Presence Of Different Scavengers Research Articles

Photocatalytic degradation of reactive dyes over Ni[sbnd]Al layered double hydroxide

Due to the uncontrolled discharge of textile effluents, the extent of reactive dyes in wastewater is rising. Due to their toxicity, efficient removal becomes quite essential. In this report, NiAl layered double hydroxide (LDH) has been prepared using the coprecipitation methodology for the photocatalytic degradation of reactive dyes. The as-prepared materials were characterized by different techniques, such as DRS, XRD, FESEM, HRTEM, and XPS etc. The XRD pattern of the LDH confirms the formation of the rhombohedral (R3m) phase. The FESEM analysis reveals the irregular hexagon-like shape of the prepared LDH. The NiAl LDH has 98(1) and 87(1)% photodegradation efficiencies towards the removal of reactive blue 19 and reactive Red 120, respectively. The control experiments in the presence of different scavengers confirm that hydroxyl radicals and superoxide anions participate in photocatalytic degradation. The HRMS studies confirm the formation of different smaller fragments, thereby providing a deeper insight into the photodegradation mechanism. Moreover, the demineralization efficiency (88.9%) is quite close to the degradation efficiency for reactive blue 19, signifying practically complete demineralization of the pollutants. The recyclability studies ascertain the high stability of the photocatalyst. Therefore, the as-prepared NiAl LDHs can be considered a promising photocatalyst for the removal of reactive dyes from wastewater.

Photocatalytic efficacy of Magnesium oxide nanoparticles in dye Degradation: A sustainable One-Pot synthesis utilizing Syzygium samarangense L. Extract

Efficient degradation of organic pollutants is a pressing environmental concern. In our current study, we propose a novel photocatalytic solution to address this challenge, harnessing the potential of advanced nanomaterials to enhance pollutant removal rates. The present work reports the synthesis of Magnesium Oxide (MgO) nanoparticles via a green technique using an aqueous extract of Syzygium samarangense leaves. The role of reducing and capping agents in the process was owned by Syzygium samarangense leaf extract. The green synthesized MgO nanoparticles (MgO NPs) were characterized for their structural, morphology, and optical details using various analytical techniques. The formation of metal oxide in the sample was evident from a strong absorbance peak at 264 nm, and the calculated Eg value of 5.5 eV. The high crystallinity of the prepared NPs was authenticated by PXRD analysis with a cubic structure of calculated average crystalline size of 18 nm. Both leaf extract and the prepared MgO NPs were subjected to FTIR analysis, and the action of phytochemicals was affirmed by the absence of major band in MgO NPs spectrum. Precursor and agglomerated morphology were confirmed on SEM analysis. The prepared sample were utilized to perform degradation of Methylene blue (MB) and congo red (CR) dyes through photocatalysis under UV irradiation. The results affirm the decrement in absorbance with the increment of irradiation time. The affirmed decrement was put forth to study the kinetics of the degradation reaction, and the results was best aligned with 1st kinetic equation with R2 value of 0.9850 and 0.976 for MB and CR dye, respectively. The same results were utilized to study the effect of dye dosage, catalyst concentration, pH level, and presence of different scavengers. All the results found compelling and suggest the prepared MgO NPs as a potent candidate for photocatalytic dye degradation of MB and CR.

ZnO-based Cu metal-organic framework (MOF) nanocomposite for boosting and tuning the photocatalytic degradation performance.

Although metal-organic frameworks (MOFs) are a viable choice for photocatalysts with large surface area and tunable pore structure, the rapid recombination of excited photogenerated charges results in low activity towards photodegradation. Aiming at improving the photocatalytic activities of MOFs, different strategies to incorporate MOF with light-harvesting semiconductors have been developed. In this research, we report an effective photocatalyst designed by incorporating Cu-MOF with ZnO for the photocatalytic degradation of Rose Bengal exhibiting excellent degradation efficiency of 97.4% in 45min under natural sunlight with catalyst dosage of 320mg/L. The optical, morphology and surface characteristics of the prepared nanocomposite were studied using scanning electron microscopy (SEM-EDX), high-resolution transmission electron microscopy (HRTEM), powder X-ray diffraction (PXRD), Brunauer-Emmett-Teller (BET) analysis, thermogravimetric (TGA) analysis, Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and ultraviolet diffused reflectance spectroscopy (UV-DRS) techniques. Further studies showed that the degradation followed first-order kinetics with a rate constant of 0.077869min-1. The degradation mechanism was investigated by photoluminescence (PL) study, XPS, zeta potential and quenching experiment in presence of different scavengers. Meanwhile, the fabricated composite displayed good recovery and reuse properties up to 5 cycles as revealed by XRD analysis proving itself a potential MOF-based photocatalyst towards environmental remediation process.

Nano-architecture of MOF (ZIF-67)-based Co3O4 NPs@N-doped porous carbon polyhedral nanocomposites for oxidative degradation of antibiotic sulfamethoxazole from wastewater

Co3O4 NPs in N-doped porous carbon (Co3O4 NPs@N-PC) materials were prepared by one-pot pyrolysis of a ZIF-67 powder under N2 atmosphere and followed by oxidation under air atmosphere (200 °C) toward promotion catalytic activity and activation of peroxymonosulfate (PMS) to degradation sulfamethoxazole (SMZ). 2-methylimidazole was used as a nitrogen source and a competitive ligand for the synthesis of Co3O4 NPs@N-PC, which in addition to affecting nucleation and growth of the crystal, promotes the production of active Co–N sites. Co3O4 NPs@N-PC nano-architecture has high specific surface areas (250 m2 g−1) and is a non-toxic, effective and stable PMS activator. The effect of operating parameters including SMZ concentration, catalyst dosage, temperature and pH in the presence of Co3O4 NPs@N-PC was investigated. The Co3O4 NPs@N-PC composite showed superior performance in activating PMS over a wide range of pH (2–10) and different temperatures so that complete degradation of SMZ (50 μM, 100 mL) was achieved within 15 min. The role of Co2+/Co3+ redox system in the mechanism before and after PMS activation was determined using XPS analysis. Surface-generated radicals led to the degradation of SMZ, in which the SMZ degradation rate attained 0.21 min−1 with the mineralization of 36.8%. The feasible degradation mechanism of SMZ was studied in the presence of different scavengers and it was revealed that the degradation reaction proceeds from the radical/non-radical pathway and in this process most of the SO4− and OH radicals are dominant. The recoverability and reuse of Co3O4 NPs@N-PC were evaluated to confirm its stability and potential for SMZ degradation and it was observed that the catalyst maintains its catalytic power for at least 5 cycles.

Photocatalytic activity enhancement of carbon‐doped g‐C3N4 by synthesis of nanocomposite with Ag2O and α‐Fe2O3

AbstractCarbon‐doped g‐C3N4 (CGNS) nanocomposite with Ag2O and α‐Fe2O3 has been synthesized to improve g‐C3N4 photocatalytic activity. The prepared CGNS/Ag2O/α‐Fe2O3 (GAF [with mass ratio 3:2:1]) nanocomposite exhibits the expanded visible‐light absorption region leading to the enhanced photocatalytic performance for Acid Red 14 (AR14) degradation. Besides, it is found that the recombination rate of the charge carriers effectively suppresses the nanocomposite. For a better understanding of the photocatalytic degradation mechanism, the reactions have been performed in the presence of different scavengers. The experiments indicate that superoxide anion radicals possess a more influential role in AR14 degradation in comparison with hydroxyl radicals and holes. The degradation efficiency has been decreased from 94.68 to 85.60 after five consecutive photocatalytic tests implying that the prepared nanocomposite is a stable photocatalyst. In the end, the kinetic study of AR14 degradation on nanocomposite with considering pseudo‐first‐order kinetics results in a nonlinear empirical kinetic model development for prediction of degradation efficiency of AR14 on nanocomposite.

Electro-Fenton process for the removal of Direct Red 23 using BDD anode in chloride and sulfate media

• Degradation of dye DR23 by EF using BDD or DSA anode in chloride and sulfate media. • BDD/carbon graphite cell achieved efficient discoloration and mineralization. • Rapid and complete discoloration was obtained in chloride medium. • Sulfate medium led to the higher mineralization rates. • Combination of chloride and sulfate as supporting electrolyte provided a beneficial effect. This paper aims to study the degradation and mineralization of the dye Direct Red 23 (DR23) by electro-Fenton (EF) process for the first time using BDD and DSA anode and carbon graphite (CG) cathode in NaCl and Na 2 SO 4 media. The effect of different parameters such as the nature, concentration, and combination of the supporting electrolyte, the nature of the anode, the concentration of the catalyst and DR23 and the current density on H 2 O 2 generation and mineralization rate was investigated. The best treatment efficiencies were achieved by BDD/CG cell. The degradation of DR23 solution was faster in NaCl medium. The mineralization was more efficient in Na 2 SO 4 , where the main oxidizing species were the hydroxyl radicals, generated both in the bulk solution ( • OH) and at the anode surface (M( • OH)). The TOC removal, the energy consumption, and electrical cost per m 3 were 90%, 2.41 kWh g −1 TOC, and 3.21 US $ m −3 , respectively, after 6 h of electrolysis in sulfate medium while lower mineralization rate (83%) and higher energy consumption (2.86) and electrical cost per m 3 (3.27 US $ m −3 ) were achieved in chloride medium. As the textile wastewater contain generally sulfate and chloride ions, experiences were also performed in a medium formed of Na 2 SO 4 and NaCl. The following combination of these salts (75% Na 2 SO 4 + 25% NaCl) as supporting electrolyte was beneficial to further increase the mineralization rate of DR23 solution, current efficiency and reduce the energy consumption. Degradation of DR23 in the presence of different scavengers (methanol, 2-propanol, and tert-butanol) asserted that the elimination of DR23 is mainly attributed to the action of • OH/M( • OH) on the target pollutant.

Synthesis and characterization of the magnetic submicrocube Fe3O4/TiO2/CuO as a reusable photocatalyst for the degradation of dyes under sunlight irradiation

Throughout this study, the magnetic submicrocube Fe 3 O 4 was synthesized and then coated by TiO 2 . The resultant (Fe 3 O 4 /TiO 2 ) was loaded via CuO yielding to Fe 3 O 4 /TiO 2 / CuO. The intermediate and final products were characterized by using different methods. Based on the PL spectra, the electron/hole recombination of Fe 3 O 4 /TiO 2 /CuO was reduced compared to Fe 3 O 4 /TiO 2 . Moreover, the DRS spectrum revealed that the Fe 3 O 4 /TiO 2 /CuO band gap was narrower than that of Fe 3 O 4 /TiO 2 . XRD and HRTEM results denoted that Fe 3 O 4 , TiO 2 and CuO were crystallized in cubic, tetragonal and monoclinic phases, respectively. The photocatalytic effect of the Fe 3 O 4 /TiO 2 /CuO on degradation of methylene blue (MB), methyl red (MR), congo red (CR) and methyl orange (MO) was investigated by being exposed to sunlight irradiation. The photocatalyst could be simply separated from the reaction mixture and thereafter be reutilized in dyes degradation reaction. Having the reaction mixture recycled, the obtained photocatalyst could be reutilized for further usages. The MB degradation was examined in the presence of different scavengers to suggest the mechanisms. The scavenger test results showed that the hydroxyl radical could play a prominent role in the photocatalytic degradation of MB with Fe 3 O 4 /TiO 2 /CuO under the sunlight irradiation. • The magnetic submicrocube Fe 3 O 4 /TiO 2 /CuO is regarded as an efficient photocatalyst in degradations of dyes. • Formation of p–n heterojunction between CuO and Fe 3 O 4 /TiO 2 greatly reduced the band gap and electron/hole recombination rate. • Magnetic properties of Fe 3 O 4 /TiO 2 /CuO facilitated the recovery of the photocatalyst from the reaction mixture. • • OH played a prominent role in the degradation of MB.

Improved photodegradation and antimicrobial activity of hydrothermally synthesized 0.2Ce-TiO2/RGO under visible light

Highly water-dispersible cerium doped titania nanoparticles deposited reduced graphene oxide (Ce-TiO2/RGO) has been prepared by a hydrothermal technique. The uniform deposition of Ce-TiO2 on RGO increases the absorption of titania from ultraviolet to visible region. From the photocurrent study, it was found that the optimum deposition of 0.2% cerium doped titania with 10 wt% RGO significantly increases the photocurrent density under visible light. During the photocatalytic process, the generated active species can be detected by trapping reactive species in presence of different scavengers. It was observed that h+ and ˚O2- are responsible for the photocatalytic action of the composite. The developed heterogeneous photocatalyst has more degradation efficiency for a cationic dye methylene blue, and two pesticides quinalphos and imidacloprid as compared to conventional TiO2 catalyst under visible light. Incorporation of Ce into TiO2 imparts bifunctional properties such as degradation of toxic pesticides and antimicrobial property against human pathogenic bacteria.

Lanthanum ions decorated 2-dimensional g-C3N4 for ciprofloxacin photodegradation

The low band gap energy and high surface area two-dimensional materials allow it to tune its basic properties using surface decoration. Here, La3+ are decorated on two-dimensional graphitic carbon nitride using a simple and easily scalable chemisorption process with an adsorption capacity of 657.32 mg g−1. In the X-ray diffraction (XRD) study, the positive slope of the W–H plot elucidates the tensile strain generation (0.103) in La3+ ions decorated 2D-g-C3N4 (La3+-2D-g-C3N4). The high-resolution transmission electron microscope (HR-TEM) study and the higher ID/IG ratio (0.82) in the Raman spectroscopy study confirm the more defects intensification in La3+-2D-g-C3N4. The reduction in band gap energy for La3+-2D-g-C3N4 (from 2.83 eV to 2.21 eV) has shown a good correspondence with the band structures study as obtained from the DFT study. In the DFT study, the significant contributions of N atoms in charge transfer validate the N 1s findings from the X-ray photoelectron spectroscopy (XPS) study for La3+-2D-g-C3N4. La3+-2D-g-C3N4 shows the photodegradation efficiency (93%) of ciprofloxacin under UV irradiation, which is superior to pristine 2D-g-C3N4 (82%) as well as other g-C3N4 based nanocatalysts. Also, La3+ decoration results in enhancement (32.3%) in photodegradation kinetics rate. The degradation and kinetics studies in the presence of different scavengers ensure that the O2ˉ and OH− radicals are mostly responsible for the ciprofloxacin photodegradation. The Liquid chromatographic-mass spectroscopy and the high-performance liquid chromatography studies confirm the photodegradation. The reusability of La3+-2D-g-C3N4 is tested up to the fifth cycle. FTIR and UV–visible absorption spectroscopy confirm the stability of the used photocatalyst.

Tungsten oxide modified with carbon nanodots: Integrating adsorptive and photocatalytic functionalities for water remediation

Abstract We report for the first time the green synthesis of carbon nanodots (g-CDs) from the peels of T. cucumerina by simple hydrothermal route. An in-situ liquid phase process was adopted for the design of the monoclinic tungsten trioxide (m-WO3)- based nanostructure with g-CDs to obtain a bi-functional g-CDs/m-WO3 system. Characterization techniques, such as X- Ray Diffraction (XRD), Transmission Electron Microscopy (TEM), Field Emission Scanning Electron Microcsopy (FESEM), Energy Dispersion X-Ray Analysis (EDX), Fourier Transformed Infra-Red (FTIR), Ultra Violet Defuse Reflectance Spectroscopy (UV-DRS) and Photoluminescence Emission Spectroscopy (PLES) were employed for the morphological, dimensional, chemical and optical analysis. The efficiency in the adsorption of the heavy metal, namely Cd2+ ions of the m-WO3 was found improved in the formated nanocomposite with g-CDs to 81%. The detailed adsorption kinetics study through the adsorption isotherms revealed that the reaction mechanism can be described by the pseudo-second-order kinetic model determined by Freundlich isotherms. Furthermore, the photocatalytic degradation efficiency of the crystal violet dye under the visible light was found significantly enhanced to 95% for the studied composite. The photocatalytic ability of the nanocomposite was found remaining almost intact even after four repeated cycles. A study in the presence of different scavengers suggested that the hydroxyl radicals play a crucial role in determining the photocatalytic activity of the nanocomposite. An improvement in the structural stability and charge carrier separation kinetics was achieved by carefully growing the m-WO3 nanostructures in g-CDs. These resultes have revealed the integrated adsorptive and photocatalytic capabilities of the studied nanocomposites for the waste water treatment.

Studies on growth of Au cube-ZnO core-shell nanoparticles for photocatalytic degradation of methylene blue and methyl orange dyes in aqueous media and in presence of different scavengers

Au-ZnO core-shell nanoparticles with cubic Au core were synthesized using ascorbic acid assisted hydrothermal growth method. Variation in optical response, surface plasmon resonance of Au nanocubes during shell layer growth was studied and explained with numerical calculations. Annealing induced changes in optical absorption, crystalline quality and morphology of these nanoparticles was addressed. Annealing at high temperatures (≥ 400 °C) was found to be important for significant improvement of photocatalytic activity of these nanoparticles. Photocatalytic response of the nanoparticles was studied through degradation of methylene blue (MB) and methyl orange (MO) dyes. Role of different process parameters mainly dye concentration, type of UV lamp, nanoparticle loading, presence of different scavengers at varied concentrations and solution pH on dye degradation was addressed. The results reveal that hydroxyl radical plays vital role in the degradation process. The effect of scavengers and their concentration is almost similar for both these dyes degradation. High pH was found to enhance the degradation process and its rate constant increased by 15 and 8 times at pH 12 for MB and MO respectively. These nanoparticles of 1 g/L loading were efficient to degrade the dyes with concentration of about 15 mg/L, within an hour (three hrs.) in high pH (neutral) solutions. The growth process was optimized for easy collection of the nanoparticles for large quantity handling. The core-shell nanoparticles used in the study are environmental friendly and their synthesis along with dye degradation in low power light is cost effective for treatment of industrial wastewater containing different dyes.

Reactive magnetron sputtering based synthesis of WO3 nanoparticles and their use for the photocatalytic degradation of dyes

Current study explores the synthesis of WO3 nanoparticles using highly effective novel physical vapour deposition process, reactive magnetron sputtering technique followed by annealing at different temperatures. The characterization of the synthesized samples were carried out by powder XRD, Raman spectroscopy, FE-SEM, TEM, BET, and diffuse reflectance spectroscopy (DRS) to check the crystallinity, morphology, surface area, and optical properties, respectively. Results display that the crystallinity and the crystallite size increases after heating the samples continuously. The morphology was found to be spherical type with high aggregation at low temperature. As-deposited nanoparticles display the highest surface area 66.78 m2/g and it decreases up to 20.45 m2/g with increasing the particle size up to 48 nm. The photocatalytic activity of the WO3 nanoparticles was evaluated in the degradation reactions of rhodamine B (Rh B), indigo carmine (IC), and Congo red (CR) in aqueous solution under UV–vis radiation. The highest photocatalytic activity was observed with highly crystalline WO3 nanoparticles and the order of the different organic dyes degradations was: IC > Rh B > CR. The degree of mineralization of organic dyes by WO3 nanoparticles was determined by total organic carbon (TOC) analysis and reaching percentages of mineralization of 76% Rh B, 87% for IC, and 8% for CR for 96 h of lamp irradiation. A proposed mechanism for the photocatalytic activity of synthesized WO3 was investigated in the presence of different scavengers which suggested that mechanism occurs through hydroxyl radicals rather than holes and peroxide radicals.

Insight into heterogeneous Fenton-sonophotocatalytic degradation of nitrobenzene using metal oxychlorides

Abstract Heterogeneous Fenton degradation of nitrobenzene (NB, 20 ppm) was investigated at room temperature and pH = 7 using 0.1 g L−1 of FeOCl (I), CuOCl (II), ZnOCl (III) and BiOCl (IV) metal oxychlorides catalysts in presence of ultrasonic (US, 20 kHz), ultraviolet (UV, 6 W, λ = 254 nm) and UV/US double irradiation with H2O2 (5 mM) as an oxidant. The results showed that the order of the investigated systems with regard to their degradation performance was US/UV > UV > US, with I > II > IV > III but with mineralization extents of 46%, 41%, 35% and 33%, respectively under dual irradiation for 60 min. The synergistic effect correlates with the values of band gap of used oxychlorides and plays a vital role in enhancing the degradation performance of the dual system through generated reactive radicals ( OH & O2 −) besides photo-born holes (h+) and electrons (e−). Experiments conducted in presence of different scavengers indicated that ( OH) and (h+) play a major and more important role than that of (O2 −) in the degradation process. Scavenging the generated electrons indicated that they act as degradation inhibitors. Band gap values dictated the variable activities shown by different metal oxychlorides.

Enhanced superoxide radical production for ofloxacin removal via persulfate activation with Cu-Fe oxide

Cu-Fe composite oxides with different Cu:Fe ratios were synthesized by a hydrothermal method and investigated as a heterogeneous catalyst for persulfate activation. The obtained samples exhibited much higher activity than CuFe2O4 for the degradation and mineralization of ofloxacin with persulfate, and the optimized Cu:Fe ratio was 1:1 (CuFe1). The results of catalyst characterization and electron paramagnetic resonance analysis indicate that the activities of the catalysts for ofloxacin degradation and superoxide radical (O2−) production are highly positively correlated with their redox ability. The removal efficiencies of ofloxacin in the presence of different scavengers further demonstrate that O2− is the dominant reactive species in this process, which is quite different from previous studies. It is suggested that CuFe1 with higher oxidation ability could weaken the SO bond of adsorbed persulfate, thus promoting the decomposition persulfate into O2−. Finally, the possible degradation pathway of ofloxacin was proposed according to the liquid chromatography−mass spectrometry result.

Synthesis of the novel nanostructured AgI-BiOI/PAN composite photocatalyst with highly enhanced visible-light catalytic performances

In this work, a novel highly efficient visible-light-driven AgI-BiOI/PAN composites was successfully synthesized and characterized by several tools. Based on the results of XRD, SEM and TEM of the AgI-BiOI/PAN composites, we could concluded that AgI nanoparticles and BiOI nanoparticles had been formed successfully on the PAN nanofibers. Compared with AgI/PAN and BiOI/PAN, AgI-BiOI/PAN showed highest photocatalytic performances and photochemical stability in degrading RhB, which is believed to be related to the larger number of surface active sites and faster spatial charge transfer between AgI and BiOI. The photocatalytic degradation efficiencies of AgI-BiOI/PAN after 210 min light irradiation was 98.5%. Meanwhile, the degradations of RhB by AgI-BiOI/PAN remained at 98.2% after six recycling runs. The application of PAN nanofibers made it easy to separate the catalysts from an aqueous solution without any loss. The degradation experiments of RhB in the presence of different scavengers suggested that h+ and O2− were the main reactive species. According to the experimental and characterization results, one plausible mechanism for enhanced RhB performance over AgI-BiOI/PAN composites was proposed.

The layered double hydroxide route to Bi–Zn co-doped TiO2 with high photocatalytic activity under visible light

In this work, a co-doped Bi–Zn–TiO2 photocatalist is synthesized by an original synthesis route of layered double hydroxide followed by heat treatment at 670°C. After characterization the photocatalyst efficiency is estimated by the photo-discoloration of an anionic dye (indigo carmine) under visible light and compare to TiO2–P25 as reference material. In this new photocatalyst, anatase and ZnO wurtzite are the only identified crystalline phase, rutile and Bi2O3 being undetected. Moreover, the binding energy of Bi determined (XPS analysis) is different from the one of Bi in Bi2O3. Compared to TiO2–P25, the absorption is red shifted (UV–vis DRS) and the Bi–Zn–TiO2 photocatalyst showed sorption capacity toward indigo carmine higher than that TiO2–P25. The kinetics of the photo-discoloration is faster with Bi–Zn–TiO2 than with TiO2–P25. Indeed, a complete discoloration is obtained after 70min and 120min in the presence of Bi–Zn–TiO2 and TiO2–P25 respectively. The identification of the responsible species on photo-discoloration was carried out in the presence of different scavengers. The study showed that the first responsible is h+ specie with a moderate contribution of superoxide anion radical and a minor contribution of the hydroxyl radical. The material showed high stability after five uses with the same rate of photo-discoloration.

Enhanced photocatalytic activity of Ce-doped ZnO nanorods under UV and visible light

Ce-doped ZnO nanorod photocatalysts with high visible light-driven activity were synthesized by a hydrothermal process. Effects of doping on the adsorption ability, band gap modification, surface chemistry, separation of electron–hole pairs, and photocatalytic activity of ZnO photocatalysts were investigated by combining the diffuse reflectance spectra, photoelectrochemical scanning electrochemical microscopy (PEC–SECM), and X-ray photoelectron spectroscopy (XPS) analysis. The mechanism of cerium ion doping induced photocatalytic activity enhancement was proposed and evaluated by studying the degradation performances in the presence of different scavengers. Introducing an appropriate amount of Ce ion dopant can enhance the photocatalytic activity, which can be attributed from the increased surface oxygen vacancies, higher adsorption capacity and better separation of electron–hole pairs in nanostructured photocatalyst. Excess concentration of dopant precursor leads to the formation of cerium oxide aggregates around the nanorods and deteriorated photocatalytic activity. The optimized photocatalyst shows almost no activity loss after three repeated degradation experiments.

Phosphorous-Modified TiO2 with Excellent Thermal Stability and Its Application to the Degradation of Pollutants in Water

The phosphorous-modified TiO 2 (P-TiO 2 ) was synthesized by a hydrothermal method. The as-prepared P-TiO 2 was evaluated for the degradation of methylene blue, the dechlorination of 4-chlorophenol, and the inactivation of Escherichia coli . In all these experiments, P-TiO 2 shows superior activity compared with pure TiO 2 and even better activity than the commercially available P25 in most cases. By carrying out methylene blue degradation in the presence of different scavengers, ·OH radicals were found to be the dominant reactive oxidizing species. The excellent performance of P-TiO 2 was correlated with its pronounced ability to generate ·OH radicals under illumination. We also found that P-TiO 2 is extraordinarily stable against annealing. Its transformation from anatase to rutile does not occur until calcination as high as 950 °C. This phase transformation is retarded since the phosphate species on the surface of the particles acts as a barrier to grain boundary nucleation. This peculiar feature of P-TiO 2 gives it reliable performance during water decontamination even after calcination at 900 °C since it retains a 100% anatase phase at this stage.

Radiation removal of lead and cadmium complexed with ethylenediamine tetraacetic acid from aqueous solutions

The removal of lead (100 mg/L) and cadmium (27 mg/L) complexed with ethylenediamine tetraacetic acid (EDTA) in presence of different scavengers has been investigated. The experiments show that in acidic solutions, the EDTA complexed lead may be reduced at a dose of 40 kGy up to 97 % without the addition of typical OH radical scavengers such as Na(K) formate. The addition of OH radical scavengers as 1×10−3 mol/L HCOOK, 2×10−3 mol/L carbonate or 2×10−3 mol/L bicarbonate (wide range of pH) results in no further improvement. The bubbling of the solution with nitrogen or oxygen also exhibits no positive effect. On the contrary, saturation with nitrous oxide in the presence of scavengers has a modest positive influence, whereas in the system which is scavenger-free, high negative effect (30 %) was observed. The presence of nitrate (e− aq scavenger) appears to be important for an effective reduction of complexed lead. The efficient removal of cadmium complexed with EDTA proceeds up to 96 % at a dose of 40 kGy with an addition of 5×10−3 mol/L of carbonate as the OH radical scavenger and simultaneously pH buffer (pH 10.5). After irradiation, the cadmium is present in the final form of CdCO3.

Study on the interaction of ions of transient metals with ascorbic acid in the presence of different scavengers of active oxygen species in SOS chromotest.

SOS chromotest was employed to study the interaction of ascorbic acid with free ions of transient metals in the presence of added catalase, superoxide dismutase or D-mannitol. Catalase diminished the genotoxic activity of the mixture of ascorbic acid with copper ions in E. coli strains PQ37 and PQ 300, but genotoxicity of this mixture was not suppressed by superoxide dismutase and D-mannitol. The results suggest that copper ions diminished the content of peroxide generated by ascorbic acid.