scholarly journals Highly Stable Photocatalytic Removal of Paraquat Dichloride using ZnO/TiO2 supported on PVC

2021 ◽  
Vol 17 (5) ◽  
pp. 647-658
Author(s):  
Abubakar Garba Ashiru ◽  
Juan Matmin ◽  
Susilawati Toemen
Keyword(s):  
Zno Nanorods ◽  
Supported Catalyst ◽  
Degradation Process ◽  
High Reactivity ◽  
Xrd Pattern ◽  
Tio2 Anatase ◽  
Photocatalytic Removal ◽  
Amorphous Structures ◽  
The Stability ◽  
Reduced Surface

This study presents on ZnO/TiO2 supported on PVC (ZnO/TiO2@PVC) in the photocatalytic removal of paraquat dichloride. The ZnO/TiO2@PVC was characterized using XRD, FESEM-EDX, FTIR, and AFM. Findings indicated that ZnO/TiO2@PVC allowed degradation of paraquat dichloride under UV irradiation by the rate of up to 73%. XRD pattern indicated the presence of both TiO2(anatase) and ZnO (zincite) crystalline as well as PVC amorphous structures. FESEM and AFM results revealed the observed shape and surface of TiO2 interconnected nanowires with ZnO nanorods uniformly distributed according to EDX mapping. The reduced surface roughness was also shown in the supported photocatalyst. FTIR analysis clearly demonstrate the combined spectra of immobilised ZnO/TiO2 powder catalyst onto the PVC in the composite. Kinetic study of the degradation process was performed according to pseudo-first-order and the influence of ZnO/TiO2 coating onto PVC polymer and initial paraquat concentration were investigated on the treatment performance. Under optimized condition (pH = 7, PQ =20 mg/L and catalyst coating =15%), the stability and reusability of the supported catalyst was also evaluated over ten sequential treatment runs, and the catalyst maintain high reactivity. High recyclability of the ZnO/TiO2@PVC composites as catalyst in photodegradation processes are also reported in this study.

scholarly journals Degradasi Zat Warna Malachite Green Secara Ozonolisis Dengan Penambahan Katalis TiO2 – anatase dan ZnO

Elkawnie ◽  
2017 ◽  
Vol 3 (1) ◽  
Author(s):  
Bhayu Gita Bhernama
Keyword(s):  
Malachite Green ◽  
Degradation Process ◽  
Optimum Time ◽  
Ph Optimum ◽  
Green Is ◽  
Tio2 Anatase ◽  
The Stability

Degradation of malachite green has been done. In this research, degradation process of malachite green was done by ozonolisis method, using TiO2- anatase and ZnO catalyst. The residu of malachite green was centrifuged and measured by spectroscopy UV / Vis at 200-800 nm after degradation. 6 mg / L malachite green diozonolisis for 5 minutes obtained pH optimum at pH 7. 6 mg / L malachite green was added 0.025 mg TiO2-anatase catalyst, and 0.025 mg ZnO at pH 7 with a variation time obtained optimum time of 5 minutes. Percent degradation of malachite green is generated by the addition of 0.0250 grams of TiO2-anatase 99.77% and 0.0250 grams of ZnO 93.59%. Percent of the results showed that the degradation of degradation with the addition of TiO2-anatase is greater than the addition of ZnO, because of the stability of TiO2- anatase is large.

Distribution of Acidity and Alkalinity on Degraded Manuscripts Containing Iron Gall Ink

2015 ◽  
Vol 36 (3) ◽  
Author(s):  
Eva Marín ◽  
Maria Carme Sistach ◽  
Jessica Jiménez ◽  
Miguel Clemente ◽  
Guillem Garcia ◽  
...  
Keyword(s):  
Good Condition ◽  
Degradation Process ◽  
Degradation Processes ◽  
Alkaline Reserve ◽  
Hydrolysis Of Cellulose ◽  
Relevant Variables ◽  
Long Time ◽  
Iron Gall ◽  
The Stability

AbstractLong-time preservation of manuscripts depends on the stability of their support. One of the most important degradation processes of paper manuscripts containing iron gall ink is the acid hydrolysis of cellulose. The heterogeneity of the distribution of their constituent materials, together with the defined position of ink as a source of degradation agents, makes it difficult to obtain reliable and detailed information about degradation processes. The aim of this study is to contribute to the knowledge of the acid degradation process by looking at the distribution of relevant variables (pH, acidity and alkaline reserve) on real untreated iron gall ink containing manuscripts at different degradation stages. The study discusses the well-known differences between surface and cold extraction pH determination. It corroborates the relationship between pH, acidity and alkalinity and degradation stages, pointing out that acidity values for some manuscripts in apparent good condition are not far from those obtained for degraded manuscripts. The results indicate that in some partially degraded manuscripts, the coexistence of acid areas and areas with an alkaline reserve which do not participate in the neutralization process is possible. The role of water as a solvent for this equilibrium has also been evaluated.

scholarly journals Investigation of the β-pinene photooxidation by OH in the atmosphere simulation chamber SAPHIR

2016 ◽  
Author(s):  
Martin Kaminski ◽  
Hendrik Fuchs ◽  
Ismail-Hakki Acir ◽  
Birger Bohn ◽  
Theo Brauers ◽  
...  
Keyword(s):  
Degradation Mechanism ◽  
Degradation Process ◽  
Product Distribution ◽  
High Reactivity ◽  
Oxidation Products ◽  
Chemical Mechanism ◽  
Emission Rates ◽  
Photochemical Degradation ◽  
Atmosphere Simulation Chamber ◽  
Simulation Chamber

Abstract. Beside isoprene, monoterpenes are the non-methane volatile organic compounds (VOC) with the highest global emission rates. Due to their high reactivity towards OH, monoterpenes can dominate the radical chemistry of the atmosphere in forested areas. In the present study the photochemical degradation mechanism of β-pinene was investigated in the Jülich atmosphere simulation chamber SAPHIR. The focus of this study is on the OH budget in the degradation process. Therefore the SAPHIR chamber was equipped with instrumentation to measure radicals (OH, HO2, RO2), the total OH reactivity, important OH precursors (O3, HONO, HCHO), the parent VOC beta-pinene, its main oxidation products, acetone and nopinone, and photolysis frequencies. All experiments were carried out under low NOx conditions (≤ 2 ppb) and at atmospheric beta-pinene concentrations (≤ 5 ppb) with and without addition of ozone. For the investigation of the OH budget, the OH production and destruction rates were calculated from measured quantities. Within the limits of accuracy of the instruments, the OH budget was balanced in all β-pinene oxidation experiments. However, even though the OH budget was closed, simulation results from the Master Chemical Mechanism 3.2 showed that the OH production and destruction rates were underestimated by the model. The measured OH and HO2 concentrations were underestimated by up to a factor of two whereas the total OH reactivity was slightly overestimated because of the poor reproduction of the measured nopinone by the model by up to a factor of three. A new, theory-derived first-generation product distribution by Vereecken and Peeters was able to reproduce the measured nopinone time series and the total OH reactivity. Nevertheless the measured OH and HO2 concentrations remained underestimated by the numerical simulations. These observations together with the fact that the measured OH budget was closed suggest the existence of unaccounted sources of HO2.

scholarly journals Facile Synthesis of Porous ZnO Nanoparticles Efficient for Photocatalytic Degradation of Biomass-Derived Bisphenol A Under Simulated Sunlight Irradiation

2021 ◽  
Vol 8 ◽  
Author(s):  
Yujie Wang ◽  
Kang Hu ◽  
Zhiyu Yang ◽  
Chenlu Ye ◽  
Xin Li ◽  
...  
Keyword(s):  
Bisphenol A ◽  
Photocatalytic Degradation ◽  
Inorganic Ions ◽  
Endocrine Disrupting Compounds ◽  
Degradation Process ◽  
Sunlight Irradiation ◽  
Calcination Temperatures ◽  
Endocrine Disrupting Compound ◽  
Endocrine Disrupting ◽  
Photocatalytic Removal

Bisphenol A (BPA) produced from biomass is a typical endocrine disrupting compound that is carcinogenic and genotoxic and can be accumulated in water due to its extensive use and difficult degradation. In this study, the porous ZnO photocatalyst with core-shell structure and large surface area was successfully developed for the efficient photocatalytic degradation of BPA. The various effects of calcination temperatures, BPA concentrations, ZnO dosages, pH and inorganic ions on the degradation performance were systemically studied. The results showed that 99% degradation of BPA was achieved in 1 h using the porous ZnO calcined at 550°C under the conditions of 30 mg/L BPA, 1 g/L ZnO, and pH of 6.5. Besides, the inhibition effects of anions for the photocatalytic removal of BPA decreased in the order of H2PO4- > HCO3- > SO42- > Cl−, while the cations K+, Ca2+, and Na+ had little effect on the photocatalytic degradation of BPA. The results of scavenging experiments showed that h+, ·O2-, and e− played the key role in the photocatalytic degradation process. Finally, the main pathways of BPA degradation were proposed based on ten intermediates found in the degradation process. This work may provide a good guideline to degrade various endocrine disrupting compounds in wastewater treatment.

Formation and stability of porphyrin and phthalocyanine self-assembled monolayers on ZnO surfaces

2016 ◽  
Vol 20 (08n11) ◽  
pp. 1264-1271 ◽  
Author(s):  
Hanna Hakola ◽  
Essi Sariola-Leikas ◽  
Paavo Jäntti ◽  
Thomas Mokus ◽  
Kati Stranius ◽  
...  
Keyword(s):  
Thin Films ◽  
Zno Nanorods ◽  
Self Assembled Monolayers ◽  
Layer Formation ◽  
Zno Film ◽  
Assembled Monolayers ◽  
Self Assembled ◽  
Anchoring Groups ◽  
The Stability ◽  
Phosphate Groups

Formation of self-assembled monolayers (SAMs) of three porphyrin and one phthalocyanine derivatives on thin ZnO film was studied by monitoring absorption spectra of the samples. The compounds were equipped with carboxylic or phosphate groups to bind to the surface. The SAM formation was found to be fast. The layer was formed in less than 15 min for all studied porphyrins, and 30 min was sufficient to form phthalocyanine layer. For porphyrins with different anchor groups the SAM formation was too fast to see any difference between the anchoring groups. The stability of SAMs was tested then by immersing the samples into neat solvents. Upon immersion the SAMs were gradually losing the absorbance for all the compounds with degradation trends being in line with p[Formula: see text] values of the binding groups of the same type. However, even for the weakest binding group the SAM was relatively stable after a few tens of minutes of washing, which was sufficient to remove physisorbed compounds but the SAM was essentially not destroyed. Comparison of SAMs on thin films with SAMs on ZnO nanorods and TiO2 nanoparticle films indicated the same fast layer formation but relatively weaker SAMs stability, showing 20–40% faster absorption losses during the washing.

scholarly journals Stability and Degradation Mechanismof Si-based Photocathodes for Water Splitting with Ultrathin TiO2 Protection Layer

2019 ◽  
Vol 0 (0) ◽  
Author(s):  
Emanuel Ronge ◽  
Thorsten Cottre ◽  
Katharina Welter ◽  
Vladimir Smirnov ◽  
Natalie Jacqueline Ottinger ◽  
...  
Keyword(s):  
Water Splitting ◽  
Atomic Layer ◽  
Degradation Process ◽  
Alkaline Media ◽  
Semiconductor Surface ◽  
Nucleation Sites ◽  
Enhanced Solubility ◽  
High Structural Perfection ◽  
Protection Layer ◽  
The Stability

Abstract Using transmission and scanning electron microscopy, we study mechanisms which determine the stability of Silicon photocathodes for solar driven water splitting. Such tandem or triple devices can show a promising stability as photocathodes if the semiconductor surface is protected by an ultrathin TiO2 protection layer. Using atomic layer deposition (ALD) with Cl-precursors, 4–7 nm thick TiO2 layers can be grown with high structural perfection. The layer can be electrochemically covered by Pt nanoparticels serving as electro-catalysts. However, Cl-remnants which are typically present in such layers due to incomplete oxidation, are the origin of an electrochemical degradation process. After 1 h AM1.5G illumination in alkaline media, circular shaped corrosion craters appear in the topmost Si layer, although the TiO2 layer is intact in most parts of the crater. The crater development is stopped at local inhomogenities with a higher Pt coverage. The observations suggests that reduced Titanium species due to Cl−/O2− substitution are nucleation sites of the initial corrosion steps due to enhanced solubility of reduced Ti in the electrolyte. This process is followed by electrochemical dissolution of Si, after direct contact between the electrolyte and the top Si layer surface. To increase the stability of TiO2 protected photocathodes, formation of reduced Ti species must be avoided.

scholarly journals Massaranduba Sawdust: A Potential Source of Charcoal and Activated Carbon

Polymers ◽  
2019 ◽  
Vol 11 (8) ◽  
pp. 1276 ◽  
Author(s):  
Castro ◽  
Nobre ◽  
Napoli ◽  
Bianchi ◽  
Moulin ◽  
...  
Keyword(s):  
Activated Carbon ◽  
Surface Area ◽  
Value Added ◽  
High Reactivity ◽  
Large Surface Area ◽  
Scanning Calorimetry ◽  
Co2 Gas ◽  
Heat Treated ◽  
Amorphous Structures ◽  
Adsorption Desorption

This paper provides proof of concept that activated carbon (AC) may be readily produced using limited conversion methods and resources from sawdust of massaranduba (Manilkara huberi) wood, thereby obtaining value-added products. Sawdust was sieved and heat-treated in an oxygen-free muffle furnace at 500 °C to produce charcoal. The charcoal was activated in a tubular electric furnace at 850 °C while being purged with CO2 gas. Microstructural, thermal and physical properties of the three components: sawdust, charcoal and AC were compared by means of field emission scanning electron microscopy (FESEM), X-ray diffractometry (XRD), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), density and water adsorption/desorption measurements. The resulting AC had a large surface area as measured by Brunauer-Emmett-Teller (BET) comparable to other such values found in the literature. The large surface area was due to pore development at the microstructural level as shown by FESEM. XRD illustrated that sawdust had a semi-crystalline structure whereas charcoal and AC evidenced mostly amorphous structures. TGA and DSC showed that AC had high reactivity to moisture compared to sawdust and charcoal.

Structural and Electrical Properties of Hydrothermal Growth ZnO Nanorods

2015 ◽  
Vol 1109 ◽  
pp. 104-107
Author(s):  
K.L. Foo ◽  
U. Hashim ◽  
Chun Hong Voon ◽  
M. Kashif
Keyword(s):  
Electrical Properties ◽  
Zno Nanorods ◽  
Wide Band ◽  
Hydrothermal Growth ◽  
Oxide Semiconductor ◽  
Wide Band Gap ◽  
Interdigitated Electrode ◽  
Growth Technique ◽  
Xrd Pattern ◽  
Structural And Electrical Properties

ZnO nanorods, type of the metal-oxide semiconductor deposited on interdigitated electrode (IDE) substrate using hydrothermal growth technique. The growth ZnO nanorods was annealed in furnace at 500°C for 2 hours as to obtain highly crystallite of ZnO nanorods. XRD pattern indicated the synthesized ZnO nanorods have preferred orientation along the (002) plane. Moreover, FESEM images showed that the nanorods with the size less than 60 nanometer were successfully synthesized using hydrothermal growth technique. The investigation on optical properties using UV-Vis-NIR spectrophotometer confirmed ZnO is classified as a wide band gap semiconductor material. Furthermore, the growth ZnO nanorods which undergo electrical properties testing using dielectric analyzer and source meter show that the ZnO nanorods demonstrated rectifying behaviour.

The influence of X-rays on the stability of selected properties of polyethylene

2018 ◽  
Vol 23 (1) ◽  
pp. 3-11
Author(s):  
Anna Wiśniewska ◽  
Gabriela Chwalik ◽  
Sylwia Łagan
Keyword(s):  
Free Energy ◽  
Surface Free Energy ◽  
Living Organism ◽  
Degradation Process ◽  
Material Surface ◽  
Control Group ◽  
X Rays ◽  
X Ray ◽  
The Stability

The evaluation of a degradation process of polyethylene (PE) in in vitro conditions under the influence of X-rays (X) and an in-cubation in two solutions simulating the environment of a living organism (SBF – simulated body fluid) was carried out. A dose corresponding to 10 standard X-ray pictures of the skeletal system as well as Ringer's and saline solutions at 40°C were used in the study. The paper presents the results of the influence of the 12-month studies on the selected surface properties of the material: surface wettability and abrasiveness. The value of surface free energy (SFE) was determined on the basis of the wetting angle measurements. The conductivity of the incubation fluids was also analyzed. The obtained results indicate that the adopted dose of X-ray radiation has no significant effect on the wettability of the surface of polyethylene. The nature of the surface layer of polyethylene did not change as a result of the 12-month incubation and remained hydrophilic. For the samples incubated in both immersion fluids, a decrease in surface free energy (SFE) was observed. For both the irradiated material and the control group, no significant changes in the mass of the samples and the conductivity of the incubation fluids were found, which indicates the stability of polyethylene. However, the abrasion value increased by approximately 26%. With the passage of the incubation time, a decrease in the value of this parameter was observed for the polyethylene subjected to radiation. No significant changes were found for the control group.

scholarly journals Photochemical degradation of isoprene-derived 4,1-nitrooxy enal

2016 ◽  
Vol 16 (9) ◽  
pp. 5595-5610 ◽  
Author(s):  
Fulizi Xiong ◽  
Carlos H. Borca ◽  
Lyudmila V. Slipchenko ◽  
Paul B. Shepson
Keyword(s):  
First Generation ◽  
Degradation Process ◽  
Reaction Chamber ◽  
High Reactivity ◽  
Uv Absorption ◽  
Ionization Mass ◽  
Photochemical Degradation ◽  
Photolysis Frequency ◽  
Isoprene Oxidation ◽  
Uv Absorption Spectrum

Abstract. In isoprene-impacted environments, carbonyl nitrates are produced from NO3-initiated isoprene oxidation, which constitutes a potentially important NOx reservoir. To better understand the fate of isoprene carbonyl nitrates, we synthesized a model compound, trans-2-methyl-4-nitrooxy-2-buten-1-al (4,1-isoprene carbonyl nitrate, or 4,1-isoprene nitrooxy enal), and investigated its photochemical degradation process. The measured OH and O3 oxidation rate constants (298 K) for this nitrooxy enal are 4.1(±0.7)  ×  10−11 cm3 molecules−1 s−1 and 4.4(±0.3)  ×  10−18 cm3 molecules−1 s−1, respectively. Its UV absorption spectrum was determined, and the result is consistent with TDDFT calculations. Based on its UV absorption cross section and photolysis frequency in a reaction chamber, we estimate that the ambient photolysis frequency for this compound is 3.1(±0.8)  ×  10−4 s−1 for a solar zenith angle of 45°. The fast photolysis rate and high reactivity toward OH lead to a lifetime of less than 1 h for the isoprene nitrooxy enal, with photolysis being a dominant daytime sink. The nitrate products derived from the OH oxidation and the photolysis of the nitrooxy enal were identified with an iodide-based chemical ionization mass spectrometer. For the OH oxidation reaction, we quantified the yields of two nitrate products, methyl vinyl ketone nitrate and ethanal nitrate, which together contributed to 36(±5) % of the first-generation products.

Sign in / Sign up

Export Citation Format

Share Document