Langmuir-Hinshelwood Kinetic Model Research Articles

The effect of Fe3+ based visible light receptive interfacial phases on the photocatalytic activity of ZnO for the removal of 2,4-dichlorophenoxy acetic acid in natural sunlight exposure

Abstract The use of inexpensive semiconducting materials and abundant natural sunlight can deliver the sustainable as well as cost-effective cleaning of contaminated water. In the current effort, the low photocatalytic activity of ZnO in sunlight exposure has been addressed by the slow deposition and after calcination, the deposition pattern of Fe 3+ ions was investigated. The appearance of distinct multiple absorption edges in the optical spectra verified the composite nature of the synthesized materials whereas the absorption edge at ∼2.5 eV indicated the formation of visible light responsive structures other than Fe 2 O 3 . The additional reflections, besides the characteristic reflections of ZnO and Fe 2 O 3 , in the X-ray diffraction patterns and the appearance of discrete assortments in HRTEM analysis exposed the formation of surface ZnFe 2 O 4 in the interfacial region between the ZnO and Fe 2 O 3 . The X-ray photoelectron analysis revealed the minor transitions in the oxidation state, more pronounced at higher Fe 3+ loadings, during the synthetic route. The electrochemical characterization revealed the p-type nature of the oxides of Fe 3+ whereas the flat-band potentials of the composites were assessed by Mott-Schottky analysis. As compared to pure ZnO, the composites loaded with lower concentrations (0.5% and 1%) of Fe 3+ showed substantially high activity for the removal of 2,4-dichlorophenoxy acetic acid (2,4-D) in the complete spectrum whereas 3% Fe 3+ loading exhibited optimum activity in the exposure of the visible region of natural sunlight. The higher Fe 3+ loadings revealed the detrimental effect on the photocatalytic removal process. The variations in the photocatalytic activity with the increasing Fe 3+ were discussed in correlation with electrochemical properties. The key intermediates were identified and the plausible mechanisms of the removal of 2,4-D were proposed by correlating the evidence from various experimental tools such as HPLC, IC, and TOC. The probable contribution of the reactive oxygen species (ROS) involved in the degradation process was estimated and discussed. The validity of the Langmuir-Hinshelwood kinetic model was also examined for the degradation as well as mineralization process.

Syngas production from CO2 reforming of methane over neodymium sesquioxide supported cobalt catalyst

This paper reports for the first time the catalytic dry (CO2) reforming of methane over 20 wt%Co/80 wt%Nd2O3 catalyst. The catalyst was synthesized by wet-impregnation procedure and its physicochemical properties were characterized by TGA, XRD, FESEM, EDX, FTIR, H2-TPR and TPD followed by activity testing in a fixed-bed reactor. The effects of feed ratios (CH4: CO2) ranged 0.1–1.0, reactant (CH4 and CO2) partial pressure (0–50 kPa) and temperature ranged 923–1023 K on the activity of the catalyst were investigated. The conversion of both reactants increased with the feed ratio and reaction temperature reaching maximum values of 62.7% and 82% for CH4 and CO2, respectively. The CO2 reforming of methane resulted into the formation of syngas with maximum yields of 59.91% and 62.02% for H2 and CO, respectively, leading to formation of syngas ratio of 0.97. The mechanistic proposition includes the CH4 and CO2 adsorption, activation of CH4 by methane cracking and gasification of carbon deposited on the catalyst surface. The experimental data were fitted by Langmuir Hinshelwood kinetic models. Activation energy values of 21.89 and 62.04 kJ mol−1 were obtained for the consumption of CO2 and CH4 respectively from Langmuir-Hinshelwood models. The lower values of activation energy obtained for CO2 compared to that of CH4 shows that the rate of consumption of CO2 was faster than that of CH4 leading to higher conversion of CO2.

Reaction mechanism and kinetics for hydrolytic dehydrogenation of ammonia borane on a Pt/CNT catalyst

A reaction mechanism is proposed for hydrolytic dehydrogenation of ammonia borane on a Pt/CNT catalyst. A combination of thermodynamic analysis and FTIR measurement reveals that B‐containing byproducts are mainly in the form of an NH4B(OH)4‐B(OH)3 mixture rather than NH4BO2 reported previously. The revised main reaction is , involving the B–H, B–N, and O–H bond cleavages. Isotopic experiments using D2O instead of H2O as reactant or introducing D2 into the reaction atmosphere suggest the O–H bond cleavage being in the rate‐determining step, and an unfavorable occurrence of the chemisorbed H2O dissociation (i.e., the direct O–H bond cleavage), respectively. Different reaction pathways with indirect O–H bond cleavages are analyzed, and then is suggested as the rate‐determining step. Subsequently, a Langmuir–Hinshelwood kinetic model is developed, which fits well with the experimental data. © 2016 American Institute of Chemical Engineers AIChE J, 63: 60–65, 2017

Preparation of hierarchical micro/nanostructured Bi2S3-WO3 composites for enhanced photocatalytic performance

Novel hierarchical micro/nanostructured photocatalysts composed of WO3 microspheres and needle-like Bi2S3 nanocrystals were successfully synthesized by a simple combination of hydrothermal and post-calcination method. The as-obtained Bi2S3-WO3 composites was applied for photocatalytic removal of Rhedamine B (RhB) organic pollution in water under visible light irradiation. The morphology and structure of the as-obtained samples were characterized by XRD, SEM, TEM, N2 adsorption–desorption techniques, UV–vis DRS, XPS and PL spectra. It was found that 70%-Bi2S3-WO3 has the highest photocatalytic activity and more than 90% (over 3 times than pure WO3) of the RhB solution were degraded in 100 min. The degradation kinetics data were found to be consistent with the Langmuir-Hinshelwood (L-H) kinetics model. Furthermore, the kinetic rate of 70%-Bi2S3-WO3 composites is 9 times more than the pure WO3. The modification of WO3 by deposited Bi2S3 could improve charge separation and transfer with the increase of special surface area and higher utilization of visible light. These favorable factors lead to significantly enhanced visible photocatalytic performance; and Bi2S3-WO3 composites had an excellent stability in cycling experiments. At last, a tentative mechanism of enhanced photocatalytic activity for Bi2S3-WO3 composite was discussed according to the calculation of the energy band position.

The visible light-driven photodegradation of dimethyl sulfide on S-doped TiO2: Characterization, kinetics, and reaction pathways

Sulfur-doped TiO2 prepared by a sol-gel method to degrade dimethyl sulfide (DMS) under visible light irradiation was investigated. The degradation reactions of DMS were performed under various operation conditions. The results indicate that S-doped TiO2 photocatalysts are mainly nano-size with an anatase-phase structure. Relative humidity and inlet DMS concentration significantly influence the DMS conversion and mineralization. Langmuir-Hinshelwood kinetic models have been used in the analysis of the experimental data obtained. The main oxidation products of DMS photodegradation are SO2, CO2, DMDS, DMSO, DMSO2, CO, and MSA. Two possible mechanisms have been developed for photodegradation of DMS in a dry and a humid environment.

Template synthesis of ZnIn2S4 for enhanced photocatalytic H2 evolution using triethanolamine as electron donor

A series of ZIS-x [ZIS and x represent the ZnIn2S4 and the addition amount of TEOA (mmol) in the synthesis process, respectively] were synthesized via a hydrothermal method using triethanolamine (TEOA) as a template. The as-synthesized photocatalysts were characterized by X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX), scanning electron microscopy (SEM), Ultraviolet-visible (UV–vis) diffuse reflection spectroscopy and Brunauer–Emmett–Teller (BET) surface area measurement. The effects of TEOA on the crystal structures, morphologies and optical properties of ZIS-x products were investigated. The photocatalytic activity was tested in the reaction of H2 evolution from aqueous TEOA solution under visible light irradiation (λ≥420nm). It was found that the activity of ZIS-x synthesized in TEOA solution was higher than that of ZIS-0 synthesized in pure water. This can be attributed to the facts that ZIS-x is composed of single ZnIn2S4 and more TEOA can be adsorbed on ZIS-x surface, which improves the separation of an electron-hole pair. When TEOA was used as an electron donor, it can enhance notably photocatalytic H2 evolution with its simultaneous degradation. The effect of TEOA concentration on the H2 evolution rate is consistent with a Langmuir–Hinshelwood kinetic model. The optimal amount of Pt loaded on the photocatalyst is 0.50wt%, and the optimal pH for photocatalytic H2 evolution is 13. On the optimal condition, the rate of hydrogen evolution over ZIS-2.0 is 2 times as high as that of ZIS-0 during 20h irradiation.

Immobilized TiO2-reduced graphene oxide nanocomposites on optical fibers as high performance photocatalysts for degradation of pharmaceuticals

A series of TiO2-reduced graphene oxide (rGO) coated side-glowing optical fibers (SOFs) were synthesized by polymer assisted hydrothermal deposition method (PAHD), and characterized by crystallographic and spectroscopic methods. Fourier transform infrared spectroscopy showed that the mixed graphene dioxide (GO) was reduced during PAHD coating of TiO2-GO nanocomposites. X-ray diffraction patterns revealed TiO2 presented as a mixture phase of anatase, rutile and brookite in the TiO2-rGO nanocomposites. UV–vis absorption spectra of TiO2-rGO nanocomposites indicated that mixing rGO into TiO2 particles could reduce band gap energy, thereby enhancing utilization efficiency of visible light. Photocatalytic performance of the synthesized nanocomposites was measured by the degradation of three pharmaceuticals under UV and visible light irradiation, including carbamazepine, ibuprofen, and sulfamethoxazole. TiO2-rGO nanocomposites exhibited significantly higher photocatalytic activities as compared to pure TiO2, and were strongly affected by the amount of rGO in the catalysts. While photocatalysis with 2.7% rGO achieved 54% degradation of carbamazepine, 81% of ibuprofen, and 92% of sulfamethoxazole after 180min UV irradiation, the mineralization rates of the pharmaceuticals were similar between 52% and 59%. The photocatalytic oxidation of pharmaceuticals by the prepared nanocomposites followed the Langmuir–Hinshelwood kinetic model. There was an obvious positive correlation between degradation rate constant and quantum flux for both UV and visible light, with correlation coefficient of 0.991. In addition, long-term photoactivity testing of TiO2-rGO coated SOFs demonstrated the durability of the immobilized TiO2-rGO nanocomposites on optical fibers for water treatment.

Mechanism pathway and kinetics of p-cresol photocatalytic degradation over titania nanorods under UV–visible irradiation

Titania nanorods (TNRs) in pure anatase phase were synthesized by a hydrothermal technique and calcined at 450°C. The material was characterized by X-ray diffraction (XRD), N2 adsorption, transmission electron microscopy (TEM), UV-DR spectroscopy, and X-ray photoelectron spectroscopy (XPS). The photocatalytic degradation of p-cresol was carried out under UV–vis irradiation. The photodecomposition of p-cresol could be expressed by pseudo-first order in Langmuir–Hinshelwood kinetic model. The rate constant obtained of the TNRs catalyst was higher than that over P25 catalyst. Intermediates produced during the reaction were 4-methylcatechol, 4-hydroxybenzoic acid, 4-hydroxybenzyl alcohol and 4-hydroxybenzaldehyde. All intermediates are indicated to be less hazardous compared to p-cresol. More than 96% TOC mineralization was achieved during the degradation time. In addition, the reaction mechanism and pathway has been proposed and the rate constants for each elementary reaction were evaluated.

Removal of 2-ClBP from soil–water system using activated carbon supported nanoscale zerovalent iron

We explored the feasibility and removal mechanism of removing 2-chlorobiphenyl (2-ClBP) from soil–water system using granular activated carbon (GAC) impregnated with nanoscale zerovalent iron (reactive activated carbon or RAC). The RAC samples were successfully synthesized by the liquid precipitation method. The mesoporous GAC based RAC with low iron content (1.32%) exhibited higher 2-ClBP removal efficiency (54.6%) in the water phase. The result of Langmuir–Hinshelwood kinetic model implied that the different molecular structures between 2-ClBP and trichloroethylene (TCE) resulted in more difference in dechlorination reaction rates on RAC than adsorption capacities. Compared to removing 2-ClBP in the water phase, RAC removed the 2-ClBP more slowly in the soil phase due to the significant external mass transfer resistance. However, in the soil phase, a better removal capacity of RAC was observed than its base GAC because the chemical dechlorination played a more important role in total removal process for 2-ClBP. This important result verified the effectiveness of RAC for removing 2-ClBP in the soil phase. Although reducing the total RAC removal rate of 2-ClBP, soil organic matter (SOM), especially the soft carbon, also served as an electron transfer medium to promote the dechlorination of 2-ClBP in the long term.

Synthesis, characterization, and photocatalytic activity of porous La–N–co-doped TiO2 nanotubes for gaseous chlorobenzene oxidation

The photocatalytic oxidation of gaseous chlorobenzene (CB) by the 365nm-induced photocatalyst La/N–TiO2, synthesized via a sol–gel and hydrothermal method, was evaluated. Response surface methodology (RSM) was used to model and optimize the conditions for synthesis of the photocatalyst. The optimal photocatalyst was 1.2La/0.5N–TiO2 (0.5) and the effects of La/N on crystalline structure, particle morphology, surface element content, and other structural characteristics were investigated by XRD (X-ray diffraction), TEM (Transmission Electron Microscopy), FTIR (Fourier transform infrared spectroscopy), UV–vis (Ultraviolet–visible spectroscopy), and BET (Brunauer Emmett Teller). Greater surface area and smaller particle size were produced with the co-doped TiO2 nanotubes than with reference TiO2. The removal of CB was effective when performed using the synthesized photocatalyst, though it was less efficient at higher initial CB concentrations. Various modified Langmuir-Hinshelwood kinetic models involving the adsorption of chlorobenzene and water on different active sites were evaluated. Fitting results suggested that competitive adsorption caused by water molecules could not be neglected, especially for environments with high relative humidity. The reaction intermediates found after GC–MS (Gas chromatography–mass spectrometry) analysis indicated that most were soluble, low-toxicity, or both. The results demonstrated that the prepared photocatalyst had high activity for VOC (volatile organic compounds) conversion and may be used as a pretreatment prior to biopurification.

Stabilization of Pickering emulsion with surface-modified titanium dioxide for enhanced photocatalytic degradation of Direct Red 80

Surface modification of titanium dioxide (TiO2) was carried out with salicylic acid (SA) to generate an efficient Pickering emulsion (PE)-based photocatalytic system. The PE was stabilized with 0.5 and 1.0mgmL−1 of TiO2 and SA-TiO2 by using cyclohexane and a synthetic aqueous Direct Red 80 (DR 80) solution (0.4:1) as the oil and water phases, respectively. The photocatalytic activity of solution-dispersed TiO2 was compared with that of the PE-based photocatalytic system for DR 80 degradation. In almost all PE-based photocatalytic systems, 100% color removal of DR 80 was observed within 15–60min, compared to 76% and 100% color removal, achieved after 120min, using 0.5 and 1.0mgmL−1 solution-dispersed TiO2, respectively. The estimated reaction rates of the PE-based photocatalytic system, as calculated using the Langmuir–Hinshelwood kinetics model, were almost double to those obtained for solution-dispersed TiO2. However, the addition of a free oil phase adversely affected the photocatalytic activity, and the lowest DR 80 degradation percentage was observed using 0.5 or 1.0mgmL−1 TiO2. The results demonstrated that a functional PE was successfully stabilized with SA-TiO2, and enhanced photocatalytic degradation of the azo dye was achieved in an effective and novel way.

Production of CO-rich hydrogen from methane dry reforming over lanthania-supported cobalt catalyst: Kinetic and mechanistic studies

In this study, the production of CO-rich hydrogen from methane dry reforming over lanthania-supported Co catalyst was investigated. The Co/La2O3 catalyst was synthesized via wet-impregnation method and characterized using instrument techniques such as TGA, FTIR, XRD, FESEM-EDX and N2 adsorption-desorption analysis. The catalytic activity of the Co/La2O3 catalyst tested in a fixed bed stainless steel reactor yielded highest CH4 and CO2 conversion of 50% and 60% respectively at 1023 K and feed ratio of 1.0. The methane dry reforming reaction gave highest H2 and CO yield of 45% and 58% respectively. Furthermore, kinetics and mechanistic behavior of the La2O3 supported Co catalyst in methane dry reforming reaction was investigated as a function of temperature and partial pressure of reactants (CH4 and CO2). The experimental data obtained from the kinetics measurements were fitted using the empirical power-law rate expression, as well as six different Langmuir–Hinshelwood kinetics models. The six models were then statistically and thermodynamically discriminated. Consequently, the Langmuir–Hinshelwood kinetics model (dual-site associative adsorption of both CH4 and CO2 with bimolecular surface reaction) was adjudged the best representative model. Activation energy values of 96.44 and 98.11 kJ mol−1 were obtained for the CH4 consumptions from the power-law and Langmuir–Hinshelwood models, respectively. A lower activation energy of circa 72 kJ mol−1 obtained for CO2 consumption showed that the rate of consumption of CO2 consumption was speedier than CH4.

Flow controlled fabrication of N doped ZnO thin films and estimation of their performance for sunlight photocatalytic decontamination of water

To address the technological aspect of photocatalyst removal after decontamination, radio frequency (RF) magnetron sputtered nitrogen (N) doped zinc oxide (ZnO) nanoparticles films on glass substrates were fabricated by varying the flow rate of nitrogen. The optical characterization of N-doped ZnO films revealed the shifting of the spectral response to the visible region. The shift of (002) reflections of the films as compared to pure ZnO, in X-ray diffraction (XRD) analysis confirmed the insertion of N in the lattice. The cross-section measurements by FESEM revealed the uniform thickness of ∼70nm of each film. Compared to pure ZnO, the as-fabricated N-doped films showed significantly enhanced degradation/mineralization of 2-chlorophenol, 4-chlorophenol and 2,4-dichlorophenoxyacetic acid in natural sunlight exposure. The applicability of Langmuir-Hinshelwood kinetic model was also evaluated. The measurement of Zn2+ ions in the solution during the course of exposure revealed significantly lower magnitude of photocorrosion for the fabricated films compared to pure ZnO. The consistent activity of the films in three successive cycles for the removal of 2-CP established their consistent performance without any loss of activity.

Photocatalytic degradation of p-nitrotoluene (PNT) using TiO2-modified silver-exchanged NaY zeolite: kinetic study and identification of mineralization pathway

Nitroaromatic compounds are suspected hormone disrupter and considered as toxic priority pollutants. In the present study, different amounts of titanium dioxide impregnated zeolite Y (Si/Al ratio 5.5) was modified by silver metal ion exchange and its photocatalytic activity was studied for the mineralization of p-nitrotoluene (PNT) in aqueous medium. The synthesized catalysts were characterized by XRD, SEM, inductively coupled plasma, diffuse reflectance spectroscopy, and N2 adsorption techniques. The analysis of degradation intermediates and mineralization pathways were established using high performance liquid chromatography and mass spectroscopy. The mineralization of PNT into final products: CO2, H2O, NO3-, and NH4+ was assessed by chemical oxygen demand (COD) analysis. Langmuir–Hinshelwood kinetic model was proposed for the degradation and the reaction rate constant values were determined from the experimental data using the model. TiO2 loading was optimized from the percentage degradation, rate constant, and mineralization values. COD study reveals up to ~60% mineralization in 240 min of irradiation to 75 mg L−1 PNT with TiO2/AgY2 catalyst.

Optical, Structural and Morphological Properties of Photocatalytic ZnO Thin Films Deposited by Pray Pyrolysis Technique

Photocatalytic ZnO thin films have been deposited onto glass substrate by spray pyrolysis technique. The sprayed solution consists of 0.1 M of zinc acetate dihydrate dissolved in double distilled water and sprays onto ultrasonically cleaned glass substrates maintained at 350°C, through an air-atomizing nozzle. The X-ray diffraction (XRD), scanning electron microscopy (SEM), EDX and UV-VIS spectrophotometer were applied to describe the structural, morphological, compositional and optical properties of ZnO catalyst. XRD analysis confirms that the films were found to be single phase hexagonal wurtzite structure. The SEM micrograph of the films is shown highly uniform, crack free and found to be fiber like structures. The optical transmittance spectra of the ZnO thin films were found to be transparent to visible light and the average optical transmittance was greater than 85%. The direct optical band gap energy values of the films shift towards the lower energy as a consequence of the thermal annealing. The Urbach energy of the films was found to increase with annealing temperature. The refractive index of the films was calculated and the refractive index dispersion curve of the films obeys the single oscillator model. The values of oscillatory energy Eo, dispersion energy Ed, and static dielectric constant es for the ZnO thin films were determined. The films were evaluated for their ability to degrade methylene blue. The Langmuir-Hinshelwood kinetic model was used to interpret quantitatively the observed kinetic experimental result. The photocatalytic activity of ZnO thin films was enhanced by annealing temperature.

Copper oxide supported on graphene for phodegradation of rhodamine B

In recent years, dyes are one of the major sources of the water contamination that lead to environmental problems. For instance, Rhodamine B (RhB) which was extensively used as a colorant in textile industries is toxic and carcinogenic. Among many techniques, photocatalytic degradation become the promising one to remove those dyes from industrial wastewater. Recently, graphene has shown outstanding performance in this application due to its intrinsic electron delocalisation which promotes electron transport between composite photocatalyst and pollutant molecules. While, copper oxide (CuO) is well-known has a lower bandgap energies compared to other semiconductors. Therefore, in this study, copper oxide supported on graphene (CuO/G) was prepared and its photocatalytic activity was tested on degradation of RhB. The catalysts were characterized by X-Ray Diffraction (XRD) and Fourier Transform Infrared (FTIR) Spectroscopy. The results showed that the interaction between copper and graphene support could enhance the photocatalytic activity. The 5 wt% CuO/G was found to give the highest degradation (95%) of 10 mg L-1 of RhB solution at pH 7 using 1 g L-1 catalyst after 4 hours under visible light irradiation. The photodegradation followed the pseudo first-order Langmuir-Hinshelwood kinetic model. This study demonstrated that the CuO/G has a potential to be used in photocatalytic degradation of various organic pollutants.

Photocatalytic decolorization of methylene blue using zinc oxide supported on mesoporous silica nanoparticles

Various dyes that are used in textile, paper, cosmetics and plastics industries may produce harmful effects on the health of living organisms and the environment if not treated properly before being discharged into water bodies. Among many techniques, photocatalytic process is one of the promising treatment for these dyes. Zinc oxide (ZnO) is well-known comparable with TiO2 due to its unique properties and numerous advantages. While, mesoporous silica nanoparticles (MSN) is an excellent solid support for heterogeneous catalysts due to its high surface area, thermal and mechanical stability, highly uniform pore distribution, tunable pore size, and unique hosting properties. Therefore, in this study, ZnO/MSN (ZM) catalysts were prepared and its physicochemical properties was characterized by X-Ray Diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FTIR). The catalyst was tested on the photodecolorization of methylene blue (MB) dye. The results showed that the interaction between ZnO and MSN support could enhanced the photocatalytic activity. The 0.5 g L-1 of 5ZM was found to give the highest degradation (80 %) of 10 mg L-1 of MB solution at pH 7 after 3 h under UV light irradiation. The photodecolorization followed the pseudo first-order Langmuir-Hinshelwood kinetic model. This study demonstrated that the prepared 5ZM has a potential to be used in photocatalytic degradation of various dyes as well as organic pollutants.

Effect of cold plasma pre-treatment on photocatalytic activity of 3D fabric loaded with nano-photocatalysts: Response surface methodology

In this study, the physico-chemical effects occasioned by the cold plasma discharge (CPD) on the photo-decolorization of Reactive Orange 16 (RO16) by 3D fabrics (spacer fabrics) loaded with ZnO:TiO2 nano-photocatalysts (nphs) were optimized via response surface methodology (RSM). CPD was employed to improve the surface characteristics of the spacer fabrics for nphs loading. Surface morphology and color variation were studied utilizing scanning electron microscopy (SEM) and CIE-Lab system, respectively. The effect of CPD on the wetting ability of the spacer fabrics was examined using dynamic adsorption measurement (DAM). Also, X-ray fluorescence (XRF) was utilized to investigate the durability of the nphs on the spacer fabrics. All the experiments were implemented in a Box–Behnken design (BBD) with three independent variables (CPD treatment time, dye concentration and irradiation time) in order to optimize the decolorization of RO16. The anticipated values of the decolorization efficiency were found to be in excellent agreement with the experimental values (R2=0.9996, Adjusted R2=0.9992). The kinetic analysis demonstrated that the photocatalytic decolorization followed the Langmuir–Hinshelwood kinetic model. In conclusion, this heterogeneous photocatalytic process is capable of decolorizing and mineralizing azoic reactive dye in textile wastewater. Moreover, the results confirmed that RSM based on the BBD was a suitable method to optimize the operating conditions of RO16 degradation.

Photocatalytic parameters and kinetic study for degradation of dichlorophenol-indophenol (DCPIP) dye using highly active mesoporous TiO2 nanoparticles

Highly active mesoporous TiO2 of about 6nm crystal size and 280.7m2/g specific surface areas has been successfully synthesized via controlled hydrolysis of titanium butoxide at acidic medium. It was characterized by means of XRD (X-ray diffraction), SEM (scanning electron microscopy), TEM (transmission electron microscopy), FT-IR (Fourier transform infrared spectroscopy), TGA (thermogravimetric analysis), DSC (differential scanning calorimetry) and BET (Brunauer–Emmett–Teller) surface area. The degradation of dichlorophenol-indophenol (DCPIP) under ultraviolet (UV) light was studied to evaluate the photocatalytic activity of samples. The effects of different parameters and kinetics were investigated. Accordingly, a complete degradation of DCPIP dye was achieved by applying the optimal operational conditions of 1g/L of catalyst, 10mg/L of DCPIP, pH of 3 and the temperature at 25±3°C after 3min under UV irradiation. Meanwhile, the Langmuir–Hinshelwood kinetic model described the variations in pure photocatalytic branch in consistent with a first order power law model. The results proved that the prepared TiO2 nanoparticle has a photocatalytic activity significantly better than Degussa P-25.

Photocatalytic activity of zinc oxide (ZnO) synthesized through different methods

Derivatives of phenol are considered as part of the persistent organic pollutants with endocrine effects persist in the environment and resist to bio-degradation which is difficult to be degraded. The objective of this study was to investigate the solar-photocatalytic degradation of phenol with synthesized ZnO through precipitation (ZnO-P) and hydrothermal (ZnO-H) method as photocatalysts. ZnO-P is capable to achieve total degradation of phenol up to 30 mg/l of initial phenol concentration and 20 mg/l for ZnO-H within 6 h of reaction time. The degradation of ZnO-P and ZnO-H is favored in acidic condition (pH 3) and followed by natural condition (pH 6). The results obtained fitted well with Langmuir–Hinshelwood kinetic model. The apparent rate constant is proportional to the efficiency of the photocatalysts. Chemical oxygen demand results attested the complete degradation of phenol concentration and possibility for mineralization.