Phenol In Aqueous Media Research Articles

Adsorption Performance and Evaluation of Activated Carbon from Coconut Shell for the Removal of Chlorinated Phenols in Aqueous Medium

In this study, the removal of 2,4-dichlorophenol (2,4-DCP) from aqueous solutions was performed using coconut shell activated carbon prepared by a two-stage self-generated atmosphere method. Coconut shell was first semi-carbonized at 300 °C for an hour followed by chemical activation with zinc chloride (ZnCl2) as activating agent at 500 °C for 2 h. The effect of impregnation ratio on the physical and chemical properties of activated carbons (ACs) was studied. The morphology and surface chemistry of the prepared carbons were characterized using Scanning Electron Microscope (SEM) and Fourier Transform Infrared spectroscopy (FTIR) respectively. The percentage of yield for the prepared AC was found to be in the range of 26.40-38.82 %. AC registered the highest adsorption capacity and was used in subsequent batch adsorption studies consisting of parameters such as initial concentration, adsorbent dosage and solution pH. The maximum surface area of the best produced AC was recorded as 1482 m2 g-1. The adsorption capacity was found to increase in proportional to the initial concentration and adsorbent dosage, while acidic solution pH was more favourable for the adsorption of 2,4-DCP by the prepared AC. The equilibrium time for the adsorption of 20 mg L-1 of 2,4-DCP on 0.5 g of AC was achieved in 180 min. Adsorption isotherms such as Langmuir, Freundlich and Temkin isotherm models were employed to examine the experimental isotherms while the reaction kinetic data was analysed using pseudo-first-order, pseudo-second-order and intraparticle diffusion model. The 2,4-DCP adsorption results fitted best in the Freundlich isotherm as indicated by the high correlation coefficient value (R2 > 0.9949) while the adsorption kinetic fitted to the pseudo second-order model (R2 > 0.9621).

Electro-organic synthesis of 2-(4,5-diphenyl-1H-imidazol-2-yl)phenol in Aqueous medium for organic monomer based Supercapacitor electrode

An efficient cost-effective and eco-friendly electro-organic synthesis of 2-(4,5-diphenyl-1H-imidazol-2-yl)phenol (DIP) in aqueous medium and its application as an electrode material for supercapacitor are reported here. The as-synthesized derivative was characterized by various spectral and analytical techniques. The optical and physical properties were analyzed by PL studies and by XRD, SEM, BET, TG- DTA and DSC techniques. The electrochemical studies of the electroactive material, DIP were carried out using Cyclic Voltammetry (CV), Galvanostatic Charge – Discharge analysis (GCD) and Electrochemical Impedence Spectroscopy (EIS). DFT calculation of DIP was also performed to evaluate the bandgap energy theoretically. DIP as a monomer exhibited a good capacitive behavior with a specific capacitance of 325F/g at the scan rate of 5mV/s. The results revealed that DIP can be potentially used as a promising electrode material for high performance supercapacitor applications.

Degradation of phenol by heterogeneous Fenton process in an impinging streams reactor with catalyst bed

AbstractIn the present study, the decomposition of phenol in aqueous solutions was investigated in both impinging system and batch reactor. In impinging reactor, catalyst particles with an average diameter of 1.5 × 103μm were confined in a wired cage located in the middle of the reaction vessel. The catalyst was synthesized by impregnation of iron on clinoptilolite zeolite as the support. The mean residence time of the solution in this reactor was 3 s. Therefore, the number of impingements required for the complete degradation of phenol was assessed to be 8 times. The advantage of performing the impinging reactor over a conventional reaction system has been demonstrated in this study. In the impinging reactor at 55 °C, time needed for degradation of phenol in aqueous media was measured to be as low as 24 s; however, phenol degraded completely in 10 min in batch stirred reactor. The optimum operating conditions for the impinging reactor were found as: catalyst containing 5 wt% iron, pH = 3.25, weight ratio of H2O2/phenol = 20, temperature = 55 °C. © 2017 Curtin University of Technology and John Wiley & Sons, Ltd.

Comparison of Pd-UiO-66 and Pd-UiO-66-NH2 catalysts performance for phenol hydrogenation in aqueous medium

UiO-66, a kind of Metal-organic framework materials (MOFs) was used as a support for nano-palladium particles (i.e., Pd-UiO-66) which was used in the catalytic hydrogenation of phenol in aqueous media in this work. The performance of Pd-UiO-66 was compared with Pd-UiO-66-NH2, in which the UiO-66 support had been modified through the introduction of NH2 groups. Pd-UiO-66 and Pd-UiO-66-NH2 were characterized by BET, XRD, XPS and TEM. The results indicated that the Pd particles are embedded in Pd-UiO-66 and fixed on Pd-UiO-66-NH2. With NH2 groups, the crystalline structure of UiO-66-NH2 is somewhat damaged and the interaction between Zr and Pd in Pd-UiO-66-NH2 is rather weaker than in Pd-UiO-66. Pd-UiO-66 has high activity for aqueous phenol hydrogenation, with 100% conversion of phenol being achieved within 2h at 120°C, which is much higher than with the Pd-UiO-66-NH2 catalyst. Pd-UiO-66 has higher selectivity for cyclohexanol, and Pd-UiO-66-NH2 has higher selectivity for cyclohexanone under the same conditions. The study of the chemical kinetics portion revealed that the hydrogenation reaction rates with the Pd-UiO-66 catalyst are over 10 times higher than those with Pd-UiO-66-NH2 under the same conditions. The phenol hydrogenation catalyzed by Pd-UiO-66 is more sensitive to the reaction temperature than when catalyzed by the Pd-UiO-66-NH2 catalyst. Thus, it has been shown that modifications of an MOF support for a catalyst can result in structural changes that lead to different catalytic activities and selectivities in aqueous phenol hydrogenation.

Degradation and mineralization of phenol in aqueous medium by heterogeneous monopersulfate activation on nanostructured cobalt based-perovskite catalysts ACoO3 (A = La, Ba, Sr and Ce): Characterization, kinetics and mechanism study

This study reports the heterogeneous catalytic degradation and mineralization of phenol in aqueous solution by means of potassium monopersulfate (PMS or Oxone) process mediated by cobalt perovskite-based catalysts (P-Co). Four nanostructured perovskites oxides with formula ACoO3 (A=Ba, Ce, La, Sr) were synthesized as heterogeneous catalysts by the citrate sol gel method and characterized by means of nitrogen isotherm adsorption (BET), Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectrometry (EDX), x-ray photoelectron spectroscopy (XPS), X-ray Diffraction (XRD), transmission electron microscopy (TEM) and Fourier transform infrared (FT-IR) techniques. All the examined samples had perovskite structure. The influences of PMS dosage, catalyst loading, initial target compound concentration and solution pH on the removal efficiency were studied. The activity showed an order of SrCoO3>LaCoO3>BaCoO3>CeCoO3. LaCoO3 and SrCoO3 catalysts exhibit the better performance in terms of reaction rate and stability for the phenol degradation and mineralization by advanced oxidation technology based on sulfate radicals. Catalyst stability was assessed by means of consecutive reuse cycles. No significant loss of activity was noticed after five consecutive cycles. The role of reactive oxygen species produced in the system, mainly SO4− and OH, in the overall oxidation of phenol was determined by using suitable scavenger compounds. Under optimal conditions (10−4M PMS, natural pH, 0.3 gL−1 catalyst loading) complete removal of 20mgL−1 phenol was achieved in 90min. In terms of organic carbon removal, about 81% mineralization yield was reached in the optimal conditions for 6h heterogeneous P-Co/PMS system, suggesting an effective process for phenol mineralization. Four organics intermediates were observed and three of them were identified as catechol, hydroquinone and benzoquinone. A reaction sequence was therefore proposed for the degradation according to the detected products. Subsequent attack of these intermediates by SO4− radicals led to the formation of short chain acids such as, acetic, formic and oxalic acid which were identified by ion-exclusion chromatography.

Promotion effect of ZnO on the photocatalytic activity of coupled Al2O3-Nd2O3-ZnO composites prepared by the sol − gel method in the degradation of phenol

The photocatalytic activity of coupled Al2O3-Nd2O3-ZnO composites (Al-Nd-Zn-x; where x=0.8, 1.2, 2.0, 5.0, and 15.0wt% of ZnO) prepared by the sol-gel method was studied in the photo-degradation of phenol in aqueous medium. The Al-Nd-Zn-x composites were characterized by physical adsorption of N2, XRD, TEM, SEM, Raman, UV–vis, XPS and fluorescence spectroscopies. Al-Nd-Zn-x composites with ZnO concentration in the range 0.8–2.0wt% showed high efficiency to photo-convert phenol and mineralize dissolved organic carbon to CO2with UV light irradiation. The Al-Nd-Zn-1.2 composite was the material with the highest efficacy to photodegradate phenol in aqueous medium photo-converting about 90.0% of phenol and mineralizing 75.0% of dissolved organic carbon after 3h of UV light. It is proposed that the intimate contact between Al2O3, Nd2O3 and ZnO phases of the coupled Al-Nd-Zn-x composites are beneficial characteristics for the separation of the photogenerated charge carriers in order to decrease the recombination rate of photogenerated electron-hole pairs. These Al-Nd-Zn-x composites are characterized by a high BET specific surface area and a bimodal pore size distribution which are excellent characteristics for the adsorption and diffusion of phenol molecules to the active sites resulting in enhanced photocatalytic properties for the degradation of phenol in aqueous medium.

Shock-induced cavitation as a way of accelerating phenol oxidation in aqueous media

Shock-induced cavitation phenomena, resulting from the propagation of the trail of shock-waves generated upon the impact of a solid piston on a liquid surface, was used as an innovative way of intensifying the oxidation of phenol in aqueous media. The amount of energy communicated by the impact was found to be proportional to the impact height, and was directly related to the maximal pressure attained, i.e. in the order of several tens of bars. This peak was followed by a rarefaction period that results in the origination of several cavitation phenomena, which continued upon piston rebound and further shock-wave generation and propagation. The multi-frequency nature of shock-induced cavitation, capable of exciting a wide range of frequencies between 1kHz and 100kHz, was confirmed by means of wavelet analysis. Under shock-induced cavitation conditions, phenol degradation was found to be possible even in the absence of any oxidizing agent. High extents of mineralization, i.e. 45.3 and 56.2% TOC elimination, 50mg/L solution, neutral pH, were obtained in the presence of H2O2 (aprox. 10% vol.), pointing to an acceleration of the oxidation reaction based in a faster and more efficient creation of radical species.

Wettability Control on Chitosan-Wrapped Carbon Nanotube Surface Through Simple Octanal-treatment: Selective Removing Phenol from Water

Chitosan-carbon nanotube membrane (Chit-CNTs) and octanal-modified Chit-CNTs (ocChit-CNT) membranes were obtained by chitosan-wrapping of individual carbon nanotube molecules, by self-assembly of chitosan shell-CNT core units, and by surface modification using octanal. Coexistence of diverse nano-pores (with BET pore size of about 2.0-5.3 nm and BET surface area of about 65.3-86.7 m2/g) and micro-pores (with porosity of average 10.9-12.2%) created between three-dimensionally interconnected Chit-CNT units within Chit-CNTs were observable in SEM images of Chit-CNT and ocChit-CNT membranes. As an application, they exhibit high selective affinity for phenol in aqueous medium. The sorption capacity (SC) (weight of phenol picked up by a given weight of sorbent) after draining was about 6 g/g and the sorption efficiency (SE) (weight of phenol picked up by a given weight of sorbent in water system) was >98%. Chit-CNT and ocChit-CNT membranes as a sorbent were reusable after centrifugation or washing with organic solvent such as acetone.

Efficient photocatalytic degradation of phenol in aqueous solution by SnO2:Sb nanoparticles

Photodegradation of phenol in the presence of tin dioxide (SnO2) nanoparticles under UV light irradiation is known to be an effective photocatalytic process. However, phenol degradation under solar light is less effective due to the large band gap of SnO2. In this study antimony (Sb) doped tin dioxide (SnO2) nanoparticles were prepared at a low temperature (80°C) by a sol–gel method and studied for its photocatalytic activity with phenol as a test contaminant. The catalytic degradation of phenol in aqueous media was studied using high performance liquid chromatography and total organic carbon measurements. The change in the concentration of phenol affects the pH of the solution due to the by-products formed during the photo-oxidation of phenol. The photoactivity of SnO2:Sb was found to be a maximum for 0.6wt.% Sb doped SnO2 nanoparticles with 10mgL−1 phenol in water. Within 2h of photodegradation, more than 95% of phenol could be removed under solar light irradiation.

Combination of Mn oxidation states improves the photocatalytic degradation of phenol with ZnAl LDH materials without a source of O2 in the reaction system

Mn-doped Zn/Al layered double hydroxides (LDH) materials were synthesized by the co-precipitation method. X-ray diffraction (XRD) analysis confirmed the polytype structure of LDH materials obtained as well as the successful incorporation of Mn into the structure. Atomic absorption spectroscopy (AAS) and energy dispersive X-ray spectroscopy (EDS) studies showed a well dispersion of Mn and a good correlation between the nominal and experimental composition. Scanning electron microscopy (SEM) revealed the formation of grains close to 1μm length. Energy band gap (Eg) of the solids determined by UV–vis diffuse reflectance spectroscopy (DRS) showed high photoresponse in the ultraviolet (UV) region, which was increased with Mn incorporation into the LDH structure. The LDH materials were evaluated in the photocatalytic degradation of phenol in aqueous medium, under UV radiation with and without O2 source in the reaction system. The results showed that the O2 is not an effective electron scavenger as usually occurs in TiO2 photocatalyst. The Mn effect in the photocatalytic activity was notably marked in anaerobic condition however in aerobic or anaerobic conditions the presence of Mn increases the photoactivity. The phenol mineralization reached in anaerobic conditions was 95% (1.5ppm) of the initial concentration (30ppm) and it is maintained constant after 6h of radiation while in aerobic conditions the TOC reaches only 55% (13.5ppm). The role of Mn as charges separator is discussed and a suitable mechanism is proposed. This study shows that the Mn doped-Zn/Al LDH materials could be a promising photocatalysts under anaerobic conditions for the removal of phenol from aqueous medium.

Ortho-Quinone methides: TFA-mediated generation in water and trapping with lactams and styrenes

A simple and efficient trifluoroacetic acid mediated protocol for ortho-amidomethylation of phenols in aqueous medium has been described. Developed protocol has a good substrate scope, involves mild reaction conditions, and products are obtained in good yields. The quantum chemical calculations were performed in implicit solvent (water) conditions, which helped in tracing the reaction mechanism and getting insights on the possible reaction pathway, which involves the NC bond formation and simultaneous hydrogen transfer to give final product. The applicability of this protocol for one-pot synthesis of flavans from phenols, formaldehyde and styrene has also been demonstrated.

Ruthenium Nanoparticles Stabilized in Cross‐Linked Dendrimer Matrices: Hydrogenation of Phenols in Aqueous Media

AbstractNovel catalysts consisting of ruthenium nanoparticles encapsulated in cross‐linked matrices based on the poly(propylene imine) dendrimers of the 1st and 3rd generations have been synthesized with a narrow particle size distribution (3.8 and 1.0 nm, respectively). The resulting materials showed high activity for the hydrogenation of phenols in aqueous media (specific catalytic activity reached turnover frequencies of 2975 h−1with respect to hydrogen uptake). It has been shown that the use of water as a solvent leads to a 1.5 to 50‐fold increase in the reaction rate depending upon the nature of the substrate. It has been established that unlike the traditional heterogeneous catalysts based on ruthenium, during the hydrogenation of dihydroxybenzenes, the hydrogenation rate decreases in the order: resorcinol>hydroquinone≫catechol. The maximum specific activity for resorcinol was a turnover frequency of 243150 h−1with respect to hydrogen uptake. The catalyst based on the dendrimer of the 3rd generation containing finer particles has significantly inferior activity to the catalyst based on the dendrimer of the 1st generation by virtue of steric factors, as well as the need for prereduction of the ruthenium oxide contained on the surface. These catalysts showed resistance to metal leaching and may be reused several times without loss of activity.

A novel approach for the synthesis of SnO2 nanoparticles and its application as a catalyst in the reduction and photodegradation of organic compounds

Tin oxide (SnO2) nanoparticles of sizes ∼4.5, ∼10 and ∼30nm were successfully synthesized by a simple chemical precipitation method using amino acid, glycine which acts as a complexing agent and surfactant, namely sodium dodecyl sulfate (SDS) as a stabilizing agent, at various calcination temperatures of 200, 400 and 600°C. This method resulted in the formation of spherical SnO2 nanoparticles and the size of the nanoparticles was found to be a factor of calcination temperature. The spherical SnO2 nanoparticles show a tetragonal rutile crystalline structure. A dramatic increase in band gap energy (3.8–4.21eV) was observed with a decrease in grain size (30–4.5nm) due to three dimensional quantum confinement effect shown by the synthesized SnO2 nanoparticles. SnO2 nanoparticles were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), selected area electron diffraction (SAED) and fourier transformed infrared spectroscopy (FT-IR). The optical properties were investigated using UV–visible spectroscopy. These SnO2 nanoparticles were employed as catalyst for the reduction of p-nitro phenol to p-amino phenol in aqueous medium for the first time. The synthesized SnO2 nanoparticles act as an efficient photocatalyst in the degradation of methyl violet 6B dye under direct sunlight. For the first time, methyl violet 6B dye was degraded by SnO2 nanoparticles under direct sunlight.

Photoactive polymer–nanoclay hybrid photosensitizer for oxidation of phenol in aqueous media with the visible light

The intercalation of a photoactive polymer, polyethylene glycol (PEG2000) containing covalently attached 5,10,15,20-tetrakis(4-hydroxyphenyl)porphyrin chromophores (p-THPP), in Cloisite® 30B (C30B) resulted in formation of a hybrid photosensitizer C30B/p-THPP-PEG2000. The photosensitizer acts as an efficient generator of singlet oxygen in aqueous medium on irradiation with visible light. Structural and photophysical properties of C30B/p-THPP-PEG2000 were determined using complementary physicochemical techniques: X-ray diffraction, laser scanning fluorescence confocal microscopy, and electronic absorption/emission spectroscopies. The C30B/p-THPP-PEG2000 was found to act as an efficient photosensitizer for oxidation of phenol in aqueous solution under irradiation with light at λ > 470 nm. The mechanism and the quantum yield of that process were shown to be strongly pH dependent. The pH effect on acid–base equilibria of porphyrin associated with imine N-protonation as well as the ionization of the phenol molecule were evaluated.

Porphyrin–Nanoclay Photosensitizers for Visible Light Induced Oxidation of Phenol in Aqueous Media

A new type of hybrid photosensitizer (Po–C30B) was obtained by efficient adsorption of a 5,10,15,20-tetrakis(4-carboxyphenyl)porphyrin (Po) by Cloisite 30B (C30B)—a monotallow bis(hydroxyethyl)ammonium-modified montmorillonite clay—from acidic solution in methanol. Structural and spectroscopic properties of Po-nanoclay photosensitizer were determined using X-ray diffraction, laser scanning fluorescence confocal microscopy, and electronic absorption/emission spectroscopies. Po is present not only at the surface of the nanoclay but also in the interior of the Po-C30B hybrid material. The obtained material was found to be an efficient photosensitizer for the oxidation of phenol in aqueous solution under irradiation with the visible light (λ > 470 nm). The mechanism and the quantum yield of that process were shown to be strongly pH-dependent. They were controlled by the acid–base equilibria of porphyrin associated with imine N-protonation as well as by the ionization of the phenol molecule. The quantitative i...

Hydrogenation by nanoscale ruthenium embedded into the nanopores of K-10 clay

Ruthenium(0) nanoparticles in the size range 1–4 nm were generated in the nanopores of the fine fraction of Montmorillonite K-10 clay by in situ glycol reduction of RuCl3·3H2O impregnated clay. The synthesized catalyst was characterized by Powder XRD, SEM, TEM, DRS and BET surface area determination. TEM/HRTEM/SAED images revealed the growth of well dispersed Ru(0) nanoparticles having lattice fringes with interplanar spacing 0.21 nm corresponding to the [101] plane of hexagonal close packed ruthenium. The catalytic activity of the synthesized catalyst was tested for hydrogenation of cyclohexene to cyclohexane. The clay embedded Ru nanoparticles act as an efficient and recyclable environmentally friendly catalyst in hydrogenation of dextrose and phenol in aqueous medium under mild reaction conditions. Turn over frequency (TOF) of the catalyst was also calculated considering true active sites calculated on the basis of surface statistics and a model for full shell clusters.

Synthesis of Poly(methacrylic acid)-functionalized SBA-15 and its Adsorption of Phenol in Aqueous Media

Poly(methacrylic acid)-functionalized SBA-15 silicas (denoted as P-x-PMA/SBA-15 where x is molar ratio of TSPM/(TEOS+TSPM) in percentage in the initial mixture) were synthesized by co-condensation of tetraethoxysilane and varying contents of 3-(trimethoxysilyl)propyl methacrylate in acidic medium with the block copolymer Pluronic 123 as a structure directing agent and then polymerization by methacrylic acid in the presence of ammonium persulfate as an initiator. The functionalized materials were characterized by PXRD, TEM, SEM, IR, and adsorption-desorption at 77 K. The investigation of phenol adsorption in aqueous solution on the materials showed that the poly(methacrylic acid)-functionalized mesoporous silicas possess strong adsorption ability for phenol with interaction of various kinds of hydrogen bonds. The adsorption data were fitted to Langmuir isotherms and the maximum adsorption capacity of the three functionalized materials P-5-PMA/SBA-15, P-10-PMA/SBA-15, and P-15-PMA/SBA-15 to be 129.37 mg/g, 187.97 mg/g, and 78.43 mg/g, respectively, were obtained. The effect of the pH on phenol adsorption was studied.

Modeling and optimization of photocatalytic/photoassisted-electro-Fenton like degradation of phenol using a neural network coupled with genetic algorithm

Oxidation of phenol in aqueous media using supported TiO2 nanoparticles coupled with photoelectro-Fenton-like process using Mn2+ cations as catalyst of electro-Fenton reaction was studied. The influence of the basic operational parameters such as initial pH of the solution, applied current, initial Mn2+ concentration, initial phenol concentration and kind of ultraviolet (UV) light on the oxidizing efficiency of phenol was studied. An artificial neural network (ANN) model was coupled with genetic algorithm to predict phenol oxidizing efficiency and to find an optimal condition for maximum phenol removal. The findings indicated that ANN provided reasonable predictive performance (R2=0.949).

Synthesis of a novel piperidine-functionalized poly(ethylene glycol) bridged dicationic ionic liquid and its application in one-pot synthesis of substituted 2-amino-2-chromenes and 3,4-dihydropyrano[3,2-c]chromenes in aqueous media

A novel piperidine-functionalized poly(ethylene glycol) bridged dicationic ionic liquid was prepared and identified. It was used as a recyclable catalyst for the synthesis of substituted 2-amino-2-chromenes and 3,4-dihydropyrano[3,2-c]chromenes with excellent yields through a one-pot three-component reaction of aromatic aldehydes, malononitrile, and activated phenols in aqueous media. This environmentally benign protocol was found to be fairly efficient and offer wide substrate flexibility. The basic ionic liquid could be reused several times without any obvious loss of catalytic activity.

Reusable PdO/Al2O3–Nd2O3 photocatalysts in the UV photodegradation of phenol

The UV photodegradation of phenol in aqueous medium using PdO supported on binary Al2O3–Nd2O3 oxides as photocatalysts was studied. The PdO/Al2O3–Nd2O3 photocatalysts were prepared by the sol–gel method and characterized by N2 physisorption, XRD, Raman spectroscopy and UV–vis diffuse reflectance spectroscopy. Bare PdO/γ-Al2O3 was found active for the photodegradation of phenol in aqueous medium. However, the addition of Nd2O3 to the γ-Al2O3 improves the photocatalytic activity of PdO photocatalysts as well as the decrease of dissolved organic carbon in aqueous milieu. Highest photocatalytic activity of PdO photocatalysts was observed for 10wt% of Nd2O3 added to the γ-Al2O3 increasing the activity by a factor of two with respect to that of PdO/γ-Al2O3 after six hours of irradiation. The photocatalytic activity in the degradation of phenol by using the recovered PdO/Al–Nd photocatalysts is preserved after reaction.