First-order Reaction Equation Research Articles

Photoisomerization and photoorientation of brilliant yellow in the thin film state

The features of photoisomerization and photoorientation of azo dye brilliant yellow (BY) in the thin film state are studied. The trans-cis-isomerization of the dye molecules is established to proceed upon irradiation of the films based on BY with a full light of an ultra-high pressure lamp DRT-1000 (UV / VID light), this reaction is described by the first-order reaction equation. Under the action of linearly polarized blue light (λ = 457 nm), an optical anisotropy arises in films of BY. Optically anisotropic films of BY with a high dichroic ratio (>10) are shown to be formed using N-methylpyrrolidone and N, N-dimethylformamide as solvents and cellulose acetate as the polymer matrix.

Surface segregation modeling in the case of evaporation

A kinetic model is proposed to characterize surface segregation in the case of evaporation. The kinetics is formulated using the difference between the diffusion rate of solute atom in the bulk and the evaporation rate of solute atom from the surface layer. The first-order reaction equation is applied to quantify evaporation flux. A balanced state is quantified when the vapor and ambient pressure is equal and thus a complete quantification of the kinetics forms. The kinetic curve is convex prior to critical time and concave after. The maximum surface concentration decreases as evaporation parameter decreases. The kinetics of Mg surface segregation of Al-0.8 wt%Mg alloy is fitted. An enrichment ratio of 16.484 and evaporation parameter of 0.57 are the values that fit the experimental results the best. The balanced surface concentration of Mg is calculated and implies further evaporation with prolonged time. The proposed model can adequately describe surface segregation in the case of evaporation, and the formulated kinetics can satisfactorily quantify this phenomenon.

Drying guideline to control colour quality of para rubber sheet by computation method

Colour is one of the most important basic physical characteristics of dried para rubber sheets. This characteristic is used to determine the standards and trading prices. In this research, a mathematical model and a colour change equation were developed for para rubber sheet drying in a hot air oven, with the yellowness index (YI) as an indicator. The results show that the mathematical model provides validation of the moisture change and that the first-order rate reaction equation gives a satisfactory prediction of the colour change. The determination coefficient for every drying condition is between 0.9080–0.9742 and 0.9273–0.9813. Suitable drying conditions were used in the simulation using the model and equation, and the shortest drying time was applied in the study. Moreover, the colour value of the simulated para rubber sheet is not higher than that of the reference Unsmoked Sheet (USS) whose moisture is decreased by sun drying and is still in the best standard range.

Significantly photoinduced synergy between sodium sulfite and ammonium nitrate and the mechanism study.

In this paper, a significantly photoinduced synergy between ammonium nitrate and sodium sulfite via dye decolorization was first found. This study mainly aims to explore the influences of several fundamental aspects on the photoinduced synergy as well as discuss the detailed mechanisms. The dye removal efficiencies of methyl orange and methylene blue of the synergistic system are much higher than that of a single one, and they reach 96.4% and 90.7% when the illumination is 6 and 14 min, respectively. The optimum mass ratio of sodium sulfite and ammonium nitrate in the reaction system is 1:1. The reaction process of photoinduced synergy follows the first-order reaction equation. Effects of different structures of dyes, amount of sodium sulfite and initial dye concentration on the synergistic effect were investigated. The changes of UV-vis spectra in the course of photoinduced synergy were also examined. The excellent synergistic effect can owe to the simultaneous photoreduction and photooxidation reaction with respect to photoinduced hydrated electrons (eaq-) and SO4•- active species, respectively. This work may provide some insight into detoxifying water contaminants in practical applications as well as developing other novel photoinduced synergistic systems with high performance.

Photodecomposition of surfactants using Ti(IV)-doped calcium hydroxyapatite particles

The decomposition of surfactants under UV irradiation was carried out using Ti(IV)-doped calcium hydroxyapatite (TiHap) particles with various Ti/(Ca+Ti) atomic ratios (XTi). The typical cationic, anionic, and nonionic surfactants, namely, cetyltrimethylammonium bromide (CTAB), sodium dodecyl sulfate (SDS), and polyoxyethylene nonylphenyl ether (NP-15, which has 15 oxyethylene units on average), respectively, were used. CTAB readily decomposed in the presence of TiHap particles with XTi values of 0.10 and 0.20. The plot of CTAB concentration versus time for the decomposition was fitted with a first-order reaction rate equation, and rate constants (k) were obtained. k values for the CTAB system were independent of the XTi values of TiHap particles, that is, TiHap particles facilitated the decomposition of CTAB under UV irradiation. A considerable amount of the hydrocarbon chains in CTAB molecules decomposed because the percentage of CO2 produced (PCP) increased to 55–70% after UV irradiation for 240 h. We also obtained k values for the SDS system using the first-order reaction equation, although the fit was slightly inferior to that observed with the CTAB system. This result may be explained by the electrostatic repulsive force between negatively charged SDS and TiHap particles. In addition, the PCPs after UV irradiation for 120 h slowly increased to 20–35%, which are less than those obtained for CTAB. Nevertheless, few NP-15 molecules (15%) decomposed after UV irradiation for 240 h. The decomposition rates for the three surfactants followed the order CTAB > SDS >> NP-15.

Characteristics of DO, organic matter, and ammonium profile for practical-scale DHS reactor under various organic load and temperature conditions

ABSTRACTProfile analysis of the down-flow hanging sponge (DHS) reactor was conducted under various temperature and organic load conditions to understand the organic removal and nitrification process for sewage treatment. Under high organic load conditions (3.21–7.89 kg-COD m−3 day−1), dissolved oxygen (DO) on the upper layer of the reactor was affected by organic matter concentration and water temperature, and sometimes reaches around zero. Almost half of the CODCr was removed by the first layer, which could be attributed to the adsorption of organic matter on sponge media. After the first layer, organic removal proceeded along the first-order reaction equation from the second to the fourth layers. The ammoniacal nitrogen removal ratio decreased under high organic matter concentration (above 100 mg L−1) and low DO (less than 1 mg L−1) condition. Ammoniacal nitrogen removal proceeded via a zero-order reaction equation along the reactor height. In addition, the profile results of DO, CODCr, and NH3-N were different in the horizontal direction. Thus, it is thought the concentration of these items and microbial activities were not in a uniform state even in the same sponge layer of the DHS reactor.

Bioremediation of synthetic high–chemical oxygen demand wastewater using microalgal species Chlorella pyrenoidosa

ABSTRACTThe microalgal species Chlorella pyrenoidosa was cultivated in synthetic wastewater of initial chemical oxygen demand (COD), nitrate, and phosphate concentrations of 5000, 100, and 40 mg/L, respectively. The aim of the study was to find out the tolerance of microalgae to different COD concentrations and the extent of COD degradation at those concentrations. Three dilutions of wastewater (initial COD concentrations 5000, 3000, and 1000 mg/L) and three inoculum sizes (0.1, 0.2, and 0.3 g/L) were considered for the study. The experimental parameters such as total organic carbon, total inorganic carbon, COD, optical density, total solids, nitrate, and phosphate were measured on a daily basis. Biodegradation kinetics was determined for all cases using first-order reaction and Monod degradation equations. Optimal results showed that up to 90% reduction in TOC was obtained for 1000 COD wastewater while only 38% reduction in total organic carbon (TOC) was achieved for 5000 COD wastewater. Over 95% reduction in nitrate and nearly 90% removal of phosphate were obtained with the lowest microalgal inoculum concentration (i.e., 0.1 g/L) for all COD dilutions. This study showed that microalgal species C. pyrenoidosa can successfully degrade the organic carbon source (i.e., acetate) with significant removal efficiencies for nitrate and phosphate.

Chemisorption of sulfur (IV) oxide using the horizontal apparatus with bucket-like dispersers

Due to the growing energy consumption and increasing share of fuels with high sulfur content in the global energy balance, there is a need for new, highly efficient methods and apparatus for recycling exhaust SO 2 -containing gases. It is found that SO 2 -low-concentrated gases are advisable to recycle by the liquid-oxidation method using NaOH as an intermediate absorbent and air oxygen as oxidant. Effective head apparatus – horizontal apparatus with bucket-like dispersers (HABD) is proposed for the cleaning process. To confirm the effectiveness of this apparatus in the processes of chemisorption and liquid phase oxidation of SO 2 , a pilot study on enlarged laboratory setup, the head apparatus of which was a scale model of HABD is carried out. The study is conducted in a wide range of concentrations of SO 2 (0,4...34·g/Nm 3 ) and pH of absorbing solutions (pH=3...13) using modern gas-analyzing devices. It is found that the irrigation density of 0.5 m 3 /Nm 3 is technologically feasible. The cleaning process is appropriate to perform under counterflow motion of phases, which will allow combining chemisorption and oxidation in one HABD, provide high degrees of recovery (99.9...100 %) and liquid phase oxidation (80...99 %) of SO 2 . Due to the high velocity of dispersed droplets of ~ 10 m/s and intensive interphase renewal, it is managed to significantly reduce the diffusion resistance in the gas phase and transfer the process to the liquid film and provide high mass transfer coefficients of 0,82·10 -4 …1,80·10 -4 (Pa·s·m 3 ). It is found that at low initial concentrations of SO 2 (0,4...7,74 g/Nm 3 ), the process rate is limited by SO 2 diffusion, and at high (10.54...33.89 g/Nm 3 ) - NaOH diffusion. The process under study is described by the first-order reaction equation and is characterized by high values of the process rate constant – 0.46 s -1 . Pilot studies confirm the high efficiency of HABD in the studied processes, prove the possibility of combining dust collection, chemisorption and oxidation stages in one apparatus.

Preparation of Coated CMC-nZVI Using Rheological Phase Reaction Method and Research on Degradation of Chloroform in Water

This study reported the synthesis of nanoscale zero-valent iron (nZVI) by rheological phase reaction method in the presence of sodium (CMC). The synthesized CMC coated nZVI (CMC-nZVI) was then characterized with x-ray diffraction (XRD) and transmission electron microscope (TEM) and was tested for the removal of chloroform from simulated groundwater. The investigated parameters in the uptake experiments included different adsorbents, initial concentrations of chloroform and different water flow. The results show that:(1) the prepared CMC-nZVI has good stability and dispersibility; (2) when the concentration of chloroform is 0.1 mg/L, the dosage of CMC-Fe0 is 0.01 g, the removal rate of chloroform is 91.2%;(3)The reaction follows the first-order kinetic reaction equation, and the apparent reaction rate constant increases with decreasing the concentration of chloroform.

Modelling of Changes in Postharvest Quality Parameters of Stored Carrots Subjected to Pre- and Postharvest Treatments

Abstract The aim of this study was to develop qualitative models that enable prediction of quality of carrots. A full factorial experiment including preharvest biocatalyst application, dipping treatments and storage temperatures was employed. Eleven different biochemical and microbiological quality parameters of carrot (Daucus carota L.) were investigated. The effects of treatments on the shelf-life were investigated using discriminant analysis (DA). The lower storage temperatures (1°C) maintained the superior quality. Kinetic functions were applied to each parameter using the Levenberg–Marquardt algorithm to characterize the rate of change of quality. DAs significantly (P < 0.001) differentiated between the combined effects of the preharvest biocatalyst treatment and storage temperatures. Four discriminant functions factored the differentiation of the quality attributes based on storage time. The models fit well to the experimental data for storage at 1°C. The second-order reaction equations allowed for prediction of ascorbic acid, sucrose and sugar–hexose ratio. First-order reaction equations that allow estimation of fructose, sucrose equivalent, total coliform and total fungi and O2 were developed. The empirical evidence suggests that freshness was maintained in the carrots until day 14 (P < 0.001). Ascorbic acid, sucrose and sugar–hexose ratio were the most relevant parameters to rapidly detect the postharvest changes following the second-order decay rate.

Дослідження кінетики осадження нікелю з розчину

Background. In the nickel-containing catalysts production there is the technological stage of the intermediate insoluble nickel compounds. The studies of the nickel precipitation kinetics by the urea from the nickel nitrate solution were carried out that are useful for the design and characteristics calculation of these processes,Objective. The purpose is in constructing of mathematical model for the nickel precipitation process.Methods. A thermodynamic evaluation of possible reactions in solution was carried out. In isothermal conditions at the temperatures of 90 and 100 °C the kinetic curves of nickel precipitation from solutions were obtained at different initial concentrations. On the curves several sections were marked: the induction period and the main reaction period that are analyzed by different methods. The dependence of the induction period value from the conditions of the process was analyzed using multiple regression approach. The kinetic equation of first order reaction was chosen for the main period and the temperature dependence of the rate according to Arrhenius equation was determined.Results. It is established that the value of the induction period depends on the process temperature and the concentration of nickel, the regression equation was obtained. It is shown that the basic section of the precipitation process kinetic curves are described by the equation of the first order at the different initial concentrations of metal in all the investigated temperature range, reaction rate constant of the first order and the activation energy of the process were calculated.Conclusions. The proposed kinetic model of precipitation that consists of equations system for calculating the time of reaction was obtained. The value of the activation energy of the process indicates a kinetic stage of process tendency.

Kinetic study on the protein decomposition by photocatalytic Ti(IV)-doped calcium hydroxyapatite particles

Green Platform Laboratory, Device & Materials Laboratory Fujitsu Laboratories Ltd.,10–1 Morinosato-Wakamiya, Atsugi, Kanagawa 243–0197, JapanKinetic study was done for the decomposition process of lysozyme (LSZ) on the surface of Ti(IV)-doped calcium hydroxyapatite(TiHap) particles. The decomposition of LSZ was examined by changing the weight of TiHap particles dispersed and reactiontemperature. The decomposition of LSZ was analyzed by using the first order reaction. The obtained data fairly fit to the firstorder reaction equation, and the rate constant (k) was obtained. Since a good linear relationship was obtained between k valuesand particle weigh of TiHap, it was concluded that the decomposition of LSZ molecules occurs on the surface of TiHap. Theactivation energy of the reaction of LSZ decomposition on the surface of TiHap particles was determined as 30.2kJ/mol byvarying the decomposition temperature from 5 to 45°C. The comparison experiments between 0h UV and 24h UV methodsrevealed that the decomposition of LSZ needs appropriate rates of adsorption and decomposition at the TiHap particle surface. Itwas ascertained that the decomposition temperature at 25­45°C is appropriate to proceed continuous decomposition of LSZ for along time. The LC-MS measurements reveled that LSZ molecules were decomposed to the small molecules with molecular weightof 1/35­1/50 to LSZ one and they converged to the compounds with low molecular weight of 288­316 after a long time UVirradiation.

Photodecomposition of dodecyltrimethylammonium bromide in aqueous solutions in presence of hydrogen peroxide

It is established that the cationic surfactant (dodecyltrimethylammonium bromide, DTAB) efficiently decomposes in an aqueous solution in the presence of H2O2 upon exposure to UV radiation. The presence of bicarbonate ions decreases the rate of photodecomposition, which is due to the acceptance of OH radicals generated in the photochemical reaction. The rate constant of OH radicals and DTAB reaction equals ∼109 L mol−1 s−1. The kinetics of DTAB decomposition are described by the first-order reaction equation, and the effective rate constant is proportional to the H2O2 content in the solution.

Method of calculation of calcite thermal analysis curves

The technique of data processing for thermogravimetry of calcite with use of MathCad 11 is developed. There are designed basic kinetic parameters of processes of calcite powder thermal decomposition with use of the equation of first order reaction: size of critical increment of energy, a kinetic constant of decomposition process. Decomposition point of calcite is experimentally determined.

Influence of Trace Elements on Stabilization of Aqueous Solutions of Ascorbic Acid

Together with vitamin C, zinc, selenium, manganese, and magnesium play a vital role in the preservation of organs scheduled for transplantation. In the present study, it is shown that addition of 1 mg/l of these elements influences the stability of 0.3 mM ascorbic acid solutions. The solution’s stability was estimated using an accelerated stability test. The concentration of vitamin C was measured using a validated spectrophotometric method, which uses the reduction of 2,6-dichlorophenoloindophenol by ascorbic acid. Elevated temperatures, the factor accelerating substances’ decomposition reaction rate, were used in the tests. The research was conducted at two temperatures at intervals of 10 °C: 80 ± 0.1 and 90 ± 0.1 °C. It was stated that the studied substances’ decomposition occurred in accordance with the equation for first-order reactions. The function of the logarithmic concentration (log%C) over time was revealed to be rectilinear. This dependence was used to determine the kinetics of decomposition reaction rate parameters. The stabilization of vitamin C solutions was measured as the time in which 10 % of the substance decomposed at 20 and 0 °C. Addition of Se(IV) or Mg(II) ions significantly increase the stability of ascorbic acid solution (∼34 and ∼16 %, respectively), but Zn(II) causes a significant decrease in stability by ∼23 %. Addition of Mn(II) has no significant influence on vitamin C stability.

Study on the Predictive Models of the Quality of Silver Carp (Hypophthalmichthys Molitrix) Fillets Stored under Variable Temperature Conditions

Predictive models about the quality changes of silver carp (Hypophthalmichthys molitrix) fillets stored under variable temperatures were investigated. Electrical conductivity (EC), total aerobic count (TAC), total volatile base nitrogen (TVB-N) and sensory score of silver carp fillets stored at 270, 273, 276, 282 and 288 K were determined. Different reaction orders (zero, first and second) were tested; EC, TAC and TVB-N followed a first-order reaction equation; and sensory score followed a zero-order reaction equation based on the total coefficient of determination (ΣR2). The effect of temperature and storage time on the quality of silver carp fillets was modeled by using Arrhenius equation. All the relative errors of validation experiments for EC, TAC and sensory score varied by <13% and for TVB-N varied by <13% within 12 days. Therefore, the models can predict the quality of silver carp fillets effectively within 270–288 K. Practical Applications In this work, the efficient quality models for silver carp fillets during refrigerated storage were established. The useful information about quality changes in silver carp fillets stored under different temperatures could be obtained by the predictive models. In addition, fast calculations of the quality changes based on the stored temperature allow optimizing their storage management and reducing the economic losses during cold chain. Therefore, the quality models of silver carp fillets have a brilliant prospect in predicting quality changes during the cold chain.

Adsorption, mobility and degradation of diphenamid in chinese soils

The present study was conducted to determine adsorption, mobility, and degradation characteristics of diphenamid in five Chinese soils and their relationships. The adsorption of diphenamid in soils tested could accurately be described by a Freundlich equation. Based on the mobility factor (Rf), diphenamid was seen to be slightly or moderately mobile in soils studied. Regression of Kf and Rf against selected soil properties indicated that Organic Matter (OM) was the most influential factor governing adsorption and mobility of diphenamid (r2 > 0.92) followed by clay (r2 > 0.61). There was a significant correlation (p > 0.01) between Kf and Rf of diphenamid. Diphenamid degradation data were fitted the first-order reaction equations, yielding half-lives (T1/2) ranging from 187.3 to 247.5 days in unsterilized soils but prolonging to 577.5–630.0 days in sterilized soils. The prolonged T1/2 by sterilization showed that microbial degradation was the dominant pathway for diphenamid degradation in soils. Degradation of diphenamid in soils appeared to be influenced by soil OM (r2 < 0.97) and clay content (r2 < 0.85). The T1/2 of diphenamid was significantly related to both Kf and Rf (p > 0.05), indicating that either Kf or Rf might be used as a model for predicting degradation of diphenamid in soils involved.

Benefits of Combinations of Vitamin A, C and E Derivatives in the Stability of Cosmetic Formulations

Chemically stable ester derivatives of vitamins A, C and E have become a focus of interest for their role in the satisfactory results in skin aging treatments. Accordingly, the aim of this study was to evaluate the physical and chemical stability of a cosmetic formulation containing 1% retinyl palmitate, ascorbyl tetraisopalmitate and tocopheryl acetate, alone or in combination. In the studies of physical stability, a Brookfield rheometer was used to determine rheological behavior of formulations containing the vitamins. Chemical stability was determined by HPLC on a Shimadzu system with UV detection. Results showed that formulations had pseudoplastic behavior and that vitamins did not alter their apparent viscosity and thixotropy. In the chemical stability studies, first-order reaction equations were used for determinations of the shelf-life of vitamins derivatives considering a remaining concentration of 85%. Combined vitamins in a single formulation had a slightly lower degradation rate as compared to different preparations containing only one of the vitamins. Considering that many cosmetic formulations contain vitamin combinations it is suggested that the present study may contribute to the development of more stable formulations containing liposoluble vitamins.

Photocatalytic Activity of TiO&lt;sub&gt;2&lt;/sub&gt; Coated on HZSM-5 Prepared by Oxalic Acid Treatment

Zeolite HZSM-5 was pre-treated by oxalic acid and used as support for TiO2film prepared by sol-gel method. Decoloration rates increased with TiO2concentration both for pure TiO2and TiO2/HZSM-5. Meanwhile, the total decoloration rate on TiO2/HZSM-5 is much higher than using pure TiO2on all TiO2concentrations. Methyl orange degradation on TiO2/HZSM-5 reached its maximum value at TiO2concentration of 600 mg/l. After 120 min of irradiation, decoloration rate on TiO2/HZSM-5 was near 100%, compared with 50% decoloration on pure TiO2. Photocatalytic degradation of methyl orange on both TiO2/HZSM-5 and TiO2follows the equation of first order reaction. Kinetic constant on TiO2/HZSM-5 is k1=0.02663 min-1, which is much higher than that on pure TiO2, k2=0.010154 min-1.

Impact of Microwave Drying on the Quality Attributes of Okra Fruit

The impact of microwave drying on quality attributes of dried okra was investigated at three levels of power between 500 and 800 W during microwave drying and was compared with that of hot air drying at four temperatures ranging from 40 to 70°C. The drying characteristics, the decreasing rate of the ascorbic acid and the total color change of okra during microwave and hot air drying were examined. An exponential model was suitable to describe the microwave and the hot air drying characteristics of okra. The drying constant k1 ranged from 0.27 to 0.36 min-1 for microwave drying and from 0.15 to 0.49 h-1 for the hot air drying. The ascorbic acid content during microwave and hot air drying was measured and then a first-order reaction equation was used to calculate the decomposition rate of the ascorbic acid. Values of the coefficient of decomposition rate ranged from 0.40 to 0.46 min-1 for microwave drying. Using the change on standing in the total color difference during microwave and hot air drying, the extent of browning, B and the coefficient of browning rate k2 were estimated. In addition, the rehydration rate of the sample which was dried with the seven conditions in this test was highest at 800 W for the microwave drying. Therefore, it was confirmed that the microwave drying at 800 W was most suitable for okra drying within this test.