Comparative Kinetic Study Research Articles

Green chemical pathway of plasma synthesis of ammonia from nitrogen and water: a comparative kinetic study with a N2/H2 system

This work demonstrates alternative green ammonia processing using nitrogen and water based non-thermal plasma without pure hydrogen supply which results in an enormous amount of CO2 emission.

Kinetic Study on the Reactivity of Azanone (HNO) toward Cyclic C-Nucleophiles.

Azanone (HNO) is an elusive electrophilic reactive nitrogen species of growing pharmacological and biological significance. Here, we present a comparative kinetic study of HNO reactivity toward selected cyclic C-nucleophiles under aqueous conditions at pH 7.4. We applied the competition kinetics method, which is based on the use of a fluorescein-derived boronate probe FlBA and two parallel HNO reactions: with the studied scavenger or with O2 (k = 1.8 × 104 M−1s−1). We determined the second-order rate constants of HNO reactions with 13 structurally diverse C-nucleophiles (k = 33–20,000 M−1s−1). The results show that the reactivity of HNO toward C-nucleophiles depends strongly on the structure of the scavenger. The data are supported with quantum mechanical calculations. A comprehensive discussion of the HNO reaction with C-nucleophiles is provided.

Effects of pyrrolidine on methane hydrate formation: Thermodynamic, kinetic, and morphology perspectives

Solidified natural gas (SNG) via clathrate hydrates has been proposed as an alternative approach for natural gas storage and transportation. In this work, the roles of 5.56 mol% pyrrolidine were investigated for the methane hydrate formation in terms of thermodynamics and kinetics along with morphology. The results showed that pyrrolidine generally improved the thermodynamic stability of mixed methane hydrates, enhancing the formation at milder conditions than those of pure methane hydrates. To demonstrate the kinetic performance of pyrrolidine, the experiments were performed at 8 MPa and 285.2 K in a quiescent configuration. The results showed that a very short induction time and a rapid rate of hydrate formation with desirable methane uptake were achieved. In addition, a distinct methane bubble with breathing effect, assisting methane gas to interact with the bulk solution, was observed during the hydrate formation morphology. The comparative kinetic study with 5.56 mol% tetrahydrofuran (THF) was also carried out under the same driving force and the same experimental condition. Surprisingly, although THF gave a high methane uptake, pyrrolidine could give more than 10 times higher rate of hydrate formation at the same driving force; moreover, it provided a competitive rate with THF at the similar formation condition.

Optimization, upscaling and kinetic study of famine technique in a microalgal biofilm-based photobioreactor for nutrient removal

Microalgal wastewater treatment systems are promoted as promising, while harvesting costs, low removal efficiency, and long process time are major obstacles. The present study aims to introduce a comprehensive solution to overcome the difficulties by combining two methods of depletion and biofilm in the culture of Scenedesmus sp. using synthetic wastewater. For this purpose, two factors of depletion periods (one, two, three, and five days) and types of depletion (nitrogen, phosphorus, and both) were optimized by Taguchi design for the wastewater nutrient removal rate in lab-scale. The analysis of factors showed that a five-day complete depletion of nitrogen and phosphorus had the most significant effect on the removal of nitrogen compounds and phosphate, respectively. Optimization of factors led to 35, 8, 28 percent increases in ammonium, nitrate, and phosphate removal efficiencies, respectively and about 50 percent decrease in the process time in flasks. Lab-scale results were validated in cylindrical photobioreactors with external recycling (CPBERs) that achieved 73.2, 76.6, and 65.3 percent in ammonium, nitrate, and phosphate removal efficiencies, respectively. Finally, the comparative kinetic study of starved and non-starved processes led to a remarkable change in concentration dependency from first- to second-order after depletion. The optimized system that was provided can be of benefit for further researches in this area.

Mono- and dinuclear zinc complexes bearing identical bis(thiosemicarbazone) ligand that exhibit alkaline phosphatase-like catalytic reactivity.

Mono- and dinuclear zinc(II) complexes bearing bis(thiosemicarbazone) (bTSC) ligand were employed in the cleavage of phosphoester bonds. Comparative kinetic studies combined with theory suggested that the P-O bond cleavage is much accelerated by dinuclear zinc(II) complex in the presence of base. Based on the DFT-optimized structures of the proposed intermediates, it is plausible that (1) the removal of sulfur atoms of bTSC ligand from the zinc center provides two vacant sites for the binding of water (or hydroxide ion) and phosphoester and (2) the H-bonding between water (or hydroxide ion) and phosphoester, through several water molecules, may also assist the P-O bond cleavage and facilitate the nucleophilic attack. The kinetic and catalytic studies on the hydrolysis of phosphoester by dinuclear zinc complex showed a much-enhanced reactivity under basic reaction conditions, reaching over 95% conversion yield within 4h. The currently presented compounds are arguably one of the faster synthetic Zn-based model performing phosphatase-like activity presented so far.

Drug loading to mesoporous silica carriers by solvent evaporation: A comparative study of amorphization capacity and release kinetics

The sorption of poorly aqueous soluble active pharmaceutical ingredients (API) to mesoporous silica carriers is an increasingly common formulation strategy for dissolution rate enhancement for this challenging group of substances. However, the success of this approach for a particular API depends on an array of factors including the properties of the porous carrier, the loading method, or the attempted mass fraction of the API. At present, there is no established methodology for the rational selection of these parameters. In the present work, we report a systematic comparison of four well-characterised silica carriers and seven APIs loaded by the same solvent evaporation method. In each case, we find the maximum amorphization capacity by x-ray powder diffraction analysis and measure the in vitro drug release kinetics. For a selected case, we also demonstrate the potential for bioavailability enhancement by a permeation essay.

Surfactants assisted SiO2-Cu@Fe2O3 nanofibers: Ultra efficient photocatalyst for photodegradation of organic compounds and transesterification of waste edible oil to biodiesel

The researchers are trying to synthesize such materials which have desirable stability, high efficiency and cost effective. In the present work, SiO 2 -Cu@Fe 2 O 3 nanofibers were synthesized by a novel protocol in which tween-80 and cetyltrimethylammonium bromide was used as a surfactant. The photodegradation of dyes and transesterification of waste edible oil to biodiesel had been investigated. Copper nanoparticles were relatively well dispersed over the surfaces of silica and iron oxide nanofibers with the diameter of 20 nm and Fe 2 O 3 and SiO 2 composite mesopores with a high specific surface area (116 m 2 /g). Photocatalytic degradation of Methylene blue (MB) and rhodamine B (Rhod B) dyes has been tested against As-synthesized SiO 2 -Cu@Fe 2 O 3 nanostructures. At optimum processing conditions SiO 2 -Cu@Fe 2 O 3 displayed a far higher effectiveness of reaction and dyes degradation than many others. A comparative kinetic study of the reduction of dyes (MB and Rhod B) in the presence and absence of nanocatalyst shows the efficiency of synthesized SiO 2 -Cu@Fe 2 O 3 . Furthermore, the reusability of the as-prepared composite was measured and there is no considerable catalytic activity loss even after 5 cycles. The efficiency of SiO 2 -Cu@Fe 2 O 3 was tested both in light and dark. The visible light efficiency of SiO 2 -Cu@Fe 2 O 3 nanofibers against the said dyes were several time higher than in dark. The degradation patterns at a temperature range of 30 °C were so well equipped with a 1st order kinetic framework and proposed a dyes reaction mechanism. The synthesized nanofibers were also applied as a catalyst against transesterification of waste edible oil to biodiesel. The results indicated that 98% biodiesel production was obtained in a 7 h reaction time, and 70 °C reaction temperature. On the basis of the above high efficiency further research is required on the said nanofibers to investigate their hidden applications. • Preparation of SiO 2 -Cu@Fe 2 O 3 nanofibers by new method. • Photocatalytic​ degradation of methylene blue and Rhodamine B. • Catalytic conversion of waste edible oil to biodiesel. • Investigated different factors effecting the catalytic activity.

Comparative growth kinetic study of Newcastle disease virus, infectious bursal disease virus and avian influenza virus in chicken embryo fibroblast and DF-1 cell lines.

Viral diseases have caused devastating effect on poultry industry leading to significant losses in economy of world. In the presented study, the ability of Newcastle disease virus (NDV), infectious bursal disease virus (IBDV) and avian influenza virus (AIV) to grow in two cell lines was evaluated. Both chicken embryo fibroblast (CEF) and DF-1 cells were used and cytopathic effects (CPE) produced by these viruses were observed. The titer of virus in terms of TCID was determined after 24h up to four days for each virus. The same type of CPE was observed for all virus- es used in the study in both DF-1 and CEF cells. IBDV showed CPE causing rounding of cells while NDV caused formation of multicellular large nuclei, cell fusion and rounding of cells. Giant cells with inclusions and aggregation of cells with intact monolayer was observed for AIV. In growth kinetic study, higher titer of IBDV and NDV was observed in CEF cells than DF-1 cells while for AIV, DF-1 cells showed higher titer than CEF cells. These results would be useful for furthers comparative studies on growth of different cell lines of various viruses to find a suitability for vaccine production.

Ammonium Persulphate Initiated Graft Copolymerization of Aniline onto Chitosan-A Comparative Kinetic Study

Ammonium persulphate (APS) has been used as efficient initiator for graft copolymerization of the aniline (ANI) onto chitosan at 25±0.1°C. Graft copolymerization of ANI onto chitosan has taken place through the cation radical initiation process. The grafting parameters have been evaluated by varying concentration of ANI, APS and chitosan. The effects of concentration of APS, ANI, chitosan and reaction time on graft copolymerization were studied by determining the grafting percentage (%G), grafting efficiency (%E) and percentage add-on. It was observed that bout rate of homopolymerization (Rh) and rate of graft coplymerization (Rg) increased with the increase in concentration of each component. On the basis of the experimental observations, initiating steps have been proposed and a suitable rate expression for graft copolymerization has been derived. Electrical conductivity of grafted polyaniline (PANI) onto chitosan (Chit-g-PANI, chitaline) was measured by the four probe method.

Comparative kinetic study on biodecolorization of synthetic dyes by Bjerkandera adusta SM46 in alginate beads-packed bioreactor system and shaking culture under saline-alkaline stress

Industrial dye wastewater contains a high saline concentration and is of an alkaline condition that may inhibit biological treatment. Finding suitable methods for the application of biological decolorisation is important. This research aimed to compare dye biodecolorization by Bjerkandera adusta SM46 using three different methods: (1) alginate-packed bioreactor (APB), (2) submerged-immobilised beads (SIB), and (3) submerged-free cell (SFC) under saline-alkaline and non-saline conditions. Five synthetic dyes with different molecular properties were used: Remazol brilliant blue R (RBBR), Azure B (AB), Brilliant red (BR), Brilliant green (BG), and Reactive green (RG). The results show that B. adusta SM46 was able to decolourise 10.8–97.3% of the dye samples in all methods and conditions, and even up to concentration 500 mg/L under the saline-alkaline condition. Evaluation of kinetic studies revealed the effectivity of the dye removal in SFC over SIB and APB. The highest degradation rate constant (k 1) was achieved for RBBR and the lowest k 1 was for RG. The values of k 1 for SFC, SIB and APB were 0.034, 0.024, and 0.015 respectively for RBBR and 0.013, 0.003, and 0.004 respectively for RG. Treatment using submerged-free cell (SFC) resulted in the greatest and most rapid decolorisation, compared with all other treatments except BR. However, immobilisation on alginate beads increased the reusability of the fungus for sequential batches under saline-alkaline stress. Therefore, selection of a suitable method for dye decolorisation could be proposed, allowing enhancement of the removal process under high saline-alkaline stress, which is usually found in industrial dye wastewater.

Comparative biosorption kinetics study of Ni and Zn metal ions from the aqueous phase in sulfate medium by the wooden biomass of Dalbergia sissoo

Comparative biosorption kinetics study of Ni and Zn metal ions from the aqueous phase in sulfate medium by the wooden biomass of <i>Dalbergia sissoo</i>

A systematic molecular investigation on Sodium Dodecyl Benzene Sulphonate (SDBS) as a Low Dosage Hydrate Inhibitor (LDHI) and the role of Benzene Ring in the structure

Thermodynamic hydrate inhibitors (THIs) are water-loving additives that in an aqueous phase preferentially interact with water and inhibit hydrate nucleation at given temperature and pressure conditions. Hydrate inhibition is one of the flow assurance challenges in oil and gas facilities, primarily for the production and transmission pipelines. In this era of a shift towards offshore production of oil and gas that is usually accompanied by large water cuts in production pipelines, the use of THIs requires a huge onboard inventory (of these additives); further, associated higher recovery costs and environmental issues has resulted in the identification and use of low dosage hydrate inhibitors (LDHIs). Thus, as the name suggests they are used in lower concentrations and do not present any space/storage problem on the offshore platforms. However, LDHI works differently, it primarily inhibits the growth and agglomeration of hydrate crystals thus ensuring flow assurance for a given period of time. Hence, an effective LDHI, may or may not delay hydrate nucleation, however, it should certainly reduce the kinetics of hydrate growth and should act as an anti-agglomerant. This work comparatively investigates the effect of three such additives on methane gas hydrate formation kinetics at very low concentrations. Sodium Dodecyl Sulphonate (SDS) is a well-studied molecule for gas hydrate formation kinetics, while SDS is a good anti-agglomerant (and has been used as anti-agglomerant in multiple gas hydrate studies), it is also a well-known hydrate promoter. In this work, additives having some similar molecular fragments to that of SDS were tested for better gas hydrate inhibition insights at molecular level. Sodium Benzene Sulphonate (SBS), Sodium Dodecyl Benzene Sulphonate (SDBS) and SDS was screened for methane gas hydrate formation experiments. A comparative kinetic study with these additives at two different concentrations (0.05 M and 0.1 M) has been presented for methane gas hydrate formation at 5 MPa (at the beginning of the experiments) and 274.15 K in n-heptane with 50% water cut, in a stirred tank isothermal reactor. The presence of a benzene ring in the molecular structure of the additive along with varying lipophilic tail and hydrophilic head on the methane gas hydrate formation kinetics are thoroughly investigated.

Comparative study of catalytic performance and degradation kinetics of biodiesels produced using heterogeneous catalysts from kaolinite

This study comparatively investigates the catalytic activities and degradation kinetics of the produced biodiesels using kaolinite-based heterogeneous catalysts to examine the stability. The performance of the catalysts was tested under the same operating parameter (methanol/oil ratio, 5:1, at 200 °C for 6 h). The obtained biodiesel was analyzed using TGA equipment to obtain the yield, as well as the degradation kinetic parameters. It was observed that the solid superacid SHY zeolite gave the highest biodiesel yield (90.76%) because of higher acid strength. The catalysts performance is in the order of HY<ALK<HLK<NaLK<SHY zeolite. The lower performance of HY (72.42% yield) is attributed to the presence of high basic sites, being that shea butter has high FFA. The degradation kinetics of each biodiesel sample was performed using the TGA data to examine the thermal and oxidative stability. The frequency factor (A), activation energy, and reaction order were determined by employing the Coats-Redfern model. It was observed that first-order reaction mechanism can satisfactorily describe all the biodiesel kinetics. Further, the biodiesel from SHY zeolite gives the highest EA (98.65 kJ/mol). This result indicates that SHY zeolite is the best catalyst in terms of biodiesel yield and stability.

Comparative study of the reaction kinetics of three residual biomasses

Kinetic analysis for the combustion of three agro-industrial biomass residues (coconut husk, corn husk, and rice husk) was carried out in order to provide information for the generation of energy from them. The analysis was performed using the results of the data obtained by thermogravimetric analysis (TGA) at three heating rates (10, 20, and 30 K/min). The biomass residues were characterized in terms of proximate analysis, elemental analysis, calorific value, lignin content, α-cellulose content, hemicellulose content, and holocellulose content. The biomass fuels were thermally degraded in an oxidative atmosphere. The results showed that the biomass thermal degradation process is comprised of the combustion of hemicellulose, cellulose, and lignin. The kinetic parameters of the distributed activation energy model indicated that the activation energy distribution for the pseudocomponents follows lignin, cellulose, and hemicellulose in descending order. The activation energy values for each set of reactions are similar between the heating rates, which suggests that it is independent of the heating rate between 10 K/min and 30 K/min. For all the biomass samples, the increased heating rate resulted in the overlap of the hemicellulose and cellulose degradation events.

Pyrolytic characteristics and kinetics of Guanzhong wheat straw and its components for high-value products

Wheat straw produced annually in the Shaanxi Guanzhong region is a potential biomass feedstock for the production of transportation fuels and specialized chemicals through combustion, pyrolysis, or gasification. In this work, the pyrolytic characteristics, evolved gas products, and kinetics of Guanzhong wheat straw and its components were first investigated with a thermogravimetry-Fourier infrared spectroscopy (TG-FTIR) system. A comparative kinetic study was conducted using different model-free methods of Flynn-Wall-Ozawa (FWO), Kissinger-Akahira-Sunose (KAS), Kissinger, and the Coats-Redfern methods. The main pyrolysis products identified by FTIR include H2O, CH4, CO2, and CO as well as aromatics, acids, ketones, and aldehydes. Kinetic results showed that the pyrolytic apparent activation energy of the straw is approximately 200 kJ/mol obtained via FWO and KAS methods at the conversion range of 0.4 to 0.75, which was 30 kJ/mol higher than the value 171.1 kJ/mol obtained by the Kissinger method. The apparent activation energy of cellulose in its main pyrolysis region is 135.5 kJ/mol and is about three times larger than that of hemicellulose (49.5 kJ/mol). The apparent activation energy of lignin at the temperature range of 45 to 116 °C was 34.5 kJ/mol, while that value at the temperature range of 120 to 252 °C was 6.64 kJ/mol.

The use of semi-coke for phenol removal from aqueous solutions

The paper deals with a comparative study of equilibrium and kinetics of phenol adsorption from aqueous solutions by means of commercial activated carbons and semi-cokes, differing in the nature of feedstock, production technology and structural characteristics. The main adsorption parameters are calculated with the usage of Langmuir and Dubinin–Radushkevich equations. The change in the characteristics of the structure and state of the surface of semi-coke P2 as a result of modification is estimated. It was found that phenol adsorption kinetics is described by a pseudo-second-order model. The adsorption rate constants and the coefficient of external diffusion mass transfer are calculated. It is proved that phenol extraction from aqueous solutions presents a mixed-diffusion nature, and the process rate is limited by external mass transfer for 13 min for SKD-515 and 22 min for ABG. To increase the adsorption capacity, the oxidative modification of the semi-coke P2 was carried out. Considering the economic and technological aspects, ABG semi-coke is recognized as a promising sorbent for phenol extraction from aqueous media.

A comparative study of the kinetics and isotherm of adsorption of a cationic dye by different natural wastes

In many countries, water pollution from industrial wastewater is a serious problem. This type of pollution can have a harmful impact on the environment, to reduce the effects of these pollutants, several physico-chemical methods are implemented, in particular adsorption on bioadsorbents, it is a common process to remove traces of pollutants from water, the aim of our work is to realize a comparative experimental study of isotherms and adsorption kinetics of methylene blue (MB) on three substrates: sugar cane bagasse (SCB), almond shell (AS) and walnut shell (WS). The results of equilibrium kinetics show that walnut shell (WS) binds better to methylene blue than other substrates. The results also show that the adsorption kinetics are described by the expression of the pseudo-second order model. The isotherms of adsorption of methylene blue (MB) by sugarcane bagasse (SCB), walnut shell (WS) and almond shell are perfectly described by Langmuir's model and that walnut shell adsorbs methylene blue better than other substrates.

Comparative study of polymer looping kinetics in passive and active environments.

Intra-chain looping in complex environments is significant in advancing our understanding of biological processes in life. We adopt Langevin dynamics simulations to perform a comparative study of polymer looping kinetics in passive and active environments. From the analysis of looping quantities, including looping-unlooping times and looping probabilities, we unraveled the intriguing effects of active crowder size, activity and crowding. Firstly, we figured out the phase diagram involving a novel facilitation-inhibition transition in the parameter space of active crowder size and active force, and the two-fold roles of activity are clarified. In particular, we find that active particles of a size comparable to the polymer monomer are most favorable for facilitated looping, while those with a similar size to the polymer gyration radius impede the looping most seriously. Secondly, the underlying looping mechanisms in different active crowder size regimes are rationalized by the interplay among diffusion, polymer conformational change and the free-energy barrier. For small active crowders, activity significantly promotes end-to-end distance diffusion, which dominantly facilitates both looping and unlooping processes. In the case of moderate active crowders, the polymer chain suffers from prominent swelling, and thus inevitable inhibited looping will occur. For large active crowders, activity induces a counterintuitive non-cage effect on the looping kinetics, through yielding a higher effective temperature and larger unlooping free-energy barrier. This is in sharp contrast to the caging phenomena observed in passive media. Lastly, the volume-fraction dependence of the looping quantities in an active bath demonstrates dramatic discrepancies from that in a passive bath, which highlights the contrasting effects of activity and crowding.

Comparative adsorptive and kinetic study on the removal of Malachite Green in aqueous solution using titanium coated graphite and titanium coated graphite with CNT-ABS nanocomposite

Comparative adsorptive and kinetic study on the removal of Malachite Green in aqueous solution using titanium coated graphite and titanium coated graphite with CNT-ABS nanocomposite

Pyrolysis of waste tire rubber: a comparative kinetic study using different models

ABSTRACT With increase in number of vehicles worldwide the amount of waste tires is also increasing. These waste tires are either discarded to a dump site or burnt in open air. In both the cases they contaminate the soil, water and air. Due to its high heating value waste tire is a good source of energy if used under controlled conditions. In this connection pyrolysis has emerged as the ultimate solution for judicious use of waste tire. However, before going through the pyrolysis process on industrial scale, understanding the kinetics of pyrolysis reaction on laboratory scale is mandatory. Therefore, in this work our focus is on the kinetics of pyrolysis of waste tire using various kinetic models. Activation energy (E) and frequency factor (A) were determined and observed to increase with fraction conversion which shows a multistep reaction. The E and A values calculated at different conversions were found in the range of 100.73–216.99 kJmol−1 and 2.5 × 109–9.0 × 1013 min−1 respectively. Based on kinetics parameters, a comparison among the different models was made. Any small variation in kinetics parameters was attributed to the selection of model chosen and the method adopted for investigation of kinetic results. The kinetic modeling will provide insights into pyrolysis reaction and the kinetic parameters determined will assist in pyrolysis of waste tire for its use as energy source on industrial scale.