Comparative analysis of ZnO-catalyzed photo-oxidation of p-chlorophenols

Abstract

KEYWORDSThe present study compares for the first time the photocatalytic oxidation of three p-chlorophenols (4-chlorophenol, 2,4-dichlorophenol and 2,4,6-trichlorophenol) in irradiated ZnO suspensions. The effect of operating parameters such as catalyst and concentration doses on the decomposition rate of these p-chlorinated compounds has been studied and optimized. The optimal feed concentration for each of the chlorinated phenolic compounds is 50 mg/L whereas the ZnO doses decreased as the number of chlorine substituent is increased. Kinetic profiles on the decomposition of chlorophenols over ZnO agreed with the pseudo-zeroeth order rate scheme with rate constants following the order 2,4,6-trichlorophenol > 2,4dichlorophenol > 4-chlorophenol. The validity of the pseudo zero order model could be linked to the initial doses of the chlorophenols used vis-à-vis the catalyst. The study revealed stable intermediates of photocatalytic chlorophenol transformation by high performance liquid chromatography (HPLC) and gas chromatography-mass spectrometry (GC-MS) technique. A combined mechanism is given to account for the photocatalytic destruction of the chlorophenols. OxidationMechanism Chlorophenol ZnO Photodegradation Intermediates

Influence of Synthesis Conditions on the Structural, Optical, and Electrophysical Properties of TiO-=SUB=-2-=/SUB=-/Cu-=SUB=-x-=/SUB=-O Nanocomposites

“…5 shows the results of the study by this method. In the EPR spectrum of the initial TiO 2 samples, the signal from dangling carbon bonds (C•) dominates, Land g-factor is g = 2.0027 [20]. The carbon presence in the composition of the samples is probably due to the ethylene glycol presence in the electrolyte and is also confirmed by elemental analysis data.…”

“…3, a. Diffuse scattering spectra of light make it possible to determine the value of the optical width of forbidden band E g of semiconductor nanomaterials from the so-called intrinsic absorption edge. Despite the fact that there is no exact theory of multiple scattering, the theory of diffuse reflection and transmission of optically opaque samples is widely usedthe so-called Kubelka and Munk two-component theory (see, for example, [19,20]). This theory assumes that the reflected radiation is isotropic, i.e.…”

“…To determine the absorption coefficient α(λ) in a wide range of wavelengths it is necessary to obtain the dependence S(λ). However, in practice, when determining the forbidden band width, it is always considered that the wavelength range in which the linear approximation of the dependence α(λ) is performed, is narrow enough (in our case -20 nm) to consider S as constant in this range [19,20].…”

Influence of Synthesis Conditions on the Structural, Optical, and Electrophysical Properties of TiO-=SUB=-2-=/SUB=-/Cu-=SUB=-x-=/SUB=-O Nanocomposites

“…5 shows the results of the study by this method. In the EPR spectrum of the initial TiO 2 samples, the signal from dangling carbon bonds (C•) dominates, Land g-factor is g = 2.0027 [20]. The carbon presence in the composition of the samples is probably due to the ethylene glycol presence in the electrolyte and is also confirmed by elemental analysis data.…”

“…3, a. Diffuse scattering spectra of light make it possible to determine the value of the optical width of forbidden band E g of semiconductor nanomaterials from the so-called intrinsic absorption edge. Despite the fact that there is no exact theory of multiple scattering, the theory of diffuse reflection and transmission of optically opaque samples is widely usedthe so-called Kubelka and Munk two-component theory (see, for example, [19,20]). This theory assumes that the reflected radiation is isotropic, i.e.…”

“…To determine the absorption coefficient α(λ) in a wide range of wavelengths it is necessary to obtain the dependence S(λ). However, in practice, when determining the forbidden band width, it is always considered that the wavelength range in which the linear approximation of the dependence α(λ) is performed, is narrow enough (in our case -20 nm) to consider S as constant in this range [19,20].…”

The Effect of Light Exposure on the Degradation of Latent Fingerprints on Brass Surfaces: The Use of Silver Electroless Deposition as a Visualization Technique

“…The metal squares to which a print had been applied were suspended at the top of the beaker which was covered with a large watch glass and heated to 65°C (the boiling point of cyanoacrylate). The potassium chloride was present to add humidity – at 65°C; it is known to give a relative humidity of 79.9 ± 0.5% . For some CFM‐enhanced prints, staining with a 0.004‐M solution of Basic Yellow (BY40) dye (supplied by Crime Scene Investigation Products.…”

Влияние условий синтеза на структурные, оптические и электрофизические свойства нанокомпозитов TiO-=SUB=-2-=/SUB=-/Cu-=SUB=-x-=/SUB=-O

“…Для определения коэффициента поглощения α(λ) в широком диапазоне длин волн необходимо получить зависимость S(λ). Однако на практике при определении ширины запрещенной зоны всегда считают, что диапазон длин волн, в котором производится линейная аппроксимация зависимости α(λ), достаточно узок (в нашем случае -20 nm), чтобы можно было считать S константой в этом диапазоне [19,20].…”

Influence of Synthesis Conditions on the Structural, Optical, and Electrophysical Properties of TiO-=SUB=-2-=/SUB=-/Cu-=SUB=-x-=/SUB=-O Nanocomposites

“…5 shows the results of the study by this method. In the EPR spectrum of the initial TiO 2 samples, the signal from dangling carbon bonds (C•) dominates, Land g-factor is g = 2.0027 [20]. The carbon presence in the composition of the samples is probably due to the ethylene glycol presence in the electrolyte and is also confirmed by elemental analysis data.…”

“…3, a. Diffuse scattering spectra of light make it possible to determine the value of the optical width of forbidden band E g of semiconductor nanomaterials from the so-called intrinsic absorption edge. Despite the fact that there is no exact theory of multiple scattering, the theory of diffuse reflection and transmission of optically opaque samples is widely usedthe so-called Kubelka and Munk two-component theory (see, for example, [19,20]). This theory assumes that the reflected radiation is isotropic, i.e.…”

“…To determine the absorption coefficient α(λ) in a wide range of wavelengths it is necessary to obtain the dependence S(λ). However, in practice, when determining the forbidden band width, it is always considered that the wavelength range in which the linear approximation of the dependence α(λ) is performed, is narrow enough (in our case -20 nm) to consider S as constant in this range [19,20].…”

The Effect of Light Exposure on the Degradation of Latent Fingerprints on Brass Surfaces: The Use of Silver Electroless Deposition as a Visualization Technique

“…The metal squares to which a print had been applied were suspended at the top of the beaker which was covered with a large watch glass and heated to 65°C (the boiling point of cyanoacrylate). The potassium chloride was present to add humidity – at 65°C; it is known to give a relative humidity of 79.9 ± 0.5% . For some CFM‐enhanced prints, staining with a 0.004‐M solution of Basic Yellow (BY40) dye (supplied by Crime Scene Investigation Products.…”

Влияние условий синтеза на структурные, оптические и электрофизические свойства нанокомпозитов TiO-=SUB=-2-=/SUB=-/Cu-=SUB=-x-=/SUB=-O

“…Для определения коэффициента поглощения α(λ) в широком диапазоне длин волн необходимо получить зависимость S(λ). Однако на практике при определении ширины запрещенной зоны всегда считают, что диапазон длин волн, в котором производится линейная аппроксимация зависимости α(λ), достаточно узок (в нашем случае -20 nm), чтобы можно было считать S константой в этом диапазоне [19,20].…”

Influence of Synthesis Conditions on the Structural, Optical, and Electrophysical Properties of TiO-=SUB=-2-=/SUB=-/Cu-=SUB=-x-=/SUB=-O Nanocomposites

“…5 shows the results of the study by this method. In the EPR spectrum of the initial TiO 2 samples, the signal from dangling carbon bonds (C•) dominates, Land g-factor is g = 2.0027 [20]. The carbon presence in the composition of the samples is probably due to the ethylene glycol presence in the electrolyte and is also confirmed by elemental analysis data.…”

“…3, a. Diffuse scattering spectra of light make it possible to determine the value of the optical width of forbidden band E g of semiconductor nanomaterials from the so-called intrinsic absorption edge. Despite the fact that there is no exact theory of multiple scattering, the theory of diffuse reflection and transmission of optically opaque samples is widely usedthe so-called Kubelka and Munk two-component theory (see, for example, [19,20]). This theory assumes that the reflected radiation is isotropic, i.e.…”

“…To determine the absorption coefficient α(λ) in a wide range of wavelengths it is necessary to obtain the dependence S(λ). However, in practice, when determining the forbidden band width, it is always considered that the wavelength range in which the linear approximation of the dependence α(λ) is performed, is narrow enough (in our case -20 nm) to consider S as constant in this range [19,20].…”

The Effect of Light Exposure on the Degradation of Latent Fingerprints on Brass Surfaces: The Use of Silver Electroless Deposition as a Visualization Technique

“…The metal squares to which a print had been applied were suspended at the top of the beaker which was covered with a large watch glass and heated to 65°C (the boiling point of cyanoacrylate). The potassium chloride was present to add humidity – at 65°C; it is known to give a relative humidity of 79.9 ± 0.5% . For some CFM‐enhanced prints, staining with a 0.004‐M solution of Basic Yellow (BY40) dye (supplied by Crime Scene Investigation Products.…”

Влияние условий синтеза на структурные, оптические и электрофизические свойства нанокомпозитов TiO-=SUB=-2-=/SUB=-/Cu-=SUB=-x-=/SUB=-O

“…Для определения коэффициента поглощения α(λ) в широком диапазоне длин волн необходимо получить зависимость S(λ). Однако на практике при определении ширины запрещенной зоны всегда считают, что диапазон длин волн, в котором производится линейная аппроксимация зависимости α(λ), достаточно узок (в нашем случае -20 nm), чтобы можно было считать S константой в этом диапазоне [19,20].…”