scholarly journals Optimization of TiO2-P25 photocatalyst dose and H2O2 concentration for advanced photooxidation using the smartphone-based colorimetry

2021 ◽  
Author(s):  
Nazarii Danyliuk ◽  
Tetiana Tatarchuk ◽  
Karthik Kannan ◽  
Alexander Shyichuk
Keyword(s):  
Reaction Rate ◽  
Wastewater Treatment Plants ◽  
Organic Pollutant ◽  
Side Reaction ◽  
Reaction Rate Constant ◽  
Oh Radicals ◽  
H2o2 Concentration ◽  
Reaction Rate Constants ◽  
Photodegradation Rate ◽  
Final Degree

Abstract Color images taken by a smartphone camera were used to estimate the rate of advanced photooxidation reaction of Direct Red 23 (DR23) azo dye as a model organic pollutant. The RGB color coordinates were tested to quantify the dye. Images of the reaction mixture were taken at specified intervals to obtain kinetic lines and reaction rate constants. Both the reaction rate constant and the final degree of degradation were plotted as functions of the photocatalyst dose and the concentration of H2O2. The smartphone measurements are fully consistent with the reference spectrophotometry data. The maximum degradation efficiency of the DR23 dye was recorded at C0(H2O2) = 2.5 mM and photocatalyst dose equal to 1.0 mg/L. Higher H2O2 concentrations reduce the degradation rate as a result of the side reaction of H2O2 with OH radicals. A two-factor experimental design was used to study the effects of photocatalyst dose and H2O2 concentration with 5 and 7 levels, respectively. The ANOVA results indicated that the concentration of H2O2 had the greater influence. The smartphone provides quick and easy measurement of the photodegradation rate directly in the solutions without sampling. The proposed approach can be applied under field conditions in wastewater treatment plants.

scholarly journals Laboratory study on heterogeneous decomposition of methyl chloroform on various standard aluminosilica clay minerals as a potential tropospheric sink

2003 ◽  
Vol 3 (2) ◽  
pp. 1843-1891
Author(s):  
S. Kutsuna ◽  
L. Chen ◽  
O. Ohno ◽  
N. Negishi ◽  
K. Takeuchi ◽  
...  
Keyword(s):  
Relative Humidity ◽  
Clay Minerals ◽  
Reaction Rate ◽  
Ground Surface ◽  
Reaction Rate Constant ◽  
Pseudo First Order Reaction ◽  
Dry Air ◽  
Reaction Rate Constants ◽  
Methyl Chloroform ◽  
Bet Equation

Abstract. Methyl chloroform (1,1,1-trichloroethane, CH3CCl3) was found to decompose heterogeneously on seven types of standard clay minerals (23 materials) in dry air at 313 K in the laboratory. All reactions proceeded through the elimination of HCl; CH3CCl3 was converted quantitatively to CH2=CCl2. The activities of the clay minerals were compared via their pseudo-first-order reaction rate constants (k1). A positive correlation was observed between the k1 value and the specific surface area (S) of clay minerals, where the S value was determined by means of the general Brunauer-Emmett-Teller (BET) equation. The k1 value was anti-correlated with the value of n, a parameter of the general BET equation, and correlated with the water content that can be removed easily from the clay minerals. The reaction required no special pretreatment of clay minerals, such as heating at high temperatures; hence, the reaction can be expected to occur in the environment. Photoillumination by wavelengths present in the troposphere did not accelerate the decomposition of CH3CCl3, but it induced heterogeneous photodecomposition of CH2=CCl2. The temperature dependence of k1, the adsorption constants of CH3CC3 and CH2=CCl2, and a surface reaction rate constant were determined for an illite sample. The k1 value increased with increasing temperature. The amount of CH3CCl3 adsorbed on the illite during the reaction was proportional to the partial pressure of CH3CCl3. The reaction was sensitive to relative humidity and the k1 value decreased with increasing relative humidity. However, the reaction was found to proceed at a relative humidity of 22% at 313 K, although the k1 value was about one-twentieth of the value in dry air. The conditions required for the reaction may be present in major desert regions of the world. A simple estimation indicates that the possible heterogeneous decomposition of CH3CC3 on the ground surface in arid regions is worth taking into consideration when inferring the tropospheric lifetime of CH3CC3 and global OH concentration from the global budget concentration of CH3CCl3.

scholarly journals Fast and Efficient Piezo/Photocatalytic Removal of Methyl Orange Using SbSI Nanowires

Materials ◽  
2020 ◽  
Vol 13 (21) ◽  
pp. 4803
Author(s):  
Krystian Mistewicz ◽  
Mirosława Kępińska ◽  
Marian Nowak ◽  
Agnieszka Sasiela ◽  
Maciej Zubko ◽  
...  
Keyword(s):  
Methyl Orange ◽  
Rate Constant ◽  
Reaction Rate ◽  
Reaction Rate Constant ◽  
Sonochemical Method ◽  
Reaction Rate Constants ◽  
Short Period ◽  
Photocatalytic Removal ◽  
Antimony Sulfoiodide ◽  
Novel Method

Piezocatalysis is a novel method that can be applied for degradation of organic pollutants in wastewater. In this paper, ferroelectric nanowires of antimony sulfoiodide (SbSI) have been fabricated using a sonochemical method. Methyl orange (MO) was chosen as a typical pollutant, as it is widely used as a dye in industry. An aqueous solution of MO at a concentration of 30 mg/L containing SbSI nanowires (6 g/L) was subjected to ultrasonic vibration. High degradation efficiency of 99.5% was achieved after an extremely short period of ultrasonic irradiation (40 s). The large reaction rate constant of 0.126(8) s−1 was determined for piezocatalytic MO decomposition. This rate constant is two orders of magnitude larger than values of reaction rate constants reported in the literature for the most efficient piezocatalysts. These promising experimental results have proved a great potential of SbSI nanowires for their application in environmental purification and renewable energy conversion.

scholarly journals “Transitivity”: A Code for Computing Kinetic and Related Parameters in Chemical Transformations and Transport Phenomena

Molecules ◽  
2019 ◽  
Vol 24 (19) ◽  
pp. 3478 ◽  
Author(s):  
Hugo G. Machado ◽  
Flávio O. Sanches-Neto ◽  
Nayara D. Coutinho ◽  
Kleber C. Mundim ◽  
Federico Palazzetti ◽  
...  
Keyword(s):  
Rate Constants ◽  
Reaction Rate ◽  
Reaction Rate Constant ◽  
State Theory ◽  
Chemical Transformations ◽  
Graphical Interface ◽  
Arrhenius Behavior ◽  
Reaction Rate Constants ◽  
Kinetic And Thermodynamic Parameters ◽  
Data Documentation

The Transitivity function, defined in terms of the reciprocal of the apparent activation energy, measures the propensity for a reaction to proceed and can provide a tool for implementing phenomenological kinetic models. Applications to systems which deviate from the Arrhenius law at low temperature encouraged the development of a user-friendly graphical interface for estimating the kinetic and thermodynamic parameters of physical and chemical processes. Here, we document the Transitivity code, written in Python, a free open-source code compatible with Windows, Linux and macOS platforms. Procedures are made available to evaluate the phenomenology of the temperature dependence of rate constants for processes from the Arrhenius and Transitivity plots. Reaction rate constants can be calculated by the traditional Transition-State Theory using a set of one-dimensional tunneling corrections (Bell (1935), Bell (1958), Skodje and Truhlar and, in particular, the deformed ( d -TST) approach). To account for the solvent effect on reaction rate constant, implementation is given of the Kramers and of Collins–Kimball formulations. An input file generator is provided to run various molecular dynamics approaches in CPMD code. Examples are worked out and made available for testing. The novelty of this code is its general scope and particular exploit of d -formulations to cope with non-Arrhenius behavior at low temperatures, a topic which is the focus of recent intense investigations. We expect that this code serves as a quick and practical tool for data documentation from electronic structure calculations: It presents a very intuitive graphical interface which we believe to provide an excellent working tool for researchers and as courseware to teach statistical thermodynamics, thermochemistry, kinetics, and related areas.

Synthesis and Paclobutrazol Visible-Light Degradation of Al/S Doped TiO2 Mesoporous Materials with Pyridine as a Template

2013 ◽  
Vol 652-654 ◽  
pp. 1602-1608
Author(s):  
Shao You Liu ◽  
Fei Zhang ◽  
Chen Yan Luo ◽  
Tian Zhi Jiang ◽  
Qing Ge Feng
Keyword(s):  
Visible Light ◽  
Mesoporous Materials ◽  
Reaction Rate ◽  
Photocatalytic Property ◽  
Reaction Rate Constant ◽  
Reaction Route ◽  
Narrow Pore Size Distribution ◽  
Photodegradation Rate ◽  
Visible Light Degradation ◽  
Co Doped

Al and S co-doped TiO2 (S-Al-TiO2) mesoporous materials as a kind of visible light photo- catalysts are prepared using pyridine as a template through a solid state reaction route. The materials features are characterized by the advanced instruments. The photodegradation kinetic of paclobutra- zol is investigated. It is shown that the doping of S and Al could effectively inhibit the growth of anatase TiO2, both S and Al have entered into the lattice of TiO2. Surface area of 81.3m2/g and narrow pore size distribution (~2.1nm) are presented, it not only enables the visible-light absorption but also promotes photocatalytic property of paclobutrazol. Moreover, within 150 min of visible-light irradiation, the photocatalytic degradation of paclobutrazol approximately follows an order kinetics, and the photodegradation rate in 46.7% and reaction rate constant of 0.00414 min-1 are obtained.

scholarly journals Kinetics study the decomposition of the cellulose into cellulose nanocrystals by hydrothermal with hydrochloric acid catalyst

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Zulnazri Zulnazri ◽  
Rozanna Dewi ◽  
Sulhatun Sulhatun ◽  
Nasrun Nasrun
Keyword(s):  
Hydrochloric Acid ◽  
Cellulose Nanocrystals ◽  
Reaction Rate ◽  
Acid Catalyst ◽  
Reaction Rate Constant ◽  
X Ray Diffraction ◽  
Hydrothermal Conditions ◽  
Reaction Rate Constants ◽  
Ft Ir

The aim of this study was to hydrolyzed cellulose nanocrystals as cellulose-based biomass residues from oil palm by using hydrochloric acid under hydrothermal conditions. The characterization of cellulose nanocrystals was determined by FT-IR spectroscopy and X- ray diffraction. The infrared spectroscopy showed there has been a removal of lignin and hemicellulose in the spectrum. Crystallinity which reaches 78.59% was obtained by hydrolysis using hydrochloric acid catalyst 3 mol/L with a reaction time of 1 hour. Based on the graph of -ln CA/CA0 vs. time obtained that Cellulose nanocrystals forming reaction is of first order. The reaction rate constants to the formation of glucose (k2) is greater than the reaction rate constant to the formation of Cellulose nanocrystals (k1), which indicates that the phase of slow reaction is the reaction of the most influential on the overall reaction rate, the reaction of the formation of Cellulose nanocrystals.

scholarly journals Investigation of the oxidation of methyl vinyl ketone (MVK) by OH radicals in the atmospheric simulation chamber SAPHIR

2018 ◽  
Vol 18 (11) ◽  
pp. 8001-8016 ◽  
Author(s):  
Hendrik Fuchs ◽  
Sascha Albrecht ◽  
Ismail–Hakki Acir ◽  
Birger Bohn ◽  
Martin Breitenlechner ◽  
...  
Keyword(s):  
Quantum Chemical ◽  
Reaction Rate ◽  
Reaction Rate Constant ◽  
Oh Radicals ◽  
Methyl Vinyl ◽  
Product Yields ◽  
Reaction Channels ◽  
Ho2 Radical ◽  
Model Measurement ◽  
Simulation Chamber

Abstract. The photooxidation of methyl vinyl ketone (MVK) was investigated in the atmospheric simulation chamber SAPHIR for conditions at which organic peroxy radicals (RO2) mainly reacted with NO (“high NO” case) and for conditions at which other reaction channels could compete (“low NO” case). Measurements of trace gas concentrations were compared to calculated concentration time series applying the Master Chemical Mechanism (MCM version 3.3.1). Product yields of methylglyoxal and glycolaldehyde were determined from measurements. For the high NO case, the methylglyoxal yield was (19 ± 3) % and the glycolaldehyde yield was (65 ± 14) %, consistent with recent literature studies. For the low NO case, the methylglyoxal yield reduced to (5 ± 2) % because other RO2 reaction channels that do not form methylglyoxal became important. Consistent with literature data, the glycolaldehyde yield of (37 ± 9) % determined in the experiment was not reduced as much as implemented in the MCM, suggesting additional reaction channels producing glycolaldehyde. At the same time, direct quantification of OH radicals in the experiments shows the need for an enhanced OH radical production at low NO conditions similar to previous studies investigating the oxidation of the parent VOC isoprene and methacrolein, the second major oxidation product of isoprene. For MVK the model–measurement discrepancy was up to a factor of 2. Product yields and OH observations were consistent with assumptions of additional RO2 plus HO2 reaction channels as proposed in literature for the major RO2 species formed from the reaction of MVK with OH. However, this study shows that also HO2 radical concentrations are underestimated by the model, suggesting that additional OH is not directly produced from RO2 radical reactions, but indirectly via increased HO2. Quantum chemical calculations show that HO2 could be produced from a fast 1,4-H shift of the second most important MVK derived RO2 species (reaction rate constant 0.003 s−1). However, additional HO2 from this reaction was not sufficiently large to bring modelled HO2 radical concentrations into agreement with measurements due to the small yield of this RO2 species. An additional reaction channel of the major RO2 species with a reaction rate constant of (0.006 ± 0.004) s−1 would be required that produces concurrently HO2 radicals and glycolaldehyde to achieve model–measurement agreement. A unimolecular reaction similar to the 1,5-H shift reaction that was proposed in literature for RO2 radicals from MVK would not explain product yields for conditions of experiments in this study. A set of H-migration reactions for the main RO2 radicals were investigated by quantum chemical and theoretical kinetic methodologies, but did not reveal a contributing route to HO2 radicals or glycolaldehyde.

Progress towards machine learning reaction rate constants

2021 ◽  
Author(s):  
Evan Komp ◽  
Nida Janulaitis ◽  
Stephanie Valleau
Keyword(s):  
Machine Learning ◽  
Potential Energy ◽  
Rate Constant ◽  
Rate Constants ◽  
Potential Energy Surfaces ◽  
Reaction Rate ◽  
Reaction Rate Constant ◽  
Reaction Rate Constants ◽  
The Cost ◽  
Energy Surfaces

Quantum and classical reaction rate constant calculations come at the cost of exploring potential energy surfaces. Due to the “curse of dimensionality”, their evaluation quickly becomes unfeasible as the system...

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