photocatalytic degradation of phenol and reduction of Cr(VI). From the present results it can be concluded that there is a synergistic effect between the photocatalytic degradation of phenol and reduction of Cr(VI). Under all tested conditions, the degradation of phenol and reduction of Cr(VI) were examined to follow pseudo-first-order kinetic. The rate constant of 40 mg/L of Cr(VI) was evaluated as 4.34 × 10 −3 min −1 in the absence of phenol, and was increased up to 9.27 × 10 −3 min −1 by adding 10 mg/L of phenol, and to 10.73 × 10 −3 min −1 by adding 15 mg/L of phenol. The presence of Cr(VI) also accelerated the degradation process of phenol, with a factor of 1.84–3 times. Such a great synergistic effect was likely to be attributed to two kinds of effects from CNTs: adsorption effect and electron trap effect. The synergistic effect induced by CNTs was also confirmed by the detection of degradation intermediates of phenol.

Phenol degradation in aqueous solution by a gas-liquid phase DBD reactor

A dielectric barrier discharge (DBD) has been successfully applied to studying, both theoretically and experimentally, phenol degradation in waste water aqueous solutions. A coaxial reactor was selected where the liquid waste constitutes a part of the internal electrode itself, the liquid solution flowing up inside the hollow internal electrode impelled by a submersible pump. Thus, the solution falls by gravity on the external surface of the internal electrode. The DBD gas flows in parallel to the surface of the liquid. The cold plasma was generated from Ar-O 2 mixture and O 2 pure with the inclusion of moisture from the same solution. Two power supplies were compared delivering potentials up to 23 kV at 1.5 kHz, and up to 12 kV at 15.6 kHz respectively. The initial concentration of phenol was around 5 × 10 −3 mol/L and efficiencies up to 99% were obtained after 1 h of treatment. Finally, a simplified kinetics model was developed where the temporal evolution of the compounds generated in the phenol degradation process was analyzed. Hydroquinone, catechol and resorcinol were obtained as byproducts and H 2 O, CO 2 and some light carboxylic acids as final products.