Phenol In Aqueous Solution Research Articles

Adsorption Analyses of Phenol from Aqueous Solutions Using Magadiite Modified with Organo-Functional Groups: Kinetic and Equilibrium Studies.

Organically-modified magadiite (MAG–CTAB–KH550) was synthesized via ion-exchange method and condensation reaction in the presence of pure magadiite (MAG), cetyltrimethylammonium bromide (CTAB) and γ-aminopropyltriethoxysilane (KH550) in aqueous solution in this research. This new adsorbent material was studied using scanning electron microscope (SEM), X-ray diffraction (XRD), Fourier transforms infrared spectroscopy (FTIR), and N2 adsorption/desorption isotherms process. It was found that the MAG–CTAB–KH550 has high Brunaur-Emmet-Teller (BET) specific surface area and mesoporous pore size distribution which enhanced its ability to remove phenol in aqueous solution; and, the value of pH has a relatively large impact on the adsorption behavior of the sorbent. Finally, the adsorptive behavior of the mesoporous material on phenol was followed pseudo-second-order kinetic adsorption model. In contrast, the adsorption equilibrium isotherm was better performed Langmuir isotherm model than the Freundlich isotherm model; in addition, the results also showed that the MAG–CTAB–KH550 had a better adsorption capacity and removal efficiency than MAG.

Ag modified ZnS for photocatalytic water pollutants degradation: Influence of metal loading and preparation method

In this paper, the photocatalytic degradation of organic pollutants was investigated using Ag/ZnS nanoparticles at different noble metal loadings. The photocatalysts were prepared at room temperature by two different methods: photodeposition and chemical reduction. The obtained samples were characterized by Specific surface area measurement, X-ray photoelectron spectroscopy, X-ray Powder diffraction, ultraviolet–visible diffuse reflectance and Raman spectroscopy. The X-ray photoelectron spectroscopy spectra showed that Ag is present on ZnS surface as intermediate state between nanostructured Ag0 and Ag2O. Moreover, the addition of silver caused a significant change of the absorption spectrum of bare ZnS, resulting in higher absorbance in the visible region, due to the Ag surface plasmon band. Methylene blue (MB) was used to evaluate the photocatalytic activity of the prepared samples. The best photocatalytic activity was observed using the sample at 0.1 wt% Ag loading prepared by chemical reduction method. In particular, the almost complete MB degradation was achieved using UV-LEDs as light sources and 6 g L−1 of catalyst dosage. Finally, the optimized photocatalyst was also effective in the degradation of phenol in aqueous solution under UV irradiation.

Preparation and photocatalytic application of AgBr modified Bi2WO6 nanosheets with high adsorption capacity

Abstract

Oxidative Degradation of Phenol using in situ Generated Hydrogen Peroxide Combined with Fenton’s Process

Oxidative destruction of organic compounds in water streams could significantly reduce environmental effects associated with discharging waste. We report the development of a process to oxidise phenol in aqueous solutions, a model for waste stream contaminants, using Fenton’s reactions combined with in situ synthesised hydrogen peroxide (H2O2). Bifunctional palladium-iron supported catalysts, where Pd is responsible for H2O2 synthesis while Fe ensures the production of reactive oxygen species required for the degradation of phenol to less toxic species is reported. A comparison is made between in situ generated and commercial H2O2 and the effect of phenol degradation products on catalyst stability is explored.

Degradation of Phenol in Water Using a Novel Gas-Liquid Two-Phase Dielectric Barrier Discharge Plasma Reactor

Phenol is toxic to human and persistent in the environment. Traditional treatment methods have the disadvantages of long treatment time, large amount of agents, and secondary pollution. In this study, a novel gas-liquid two-phase dielectric barrier discharge reactor was designed to remove phenol in aqueous solution. The effects of operating conditions (applied voltage, discharge spacing, pH, and conductivity), different water matrix (deionized water, groundwater, surface water, tap water), and inorganic ions were investigated. Moreover, the reaction mechanisms and the possible degradation pathway were proposed. The removal efficiency of phenol achieved 95.5% under the optimal operating conditions (discharge voltage of 17.6 kV, discharge gap of 1 mm, air flow rate of 60 mL min−1) coupling with H2O2 at 10 mM. The presence of different concentrations of inorganic ions (0.1, 1, 10, and 20 mM) could inhibit the phenol removal efficiencies. Specially, Cl− had different effects on phenol removal efficiency. The inhibition of Cl− on phenol removal was weakened when Cl− concentration was greater than 1 mM, which allows the technology that has certain advantages in treating high-salt wastewater containing high chloride concentration. In addition, ˙OH was verified as the main active species in phenol removal. The possible degradation pathway was proposed according to theoretical calculation and GC-MS measurement.

Synthesis of highly active and stable Al/Zr pillared clay as catalyst for catalytic wet oxidation of phenol

Natural bentonite clay was used in the synthesis of single and mixed oxide Al/Zr pillared clay catalysts by means of ultrasonic treatment during the aging and intercalation steps. The raw bentonite and pillared clay catalysts were characterized using high resolution scanning electron microscopy with energy dispersive system (HRSEM-EDS), powder X-ray diffraction (PXRD), N2 adsorption/desorption, Fourier transform infrared spectroscopy, thermogravimetric analysis, cation exchange capacity, zeta potential and all the catalysts evaluated in the catalytic wet air oxidation (CWAO) of phenol. Calcination of the synthesized Al/Zr-PILCs at 500 °C for 120 min yielded optimum physical properties with BET surface area of 230 m2/g, pore volume of 0.115 cm3/g and basal spacing of 1.92 nm and with good thermal stability. Complete removal of phenol was obtained after 120 min and 88% TOC was removed after 180 min in aqueous solution under mild reaction conditions of 100 °C and 10 bar after. Catalyst reusability studies showed that the Al/Zr-PILCs catalyst demonstrated excellent chemical and structural stability with insignificant leaching of Zr4+ after six consecutive catalytic runs. The Al/Zr-PILCs catalyst therefore demonstrated excellent catalytic properties in the CWAO of phenol in aqueous solution.

Effect of pretreatment on microstructure and photocatalytic activity of kaolinite/TiO2 composite

Kaolinite/TiO2 composites were prepared by using sol-gel method and raw kaolin, pretreated kaolinite and tetrabutyl titanate as the main raw materials. X-ray diffractometer, field-emission scanning electron microscope and infrared spectrometer analysis were carried out to characterize the phase composition and microstructure of the samples. The photocatalytic performance of the kaolinite/TiO2 composites were evaluated by degrading the methylene blue (MB) and phenol aqueous solution, respectively. The results show that intercalation and exfoliation reduced the size and thickness of kaolinite particles. Acid treatment improved the distribution and the loading quantity of TiO2 grains. When the kaolinite/TiO2 composites were calcined at 500 °C, the tetragonal structure of anatase particles of 30–100 nm in size were obtained, but the exfoliated kaolinite crystals were damaged. The degradation rate of MB increased gradually with the extension of photocatalytic reaction time and the enhancement of photocatalyst dosage. The adsorption performance of acid-treated kaolinite/TiO2 composite (AKT) was nearly the same as that of raw kaolin/TiO2 composite (RKT), but that of the exfoliated kaolinite/TiO2 composite (EKT) was the most excellent. The photocatalytic performance of AKT and EKT were better than that of RKT, and AKT exhibited the optimum property. Under a certain photocatalyst dosage and photocatalysis time, the absorption rate and the degradation rate decreased gradually with the enhancement of initial concentration of MB. Similar result was also acquired for the degradation of phenol. Both the acid treating and the exfoliating to kaolinite enhanced the photocatalytic performance of the kaolinite/TiO2 composite photocatalysts, but acid treatment may be more helpful to the preparation of high performance kaolinite/TiO2 composite photocatalyst.

Ozonation of aqueous phenol catalyzed by biochar produced from sludge obtained in the treatment of coking wastewater

Sludge collected from industrial wastewater treatment possesses a threatening effect on environment, and changing it into functional material provides an alternative for its disposal. Biochar synthesized by pyrolysis of sludge obtained from coking wastewater treatment was evaluated for the catalytic ozonation of phenol in aqueous solution. The present work focused on testing the catalytic performance of biochar, deducing the kinetics of phenol removal in various reaction conditions, and finally elucidating the mechanism of biochar-enhanced phenol removal. The results demonstrated that biochars produced at pyrolysis temperatures of 700 and 900 °C revealed highly comparable catalytic activity in phenol ozonation, leading to around 95% phenol removal within 30 min reaction, due to the abundant carbonyl groups on biochar surface. The biochar, however, was suffered from poor stability, which was attributed to biochar loss and changes in surface chemistry. On the basis of examining reaction variables, an empirical kinetic model was developed well matching experimental results. It was found that ozone concentration adsorbed on biochar surface was first increased with a peak (3.8 mg/L for biochar obtained at 700 °C) at reaction time 10 min, after which it decreased along with proceeding reaction. In light of radical scavenging test, superoxide radical (O2ˉ) was identified as main radical species produced from the interaction of ozone with biochar surface, while hydroxyl radical (OH) played negligible role in biochar catalytic ozonation. The promoting mechanism of bicarbonate on phenol ozonation was verified to be the generation of O2ˉ via series reactions of HCO3ˉ with OH and ozone, apart from increase in solution pH. These results provide important implications for future recycling of coking wastewater treatment sludge in environmental remediation.

Aqueous Phase Hydrodeoxygenation of Phenol over Ni3P-CePO4 Catalysts

Unsupported Ni3P-CePO4 catalysts were prepared by coprecipitation, followed by drying, calcination, and temperature-programmed reduction. The prepared catalysts were characterized by XRD, N2 adsorption–desorption, TEM, STEM-EDS elemental mapping, XPS, NH3-TPD, FT-IR of adsorbed pyridine, and H2-TPR. Their catalytic performances in hydrodeoxygenation (HDO) were investigated using an aqueous solution of phenol (5.0 wt %) as the feed. CePO4 was generated in coprecipitation and stable in the subsequent drying, calcination, and temperature-programmed reduction (final temperature 500 °C). It is shown that the addition of CePO4 resulted in enhanced HDO activity, and a maximum activity appeared at a Ce/Ni ratio of 0.3. The presence of CePO4 improved the dispersion of Ni3P significantly, leading to enhanced hydrogenation activity. CePO4 served as the major dehydration sites as well because of its surface acidity (mainly Lewis acid). In addition, the kinetics of the aqueous phase HDO of phenol and cyclohexanol cata...

Adsorption of phenol by activated carbon in rotating packed bed: Experiment and modeling

This work assessed the feasibility of adsorbing phenol in aqueous solution by activated carbon in rotating packed bed (RPB). The effects of high gravity factor, liquid spray density and initial phenol concentration on the adsorption amounts of phenol in RPB were experimentally investigated, which was about 1.4 times of that in convention packed bed. Furthermore, the experimental adsorption isotherms curves were simulated by varies of models to assist the selection of important and characteristic parameters for the designing process of RPB, including Langmuir, Freundlich, Elovich, Temkin, Fowler–Guggenheim and Kiselev. Among the above six models, Freundlich model exhibited the best performance with the correlation coefficient (R2) of 0.9970 and average percentage errors (APE) of 0.241. Besides, the intraparticle diffusion model with the correlation coefficient (R2) above 0.990 could well simulate the adsorption performance for variety of operation conditions in RPB. The intraparticle diffusion coefficient (kr) in RPB could be improved 1.48 times of that in convention packed bed at high gravity factor of 44.68.

Pristine Bi2WO6 and hybrid Au-Bi2WO6 hollow microspheres with excellent photocatalytic activities

Pristine Bi2WO6 hollow microspheres have been fabricated in ethylene glycol-water system with CTAB as crystal growth director for the first time, hybrid Au- Bi2WO6 hollow microspheres was also obtained by in situ decoration of Au nanoparticles, the formation mechanisms were explored. Their photocatalytic activities on photo-reduction of Cr(VI) and photo-degradation of phenol in aqueous solution were investigated under visible light irradiation. Hybrid Au- Bi2WO6 hollow microspheres displayed the highest photocatalytic activity, exhibiting a nearly complete reduction of Cr(VI) to Cr(III) within only 20 min. The excellent photocatalytic activities of heterogeneous Au-Bi2WO6 hollow microspheres can be induced by the increased light harvesting efficiency (due to light multi-scattering effect of hollow architecture), high separation of photogenerated electron-hole pairs caused by electron trapping effect and surface plasmon resonance (SPR) effect of Au nanoparticles.

Complexes of copper(I) with aromatic compounds facilitate selective electrophilic aromatic substitution

ABSTRACTWe report on the selective formation of ortho-nitrophenol, ortho-nitrotoluene (1-Methyl-2-nitrobenzene) and ortho-phenolsulfonic acid (2-Hydroxybenzenesulfonic acid) through reaction of the Cu(I)-aromatic ring complex of phenol or toluene. In the case of nitration of phenol, the reaction could be formulated as:The copper(I)-aromatic ring complex is formed in situ from Cu(II) and metallic copper in deaerated aqueous solutions containing the aromatic compounds. Phenol or toluene shift the comproportionation reaction of copper(0) and copper(II) towards the formation of Cu(I):The stability constant of Cu(I)-phenol in aqueous solutions was reported previously as 900 ± 100 M−1. The surprisingly stable d⟶π* Cu(I)-phenol complex causes distortion of the ring structure which facilitates selective substitutions. Similar results are reported for sulfonation of phenol (in aqueous solutions) and for nitration and sulfonation of toluene in a two phase process.

In-situ construction of direct Z-scheme Bi2WO6/g-C3N4 composites with remarkably promoted solar-driven photocatalytic activity

As metal-free visible light-driven semiconductor, graphitic carbon nitride (g-C3N4) has attracted increasing attention owing to its excellent properties. However, the photocatalytic performance of the bare g-C3N4 has been significantly hampered by its inherent drawbacks. Herein, to further boost the photocatalytic performance of g-C3N4, Bi2WO6 was in-situ successfully anchored onto g-C3N4 via a routine hydrothermal method. The as-prepared Bi2WO6/g-C3N4 heterojuctions display highly efficient photocatalytic activity toward decay of rhodamine B (RhB) and phenol aqueous solution under simulated sunlight irradiation. When the molar ratio of Bi:g-C3N4 was 4%, the Bi2WO6/g-C3N4 sample prepared exhibits highest photocatalytic activity. The highest photocatalytic performance of the 4% sample can be definitely attributed to the highest separation rate of the photogenerated electron-hole pairs, supported by the results of surface photovoltage spectroscopy (SPS). The cycling experiments show that Bi2WO6/g-C3N4 composites display excellent stability. The photoinduced electron-hole separation and transfer of the Bi2WO6/g-C3N4 composites obey a direct Z-scheme mechanism based on the matched energy band, the analysis of main active species and the enhanced separation rate of photogenerated electron-hole pairs.

Synthesis of tin and molybdenum co-doped TiO2 nanotube arrays for the photoelectrocatalytic oxidation of phenol in aqueous solution

Tin and molybdenum co-doped titanium dioxide nanotube arrays was prepared by single-step anodization of titanium plate (Sn-Mo-TiO2 NTs/Ti electrode). The Sn-Mo-TiO2 NTs/Ti electrode was characterized by field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The length and inner diameter of nanotubes increased with the increase of anodization voltage. The influences of factors, such as anodization voltage, anodization time, concentrations of Sn4+ and Mo6+, and calcination temperature, on the preparation of the electrode were studied by chronoamperometry under simulated sunlight irradiation. The optical performance of Sn-Mo-TiO2 NTs/Ti electrode was tested by UV–vis spectrophotometer. Sn-Mo-TiO2 NTs/Ti electrode exhibited high adsorption in the visible region relative to pure titanium dioxide nanotube arrays. Additionally, the chronoamperometry test results highlighted that the doping of tin and molybdenum could enhance the photoelectrochemical performance of the electrode. The electrode exhibited good photoelectrocatalytic oxidation capacity on phenol at 0.5 V constant bias voltage. Applied bias voltage enhanced the photocatalytic efficiency of nanotube arrays via promoting the separation of photogenerated electron-hole pairs. A possible degradation process for phenol was proposed.

On developing ferrisilicate catalysts supported on silicon carbide (SiC) foam catalysts for continuous catalytic wet peroxide oxidation (CWPO) reactions

Fe supported catalysts show great promise for enabling practical environmental catalysis, exemplified by the catalytic wet peroxide oxidation (CWPO) process. In order to mitigate the Fe leaching issue, a strategy of assembling zeolitic coatings with intraframework Fe (ferrisilicate) on SiC foams was developed, showing a good stability in CWPO and a low Fe leaching of 2.0 mg l−1. Direct hydrothermal synthesis of ferrisilicate/SiC foam composites was systematically studied, showing that their characteristics depend on the growth time, pH value and iron concentration of the growth solution. Selected ferrisilicate/SiC foam composite was evaluated using the continuous CWPO of phenolic aqueous solution at 60 °C. The open-cell size of SiC foam was varied between 800 and 2,000 μm and showed insignificant effect on the hydrodynamics of the flow process at 1 ml min −1, but the process efficiency in terms of phenol and total-organic-carbon (TOC) conversions was favored by a high surface-to-volume ratio (i.e. small open-cell sizes). Ferrisilicate/SiC foam catalysts (average open-cell size = 800 μm) showed good stability in the model system with the stable conversions of phenol (97%), H2O2 (84%) and TOC (37%) over 24 h time-on-stream.

Photocatalytic degradation of organic pollutants in wastewater with g-C3N4/sulfite system under visible light irradiation

To develop low cost and high efficient sulfate radical (SO4−) based advanced oxidation processes (AOPs) for rapid remediation of contaminated waters is of great interest. In this study, a green and novel SO4− based AOPs, in situ visible light activation of sulfite by graphitic carbon nitride (g-C3N4), for the degradation of organic pollutants is reported. The g-C3N4+HSO3− + Vis system could achieve remarkably enhanced degradation of organic pollutants such as organic dyes and phenol in aqueous solution. The excellent reusability of the metal free catalyst was also observed during ten successive cycles. The efficiency of the system was dependent on the reaction conditions, which first increased and then decreased with the increase of HSO3− concentration and initial solution pH. The addition of HCO3− stimulated the pollutant degradation, but other water matrix components such as Cl− and humic acid showed nearly no influence on the reaction. The mechanism investigations suggested that sulfite is oxidized in the system to sulfite radicals, which then react with dioxygen and superoxide radicals to form SO5− radicals and HSO5− respectively. SO5− radicals can be also reduced by sulfite or photoelectron to HSO5−. SO4− radicals were then produced from HSO5− reduction by photoelectron, and contributed to dye degradation in the system together with superoxide radicals. This study provides a novel new approach for efficient degradation of organic degradation via sulfite activation.

Valorization of Biomass Hydrolysis Waste: Activated Carbon from Humins as Exceptional Sorbent for Wastewater Treatment

Humins, waste from biomass hydrolysis, are the main factor limiting the utilization efficiency of biomass carbon. In the present study, waste humins were employed for activated carbon production though KOH activation in a temperature range of 500–900 °C. The structure and properties of the activated carbons were studied, and a honeycomb-like macropore structure was observed. High activation temperature was demonstrated to be capable of promoting the formation of activated carbon with high surface area, high pore volume and high adsorption capacity. The activated carbon obtained by carbonization at 800 °C (KOH800) was selected as sorbent to adsorb methylene blue (MB) and phenol in aqueous solution, and the adsorption process can be explained by pseudo-second-order kinetic model. The adsorption behavior complies with Langmuir isotherm model and exhibits superior adsorption capacity of 1195 and 218 mg/g for MB and phenol, respectively. The impacts of surface area, acidic active sites and pore structures were also investigated, and it was found that the adsorption of approximately 44.0% MB and 39.7% phenol were contributed by the pores with apertures from 1.7 nm to 300 nm.

Preparation of Cu-ZSM-5 catalysts by chemical vapour deposition for catalytic wet peroxide oxidation of phenol in a fixed bed reactor.

Cu-ZSM-5 catalysts were prepared by chemical vapour deposition for catalytic wet peroxide oxidation (CWPO) of phenol in a fixed bed reactor. Firstly, Cu-ZSM-5 catalysts with Cu loading of 0.5, 2, and 6 wt% were prepared and characterized by X-ray diffraction (XRD), N2 adsorption–desorption and X-ray photoelectron spectra (XPS). The characterization results demonstrated that CuO was uniformly dispersed on ZSM-5 with slight effect on the structure properties of the support. Then, several variables, such as the copper loading, reaction temperature, catalyst bed height and feed flow rate were investigated in the CWPO of phenol in aqueous solution at high concentration (1000 ppm). Compared with the catalyst prepared by the impregnation method, the Cu-ZSM-5 prepared by chemical vapour deposition has a better capacity of further oxidizing the intermediate organic products into carbon dioxide and water with less metal loading. Based on the Cu-ZSM-5 catalyst with Cu loading of 6 wt%, complete removal of phenol and a high TOC reduction (around 70%) have been achieved at the temperature of 80°C feed flow rate of 2 ml min−1 and catalyst bed height of 3 cm. Moreover, this catalyst maintained high catalytic activity after three runs with high phenol conversion (94%) under this optimum operating condition. Finally, the reaction mechanism was studied based on the intermediates detected by high-performance liquid chromatography (HPLC).

Fabrication and photoactivity of ionic liquid-TiO2 structures for efficient visible-light-induced photocatalytic decomposition of organic pollutants in aqueous phase.

To investigate the effect of the ionic liquid (IL) chain length on the surface properties and photoactivity of TiO2, a series of TiO2 microspheres have been synthesized via a solvothermal method assisted by 1-methyl-3-octadecylimidazolium chloride ([ODMIM][Cl]) and 1-methyl-3-tetradecylimidazolium chloride ([TDMIM][Cl]). All as-prepared samples were characterized by X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), diffuse reflectance spectroscopy (DRS), scanning transmission microscopy (STEM) and the Brunauer–Emmett–Teller (BET) surface area method, whereas the photocatalytic activity was evaluated by the degradation of phenol in aqueous solution under visible light irradiation (λ > 420 nm). The highest photoefficiency (four times higher than pristine TiO2) was observed for the TiO2 sample obtained in the presence of [TDMIM][Cl] for a IL to TiO2 precursor molar ratio of 1:3. It was revealed that interactions between the ions of the ionic liquid and the surface of the growing titanium dioxide spheres results in a red-shift of absorption edge for the IL–TiO2 semiconductors. In this regard, the direct increase of the photoactivity of IL–TiO2 in comparison to pristine TiO2 was observed. The active species trapping experiments indicated that O2•− is the main active species, created at the surface of the IL–TiO2 material under visible-light illumination, and is responsible for the effective phenol degradation.

Enhanced photocatalytic degradation of phenol over Ag3PO4-BiOCl1−xBrx composites

In this paper, a series of Ag3PO4-BiOCl1−xBrx composites with adjustable band gap has been fabricated by using a facile two-step synthetic method. The photocatalytic activity of Ag3PO4-BiOCl1−xBrx was evaluated by photocatalytic decomposition of phenol aqueous solution under simulated solar light irradiation. The result shows that Ag3PO4-BiOCl0.75Br0.25 (1:5) composite possesses the best photocatalytic activity among all the as-prepared samples. The photocatalytic activity of Ag3PO4-BiOCl can be enhanced mainly owing to the strong light absorption ability by loading Ag3PO4 on the surface of BiOCl, while the photocatalytic activities of Ag3PO4-BiOCl1−xBrx (x = 0.25, 0.5, 0.75 and 1) composites could be enhanced by restraining the recombination of photo-generated electron-hole pairs. The enhanced solar-light photocatalytic activities of Ag3PO4-BiOCl1−xBrx composites could be ascribed to the adjustable energy band structure, which facilitates the separation of photoinduced carriers. In addition, superoxide radicals (O2−), holes (h+) and OH are considered to dominate the photocatalytic degration process. Moreover, a possible mechanism of deep understanding on the base of experimental results was proposed.