Synthesis of A-position Ba-doped Perovskite LaCoO_(3) and Performance of Photocatalytic Phenol Degradation

The utilization of perovskite oxide materials as catalysts for the photodegradation of organic pollutants in water is a promising and rapidly advancing field.In this study,a series of La_(1−x)Ba_(x)CoO_(3)(x=0.2,0.3,0.4,0.5,0.6)catalysts with varying Ba doping ratios were synthesized using the citric acid complexation-hydrothermal synthesis combined method for the degradation of phenol under visible light irradiation.Among the synthesized catalysts,La_(0.5)Ba_(0.5)CoO_(3) exhibited the highest photocatalytic activity.In addition,the photocatalytic mechanism for La_(0.5)Ba_(0.5)CoO_(3) perovskite degradation of phenol was also discussed.The synthesized catalysts were characterized using XRD,SEM,FT-IR,XPS,MPMS and other characterization techniques.The results revealed that the diffraction peak intensity of La_(1−x)Ba_(x)CoO_(3) increased with higher Ba doping ratios,and the La_(0.4)Ba_(0.6)CoO_(3) exhibited the strongest diffraction peaks.The catalyst particle sizes ranged from 10 to 50 nm,and the specific surface area decreased with increasing Ba content.Additionally,the paramagnetic properties of La_(0.5)Ba_(0.5)CoO_(3) were similar to that of La_(0.4)Ba_(0.6)CoO_(3).The experimental results suggested that the incorporation of Ba could significantly improve the catalytic performance of La_(1−x)Ba_(x)CoO_(3) perovskites,promote electron transfer and favor to the generation of hydroxyl radicals(•OH),leading to the efficiently degradation of phenol.

Feasibility and advantage of biofilm-electrode reactor for phenol degradation

The new biofilm-electrode method was used for the phenol degradation, because of its low current requirement. The biofilm-electrode reactor consisted of immobilized degrading bacteria on Ti electrode as cathode and Ti/PbO2 electrode as anode. With the biofilmelectrode reactor in a divided electrolytic cell, the phenol degradation rate could achieve 100% at 18 h which was higher than using traditional methods, such as biological or electrochemical methods. Chemical oxygen demand （COD） removal rate of the biofilmelectrode reactor was also greater than that using biological and electrochemical method, and could reach 80% at 16 h. The results suggested that the biofilm-electrode reactor system can be used to treat wastewater with phenol.

Size control synthesis of sulfur doped titanium dioxide (anatase) nanoparticles,its optical property and its photo catalytic reactivity for CO_2 + H_2O conversion and phenol degradation

Sulfur doped anatase TiO2 nanoparticles （3 nm- 12 nm） were synthesized by the reaction of titanium tetrachloride, water and sulfuric acid with addition of 3 M NaOH at room temperature. The electro-optical and photocatalytic properties of the synthesized sulfur doped TiO2 nanoparticles were studied along with Degussa commercial TiO2 particles （24 nm）. The results show that band gap of TiO2 particles decreases from 3.31 to 3.25 eV and for that of commercial TiO2 to 3.2 eV when the particle sizes increased from 3 nm to 12 nm with increase in sulfur doping. The results of the photocatalytic activity under UV and sun radiation show maximum phenol conversion at the particle size of 4 nm at 4.80% S-doping. Similar results are obtained using UV energy for both phenol conversion and conversion of CO2＋H2O in which formation of methanol, ethanol and proponal is observed. Production of methanol is also achieved on samples with a particle size of 8 and 12 nm and sulfur doping of 4.80% and 5.26%. For TiO2 particle of 4 nm without S doping, the production of methanol, ethanol and proponal was lower as compared to the S-doped particles. This is attributed to the combined electronic effect and band gap change, S dopant, specific surface area and the light source used.

Structural Characterization and Photocatalytic Activity of Synthesized Carbon Modified TiO2 for Phenol Degradation

To promote the photocatalytic performance TiO2 and enlarge its application in visible region, carbon doped TiO2 (C/TiO2) composites were synthesized by wet impregnation method using sucrose as a precursor and used for phenol photocatalytic reaction. The synthesized products were characterized by Nitrogen adsorption-desorption isotherms (BET), X-ray diffraction (XRD), transmission electron microscopy (TEM) and UV-visible diffuse reflectance spectroscopy (UV-vis) techniques. The results showed that the obtained TiO2 was anatase phase in the C/TiO2 products, and its crystallite size was 11.7 nm, respectively. Carbon amount and calcined temperature of C/TiO2 can promote phenol removal. In this experiment, 5% carbon and 500 ℃ are the best choice for photocatalyst preparation. Under the UV light irradiation, 5%C/TiO2 (500 ℃, 2 h) exhibited the efficiency of 70.0% for phenol degradation within 150 min whereas TiO2 (500 ℃, 2 h) had 53.0% in the same duration of time. Also 5%C/TiO2 (500 ℃, 2 h) has higher photocatalytic performance under sunlight than pure TiO2. A combination of factors that include the smallest crystalline size, higher anatase percent, less band gap energy value and more oxygen vacant resulted in higher photocatalytic activities of 5%C/TiO2 (500 ℃, 2 h).

A Novel TiO_2 Combined Pulsed Diaphragm Discharge System for Phenol Degradation

A synergistic photocatalysis combined pulsed diaphragm discharge（PDD）system with TiO_2 nanofilm deposited on the surface of quartz diaphragm is developed for the first time for phenol degradation in an aqueous solution.It is observed that the decomposition efficiency of phenol in the TiO_2 combined PDD system is higher than that of the single PDD system under the same conditions,indicating a successful collaboration between the photocatalysis and the plasma decomposition in the present system.Analysis of the solution＇s pH value confirms this collaboration and further reveals that the photocatalytic enhancement effect of phenol degradation is strong at a relatively low supplied voltage.The present TiO_2 combined PDD system exhibits improved efficiencies of pollutant degradation and energy utilization,suggesting a good candidate for wastewater treatment.

Microbial electricity-driven anaerobic phenol degradation in bioelectrochemical systems

Microbial electrochemical technologies have been extensively employed for phenol removal.Yet,previous research has yielded inconsistent results,leaving uncertainties regarding the feasibility of phenol degradation under strictly anaerobic conditions using anodes as sole terminal electron acceptors.In this study,we employed high-performance liquid chromatography and gas chromatography-mass spectrometry to investigate the anaerobic phenol degradation pathway.Our findings provide robust evidence for the purely anaerobic degradation of phenol,as we identified benzoic acid,4-hydroxybenzoic acid,glutaric acid,and other metabolites of this pathway.Notably,no typical intermediates of the aerobic phenol degradation pathway were detected.One-chamber reactors(t0.4 V vs.SHE)exhibited a phenol removal rate of 3.5±0.2 mg L^(-1) d^(-1),while two-chamber reactors showed 3.6±0.1 and 2.6±0.9 mg L^(-1) d^(-1) at anode potentials of t0.4 and t 0.2 V,respectively.Our results also suggest that the reactor configuration certainly influenced the microbial community,presumably leading to different ratios of phenol consumers and microorganisms feeding on degradation products.

Catalytic activation of peroxodisulfate using shape-controlled cerium-manganese composite oxide for phenol degradation:Kinetics and degradation pathway investigation

Phenol-containing wastewater is typical organic wastewater,and its treatment is arduous.An advanced method to treat this type of wastewater is persulfate activation.Environmentally friendly ceriummanganese composite oxide materials were synthesized by hydrothermal method and applied to the phenol degradation process.Various ratios of cerium and manganese,as well as the amount of sodium hydroxide,were investigated.The solid solutions of cerium and manganese were formed and confirmed by X-ray diffraction(XRD) and transmission electron microscopy(TEM).H_(2)-temperature programmed reduction(H_(2)-TPR) and X-ray photoelectron spectroscopy(XPS) were utilized to analyze the synergistic effect of cerium and manganese.It is found that there is a transformation between Ce^(4+)/Ce^(3+) and Mn^(2+)/Mn^(3+),which makes the material more trivalent manganese and thereby increases the catalytic activity.The effect of materials in catalyzing phenol degradation by peroxodisulfate(PDS) under various preparation conditions is discussed and high-effciency removal of phenol can be achieved and the removal rate at 180 min is close to 100%.The kinetic of this process was investigated and activation energy of phenol degradation is 62,35 kJ/mol.The degradation pathway of phenol was studied and it is found that PDS can be activated by low metal ions and the OH and SO_(4·)^(-)radicals play crucial roles according to the quenching experiments.

Honeycomb-like biochar framework coupled with Fe_(3)O_(4)/FeS nanoparticles as efficient heterogeneous Fenton catalyst for phenol degradation

Achieving an efficient and stable heterogeneous Fenton reaction over a wide pH range is of great significance for wastewater treatment.Here,a pollen-derived biochar catalyst with a unique honeycomb-like structure,coupled with the dispersion of magnetic Fe_(3)O_(4)/FeS(Fe/S)nanoparticles,was synthesized by simple impregnation precursor,followed by pyrolysis.The prepared Fe/S-biochar catalyst demonstrated outstanding phenol degradation efficiency across a wide pH range,with 98%of which eliminated even under neutral conditions(pH 7.0).The high catalytic activity was due to the multilevel porous structure of pollenderived biochar provided enough active sites and allowed for better electron transfer,then increases oxidation ability to promote the reaction.Moreover,the acid microenvironment formed by SO_(4)^(2-)group from Fe/S composite extended the pH range for Fenton reaction,and S^(2-)facilitated the conversion of≡Fe^(3+)to≡Fe^(2+),resulting in remarkable degradation efficiency.Further,biochar can effectively promote cycling stability by limiting Fe leaching.This work may provide a general strategy for designing 3D framework biochar-based Fe/S catalysts with excellent performance for heterogeneous Fenton reactions.

Synergistic degradation of phenols by bimetallic CuO-Co_3O_4@γ-Al_2O_3 catalyst in H_2O_2/HCO_3^- system

The development of new catalytic techniques for wastewater treatment has long attracted much attention from industrial and academic communities.However,because of catalyst leaching during degradation,catalysts can be short lived,and therefore expensive,and unsuitable for use in wastewater treatment.In this work,we developed a bimetallic CuO-Co3O4@γ-Al2O3 catalyst for phenol degradation with bicarbonate-activated H2O2.The weakly basic environment provided by the bicarbonate buffer greatly suppresses leaching of active Cu and Co metal ions from the catalyst.X-ray diffraction and X-ray photoelectron spectroscopy results showed interactions between Cu and Co ions in the CuO-Co3O4@γ-Al2O3 catalyst,and these improve the catalytic activity in phenol degradation.Mechanistic studies using different radical scavengers showed that superoxide and hydroxyl radicals both played significant roles in phenol degradation,whereas singlet oxygen was less important.

Optimization of phenol degradation by Candida tropicalis Z-04 using Plackett-Burman design and response surface methodology

Statistical experimental designs were used to optimize the process of phenol degradation by Candida tropicalis Z-04, isolated from phenol-degrading aerobic granules. The most important factors influencing phenol degradation （p 〈 0.05）, as identified by a two-level Plackett-Burman design with 11 variables, were yeast extract, phenol, inoculum size, and temperature. Steepest ascent method was undertaken to determine the optimal regions of these four significant factors. Central composite design （CCD） and response surface analysis were adopted to further investigate the mutual interactions between these variables and to identify their optimal values that would generate maximum phenol degradation. The analysis results indicated that interactions between yeast extract and temperature, phenol and temperature, inocuhim size and temperature affected the response variable （phenol degradation） significantly. The predicted results showed that the maximum removal efficiency of phenol （99.10%） could be obtained under the optimum conditions of yeast extract 0.41 g/L, phenol 1.03 g/L, inoculum size 1.43% （V/V） and temperature 30.04℃. These predicted values were further verified by validation experiments. The excellent correlation between predicted and experimental values confirmed the validity and practicability of this statistical optimum strategy. This study indicated the excellent ability of C. tropicalis Z-04 in degrading high-strength phenol. Optimal conditions obtained in this experiment laid a solid foundation for further use of this microorganism in the treatment of highstrength phenol effluents.

Photochemically enhanced degradation of phenol using heterogeneous Fenton-type catalysts

The degradation of phenol was carried out using heterogeneous Fenton-type catalysts in the presence of H_2O_2 and UV. Catalysts were prepared by exchanging and immobilizing Fe 2+ in zeolite 13X, silica gel or Al_2O_3. The concentration of phenol solution was 100 mg/L. The amount of H_2O_2 added was the stoichiometric amount of H_2O_2 required for the total oxidation of phenol. Under the irradiation of medium pressure light (300 W) phenol was mineralized within 1 h in the presence of Fe 2+/zeolite 13X. The COD removal rate was enhanced in the presence of Fe 2+/zeolite 13X compared to that of Fe 2+/silica gel or Fe 2+/Al_2O_3. Analogous homogenous photo-Fenton reaction with equivalent Fe 2+ was also carried out to evaluate the catalysis efficiency of Fe 2+/zeolite 13X. Results showed that the COD removal rate was near to that of homogeneous Fenton, while heterogeneous Fe 2+/zeolite 13X catalyst could be recycled.

Degradation of Phenolic Compounds in Coal Gasification Wastewater by Biofilm Reactor with Isolated Klebsiella sp.

This study was conducted to evaluate the degradation of phenolic compounds by one strain isolated from coal gasification wastewater( CGW). 16S rRNA gene sequences homology and phylogenetic analysis showed that the isolate is belonged to the genus Klebsiella sp. The effect of different phenolic compounds on the isolate was investigated by determining OD600and phenoloxidase activity,of which the results showed that the isolate can utilize phenol,4-methyl phenol,3,5-dimethyl phenol and resorcinol as carbon resources. The biofilm reactor( formed by the isolate) can resist the influent concentration of phenolic compounds as high as750 mg /L when fed with synthetic CGW and incubated at optimum conditions. The capacity of improving the biodegradability of CGW through degrading phenolic compounds was testified with fed the biofilm reactor with real CGW. Thus,it might be an effective strain for bioaugmentation of CGW treatment.

Controllable Synthesis of Titania Nanocrystals with Different Morphologies and Application to the Degradation of Phenol

Titania nanocrystals with different morphologies were prepared using the hydrothermal method via controlling the pH values of solution, the ratio of reactants, temperature, and time of the hydrothermal reaction. The experimental results showed that uniform rod-like titania particles with an average aspect ratio of 6：1 could be obtained under the conditions of pH=11, n（TBOT）：n（TEA）=1：2, hydrothermal treatment at 150 °C for 24 h. When pH〈10, spherical titania nanocrystals could be obtained; with increasing the pH value, the diameter became smaller. Finally, the smallest size of the particles could reach 7 nm. Nanocrystals with uniformly well-dispersed and perfect crystallographic form were obtained via the above method. Phenol was used as the degradation model for testing the photocatalytical activity of the titania nanocrystals with different morphologies.

Anodic-Cathodic Electrocatalytic Degradation of Phenol with Oxygen Sparged in the Presence of Iron(Ⅱ)

Under oxygen sparged, the synergetic effects of both anodic cathodic electrocatalysis(ACE) and ferrous ion catalyzed anodic cathodic electrocatalysis(FeACE) on phenol degradation were observed in an undivided cell composed of a β PbO 2 anode modified with fluorine resin and a nickel chromium titanium alloy net cathode. Oxygen sparging rate, ferrous concentration, and current significantly affect phenol destruction. The phenol was removed by 10%-13% increasingly under FeACE vs . ACE, and by 12%-15% under ACE vs . anodic electrocatalysis(AE). The phenol destruction was due to the formation of hydroxyl oxidant on the surface of lead oxide at the anode and the reduction of oxygen at the cathode.

A Novel Electrocatalysis Method for Organic Pollutants Degradation

A novel electrocatalysis, ferrous ion catalyzed anodic-cathodic electrocatalysis (FACEC), was developed for organic pollutants degradation, which could promote the degradation by achieving synergetic effects of both anodic oxidation and cathodic indirect oxidation. The degradation rate of model pollutants - phenol by FACEC could increase by nearly 30% comparing with that of anodic electrocatalysis, and the current efficiency could reach 67%.

One-step synthesis of graphitic carbon nitride nanosheets for efficient catalysis of phenol removal under visible light

Graphitic carbon nitride(g‐C3N4)nanosheet photocatalysts were synthesized via a facile impregnation‐thermal method.The as‐prepared materials were characterized and investigated as metal‐free photocatalysts for the degradation of phenol in aqueous solution under visible light.Results revealed that the g‐C3N4nanosheets exhibited a78.9%degradation for phenol after30min,which was much faster than that of the pristine g‐C3N4.Using Brunauer‐Emmett‐Teller theory,the surface area of g‐C3N4nanosheets was103.24m2/g,which was much larger than that of g‐C3N4.The larger surface area increases the contact area of the material with phenol,enhancing the photocatalytic activity.These results highlight the potential application of sustainable metal‐free photocatalysts in water purification.

Niche Differentiation of Phenol-Degrading Microorganisms in UASB Granular Sludge as Revealed by Fluorescence in situ Hybridization

A microbial community structure of granules harvested from an anaerobic sludge blanket reactor treating phenolic wastewater was investigated using fluorescence in situ hybridization(FISH)and clone library construction.Clones of Syntrophorhabdaceae and Cryptanaerobacter were observed to be responsible for phenol degradation.For accurate taxonomic assignment of Cryptanaerobacter clones,phylogenetic analysis using nearly full-length 16S ribosomal RNA(rRNA)gene sequences was necessary.Three oligonucleotide probes were designed to detect the following three taxonomic groups:Syntrophorhabdaceae,Cryptanaerobacter,and Syntrophus.FISH analysis of thin sections of anaerobic granules showed a random distribution of bacteria and archaea.However,a well-defined distribution of Syntrophorhabdaceae,Cryptanaerobacter,and Syntrophus was observed.Cryptanaerobacter and Syntrophus were found on the outer layer of the granules and were closely associated with each other,while Syntrophorhabdaceae was located in the deeper part of the granules.Such specific distribution of the bacteria is most likely due to their metabolic association and affinity for the substrate.Phenol degradation in the granular sludge was observed to be carried out in the following way.First,Cryptanaerobacter converts phenol to benzoate,which is then degraded by Syntrophus into acetate.This syntrophic degradation of phenol occurs near the surface of the granule,where the phenol concen-tration is high.In the deeper part of the granule,where the phenol concentration is lower,Syntrophorhabdaceae degrades phenol into acetate.We observed that Syntrophorhabdaceae is less likely to produce benzoate as an intermediate to feed the neighboring organisms,which contradicts the theo-ries presented by previous studies.

Metal oxide particle electrodes for degradation of high concentration phenol wastewater via electrocatalytic advanced oxidation

High-concentration phenol wastewater is pollutant of concern that pose significant risks to human health and the environment.Three-dimensional electrocatalytic oxidation is one of the most promising wastewater treatment technologies because of its high treatment efficiency,low energy consumption and low secondary pollution.Lower-cost and higher-performance particles still faces great challenges.In this work,metal oxide particle electrodes were prepared using granular activated carbon(GAC)as a substrate to study the degradation of phenol by three-dimensional electrocatalytic oxidation.GAC particle electrodes loaded with different monometallic oxides(Mn,Fe,Co,Ce)and bimetallic oxides(Fe and Ce)were prepared by the impregnation method.The effectiveness of the particle electrodes in degrading phenol was greatly improved after active components loading.Among all monometallic oxide particle electrodes,the concentration degradation efficiency was in the order of Ce/GAC>Co/GAC>Mn/GAC>Fe/GAC,and the COD degradation efficiency was Ce/GAC>Fe/GAC>Co/GAC>Mn/GAC.After optimizing the loading metal type and loading amount,it was found that the 1.1%Fe-2.7%Ce/GAC particle electrode perform the best,with a phenol degradation efficiency of 95.48%,a COD degradation rate of 94.35%,an energy consumption of 0.75 kW·h·kg^(-1)COD.This lower-cost and higher-performance particle highlights a reliable route for solving the problem of particle electrode materials limiting the efficient treatment of phenol-containing wastewater.

Relative Abundance and the Relationships between Aniline,Phenol and Catechol Degraders in Fresh Water

Relative abundance and relationships between aniline, phenol and catechol degraders were investigated in unpolluted and polluted fresh waters in Osaka prefecture, Japan. Phenol and catechol degraders were found more frequently compared to aniline degraders. The results indicate that these degraders were more abundant in polluted waters than in unpolluted waters. Aniline degraders isolated from the Ina River water showed a higher capability of degrading catechol than phenol. Analysis on sequence homology among these three kinds of degraders indicated a possible relationship between aniline degraders and certain strains of both catechol and phenol degraders.

Widespread and active piezotolerant microorganisms mediate phenolic compound degradation under high hydrostatic pressure in hadal trenches

Phenolic compounds,as well as other aromatic compounds,have been reported to be abundant in hadal trenches.Although high-throughput sequencing studies have hinted at the potential of hadal microbes to degrade these compounds,direct microbiological,genetic and biochemical evidence under in situ pressures remain absent.Here,a microbial consortium and a pure culture of Pseudomonas,newly isolated from Mariana Trench sediments,efficiently degraded phenol under pressures up to 70 and 60 MPa,respectively,with concomitant increase in biomass.By analyzing a high-pressure(70 MPa)culture metatranscriptome,not only was the entire range of metabolic processes under high pressure generated,but also genes encod-ing complete phenol degradation via ortho-and meta-cleavage pathways were revealed.The isolate of Pseudomonas also contained genes encoding the complete degradation pathway.Six transcribed genes(dmpKLMNOP_(sed))were functionally identified to encode a multicomponent hydroxylase catalyzing the hydroxylation of phenol and its methylated derivatives by heterogeneous expression.In addition,key catabolic genes identified in the metatranscriptome of the high-pressure cultures and genomes of bacterial isolates were found to be all widely distributed in 22 published hadal microbial metagenomes.At microbiological,genetic,bioinformatics,and biochemical levels,this study found that microorganisms widely found in hadal trenches were able to effectively drive phenolic compound degradation under high hydrostatic pressures.This information will bridge a knowledge gap concerning the microbial aromatics degradation within hadal trenches.