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1.
This paper discusses the possibility of immobilization of TiO2 nanoparticles onto recycled wool‐based nonwoven material, which can be utilized for removal of dyes from wastewater. The photocatalytic activity of TiO2 nanoparticles deposited on the nonwoven material was evaluated in the aqueous solution of direct dye C.I. Direct Blue 78 under the UV illumination. Nonwoven material modified with TiO2 nanoparticles provides complete removal of dye from the solution already after 4–6 h of UV illumination. However, photodegradation of the dye adsorbed on the nonwoven material was obtained within 24 h of UV illumination. The rate of dye adsorption and photodegradation depends on the amount of deposited TiO2 nanoparticles. The increase of initial dye concentration induced decrease in photocatalytic efficiency of immobilized TiO2 nanoparticles. The highest photodegradation rate was achieved in acidic conditions. Elevated temperatures positively affected the removal of dye from solution. Photocatalytic activity of TiO2 nanoparticles deposited on nonwoven material was preserved after three photodegradation cycles.  相似文献   

2.
Solar photocatalytic decolorization and detoxification of batik dye wastewater using titanium dioxide (TiO2) immobilized on poly‐3‐hydroxybutyrate (P(3HB)) film was studied. The effects of initial dye concentration, catalyst concentration, P(3HB) film thickness, and fabrication methods of the nanocomposite films were evaluated against methylene blue, a standard organic dye. It was observed that 0.4 g of P(3HB)‐40 wt% TiO2 removed 96% of the color under solar irradiation. P(3HB) and TiO2, mixed concurrently in chloroform followed by stirring for 24 h showed a more even distribution of the photocatalyst on the polymer surface and yielded almost 100% color removal. The photocatalytic films were able to completely decolorize real industrial batik dye wastewater in 3 h and induced a chemical oxygen demand (COD) reduction of 80%. Reusability of the 0.4 g P(3HB)‐40 wt% TiO2 film in decolorizing the batik dye wastewater was also possible as it gave a high consistent value of decolorization percentage (>80%) even after the sixth repeated usage. Recovery step of the photocatalysts was also not required in this simple treatment system. The decolorized batik dye wastewater had less/no toxic effects on mosquito larvae, Aedes aegypti, and microalgae, Scenedesmus quadricauda indicating simultaneous detoxification process along with the decolorization process.  相似文献   

3.
In this study, the decolorization, dearomatization, and mineralization efficiencies of different advanced oxidation processes (AOPs; namely O3, O3/Fe(II), O3/Fe(II)/UVA, and O3/TiO2/UVA) were investigated for the azo dye C.I. Reactive Red 194 (RR194). The effects of pH (3–11), amount of TiO2 (0.05–1 g/L), and concentration of Fe(II) (0.1–1.6 mM) were investigated for the applied methods. The decolorization and mineralization efficiencies of the photocatalytic ozonation system (O3/TiO2/UVA) were increased by decreasing the pH of the dye solution in contrast to the ozonation system (O3). Decolorization of RR194 was increased in the photocatalytic ozonation system with an increasing amount of catalyst however, a decreasing was occurred for the homogeneous catalytic system (O3/Fe(II)) when increasing the concentration of catalyst. The decolorization efficiency of the homogeneous catalytic system (O3/Fe(II)) was enhanced when combined with UVA light. In our study, the most efficient method for dearomatization and mineralization was the O3/TiO2/UVA among the applied AOPs.  相似文献   

4.
Two main routes of methods for the preparation of photocatalytic active titanium dioxide films on glass substrates were investigated: (1) the use of titanium dioxide powder and (2) the in situ generation of the catalyst via hydrolysis of titanium tetraisopropoxide (TTIP) or TiCl4. The activities of the catalyst films were evaluated by measuring the degradation of dichloroacetic acid (DCA), clofibric acid, and terbuthylazine used as model organic compounds. The concentration decrease of DCA and the concentration increase of chloride ions as the decomposition product allowed to distinguish between photocatalytic degradation of DCA and adsorption onto the TiO2 films. Furthermore, TiO2 films of the commercially available materials P25 (Degussa) and Hombikat UV100 (Sachtleben Chemie) were used to investigate whether there was a difference in the degradation pathways of terbuthylazine as a model compound. For the experiments mini flow‐through reactors were constructed. The investigated immobilization techniques were easy to handle without need of any expensive equipment. All TiO2 coatings showed good photocatalytic activities and mechanical stabilities with efficient long‐term stabilities. The best immobilization reproducibility was achieved by the spray coating technique and by the in situ method with the dipping sol‐gel process starting by TTIP. During the continuous use of the TiO2 films no TiO2 particles were found in the irradiated solutions.  相似文献   

5.
The photocatalytic activity of combustion synthesized nanocrystalline CeAlO3 was determined for the degradation of four anionic and four cationic dyes. The perovskite oxide showed high‐photocatalytic activity and a complete degradation of all the dyes was possible within 2 h. The photocatalytic activity of the compound was comparable with the activity of the commercial Degussa P‐25 TiO2 catalyst. The degradation of dyes was found to follow first order kinetics and the first order degradation rate constants were determined.  相似文献   

6.
Characterization, correlation and provenance determination of tephra samples in sedimentary sections (tephrochronological studies) are powerful tools for establishing ages of depositional events, volcanic eruptions, and tephra dispersion. Despite the large literature and the advancements in this research field, the univocal attribution of tephra deposits to specific volcanic sources remains too often elusive. In this contribution, we test the application of a machine learning technique named Support Vector Machine to attempt shedding new light upon tephra deposits related to one of the most complex and debated volcanic regions on Earth: the Pliocene-Pleistocene magmatism in Italy. The machine learning algorithm was trained using one of the most comprehensive global petrological databases (GEOROC); 17 chemical elements including major (SiO2, TiO2, Al2O3, Fe2O3T, CaO, MgO, MnO, Na2O, K2O, P2O5) and selected trace (Sr, Ba, Rb, Zr, Nb, La, Ce) elements were chosen as input parameters. We first show the ability of support vector machines in discriminating among different Pliocene-Pleistocene volcanic provinces in Italy and then apply the same methodology to determine the volcanic source of tephra samples occurring in the Caio outcrop, an Early Pleistocene sedimentary section located in Central Italy. Our results show that: 1) support vector machines can successfully resolve high-dimensional tephrochronological problems overcoming the intrinsic limitation of two- and three-dimensional discrimination diagrams; 2) support vector machines can discriminate among different volcanic provinces in complex magmatic regions; 3) in the specific case study, support vector machines indicate that the most probable source for the investigated tephra samples is the so-called Roman Magmatic Province. These results have strong geochronological and geodynamical implications suggesting new age constraints (1.4 Ma instead of 0.8 Ma) for the starting of the volcanic activity in the Roman Magmatic Province.  相似文献   

7.
Feasibility of photocatalytic dechlorination of PCB‐138 and Aroclor‐1254 using platinum loaded TiO2 (P25) in an alkaline 2‐propanol medium has been investigated. Experiments were conducted in batch mode using a Rayonet photo‐reactor under aerated and deaerated conditions with black lamps emitting around 350 nm as light source. Two forms of platinum deposition were investigated: Photochemically loaded P25 as well as addition of potassium hexachloroplatinate into the reaction medium. Partial dechlorination of PCBs was observed after 7 h of irradiation with pure TiO2 as catalyst when the reaction vessel was kept open to air. Complete dechlorination was observed after 5 h of irradiation in a deaerated environment. Enhanced photocatalytic efficiency was observed when platinum deposited P25 was used as catalyst, with the best result being obtained when aqueous potassium hexachloroplatinate was added into the reaction medium. Lower potassium hexachloroplatinate concentration (0.1 mM) yielded better performance.  相似文献   

8.
In the present study, the effects of initial COD (chemical oxygen demand), initial pH, Fe2+/H2O2 molar ratio and UV contact time on COD removal from medium density fiberboard (MDF) wastewater using photo‐assisted Fenton oxidation treatment were investigated. In order to optimize the removal efficiency, batch operations were carried out. The influence of the aforementioned parameters on COD removal efficiency was studied using response surface methodology (RSM). The optimal conditions for maximum COD removal efficiency from MDF wastewater under experimental conditions were obtained at initial COD of 4000 mg/L, Fe2+/H2O2 molar ratio of 0.11, initial solution pH of 6.5 and UV contact time of 70 min. The obtained results for maximum COD removal efficiency of 96% revealed that photo‐assisted Fenton oxidation is very effective for treating MDF wastewater.  相似文献   

9.
Response surface methodology (RSM) and artificial neural networks (ANNs) based on a multivariate central composite design (CCD) were applied to model and optimize the photocatalytic degradation of N,N‐diethyl‐m‐toluamide (DEET). The individual and interaction effects of three main operating factors (mass of TiO2, initial DEET concentration, and irradiation intensity) on process efficiency were estimated, proving their important effect on % DEET removal. Among the independent variables, TiO2 concentration displayed the highest effect on DEET degradation followed by initial DEET concentration and UV intensity. The optimization and prediction capabilities of ANNs and RSM were compared on the basis of root mean squared error, mean absolute error, absolute average deviation, and correlation coefficient values. Results proved the usefulness and capability of the experimental design strategy for successful investigation and modeling of the photocatalytic process. Moreover, the selected ANN gave better estimation capabilities throughout the range of variables than RSM. Based on the models and the related experimental conditions, the optimal values of each parameter were determined. Under optimum conditions, DEET and total organic carbon (TOC) followed pseudo‐first order kinetics. Nearly complete degradation of DEET took place within 15 min whereas high TOC removal percentages (>85%) was achieved after 90 min irradiation time.  相似文献   

10.
Pharmaceutical compounds, widely produced and used all around the world, are partly responsible for the widespread water pollution in the environment. Carbamazepine (CBZ) is an antiepileptic drug that persists in the environment for many years. In the present study, we used the TiO2/UV, nanoparticulate zero‐valent iron (NZVI), and NZVI/H2O2 treatment processes to compare efficiency of CBZ removal from water. Influence of NZVI loading, H2O2 concentration, TiO2 loading, UV lamp power, and the matrix (distilled water and groundwater) on CBZ removal efficiency was evaluated using full factorial design. Results indicated that the NZVI/H2O2 process oxidized CBZ within 5 min. On the other hand, the NZVI process alone did not reduce CBZ concentration after 120 min of process time. The NZVI/H2O2 process was equally effective in CBZ removal from both distilled water and groundwater whereas the TiO2/UV process was less effective due to the presence of ions in groundwater. CBZ removal efficiency of the TiO2/UV process declined 30% when the matrix was changed from distilled water to groundwater. Negative divalent ions, i.e., and , were the main cause of reduction of CBZ removal efficiency from groundwater. It is likely that these two ions adsorb onto, and consequently prevent the superoxide anion and hydroxyl radical OH? from being generated on, the surface of the TiO2.  相似文献   

11.
A glass of cordierite composition was found in a highly shocked garnet gneiss collected from Otting quarry in the Ries crater. This glass varies in color from colorless to dark brown. Despite the variation in color no compositional variation from grain to grain was found. Electron microprobe analyses of several glasses revealed: SiO2 49.07%, Al2O3 34.15%, FeO 6.07%, MgO 9.77%, CaO 0.07%, K2O 0.11%, Na2O 0.42%. In the sample investigated, all cordierite grains were transformed to isotropic cordierite glass.  相似文献   

12.
This study is undertaken to understand how calcite precipitation and dissolution contributes to depth-related changes in porosity and permeability of gas-bearing sandstone reservoirs in the Kela 2 gas field of the Tarim Basin, Northwestern China. Sandstone samples and pore water samples are col-lected from well KL201 in the Tarim Basin. Vertical profiles of porosity, permeability, pore water chem-istry, and the relative volume abundance of calcite/dolomite are constructed from 3600 to 4000 m below the ground surface within major oil and gas reservoir rocks. Porosity and permeability values are in-versely correlated with the calcite abundance, indicating that calcite dissolution and precipitation may be controlling porosity and permeability of the reservoir rocks. Pore water chemistry exhibits a sys-tematic variation from the Na2SO4 type at the shallow depth (3600-3630 m), to the NaHCO3 type at the intermediate depth (3630―3695 m),and to the CaCl2 type at the greater depth (3728―3938 m). The geochemical factors that control the calcite solubility include pH, temperature, pressure, Ca2 concen-tration, the total inorganic carbon concentration (ΣCO2), and the type of pore water. Thermodynamic phase equilibrium and mass conservation laws are applied to calculate the calcite saturation state as a function of a few key parameters. The model calculation illustrates that the calcite solubility is strongly dependent on the chemical composition of pore water, mainly the concentration difference between the total dissolved inorganic carbon and dissolved calcium concentration (i.e., [ΣCO2] -[Ca2 ]). In the Na2SO4 water at the shallow depth, this index is close to 0, pore water is near the calcite solubility. Calcite does not dissolve or precipitate in significant quantities. In the NaHCO3 water at the intermedi-ate depth, this index is greater than 0, and pore water is supersaturated with respect to calcite. Massive calcite precipitation was observed at this depth interval and this intensive cementation is responsible for decreased porosity and permeability. In the CaCl2 water at the greater depth, pore water is un-der-saturated with respect to calcite, resulting in dissolution of calcite cements, as consistent with microscopic dissolution features of the samples from this depth interval. Calcite dissolution results in formation of high secondary porosity and permeability, and is responsible for the superior quality of the reservoir rocks at this depth interval. These results illustrate the importance of pore water chemis-try in controlling carbonate precipitation/dissolution, which in turn controls porosity and permeability of oil and gas reservoir rocks in major sedimentary basins.  相似文献   

13.
The oxidation of organophosphorus pesticides (OPPs), such as malathion and parathion, in aqueous solution was studied using conventional ozonation (O3), photolytic ozonation (O3/UV, O3/UV/H2O2), and heterogeneous catalytic ozonation (O3/TiO2/UV) processes. Experiments were performed in batch mode at laboratory scale and processes were compared in terms of disappearance kinetics. The best results of pesticide mineralization were obtained when TiO2 particles in combination with ozone (O3) and UV photolysis (λ = 254 nm) were applied. Decomposition of 99% of parent compounds were achieved in 10 min and oxon derivatives were completely removed in 30 min. The initial reaction rate increases linearly with increasing catalyst amount. Toxicity measurements of the treated solutions were carried out in order to evaluate the efficiency of the treatment methods. No detoxification was achieved for O3 and O3/UV applications. Heterogeneous photocatalytic ozonation was shown to be feasible for achieving complete decomposition of OPPs and their oxon intermediates.  相似文献   

14.
南极洲万达盐湖为饱和方解石湖水。计算出的方解石饱和指数随水深增加而变化。在Ca2+及HCO3-活度值均一的上部氧化环境湖水中,pH及溶解氧(DO)是控制该变化的主要因素,在下部还原环境湖水中,Ca2+及HCO3-的活度对方解石的饱和指数SI的变化起主要作用。这充分揭示了湖底部近代沉积物中分布较多方解石矿物的原因。  相似文献   

15.
This study illustrates the degradation of an azo dye, Reactive Yellow 81 (RY81), by the combined irradiation of UV‐C and ultrasound in the presence of homogeneous (Fe2+) and heterogeneous (TiO2, ZnO) catalysts. The efficiency of homogeneous and heterogeneous oxidation systems was evaluated in regard of the decolorization and mineralization of RY81. Decolorization followed pseudo‐first‐order kinetics with homogeneous and heterogeneous catalysts. Complete color removal was accomplished by homogeneous sonocatalytic and sonophotocatalytic oxidation processes with apparent rate constants of 0.96 × 10?3 and 46.77 × 10?3 s?1, respectively, in the presence of Fe2+. However, partial color removal was obtained by heterogeneous sonocatalytic, photocatalytic, and sonophotocatalytic oxidation processes with apparent rate constants of 2.32 × 10?3, 3.60 × 10?3, and 3.67 × 10?3 s?1, respectively, in the presence of ZnO. TiO2 had the worst catalytic effect of all of the oxidation processes. The addition of hydrogen peroxide increased the rate constants of the heterogeneous oxidation processes and decreased the rate constants of the homogeneous oxidation processes. RY81 mineralization was 62.8% for the US/UV/Fe2+ homogeneous oxidation process, which was the best oxidation process, whereas it was 43.5% for the US/UV/ZnO/H2O2 heterogeneous oxidation process within 2 h reaction time.  相似文献   

16.
The amounts of CO2 and CO evolved upon shock compression and decompression of calcite to 18 GPa (180 kbar) have been determined using a new gas phase shock recovery technique and gas source mass spectrometry. The data demonstrate that from ～0.03 to 0.3 mole percent of calcite is devolatilized at shock pressures significantly lower than those predicted (30 GPa) for the onset of volatilization by continuum thermodynamic theory and are in qualitative agreement with release adiabat data for calcite and aragonite. Carbon and oxygen isotope ratios in the shock-released CO2 are the same as those in the unshocked (hydrothermal) calcite, demonstrating that the CO2 comes from the calcite rather than other potential sources.  相似文献   

17.
The aim of this research was to decompose isoproturon and adsorb its photoproducts by developing a carbon material from a juice industry waste. Carbon-TiO2 hybrid materials were obtained by impregnating carbonized guava seeds with TiO2 gels prepared from TiOSO4⋅xH2O and NH4OH using glycerol as a binder and thermally treating the materials at 500 °C. Raman studies confirmed the anatase phase of TiO2. SEM images showed isolated TiO2 agglomerates firmly attached to the carbon surface. The adsorption behavior of isoproturon on guava carbon was studied and yielded S-type adsorption isotherms. The photocatalytic activities of the prepared hybrid materials were monitored to study the kinetics and elimination process both of the herbicide and its photoproducts. The reaction was monitored by UV–Vis spectrophotometry, LC-DAD and LC-MS, enabling identification of some intermediate species. Among the photoproducts produced by carbon-TiO2 hybrid materials, amino-isopropylphenol was detected.  相似文献   

18.
Ag‐modified TiO2 nanotube arrays (Ag/TiO2 NAs) were prepared and employed as a photocatalyst for degradation of 17α‐ethinylestradiol (EE2) and inactivation of Escherichia coli. The as‐synthesized Ag/TiO2 NAs were characterized by field‐emission scanning electron microscope (FESEM), X‐ray diffraction (XRD), and X‐ray photoelectron spectroscopy (XPS). It was found that metallic Ag nanoparticles were firmly deposited on the TiO2 NAs with the pore diameter of 100 nm and the length of 550 nm. Photocatalytic degradation of EE2 and inactivation of E. coli were enhanced effectively in an analogical trend using Ag/TiO2 NAs. In particular, Ag/TiO2 NAs exhibited the antimicrobial activity even in the absence of light. The Ag acted as a disinfection agent as well as the dopant of the modified TiO2 NAs photocatalysis by forming a Schottky barrier on the surface of TiO2 NAs. Inorganic ions suppressed the rates of photocatalytic degradation of EE2, with HCO having a more pronounced effect than NO or SO. Humic acid (HA) was found to increase the rate of EE2 degradation.  相似文献   

19.
Carbon and oxygen isotopic determinations have been made of 29 species of Recent Indian Ocean planktonic foraminifera. Fourteen core-top samples were used and as many as 18 species were chosen from a single core-top sample. The δ13C of the foraminifera was compared with that of total dissolved CO2 (ΣCO2) and of calcite precipitated in isotopic equilibrium with ΣCO2. The foraminiferal calcite is always at least 1.2‰ less than the value estimated for equilibrium calcite. This carbon isotopic disequilibrium suggests the partial utilization of13C-depleted metabolic CO2. The calcite tests of several species, however, have δ13C values which are similar to the δ13C of ΣCO2 in seawater. This relationship suggests that important paleohydrographic information may be obtained from carbon isotope records based on analyses of several foraminiferal species from single deep-sea sediment samples.  相似文献   

20.
The temperatures induced in crystalline calcite (CaCO3) upon planar shock compression (95-160 GPa) are reported from two-stage light gas gun experiments. Temperatures of 3300-5400 K are obtained by fitting six-channel optical pyrometer radiances in the 450-900 nm range to the Planck gray-body radiation law. Thermodynamic calculations demonstrate that these temperatures are some 400-1350 K lower than expected for vibronic excitations of the lattice with a 3R/mole-atom specific heat (R is gas constant). The temperature deficit along the Hugoniot is larger than that expected from only melting. In addition to melting, it appears likely that shock-induced decomposition of calcite occurs behind the shock front. We modeled disproportionation of calcite into CaO (solid) plus CO2 (gas). For temperature calculations, specific heat at constant volume for 1 mole of CO2 is taken to be 6.7R as compared to 9R in the solid state; whereas a mole of calcite and a mole of CaO have their solid state values 15R and 6R, respectively. Calculations suggest that the calcite decomposes to CaO and CO2 at ∼110±10 GPa along the Hugoniot. Recent reanalysis of earlier VISAR measurements of particle velocity profiles [1] indicates that calcite shocked to 18 GPa undergoes disproportionation at much lower pressures upon isentropic expansion.  相似文献   

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