Aqueous 4-chlorophenol Research Articles

High-dispersive FeS2on graphene oxide for effective degradation of 4-chlorophenol

High-dispersive FeS2particles on graphene oxide (FeS2@GO) was prepared by a one-pot hydrothermal method for efficient removal and mineralization of aqueous 4-chlorophenol (4-CP) under slightly acidic or alkaline conditions.

Coupling the dechlorination of aqueous 4-CP with the mechanochemical destruction of solid PCNB using Fe–Ni–SiO2

A novel combined process was developed for mechanochemical destruction of pentachloronitrobenzene (PCNB) in solid waste, coupled with the dechlorination of aqueous 4-chlorophenol (4-CP) using the nonhazardous residue from the solid-phase destruction step. Using the mixture of iron powder, nickel powder and quartz sand as the additives in a planetary ball mill under the room temperature, the mechanochemical reaction was induced and a complete destruction of PCNB was realized. The resulting solid residue was characterized by various measures including X-ray diffraction (XRD), Raman spectroscopy and scanning electron microscopy/energy dispersive X-ray spectrometry (SEM/EDS), which suggested that main components were carbon, chloride besides excess additives. Such nonhazardous residue was then used to effectively dechlorinate aqueous 4-CP. The residue achieving over 93% dechlorination rate was selected as the optimized content. With a series of verification experiments, a possible dechlorination mechanism was proposed, involving the reactions occurred on three interfaces (i.e. Fe/Ni, Fe/C and Fe/C/Ni).

Effect of Gold Particle Size and Deposition Method on the Photodegradation of 4-Chlorophenol by Au/TiO2

The photoactivity of TiO2 P25 modified by surface-deposition of gold nanoparticles was investigated trough the photocatalytic degradation of aqueous 4-Chlorophenol (4-CP). The Au/TiO2 materials were prepared by three methods: photodeposition, deposition–precipitation (D–P) and colloidal deposition. Each preparation yields to different particle size, distribution and properties of gold nanoparticles. However, the photoactivity of these systems depends mainly on the gold particle size. All the materials fit well to a pseudo first order rate model and a relationship between the kinetic rate and the resulting particle sizes was found, which shows the importance of the nanoparticle size in the photoactivity of the TiO2 modified by gold. The optimal load was found to be 0.5 wt% Au/TiO2 for the material prepared by D–P, since this material increased the photoactivity degradation of commercial TiO2 in 80%.

A diffusion-reaction kinetic model for the removal of aqueous 4-chlorophenol with immobilized peroxidase

A diffusion-reaction kinetic model is presented for the kinetic analysis of the removal process of phenolic compounds using hydrogen peroxide and immobilized peroxidase. The good results obtained in the fitting of the experimental data to the model confirm its validity, in the experimental range considered, as well as the one of the extended version of the Dunford mechanism proposed in a previous paper.The phenomenon of enzyme deactivation and/or sequestration by the precipitated olygomers/polymers, which has been widely described in the literature, is here modeled as the growth of a polymeric film over the external surface and inside the pores of the catalytic particles that contain the enzyme, thus determining the appearance of diffusional limitations and an increasing loss of activity. The deactivation phenomena, interpreted and modeled in terms of the effectiveness factor, are included in the kinetic model.To confirm the validity of the model, several series of experiments were carried out in a discontinuous tank reactor. Some of these experimental series were used to obtain the values of the kinetic parameters by numerical calculation and using an error minimization algorithm. Since the model reproduces the behavior of the system for the series of experiments not used for the determination of the parameters, it can be affirmed that the model is suitable for the kinetic analysis of the system under study.

CWPO of 4-CP and industrial wastewater with Al–Fe pillared clays

Catalysts based on pillared clays with Al-Fe have been synthesised from a commercial bentonite and tested for catalytic wet peroxide oxidation (CWPO) of aqueous 4-Chlorophenol (4-CP) solution and industrial wastewater from cosmetics manufacture. The effect of the synthesis procedure, the iron load and reaction temperature on the catalytic activity was studied using 4-CP as target compound. A lower temperature in the preparation of the pillaring solution, as well as a higher Fe load, gave rise to a higher catalytic activity, but also a higher leaching of the active phase. The best catalyst, in terms of catalytic activity, was also tested for treating cosmetic wastewater by CWPO. Experiments were carried out at 90 degrees C and atmospheric pressure and the influence of Fe load, catalyst concentration and H(2)O(2)/COD ratio (between 0.5 and 2 times the stoichiometric ratio) were analysed. Higher values of these parameters favour COD reduction. The Fe leaching in all cases was lower than 1.2 mg/L, indicating that these catalysts have a high stability under these experimental conditions.

Degradation Performance of 4-Chlorophenol as a Typical Organic Pollutant by a Pulsed High Voltage Discharge System

Degradation of aqueous 4-chlorophenol (4-CP) with air bubbling was experimentally investigated in a multipoint-plate pulsed high voltage reactor. Several important parameters, including electrode distance, liquid conductivity, gas flow rate, and initial concentration, were investigated for 4-CP removal and energy efficiency. After discharge for 90 min, more than 95% of 4-CP was removed at the electrode distance of 1.5 cm, liquid conductivity of 1.06 μS/cm, gas flow rate of 0.75 m3/h, and initial concentration of 60 ppm with specific energy density of 450 J/mL. The energy efficiency of 4-CP was about 2.15 × 10-9 mol/J, and the mineralization of total organic carbon (TOC) reached to 55.8%. Hydrogen peroxide, ozone, nitrite, and nitrate were observed in the liquid phase. 4-chlorocatechol, hydroquinone, 5-chloro-3-nitropyrocatechol, chloride ion, formic, and acetic and oxalic acids were the main byproducts during 4-CP degradation. The degradation pathways were deduced including hydroxylation, N atom attack, a...

Photonic decomposition of ultrafine, rutile phasedTiO2 powder in aqueous 4-chlorophenol solutions

The redox properties of a homogeneously precipitatedTiO2 rutile powder with aBET surface area of ∼200 m2 g−1, consisting of acicular primary particles, were characterized using a photocatalyticreaction in aqueous 4-chlorophenol, Cu- and Pb-EDTA solutions underultraviolet irradiation. Results were compared to those of commercial P25TiO2 powder with spherical primary particles as well as those of home-made anataseTiO2 powderwith ∼200 m2 g−1 BET surface area. Here, the anatase powder also includes mainlythe primary particles very similar to the acicular shapes of the rutileTiO2 powder. The rutile powder showed the fastest decomposition rate and the largestamount of product in the photoredox, compared with the anatase or P25 powder,while the anatase powder unexpectedly showed the slowest rate and the smallestamount in the same experiments regardless of having almost the same surface area.The excellent photoredox abilities of this rutile powder appear to be due to aspecific powder preparation method, for example a homogeneous precipitationleading to direct crystallization from the solution, regardless of their crystallinestructures, even when the powders have similar particle shapes and surface areas.

Photocatalytic properties of rutile TiO2 acicular particles in aqueous 4-chlorophenol solution

The photocatalytic properties of TiO2 rutile powder with acicular primary particles were characterized using the photocatalytic reaction in aqueous 4-chlorophenol (4CP) solution and compared to those of TiO2 anatase with almost the same surface area of approximately 200 m2g. The characteristics of commercial P-25 TiO2 powders with the surface area of approximately 55 m2/g were also compared to rutile and anatase powders. The rutile phase powders surpassed both anatase and P-25 ones in decomposition rate for 4CP. The excellent photo-oxidative ability of the powder was dependent on the specific powder-preparation method, which led to a direct crystallization in aqueous solution, regardless of the crystalline structures of the powders.

Photoredox properties of ultrafine rutile TiO 2 acicular powder in aqueous 4-chlorophenol, Cu–EDTA and Pb–EDTA solutions

The redox properties of a homogeneously precipitated TiO 2 rutile powder with a BET surface area of ∼200 m 2/g, consisting of acicular primary particles, were characterized using a photocatalytic reaction in aqueous 4-chlorophenol, Cu–EDTA and Pb–EDTA solutions under ultraviolet irradiation. Results were compared to those of commercial P25 TiO 2 powder with spherical primary particles as well as those of home-made anatase TiO 2 powder with ∼200 m 2/g BET surface area. Here, the anatase powder also includes mainly the primary particles very similar to the acicular shapes of the rutile TiO 2 powder. The rutile powder showed the fastest decomposition rate and the largest amount of product in the photoredox, compared with the anatase or P25 powder, while the anatase powder unexpectedly showed the slowest rate and the smallest amount in the same experiments regardless of having almost the same surface area. The excellent photoredox abilities of this rutile powder appear to be due to a specific powder preparation method, for example, a homogeneous precipitation leading to direct crystallization from the solution, regardless of their crystalline structures, even when the powders have the similar particle shape and surface area.

Study on Photocatalytic Reaction Using Acicular TiO2 Rutile Powder

The redox properties of a homogeneously-precipitated <TEX>$TiO_2$</TEX> rutile powder with a BET surface area of ~<TEX>$200 m^2$</TEX>/g, consisting of an acicular primary particle, were characterized using photocatalytic reaction in aqueous 4-chlorophenol, Cu-EDTA and Pb-EDTA solutions under ultraviolet irradiation, compared to those of commercial P-25 X<TEX>$200 m_2$</TEX> powder with a spherical primary particle as well as home-made anatase <TEX>$TiO_2$</TEX> powder with ~<TEX>$200 m^2$</TEX>/g BET surface area. Here, the anatase powder also includes mainly the primary particles very similar to the acicular shapes of the rutile <TEX>$TiO_2$</TEX> powder. The rutile powder showed the fastest decomposition rate and the largest amount in the photoredor, compared with the anatase or P-25 powder, while the anatase powder unexpectedly showed the slowest rate and the smallest amount in the same experiments regardless of almost the same surface area. From results, the excellent photoredox abilities of this rutile powder appears to be due to specific powder preparation method, like a homogeneous precipitation leading to direct crystallization from the solution, regardless of their crystalline structures even when having the similar particle shape and surface area.

Photocatalytic degradation of aqueous 4-chlorophenol by silica-immobilized polyoxometalates.

The degradation of 4-chlorophenol with near-UV light by silica-immobilized polyoxometalate (POM-in-SiO2) catalysts has been studied. The silica-immobilized Na6W7O24 (SW7), H4W1032 (SW10), H3PW12O40 (SPW12), and H6P2W18O62 (SP2W18) were prepared by means of the sol-gel hydrothermal technique through the hydrolysis of tetraethoxysilane in aqueous solution of the corresponding polyoxometalate, respectively. The degradation of 4-chlorophenol was monitored by measuring Cl- and CO2 concentrations and analyzing reaction intermediates by GC/MS analysis. During irradiation, 4-chlorophenol first dechlorinated to form hydroquinone and p-benzoquinone, and then these intermediates further mineralized to form CO2 and H2O. The degree to which 4-chlorophenol was mineralized by photocatalytic oxidation was investigated. Results indicate less than 15% for SW7 but nearly complete mineralization for SW10 after 60 min of photoirradiation. The present studies suggest that POM-in-SiO2 catalysts may be a novel type of photocatalyts for the purification of the environmentally chlorophenol-contaminated water.

Redox abilities of rutile TiO2 ultrafine powder in aqueous solutions

Redox abilities of rutile TiO2 powder with an acicular primary particle, having about a 200 m2/g BET surface area obtained by a homogeneous precipitation process in aqueous TiOCl2 solution at 50°C for 4 hrs, were investigated using a photocatalytic reaction in aqueous 4-chlorophenol, Cu- and Pb-EDTA solutions. Its abilities were then compared with those of commercial P-25 powder, together with investigating those of anatase TiO2 powder obtained from the aqueous TiOCl2 solution, having a similar surface area and primary particle shape as those of the rutile powder. The powder was more effective than the anatase or P-25 powder, while the anatase powder unexpectedly showed the slowest decomposition rate and the smallest amount in the same experiments in spite of similar particle shapes and surface area. From the results, it is found that the excellent photo redox abilities of the powder is likely to be caused by the specific powder preparation method regardless of crystalline structures even when having similar particle shapes and values in the surface area. Also, many OH− attached to the surface of the TiO2 particle appeared to interfere with the adsorption of decomposing target materials to the TiO2 surface in the solution during the photocatalytic reaction, resulting in a delay in the reaction.

An Ultrasonically Facilitated Boron-Doped Diamond Voltammetric Sensor for Analysis of the Priority Pollutant 4-Chlorophenol

Electroanalysis of the ‘priority pollutant’, 4-chlorophenol, is largely unreported in the scientific literature, due mainly to the electrode passivation observed from oxidative by-products. Work is presented which details the combination of high-intensity ultrasound with a mechanically and chemically robust boron-doped diamond electrode allowing successful development of an aqueous 4-chlorophenol voltammetric sensor. The surface regeneration abilities of power ultrasound, through cavitational erosion of electrodeposited 4-chlorophenol by-products, facilitates a reproducible, insonated limiting-current oxidative signal in dilute acid conditions, with increased mass-transport offering enhanced sensitivity. A lower limit of detection of 1 μM and a linear range of 1–300 μM are reported; the technique being analytically useful over a concentration range where aquatic 4-chlorophenol pollution is known to occur. The use of power ultrasound during the electrooxidation of 4-chlorophenol at boron-doped diamond has also been shown to be advantageous in the electrochemical degradation of the substance, potentially offering further waste-water clean-up applications of this dual technology.

The role of mass transfer in solution photocatalysis at a supported titanium dioxide surface

The kinetics of Cl- production from the UV-photocatalysed degradation of aqueous 4-chlorophenol (CP), by a thin TiO2 (Degussa P25) film, in both aerated and oxygenated solutions, have been determined by the channel flow method with electrochemical detection. The experimental approach allows surface kinetics and mass transport effects to be readily resolved. For typical irradiation intensities of (0.7–2.0)×1017 quanta cm-2 s-1, the results obtained with dilute CP solutions (⩽0.5 mM), in particular, clearly demonstrate that there is a range of practically important conditions where mass transport plays a role in controlling the kinetics of the process. When these effects are considered, the surface kinetics are consistent with the Langmuir–Hinshelwood model.

Study of the aqueous photochemistry of 4-fluorophenol, 4-bromophenol and 4-iodophenol by steady state and nanosecond laser flash photolysis

The mechanisms of the aqueous photoreactions of 4-fluorophenol, 4-bromophenol and 4-iodophenol have been studied by steady state photolysis and by nanosecond laser flash photolysis. The same photoproducts are obtained as were found in the photolysis of aqueous 4-chlorophenol although the photoreaction quantum yields vary considerably across the series of compounds. As for 4-chlorophenol the carbene 4-oxocyclohexa-2,5-dienylidene is formed from the halogenophenol by loss of HX and this species reacts efficiently with oxygen to form 1,4-benzoquinone O-oxide which subsequently yields 1,4-benzoquinone. Consideration of the reaction quantum yields together with the photophysical properties of the four halogenophenols suggests that the carbene is derived from the first excited singlet state rather than a triplet excited state.

A nanosecond laser flash photolysis study of aqueous 4-chlorophenol

The mechanism of the aqueous photoreaction of 4-chlorophenol was studied by nanosecond laser flash photolysis. The carbene 4-oxocyclohexa-2,5-dienylidene is formed from the chlorophenol by loss of HCl. This species reacts efficiently with oxygen to form 1,4-benzoquinone-O-oxide which subsequently yields 1,4-benzoquinone. The carbene also undergoes reaction with water and coupling reactions to produce 1,4-hydroquinone and polyhydroxybiphenyls respectively.