Catalytic wet air oxidation of phenol over ultrasound-assisted synthesized Ni/CeO2–ZrO2 nanocatalyst used in wastewater treatment

Non-noble metal Ni with different loadings was coated on precipitated CeO₂–ZrO₂ support by the sonochemistry method and examined for catalytic wet air oxidation of phenol. The structure of the nanocatalysts was determined by BET, FESEM, XRD, and FTIR analyses. The results showed non-uniform morphology of the nanocatalyst at lower Ni contents changed to homogenous morphology with spherical nano particles at higher Ni contents. While the size of NiO crystals remained constant with rising Ni content, the crystallinity of NiO significantly increased. If the crystallinity of NiO was 100% in 20% wt Ni/CeO₂–ZrO₂, the crystallinity of NiO in 5% wt Ni was found to be 41.13%. The average particle size in Ni(15%)/CeO₂–ZrO₂ was 77 nm in which 85.71% of particle diameters were less than 100 nm. Catalytic wet air oxidation of phenol with different Ni loadings indicated improvement of phenol destruction at higher amounts of active phase. Removal of phenol increased with increasing catalyst loading from 4 to 9.0 g/l but further increase to 10 g/l declined the catalyst reactivity.     

核壳结构TiO2@SiO2催化碳酸二甲酯与苯酚酯交换合成碳酸二苯酯

以反相微乳液法和沉淀法相结合制备了核壳结构TiO₂@SiO₂,首次用于碳酸二甲酯与苯酚酯交换合成碳酸二苯酯反应,显示较好的催化活性. 采用200 ℃焙烧的TiO₂@SiO₂,用量0.20 g,反应9 h,苯酚转化率达41.8%,酯交换选择性为100%. 透射电镜显示TiO₂@SiO₂核厚壳薄,TiO₂核直径220-300 nm,SiO₂壳厚度40-60 nm,具有介孔结构. TiO₂@SiO₂对碳酸二甲酯与苯酚酯交换反应有好的重复使用性,使用4次苯酚转化率仍保持在40%以上. TiO₂与SiO₂发生相互作用,Ti进入骨架形成Ti-O-Si键,骨架Ti的形成提高了TiO₂@SiO₂的催化性能.     

Electronic absorption spectra of phenol(H2O)n and (phenol)n as studied by the MS MPI method

The initial stages of solvation and crystallization were studied in phenol(H₂O)_n and (phenol)_n by the use of the mass-selected MPI method in a supersonic free jet. The spectral position exhibits an irregular shift by the change of the cluster size, which is interpreted in terms of the role of phenol as a proton donor, a proton acceptor or both in the hydrogen bonding. The O⁰₀ band of the phenol—water cluster was found to converge to 276.0 nm. The phenol trimer was concluded to have a cyclic structure.     

Visible light induced photocatalytic degradation of phenol by polymer-modified semiconductors: Study of the influencing factors and the kinetics

To investigate the influencing factors and the kinetics of photocatalytic degradation of phenol, experiments were carried out using conjugated polymer poly(fluorene-co-thiophene) (PFT) sensitized TiO₂ and ZnO under LED (light-emitting diode) lights of the wavelength of 450–475 nm. Influencing factors, such as initial phenol concentration, photocatalyst dosage and pH value on the photocatalytic degradation of phenol were studied in detail. The reaction kinetics was found to follow pseudo first-order law.     

Optical sensor for carbon dioxide combining colorimetric change of a pH indicator and a reference luminescent dye

A new optical CO₂ sensor based on the luminescence intensity change of the europium(III) complex tris(thenoyltrifluoroacetonato) europium(III) dihydrate ([Eu(tta)₃]) caused by the absorption change of various pH indicators—thymol blue, phenol red, or cresol red—with CO₂ was developed and its CO₂ sensing properties were investigated. For all the CO₂ sensors using pH indicators the observed luminescence intensity from [Eu(tta)₃] at 613 nm increased with increasing CO₂ concentration. The linear calibration method based on the plot of (I₁₀₀–I₀)/(I–I₀) versus the inverse of CO₂ concentration was suggested, where I₀ and I₁₀₀ were luminescence intensities at 613 nm of the CO₂ sensor film in 100% nitrogen and 100% gaseous CO₂. In all cases the plots showed good linearity and the correlation factors of the plots, r², were 0.991 for thymol blue, 0.990 for phenol red, and 0.998 for cresol red. The slopes of the plots (A/B) for thymol blue, phenol red, and cresol red were 2.2, 5.2, and 9.0%, respectively. The response times of the CO₂ sensor film were 4.0 s for thymol blue, 4.4 s for phenol red, and 8.8 s for cresol red for switching from nitrogen to CO₂, and the recovery times of films were 36 s for thymol blue, 39.2 s for phenol red, and 56.6 s for cresol red for switching from CO₂ to nitrogen. The signal changes were fully reversible and hysteresis was not observed during the measurements. The highly sensitive CO₂ sensor was developed using thymol blue as an indicator for the CO₂-sensing probe.     

Obtaining thin films of “reactive polymers” on metal surfaces by electrochemical polymerization: Part II. Alcohol substituted polyphenylene oxide films

The selective electrochemical oxidation of the phenol function in the case of hydroxymethyl phenol derivatives (o^?, m^?, p-hydroxybenzyl alcohol) leads to “reactive polymer” films of polyphenylene oxide substituted by CH₂OH groups. The transformation of the hydroxyl function into an ester function by acetyl chloride indicates the reactivity of the CH₂OH group. As for the family of carbonylated polyphenylene oxide films, reactivity is limited to the superficial layers of film. Average film thickness is between 50–100 nm; however with the ferrocene-ferricinium system acting as a redox catalyst, it can reach about 300 nm. This catalytic mechanism intervenes only when the oxidation potential of the ferrocene-ferricinium couple is very similar to that of the phenol derivative.     

Photocatalysis of Au25-modified TiO2 under visible and near infrared light

Visible light-driven photocatalysis of Au₂₅-modified TiO₂ was investigated. It induces oxidation of phenol derivates and ferrocyanide and reduction of Ag⁺, Cu²⁺ and dissolved oxygen. Thermodynamically uphill reactions such as oxidation of phenol accompanied by reduction of Cu²⁺ are also driven. The photocatalysis, which is based on the excitation of Au₂₅, is observed even under 860 nm light.     

Efficient photoelectrocatalytic activity of TiO2/Ti anode fabricated by metalorganic chemical vapor deposition (MOCVD)

Nanosized TiO₂/Ti photoanodes fabricated by metalorganic chemical vapor deposition (MOCVD) under different deposition temperatures were characterized and applied to the photoelectrocatalytic degradation of model pollutant of phenol. The anode prepared at 773 K was verified in anatase phase with a size about 60 nm and achieved the best photoelectrocatalytic activity, where IPCE could reach as high as 89% and the photoconversion efficiency peaked at 8.4%. The photoelectrocatalytic degradation of phenol was found well fit a pseudo-first-order kinetics, and kept stable performance in five continuous runs, confirming potential application of the electrode prepared by MOCVD for organic pollutants abatement.     

Preparation of nanocrystalline TiO<Subscript>2</Subscript> powders for photocatalytic oxidation of phenol

Nanocrystalline TiO₂ powders in the anatase, rutile, and mixed phases prepared by hydrolysis of TiCl₄ solution were of ultrafine size (<7.2 nm) with high specific surface areas in the range 167 to 388 m²/g. In the photocatalytic degradation of phenol as model reaction, the photocatalytic properties of TiO₂ nanoparticles were evaluated by use of UV–vis absorption spectroscopy and total organic carbon (TOC) content. The synthetic mixed-phase TiO₂ powder calcined at 400 °C had higher activity than pure anatase or rutile; it degraded more than 90% phenol to CO₂ (evaluated by TOC) after irradiation with near UV light for 90 min at a catalyst loading of 0.4 g/L. The TOC results indicated that rutile TiO₂ crystallites of particle size 7.2 nm resulted in much better photocatalytic performance than particles of larger size. This result suggested that some intermediates, not determined by UV–vis absorption spectroscopy, existed in the solution after the photocatalytic process over the rutile TiO₂ photocatalysts of larger crystallite size.     

Photooxidation of phenol in aqueous nanodispersion of humic acid

Photooxidation of phenol sensitized by Aldrich humic acid (AHA) has been studied in an aqueous solution at neutral and basic pH. Solutions containing phenol and AHA of various concentrations were irradiated with monochromatic light at 253.7 nm or with polychromatic light within the wavelength range of 310–420 nm. The quantum yields of phenol photodegradation under these conditions were determined. At the wavelength of 253.7 nm direct degradation of phenol was much more effective than that sensitized by AHA. With polychromatic light the photooxidation was found to be strongly dependent on pH of aqueous solution and independent on AHA concentration.     

Glucose‐ and Cellulose‐Derived Ni/C‐SO3H Catalysts for Liquid Phase Phenol Hydrodeoxygenation

Sulfonated carbons were explored as functionalized supports for Ni nanoparticles to hydrodeoxygenate (HDO) phenol. Both hexadecane and water were used as solvents. The dual‐functional Ni catalysts supported on sulfonated carbon (Ni/C‐SO₃H) showed high rates for phenol hydrodeoxygenation in liquid hexadecane, but not in water. Glucose and cellulose were precursors to the carbon supports. Changes in the carbons resulting from sulfonation of the carbons resulted in variations of carbon sheet structures, morphologies and the surface concentrations of acid sites. While the C‐SO₃H supports were active for cyclohexanol dehydration in hexadecane and water, Ni/C‐SO₃H only catalysed the reduction of phenol to cyclohexanol in water. The state of 3–5 nm grafted Ni particles was analysed by in situ X‐ray absorption spectroscopy. The results show that the metallic Ni was rapidly formed in situ without detectable leaching to the aqueous phase, suggesting that just the acid functions on Ni/C‐SO₃H are inhibited in the presence of water. Using in situ IR spectroscopy, it was shown that even in hexadecane, phenol HDO is limited by the dehydration step. Thus, phenol HDO catalysis was further improved by physically admixing C‐SO₃H with the Ni/C‐SO₃H catalyst to balance the two catalytic functions. The minimum addition of 7 wt % C‐SO₃H to the most active of the Ni/C‐SO₃H catalysts enabled nearly quantitative conversion of phenol and the highest selectivity (90 %) towards cyclohexane in 6 h, at temperatures as low as 473 K, suggesting that the proximity to Ni limits the acid properties of the support.     

Controllable synthesis of titania/reduced graphite oxide nanocomposites with various titania phase compositions and their photocatalytic performance

A facile method is presented for preparing TiO2 /reduced graphite oxide(RGO) nanocomposites with phase-controlled TiO2 nanoparticles via redox reaction between the reductive titanium(Ⅲ) precursor and graphite oxide(GO),and a series of TiO2 /RGO composites with various TiO2 phase compositions were obtained.In all the titania/RGO composites,the TiO2 nanoparticles were uniformly distributed on the surface of the RGO.The TiO2 consisted of anatase phase particles in the form of square-plates with edges less than 10 nm and the rutile phase nanorods in diameters less than 10 nm.The performances of the as-prepared TiO2 /RGO composites were investigated on catalytically degrading phenol under visible light irradiation.The TiO2 /RGO composites can effectively degrade phenol under visible light irradiation,and the phase composition of TiO2 in the composites significantly influences the activities of these catalysts.     

HPLC Identification and Separation of Phenolic Compounds Diazotized With Sulphanilic Acid. Structural Effects on Retention Times

Abstract

A HPLC method for the separation of phenol derivatives has been developed either on a RP Phenyl-bonded or an alkyl C₁₈ -bonded columns. Derivatization with diazotized sulphanilic acid allows

a reversed-phase chromatography with spectrophotometric detection at 370 nm. The method sensitivity permits detection down to 0.08- 0.15 ng of phenols. In particular structure-retention time relationships are discussed.     

仿生光催化剂的优化制备、介孔特性表征及其在催化降解苯酚废水中的应用

以十二胺(DDA)或十八胺(ODA)为模板剂,采用焙烧或萃洗法去除模板剂制备中孔分子筛(HMS).X射线粉末衍射(XRD)及氮吸附表征结果说明,以十二胺为模板剂且采用焙烧法去除模板剂制备的分子筛具有明显的XRD介孔衍射峰,而且其氮吸附曲线具有典型的IV类等温线特征及H1型脱附滞后环,这属于典型的介孔材料特征.以此分子筛为载体,通过F—C反应将磺酸铁酞菁(FePcS)修饰在HMS上,得到新型光催化剂.催化剂的BET比表面积为675.1m2·g-1,平均孔径为5.78nm,孔容为0.587cm3·g-1,且仍保持着鲜明的介孔特征.最后在模拟可见光照射下应用催化剂处理浓度高达1000mg·L-1的模拟苯酚废水,反应400min后,苯酚的转化率达到85%以上,反应溶液pH值也由4.52降到2.65,表明有酸类降解中间产物生成,反应最终苯酚转化率接近100%,总有机碳(TOC)的去除率达81%以上.催化剂表现出了良好的催化降解有机废水的性能.     

高度分散的Pt/TiO2的制备及光催化活性

用柠檬酸作为空穴捕获剂和分散剂, 在温和条件下用光催化还原法将3 nm金属铂沉积在7 nm的锐钛矿相及介孔二氧化钛纳米晶表面. TEM观察显示铂的负载量为w＝1.0%时, 多数二氧化钛纳米晶表面沉积了岛状的铂团簇, XPS和电子衍射结果表明铂以游离态存在. 负载w＝1.0%～2.0%铂的TiO₂在苯酚光氧化反应中活性显著提高. Pt/TiO₂在氨气中经550 ℃氮化, 可制得氮掺杂的Pt/TiO₂可见光光催化剂, 氮化过程中铂团簇没有烧结和显著长大.     

Simultaneous spectrophotometric estimation of nitrobenzene,aniline, and phenol in a ternary mixture using genetic algorithm

In spectrophotometry, mixtures of chemical constituents cannot be determined simultaneously due to spectral interferences as well as the close λ_max wavelength, the wavelength at which a substance absorbs the most photons. Since the spectra of individual components in a ternary mixture overlap, determining the concentration of individual components using the wavelength of maximum absorbance, λ_max, can lead to a significant error. In this paper, the concentrations of individual components in ternary synthetic mixtures of nitrophenol, aniline, and phenol were estimated simultaneously using a model based on a genetic algorithm and partial least squares. The spectrophotometric data of ternary mixtures with almost identical spectra of nitrobenzene, aniline, and phenol were calibrated using partial least squares modeling without losing prediction capability, and a genetic algorithm method was used to select the appropriate wavelengths for partial least square calibration. The experimental calibration matrix of 27 samples containing a ternary mixture of nitrobenzene (1.0–20.0 mg L^?1), aniline (1.0–15.0 mg L^?1), and phenol (4.0–18.0 mg L^?1) was designed by measuring the absorbance between 200 and 340 nm at a 1 nm wavelength intervals. The model was verified by using six different mixtures with varying concentrations of nitrobenzene, aniline, and phenol. The root mean square error in the prediction of nitrobenzene, aniline, and phenol was 0.1411, 0.1670, and 0.2861 with the genetic algorithm, and 0.3666, 0.6149, and 0.6279 without the genetic algorithm, respectively. This method can be successfully applied to estimate the components in synthetic mixtures accurately. Since this method is accurate and robust, it can be applied to actual industrial wastewater that contains a mixture of toxic chemicals. This eliminates the complications and costs related to separation and purification prior to the analysis using costly chromatographic methods.     

One-step solid-phase UV spectrophotometric method for phenol determination in vaccines: Development and quality assessment

A solid-phase spectrophotometric technique was used to develop very sensitive, inexpensive, onestep procedure for determination of phenol (UV-SPS procedure). The proposed procedure is based on simultaneous sorption of phenol on an anion exchanger QAE Sephadex A-25 (40 mg), within 10 min at pH 11 and measurement of the intrinsic absorbance of the solid phase in a 1-mm cell at 289 and 500 nm, without previous derivatization. The optimum experimental conditions were investigated and comprehensive quality control of the new procedure was carried out using a prevalidation strategy accompanied by a very informative system of diagnosis. The UV-SPS procedure is characterized with both ideal calibration and analytical evaluation function within analyte working range from 0.3 to 3.0 μmol (6.0 to 60.0 nmol/mL). Random deviations (from ±0.3 to ±5.0%) and systematic deviations (from ?3.0 to +4.9%) confirmed the favourable precision and accuracy of the UV-SPS method. Evaluated limiting values (L _D = 1.0 μM, L _Q = 6.0 μM) showed that this method enables determination of very low levels of phenol. The sensitivity of UV-SPS procedure is 50 times higher than that provided by the corresponding method in solution. The UV-SPS method was successfully applied to the determination of phenol in vaccines (recovery 95.6–103.4%).     

Effect of supports for the direct oxidation of benzene to phenol over supported FeCl3 catalyst

The effect of supports on oxidation of benzene to phenol with hydrogen peroxide as an oxidant was tested by using supported FeCl₃ as catalysts. Their activities were affected by acid-base properties of supports. Silica gel which gave strong acid site near the active site had the highest activity among the investigated supports. Several kinds of silica gel which had different pore sizes were used. The maximum activity was obtained at the pore size of 3.5 nm and the reason was discussed.     

Enhanced photocatalytic performance of magnetite/TS-1 thin film for phenol degradation

Photocatalytic degradation method is an emerging technique for complete removal of pollutants. Several semiconductor photocatalysts are reported as photocatalysts for industrial wastewater treatment in environmental applications. In this study Magnetite/TS-1 composite materials was used for photocatalytic degradation of phenol. Magnetite nanoparticles (MNP) (10 wt%) were dispersed with nanocrystalline Titanium Silicate-1 zeolite (TS-1). The Magnetite/TS-1 composite materials were characterized with various techniques. The structural analysis reveals the presence of MNP and zeolite-MFI phases in Magnetite/TS-1 composite materials. The average particles size of the magnetite nanoparticles is less than 5 nm and that of the composite nanoparticles are in the range of about 90 nm with micropore volume 0.110 cm³/g and the external surface area 120 m²/g. The photocatalytic experiments were carried out in a thin film flow photoreactor under UV radiation. The results showed that Magnetite/TS-1 composite materials exhibited improved activity for the degradation of phenol compared to TS-1. Preliminary studies proves that aeration is necessary for the photocatalytic reaction. The reaction parameters such as flow rate, pH and phenol concentration are optimized as 8 ml/min, pH 7.0 and 75 mg/L respectively. To understand the active species involved in the degradation of phenol radical scavengers such as NaI, benzoquinone and isopropyl alcohol are used to trap hole (h⁺), superoxide anion radical and hydroxyl radical (OH), respectively. From the obtained results it is envisaged that hydroxyl radicals are predominantly involved in complete oxidation of phenol. The extent of degradation of phenol was determined by measuring the amount of CO₂ formed in the reaction. The results confirms that 99.6 % carbon in phenol is converted to CO₂.     

Peroxidase catalyzed polymerization of phenol

effect of horseradish peroxidase (HRP) and H₂O₂ concentrations on the removal efficiency of phenol, defined as the percentage of phenol removed from solution as a function of time, has been investigated. When phenol and H₂O₂ react with an approximately one-to-one stoichiometry, the phenol is almost completely precipitated within 10 min. The reaction is inhibited at higher concentrations of H₂O₂. The removal efficiency increases with an increase in the concentration of HRP, but an increase in the time of treatment cannot be used to offset the reduction in removal efficiency at low concentrations of the enzyme, because of inactivation of the enzyme. One molecule of HRP is needed to remove approximately 1100 molecules of phenol when the reaction is conducted at pH 8.0 and at ambient temperature.