Kinetics Of Stage Research Articles

Three-step kinetic model for fisetin dye diffusion into fibroin fibre

BackgroundThe study’s relevance is determined by the current desire to reduce the negative environmental impact of the textile industry. The study aims to develop and optimise dyeing processes using natural dyes in the textile industry.ResultsThe process of dye transfer from solution to Bombyx mori natural silk fibre can be divided into three successive kinetic stages. The first stage involves the adsorption of dye molecules on the active surface of the fibre, the second, their diffusion deep into the fibre towards its centre, and the third, the uniform distribution of dye molecules along the fibre starting from its centre. It is noticed that diffusion at the third stage slows down significantly, and the third stage lasts much longer than the first and second stages. The analysis of experimental data on dye concentration over time on dyed materials and their comparison with hypothetical data will make it possible to establish time intervals for each stage of the process and diffusion coefficients for each of them.ConclusionThis study has practical implications as it may contribute to more efficient and sustainable dyeing of textile materials using natural dyes, helping to reduce the negative environmental impact of the textile industry, and contributing to our knowledge of diffusion and dyeing processes.

From adsorption to crystallization of proteins: Evidence for interface-assisted nucleation

Protein crystallization is among the key processes in biomolecular research, but the underlying mechanisms are still elusive. Here, we address the role of inevitable interfaces for the nucleation process. Quartz crystal microbalance with dissipation monitoring (QCM-D) with simultaneously optical microscopy, confocal microscopy, and grazing-incidence small angle X-rays scattering (GISAXS) were employed to investigate the temporal behavior from the initial stage of protein adsorption to crystallization. Here we studied the crystallization of the Human Serum Albumin (HSA), the most abundant blood protein, in the presence of a charged surface and a trivalent salt. We found evidence for interface-assisted nucleation of crystals. The kinetic stages involved are initial adsorption followed by enhanced adsorption after longer times, subsequent nucleation, and finally crystal growth. The results highlight the importance of interfaces for protein phase behavior and in particular for nucleation.

ВЛИЯНИЕ МЕТИЛЬНОЙ ГРУППЫ НА СКОРОСТЬ РЕАКЦИИ ОКИСЛИТЕЛЬНОГО ДЕГИДРИРОВАНИЯ МЕТИЛЦИКЛОГЕКСАНОЛОВ НА МОДИФИЦИРОВАННОМ ЦЕОЛИТНОМ КАТАЛИЗАТОРЕ

In this article has been carried out the study and comparing the reactivity of cyclohexanol and methylcyclohexanol isomers in the oxidative dehydrogenation reaction over modified zeolite catalysts. For this purpose, have been investigated the kinetic laws for the two unstudied isomers of methylcyclohexanol (2- and 3-methylcyclohexanol), proposed the mechanisms, kinetic stage schemes for the formation of target products, and developed kinetic models of these processes. It has been found that the rates of oxidative dehydrogenation of all methylcyclohexanol isomers are practically the same and exceed the rate of oxidative dehydrogenation of cyclohexanol to cyclohexanone.

Numerical simulation of leakage, dispersion and explosion behavior of LPG in kitchen

ABSTRACT The frequent occurrence of kitchen gas explosion accidents has raised widespread attention to gas safety. This article takes kitchen as the research object, and explores the dispersion law of LPG leakage in kitchens and the influence of ignition at different leakage time on explosion consequences by establishing LPG leakage and explosion models. The results show that the process of LPG leakage in a closed kitchen can be divided into three stages: initial kinetic energy dominant stage, gravity expansion stage, and passive dispersion stage. Propane forms a non-uniform concentration field in the kitchen that gradually decreases from bottom to top, filling the entire kitchen in 583 s. When an explosion occurred in the kitchen center, the initial burst of flame spreads around in a fireball. After 115 ms and 122 ms, the explosion overpressure causes the door and window to be destroyed respectively, and the flames stretch toward the door and window. The flames are then concentrated mainly in the lower area where the fuel is more adequate. In the later stage of the deflagration reaction, the flame propagates toward the upper area of the kitchen under buoyancy. The explosion consequences of LPG non-uniform gas clouds show a pattern of first intensifying and then weakening with the leakage time. The explosion consequences are most severe when ignited about 300 s after the leakage. The maximum explosion overpressures at the center of the kitchen, door, and window were 67.15 kPa, 28.12 kPa, and 27.92 kPa, respectively. The research results can provide reference for emergency response, consequence assessment, and kitchen safety design for kitchen LPG leakage and explosion accidents..

Kinetics and structure analysis of CO2 mineralization for recycled concrete aggregate (RCA)

CO2 mineralization of solid waste in the construction industry for green concrete production is a promising approach for economically storing CO2 and recycling solid waste. Recent investigations have underscored the significance of CO2 sequestration and the augmentation of RCA performance engendered by the holistic reaction processes. While there is a pronounced interest in the optimization of macroscopic reaction conditions (e.g., temperature, pressure, etc.), the exploration and enhancement of the reaction kinetics stage often remains under explored. This study employed a reaction kinetics model to quantify the reaction rate unveiled two distinct reaction stages within the mineralization reaction. Early evaporation and pore formation established the groundwork for the diffusion mechanism of gas product layers in the middle and later stages, emphasizing the crucial role of water in connecting solid ion leaching and gas dissolution-diffusion in the reaction. The water content of the reaction has an optimal value (4%–6%), smaller particle size correlates with a higher optimal water content. Pre-soaking with a calcium hydroxide (CH) solution or suspension was employed to improve mineralization reaction kinetics, resulting in RCA with improved pore characteristics and strength. The crushing index decreased by 28.8% and 21.8%, the water absorption rate decreased by 11.1% for both coarse and fine RCA, and the cumulative total porosity of fine RCA decreased by 17.6%. This research aims to broaden the applications of waste concrete in the CO2 capture, utilization and storage (CCUS) industry and produce low-cost, extensively processed, and high-strength RCA products while contributing to sustainable CO2 management.

Sigma phase kinetics in DSS filler metals: A comparison of sigma phase formation in the as-welded microstructure of super duplex stainless steel and hyper duplex stainless steel

This study investigates and compares the kinetics of sigma phase formation in established Super Duplex Stainless Steel (SDSS) and recently developed Hyper Duplex Stainless Steel (HDSS) filler metal wires. Experimental sigma phase time-temperature-transformation (TTT) maps were developed, revealing nearly equivalent interface area/volume, resulting in similar sigma phase kinetics for 1% volume despite the higher Cr and Mo content in HDSS. However, the growth rate to 5% and 10% sigma phase volumes was slightly higher in HDSS. The sigma phase kinetics in both SDSS and HDSS were analyzed using the exponential Johnson-Mehl-Avrami-Kolmogorov (JMAK) approach based on experimental TTT data. Linearized plots from the JMAK calculations showed a transition in kinetics mechanism from eutectoid decomposition and interface-controlled growth to a diffusion-controlled growth stage in both materials. The higher volumes and morphologies of the sigma phase were found to be diffusion-dependent, mainly occurring during the second kinetics stage. The influence of HDSS's higher Cr and Mo content on the growth rate was observed for these higher volumes. For applications within the 1% sigma phase limit, both wires exhibited equivalent susceptibility to sigma phase formation, regardless of the higher alloying in HDSS.

Experimental determination of dynamic pseudo-equilibrium moisture content: A practical limit for the drying process

Simulation and rigorous design of industrial dryers combine a large number of models, which feed three fundamental balances: (1) mass; (2) energy; and (3) quantity of movement of the material through the dryer. Many of these models represent physical phenomena affecting the three balances at the same time, which makes these calculations extremely complex, hence, accurate models are essential. The hypothesis that the kinetic stage of drying of any material culminates in the thermodynamic moisture equilibrium between solid and drying gas has been in effect for many years. However, recent findings show that there is a transition stage between the kinetic stage and the thermodynamic equilibrium, which, experimentally, looks like an equilibrium. The beginning of this transition stage or dynamic pseudo-equilibrium stage would mark the end of the drying kinetics models, which has been named as the dynamic pseudo-equilibrium moisture contents (Xdpe). The non-observance of this phenomenon presupposes a model limited in its prediction capacity, especially in the last stages of drying and even more so at low drying temperatures. As a consequence, sizes of industrial dryers could be underestimated during the simulation and rigorous design process, or underestimate drying times, in batch dryers. On the other hand, the optimal conditions may never be found, during the optimization of existing industrial drying processes. The objective of this work is to present the procedure to determine Xdpe, during the experimental determination of drying curves of any material. Likewise, to propose the practical moisture ratio, which uses Xdpe, instead of the equilibrium moisture, to be used in the modeling of the drying kinetics.•The drying process is divided into three stages: kinetic, transition, and equilibrium.•The dynamic pseudo-equilibrium moisture content divides the kinetic and the transition stages.•The practical moisture ratio should be used in rigorous industrial dryer design calculations.

Pyrolysis characteristics and kinetics of Prunus avium L. leaves using thermogravimetric analysis

Differences in the pyrolysis characteristics of leaves of sweet cherry tree (Prunus avium L.) under rain-shelter cultivation (RS) or under open-field cultivation (CK) were analysed using thermogravimetry (TG), derivative thermogravimetry (DTG), and differential scanning calorimetry (DSC) at three heating rates of 10, 20, and 30 °C·min-1. There were two obvious mass loss peaks at 280 °C and 330 °C, which were manifested by the slow pyrolysis of hemicellulose in the low temperature region and the rapid pyrolysis of cellulose in the high temperature region, respectively. The curve in the pyrolysis range after 440 °C was stable, and the mass change corresponded to the pyrolysis of a small amount of macromolecular organic extracts and inorganic salts. When the temperature reached 600 °C, approximately 69% and 73% of the CK and RS leaves were thermally destroyed, respectively. The Coats-Redfern method was used for kinetic calculations to obtain an activation energy of 29.8 to 36.1 kJ·mol-1 in the first-order pyrolysis kinetics stage. The second-order pyrolysis kinetics stage can fit the pyrolysis process well. A significant difference was observed in the pyrolysis characteristics or the kinetics between CK and RS, which were related to the heating rate and the hemicellulose content, cellulose content, and lignin ratio in each sample.

Water–soil interactions: Unravelling the processes and stages involved in the wetting of water repellent soils

The water repellent behaviour of soils is a widely studied phenomenon given its implications for infiltration, runoff, erosion and preferential flow. However, the principles underlying the eventual penetration of water into affected soils remain poorly understood. Theoretical considerations of the energetics and kinetics involved as a water drop makes contact with a water repellent soil surface and eventually penetrates into the soil suggest three distinct stages in the overall process. These stages are 1) adhesional wetting as soil and water first make contact, followed by 2) a kinetic barrier transitional stage in which molecular reorganisation of organics on soil reduces the water-soil contact angle to allow the water drop to sit deeper over soil particles of initial contact such that there is contact with particles in directly underlying soil layers, and finally 3) branching interstitial wetting as water penetrates into the bulk soil. Studies presented here of optical microscopy, mass of soil initially wetted, penetration time through layers of soil of different thicknesses, and time-dependent measurements of contact angle, volume of water penetrated, and mass of soil wetted, all give results consistent with this model. However, only for highly water repellent soils can distinct stages in wetting be clearly resolved experimentally, presumably because only these soils have a high enough kinetic barrier in the transitional stage for good separation between stages. For less water repellent soils, while the general time dependent behaviour remains consistent with the model, the distinction between the three stages is not so easy to resolve experimentally. The roles of contact angle, particle size distribution and drop size in determining the rates of these stages is considered, and the implications of the model for understanding soil water repellency are discussed.

Photoreduced graphene oxide recovers graphene hot electron cooling dynamics

Reduced graphene oxide (rGO) is a bulk-processable quasi-amorphous 2D material with broad spectral coverage and fast electronic response. rGO sheets are suspended in a polymer matrix and sequentially photoreduced while measuring the evolving optical spectra and ultrafast electron relaxation dynamics. Photoreduced rGO yields optical absorption spectra that fit with the same Fano lineshape parameters as monolayer graphene. With increasing photoreduction time, rGO transient absorption kinetics accelerate monotonically, reaching an optimal point that matches the hot electron cooling in graphene. All stages of rGO ultrafast kinetics are simulated with a hot-electron cooling model mediated by disorder-assisted supercollisions. While the rGO room temperature 0.31 ps$^{-1}$ electronic cooling rate matches monolayer graphene, subsequent photoreduction can rapidly increase the rate by ~10-12$\times$. Such accelerated supercollision rates imply a reduced mean-free scattering length caused by photoionized point-defects on the rGO sp$^2$ sub-lattice. For visible range excitations of rGO, photoreduction shows three increasing spectral peaks that match graphene quantum dot (GQD) transitions, while a broad peak from oxygenated defect edge states shrinks. These three confined GQD states donate their hot carriers to the graphene sub-lattice with a 0.17 ps rise-time that accelerates with photoreduction. Collectively, many desirable photophysical properties of 2D graphene are replicated through selectively reducing rGO scaffolded within a 3D bulk polymeric network.

Mean-field modelling of precipitation kinetics with a Fokker-Planck equation in the Lifshitz–Slyozov–Wagner space

Mean-field theory has been widely applied in modelling the kinetics of microstructure evolution. Considering a free energy contribution by microstructure entropy, a Fokker-Planck equation for precipitation kinetics is variationally derived from thermodynamic principles. Using dimensionless transformation into the Lifshitz-Slyozov-Wagner space, the Fokker-Planck equation is effectively solved within a fixed radius interval and an explicit Euler scheme, which is computationally advantageous. Through comparisons with the Ni-12.5 Al at. % alloy, it is shown that the Fokker-Planck equation can represent the typical stages of precipitation kinetics, i.e., nucleation, growth, and coarsening.

Citrus pyrolysis temperature effect on wood vinegar characteristics

Wood vinegar, a biomass pyrolysis smoke condensed byproduct, was collected in four different temperature ranges: 110–170 °C (WV1), 170–250 °C (WV2), 250–350 °C (WV3) and 350–500 °C (WV4), according to the kinetic stages that characterize it. The chemical properties, organic compounds and concentration of metal ions for each of the fractions were analyzed and the hypothesis evaluated is that the characteristics of each of the fractions are distinct. The organic compounds identified are known valuable compounds in the chemical industries, belonging to the groups of phenols, ketones, acids, alcohols, aldehydes, alkanes, aromatic hydrocarbons and nitrogenous compounds with furan derivatives. In each of the fractions, a high content of specific compounds was identified, and in contrast to the other fractions, no significant difference was found between the organic compounds identified in WV3 and WV4. Each of the fractions contained inorganic elements that are essential for soil fertility.

Gas separation properties of PIM-1 films treated by elemental fluorine in liquid perfluorodecalin

Gas transport properties of PIM-1 films treated by elemental fluorine in a liquid perfluorodecalin were investigated. The investigation included an estimation of fluorine content in a fluorinated layer, pure and mixed gas permeability, diffusion and solubility coefficients measurement, ideal selectivity assessment and analysis of fluorination time effect on gas transport properties. An increase of treatment duration resulted in an increase of concentration of fluorine in the fluorinated layer as well as a depth of fluorination. The depths of fluorination linearly increased with square of fluorination time indicating a diffusion of fluorine in the fluorinated layer to be a restrictive stage of kinetics of fluorination. The effect of the drop in gas permeability was demonstrated to be dependent on the kinetic size of the penetrant. The comparison of liquid-phase and gas-phase regimes was performed, and it was shown that sharp decrease in gas permeability is observed for gas-phase regime at short times of fluorination already, whereas this decrease is more gradual for liquid-phase fluorination. According to a Barrie method, the gas transport parameters of the fluorinated layer of the modified PIM-1 films were calculated, which turned out to be much lower than those for the virgin PIM-1 polymer and slightly lower than the gas transport parameters for dry Nafion. The reduction of the gas permeability coefficients is mostly induced by a sharp decrease in the gas diffusion coefficients. According to combination of permeability and selectivity, the fluorinated PIM-1 samples show excellent results exceeding the 2008 Robeson upper bounds for H2/CH4, H2/CO2, H2/N2, He/CH4 and others gas pairs. Mixed gas experiments were also conducted for hydrogen-containing mixtures and fluorinated PIM-1 samples have demonstrated good separation characteristics for the model binary mixtures attaining separation factors as high as 115–143 (H2/CH4), 4.4–6.7 (H2/CO2) and 49–146 (He/CH4), which makes these materials promising for helium recovery from natural gas and hydrogen recovery from various catalytic and biohydrogen production mixtures. Ten-months aging of the PIM-1 sample fluorinated during 30 min showed a decline of permeability by 25 and 40%, respectively and a slight decrease of ideal selectivity.

Structural phenomenological concept of monitoring the load-bearing capacity of structural elements of composite materials

The authors demonstrate the potential of a methodological approach for monitoring the damage kinetics and evaluating the load-bearing capacity of composite structural elements based on the method of acoustic emission. This methodology was developed by specialists of the Blagonravov Mechanical Engineering Research Institute of the Russian Academy of Sciences. The methodology was implemented for a fatigue test of an aircraft panel represented by a complex hybrid structure with a lining made of layered composite and a cellular internal structure of aluminum foil with polymeric filler that has a continuous layered structure in the gripping area. Fatigue tests were carried out at 4 Hz from the zero-loading cycle with an amplitude of 145 kN. To record the accumulation of damages, R15–AST transducers by Mistral (USA) and an A-line 32D 8-channel acoustic emission system by Interunis-IT LLC were used. Comparing the weight content of location impulses with their threshold values in energy clusters characterizing the kinetics of micro-, meso-, and macro-damages of the composite material structure made it possible to determine the bearing capacity of the aircraft panel at respective stages of damage kinetics. The results of the acoustic emission diagnostics are given for the examined aircraft panel during cyclic loading, including the coordinate location of acoustic emission sources, accumulation of acoustic emission events by channels, the dynamics of partial activity changes, and weight content of location impulses at damage evolution stages of a composite material. Therefore, the acoustic emission diagnostics of the aircraft panel made it possible to identify the areas of intensive damage accumulation in the hybrid structure of the panel and control the actual bearing capacity by defining the extent of its damages at various scale and structural levels during cyclic loading. The described methodology of using acoustic emission diagnostics for monitoring the damage kinetics and actual bearing capacity of highly loaded composite elements extends the research potential of the acoustic emission method.

Revealing Ultrafast Carrier Dynamics of Hybrid Perovskites at Various Stages of Nucleation and Growth Kinetics

AbstractWith hybrid organic–inorganic perovskites expanding their technological reach, from photovoltaic solar cells that operate at low carrier densities (1011 − 1013 cm−3) to light‐emitting diodes and lasers that operate at higher carrier densities (1013 − 1019 cm−3), it is critical to know how microstructure dictates carrier dynamics at varying injected carrier densities. For fabrication at scale, it is equally critical to know how quickly during the growth process do hybrid perovskites develop their characteristic optoelectronic properties. This work reports on a facile fabrication method that “freezes” different stages of nucleation and growth kinetics of prototypical hybrid perovskite on the same substrate—providing a unique strategy to assess differences in optoelectronic properties and carrier dynamics from nascent nucleating microcrystals to large‐grain thin films. The solution‐processed fabrication technique, optimized to control the nucleation density of an intermediate phase, successfully decouples the nucleation and growth steps that lead to large‐grain thin films. Ultrafast broadband absorption microscopy finds that the nucleating microcrystals already possess the optoelectronic properties of hybrid perovskites and share similar femtosecond‐to‐nanosecond dynamics as large‐grain thin films. When compared to the large‐grain thin films, the confining microcrystals exhibit enhanced carrier interactions, marked by an increase in bimolecular and Auger recombination rates.

An efficient control allocation algorithm for over-actuated AUVs trajectory tracking with fault-tolerant control

Fault-tolerant control of actuator faults in over-actuated autonomous underwater vehicles (AUVs) during trajectory tracking has involved problems. First, the fault-tolerant control method of controlling typical rudder faults, including lost, jammed, and/or deformed rudders, is introduced to reconstruct the control input, and a complete scheme of self-diagnosis and fault-tolerant control is proposed based on a sliding mode observer (SMO). Secondly, an efficient nonlinear saturation constraint sequential quadratic programming (SC-SQP) algorithm is proposed to solve the control allocation problem of multi-constraint quadratic programming, in particular with the motion in the initial or kinetic cycle transition stages. Considering the time-varying and unknown disturbances that occur in oceans, the control moments are compensated by the SMO to resist the perturbation of the hydrodynamic coefficient. Finally, the simulations show that the SC-SQP algorithm is efficient and can be used to solve the typical rudder faults with perturbation of the hydrodynamic coefficient during the fault-tolerant trajectory tracking control for over-actuated AUVs.

Effect of temperature on carbon dioxide mineralisation in recycled cement paste

In this work, an approach towards a carbon-neutral cement industry using carbon dioxide mineralisation of recycled concrete paste is investigated. It focuses on the effect of temperature on the enforced carbonation of cement paste. The enforced carbonation is a rapid process at ambient temperature, which is further accelerated at elevated temperatures. Moreover, the extent of the reaction is increased when the temperature rises. The carbonation reaction is divided into two kinetic stages. During the first stage, the carbonation kinetics is controlled by the availability of carbon dioxide that increases at higher temperatures. During the second stage, the reaction kinetics is controlled by the dissolution of the hydrates. Increased temperature accelerates this process by increasing the undersaturation level of the dissolving phases. The main carbonation products are calcium carbonate and an alumina–silica gel. The increasing temperature has a limited impact on these phases, and the differences come mainly from the different degrees of carbonation.

Compatible Kinetic Model for Quantitative Description of Dual-Clock Behavior of the Complex Thiourea-Iodate Reaction.

The thiourea-iodate reaction has been investigated simultaneously by ultraviolet-visible spectroscopy and high-performance liquid chromatography (HPLC). Absorbance-time traces measured at the isosbestic point of the iodine-triiodide system have revealed a special dual-clock behavior. During the first kinetic stage of the title reaction, iodine suddenly appears only after a well-defined time lag when thiourea is totally consumed due to the rapid thiourea-iodine system giving rise to a substrate-depletive clock reaction. After this delay, iodine in the system starts to build up suddenly to a certain level, where the system remains for quite a while. During this period, hydrolysis of formamidine disulfide as well as the formamidine disulfide-iodine system along with the Dushman reaction and subsequent reactions of the intermediates governs the parallel formation and disappearance of iodine, resulting in a fairly constant absorbance. The kinetic phase mentioned above is then followed by a more slowly increasing sigmoidally shaped profile that is characteristic of autocatalysis-driven clock reactions. HPLC studies have clearly shown that the thiourea dioxide-iodate system is responsible mainly for the latter characteristics. Of course, depending on the initial concentration ratio of the reactants, the absorbance-time curve may level off or reach a maximum followed by a declining phase. With an excess of thiourea, iodine may completely disappear from the solution as a result of the thiourea dioxide-iodine reaction. In the opposite case, with an excess of iodate, the final absorbance reaches a finite value, and at the same time, iodide ion will disappear completely from the solution due to the well-known Dushman (iodide-iodate) reaction. In addition, we have also shown that in the case of the formamidine disulfide-iodine reaction, unexpectedly the triiodide ion is more reactive toward formamidine disulfide than iodine. This feature can readily be interpreted by the enhancement of the rate of formation of the transition complex containing oppositely charged reactants. A 25-step kinetic model is proposed with just 10 fitted parameters to fit the 68 kinetic traces measured in the thiourea-iodate system and the second, but slower, kinetic phase of the thiourea-iodine reaction. The comprehensive kinetic model is constituted in such a way as to remain coherent in quantitatively describing all of the most important characteristics of the formamidine disulfide-iodine, thiourea dioxide-iodine, and thiourea dioxide-iodate systems.

Nonlinear dynamics of kinetic fluctuations and quasi-linear relaxation in plasma

We propose an approximation of pair correlations for solving the equations of the kinetic theory of long-wave (or large-scale) fluctuations in gaseous media. The basic ones are the general nonlinear equations of the large-scale fluctuations theory at the kinetic stage of system evolution, derived from the first principles of statistical mechanics. We show that based on the equations of the long-wave fluctuations kinetics in the case of weak interaction between particles, in the approximation of pair fluctuations it is possible to reproduce the main results of the quasi-linear theory of plasma. Thus, the well-known quasi-linear theory of plasma is provided with a first-principle justification.

Determination of three stages for molybdenite flotation kinetics in seawater

ABSTRACT This research mainly investigated the flotation kinetics of molybdenite in seawater based on four flotation models. Molybdenite flotation presented an excellent agreement with the first-order model with rectangular distribution. The ultimate cumulative recovery (R ∞) and flotation rate constant (k) of molybdenite decreased in seawater, mainly due to the divalent cations, with the impact of Mg2+ being significantly greater than that of Ca2+. The addition of sodium silicate (SS) and sodium hexametaphosphate (SH) increased the flotation recovery and rate, probably due to the positive role of dispersants on preventing the attachment of seawater precipitates onto molybdenite surface. In addition, three different stages of flotation kinetics were proposed to reveal the molybdenite flotation for the first time, with the highest flotation recovery and rate being found at Stage I. However, seawater showed a negative role on Stage I, i.e. resulting in a longer duration and lower recovery, as compared to that in pure water. The addition of both SS and SH improved the flotation kinetics at Stage I, with SH being more significant. Therefore, it is more feasible to eliminate the negative effects of seawater on molybdenite flotation at the initial stage (Stage I).