Desorption Rate Constants Research Articles

Development and verification of a component-level hydrogen transport model for a DEMO-like HCPB breeder unit with OpenFOAM

This work describes the development of a numerical model to simulate transient tritium transport on the breeder unit (BU) level for the EU helium cooled pebble bed (HCPB) concept for DEMO. The key output quantities of the model are the tritium concentration in the purge gas and in the coolant and the tritium inventory inside the BU structure. The model capabilities should cover normal operation as well as accident conditions.The Open Source Field Operation And Manipulation framework OpenFOAM serves as the basis for the model. Equations and boundary conditions required for hydrogen isotopes transport are implemented. Realistic properties data as diffusion constants and Sieverts constants are required, too. A key model issue is solid-fluid interface mass transfer. Two correlations that (1) approaches Sieverts equilibrium in the diffusion limit and (2) a rate dependent correlation that includes the diffusion limit for very high ad-/desorption rate constants are introduced. A two species interface mass transfer correlation based on the single species rate dependent correlation is developed, too. First verification calculations are compared to analytic solutions and TMAP calculations.

Real-time measurement of the crystal violet adsorption behavior and interaction process at the silica-aqueous interface by near-field evanescent wave.

The interfacial adsorption and interaction of crystal violet (CV) at the silica-water interface was real-time measured based on a total-internal-reflection-induced near-field evanescent wave (TIR-NFEW). A silica optical fiber (SOF) was employed as a charged substrate for CV adsorption and as a light transmission waveguide for evanescent wave production for the investigation system. According to the change of evanescent wave intensity, the CV adsorption behavior could be real-time monitored at the silica-aqueous interface. The Langmuir adsorption model and two kinetic models were applied to obtain the related thermodynamic and kinetic data, including the adsorption equilibrium constant (Kads) of (5.9 ± 1.5) × 104 M-1 and adsorption free energy (ΔG) of -21.6 ± 0.6 kJ mol-1. Meanwhile, this method was shown to be able to isolate the elementary processes of adsorption and desorption under steady-state conditions, and gave an adsorption rate constant (ka) and desorption rate constant (kd) of 2089 ± 6.96 M min-1 and 0.35 ± 0.0012 min-1 for a 15 rpm flow rate. The surface interaction process was revealed and the adsorption mechanism proposed by a molecular orientation adsorption model with three-stage-concentration, indicating that CV first adsorbed on Si-O- sites through electrostatic attraction, then on Si-OH sites through hydrogen bonding, and lastly on the surface through van der Waals forces with different CV concentrations. This study can provide a molecular-level interpretation of CV adsorption and provides important insights into how CV adsorption can be controlled at the silica-water interface.

Enrichment of cellulose acetate nanofibre assemblies for therapeutic delivery of l-tryptophan

The essential amino acid l-tryptophan is naturally present in the body, and is also available as a water soluble dietary supplement. The feasibility of preparing enriched cellulose acetate (CA)-based fibres as a vehicle for therapeutic delivery of such biomolecules was investigated. A new ternary solvent system consisting of acetone: N,N-dimethylacetamide: methanol (2:1:2) has been demonstrated to permit the solution blending of CA with the water soluble l-tryptophan. Nanofibrous webs substantially free of structural defects were continuously produced with mean fibre diameters in the range of 520–1010nm, dependent on process parameters. Morphology and diameter of fibres were influenced by concentration of CA spinning solution, applied voltage and flow rates. The kinetic release profile of l-tryptophan from electrospun CA nanofibres was described by the pseudo-second order kinetic model. Fibres with mean diameter of 720nm provide both the highest initial desorption rate and rate constant, which was partially attributed to the low fibre diameter and high relative surface area, but also the fact that the 720nm fibres produced were the most bead-free, providing diffusion advantages over the fibres with lowest mean diameter (520nm). The feasibility of combining l-tryptophan within fibres provides a promising route for manufacture of transdermal delivery devices.

Desorption kinetics of organic chemicals from albumin.

When present in blood, most chemicals tend to bind to the plasma protein albumin. For distribution into surrounding tissues, desorption from albumin is necessary, because only the unbound form of a chemical is assumed to be able to cross cell membranes. For metabolism of chemicals, the liver is a particularly important organ. One potentially limiting step for hepatic uptake of the chemicals is desorption from albumin, because blood passes the human liver within seconds. Desorption kinetics from albumin can thus be an important parameter for our pharmacokinetic and toxicokinetic understanding of chemicals. This work presents a dataset of measured desorption rate constants and reveals a possibility for their prediction. Additionally, the obtained extraction profiles directly indicate physiological relevance of desorption kinetics, because desorption of the test chemicals is still incomplete after time frames comparable to the residence time of blood in the liver.

Mobile Arsenic Distribution and Release Kinetics in Sediment Profiles under Varying pH Conditions

The release of arsenic (As) from sediments poses a risk to human health especially at high pH levels. Despite this, the distribution and kinetic response of mobile As remains unclear under varying pH conditions. In this study, a microcosm incubation experiment was performed, using sediment cores in combination with dialysis (Peeper) and thin film diffusive gradients (DGT), to investigate the distributions of mobile As (soluble As in pore water and DGT-labile As) at high vertical resolutions (2–4 mm). Results show that the concentrations of soluble As present in the water column increased 1.5-fold with an increase in pH from 5.4 to 11.2. Both soluble As in pore water and DGT-labile As exhibited stable low-level distributions in the uppermost layer beneath the sediment-water interface, followed by increasing concentration distribution with decreasing layers to middle depths. The mean concentrations of mobile As species increased with increased water pH in both sediment profiles and with upward diffusion gradients, showing a 0.2-fold increase of soluble As in the top 20-mm layer and a 0.6-fold increase in deeper 20–52-mm layers, while DGT-labile As showed a 1.0- and 1.1-fold increase in these two layers, respectively. Modeling of DGT-induced flux in sediments (DIFS) showed that the desorption rate constant increased more rapidly than the absorption rate constant, resulting in the increased availability of solid As pools, therefore resupplying the soluble As in pore water from sediments.

High Performance CuO Nanorectangles-Based Room Temperature Flexible NH3Sensor

Here, we report the fabrication of a flexible room temperature ammonia gas sensor using surfactant-free hydrothermally synthesized copper oxide (CuO) nanorectangles. The structural analysis revealed that the CuO nanorectangles possessed monoclinic structure with an average length and breadth of 950 and 450 nm, respectively. The specific surface area of CuO nanorectangles was determined to be 29 m2/g. The sensor was fabricated on a flexible polyethylene terephthalate substrate by screen printing technique. The room temperature ammonia sensing measurement exhibited significant response down to 5 ppm of ammonia with a quick response time of 90 s and recovered to baseline within 120 s. Maximum response of 0.99 was recorded for 100 ppm of ammonia. The rate constants for adsorption and desorption were estimated for 6.5 to 100 ppm of ammonia from the exponential conductance changes during response and recovery process. The sensor showed appreciable stability and reproducibility of the sensing performance over a period of three months. The fabricated flexible sensor demonstrated its ability to detect a wide range of ammonia concentrations at room temperature irrespective of the mechanical deformations applied. Thus, the fabricated sensor is promising and can be suitably employed for practical applications in environments where efficient gas sensing is vitally important.

Integrated direct air capture and CO2 utilization of gas fertilizer based on moisture swing adsorption

A new concept of low-cost direct air capture technology integrated with a fertilization system is proposed, as an alternative to the application of air derived CO2. A moisture swing sorbent can elevate the CO2 concentration from 400 parts per million (ppm) to several thousand ppm, and this can be used to cultivate plants. Desorption isotherms were determined and are described well by a Langmuir model. The adsorption rate constant and the desorption rate constant were gained at 25 °C, 35 °C, and 45 °C under 1000 ppm concentration of CO2. In accelerated cultivation experiments, the effects of CO2 concentration, light intensity, and spectrum on the CO2 uptake rate of the plants were investigated. A multi-bed desorption system which is capable of providing a continuous and stable CO2 supply for a greenhouse is demonstrated based on the desorption characteristic and CO2 uptake feature of plants. An energy and cost assessment for the integrated system was performed and the results indicated that minimum energy requirements and cost estimate of CO2 are 35.67 kJ/mol and 34.68 USD/t, respectively. This makes direct air capture a competitive and sustainable carbon source for agriculture.

Partition kinetics of chlorobenzenes in a sediment-water system

The partition kinetics of chlorobenzenes (CBs) in a sediment-water system were studied to provide a basis for understanding the compounds’ behaviour in the natural aquatic environment. A series of chlorobenzenes (CBs) 1,4-dichlorobenzene (DCB), 1,3,5-trichlorobenzene (TCB), 1,2,4,5-tetrachlorobenzene (TeCB), pentachlorobenzene (QCB), and hexachlorobenzene (HCB) were spiked to the sediment, and the concentrations of CBs both in sediment and water were measured at six different mixing time periods (0.17, 1, 4, 12, 24 and 48 h). A partition kinetics model was developed to determine kinetics rate constants. Adsorption rate constants increased (DCB 15.3; HCB 26.3 L kg−1 h−1) while desorption rate constants decreased (DCB 0.41; HCB 0.01 h−1) with KOW values. The times to reach equilibrium in the system were between 6.7 h (HCB) and 14.3 h (TeCB), with no specific pattern related to the KOW values of CBs. The kinetics of CBs were fitted to a first-order kinetics with a single-compartment model. QSAR analysis showed strong linear relationships between kinetics rate constants and physicochemical properties.

Mesoscale Structures in the Adlayer of A-B2 Heterogeneous Catalysis.

This article explores the adsorbate distributions in the adlayer for a model A-B2 system of heterogeneous catalysis, i.e., A + 1/2B2 → AB, via kinetic Monte Carlo (KMC) simulations. In comparison with our previous work on the A-B model (Sun, F.; Huang, W.; Li, J. Structural characteristics of the adlayer in heterogeneous catalysis. Chem. Eng. Sci. 2016, 153, 87-92), species B2 here brings about significant new features due to its special site requirement during adsorption and desorption and a different stoichiometric ratio in reactions. The effects of various kinetic processes on the adsorbate distribution are found to be similar to those in the A-B system; that is, both desorption and diffusion (besides adsorption) processes contribute to the adlayer uniformity while reactions account for clustering. However, desorption exhibits a stronger role than diffusion in homogenizing the adlayer, which is opposite to the finding in the previous A-B model. Under a fixed partial pressure, different reaction and desorption rate constants can lead to steady states with different dominant species, which has not been observed in the A-B system. The regime of species B poisoning shrinks as well, leading to the spreading of the coexisting regime, in comparison with the A-B model.

Kinetic desorption models for the release of nanosilver from an experimental nanosilver coating on polystyrene food packaging

Abstract To predict the kinetic desorption of silver from an experimental nanosilver coated polystyrene food packaging material into food simulants (0, 1, 2 and 3% acetic acid (HAc) in distilled water (dH 2 O)) at 4 temperatures (10, 20, 40 and 70 °C), 5 sorption models were examined for their performance. A pseudo-second order kinetic sorption model was found to provide the best prediction of an unseen desorption validation dataset with R 2 = 0.90 and RMSE = 3.21. Poor predictions were witnessed for desorption at 70 °C, potentially due to re-adsorption of the silver back onto the polystyrene substrate, as shown in the kinetic migration experiments. Similarly, the temperature dependence of the desorption rate constant was satisfactorily described using the Arrhenius equation with the exception of the 70 °C scenario. The use of sorption models identified scenarios that may limit human exposure to nanosilver migrating from this experimental nanocoating, i.e. low temperature applications. Industrial relevance The use of antimicrobial packaging has the potential to reduce food spoilage and risk from pathogenic microorganisms while reducing food waste by extending the shelf life of food products. Coating of antimicrobial silver nanoparticles (AgNPs) to polymer surfaces is a highly advantageous technology as microbial contamination predominantly occurs on the surface of fresh and processed food products. However, uncertainty related to the potential release of nanoparticles from food packaging materials, subsequent potential human exposure and toxicology is a barrier to the uptake of these novel materials. In the European Union, where the safety assessment of these materials is stringent, mathematical models used to predict the worst case migration of nanoparticles from food packaging materials have supported the acceptance of some nanomaterials for use in food packaging. The performance of a number of desorption models was evaluated to predict the release of AgNPs from AgNP coated polystyrene. The model identified factors that influenced migration and possible industrial applications for the developed material to minimise human exposure. The study highlights the potential benefits of using predictive models to assess migration of NPs from polymers into food simulants instead of time consuming and expensive migration studies.

Kinetics of phosphorus desorption from calcareous soils using DGT technique

The present study investigated kinetics of phosphorus (P) release from some calcareous soils employing DGT technique. For these purpose, DGT were deployed in ten calcareous soils for different time periods between 4h and 21days and the accumulated P were used to calculate the distribution coefficient for labile metal, Kdl, desorption rate constants (k−1) and the rate at which the soil system can resupply P from solid phase to solution (Tc) using the DIFS model. The values of Kdl calculated from DIFS ranged from 0.67 to 198cm3/g. Response times (Tc) were so short in six studied soils with low Olsen-P. A short response time means that the rapid resupply from the solid phase and slow depletion over time of the available P pool occurs. By contrast, the four rests of the soils have a longer response time (about 40min) and so little the resupply from the solid phase, leading to a progressive depletion. The P desorption rate (k−1) parameter derived from DIFS were from 9.9∗10−6 to 21.12∗10−4s−1 with a mean 4.54∗10−4 and well-correlated with the content and/or the concentration of P in corn shoot (r=0.74, P<0.05) and root (r=0.71, P<0.05) confirming the importance of P desorption rate in plant P nutrition in the calcareous soils. In these study, the close correlation was obtained between clay and calcium carbonate equivalent concentration with P desorption rate that demonstrate DGT technique sensitive to soil properties and may allow the study of root-induced changes in rhizosphere.

Characterization of arsenic availability in dry and flooded soils using sequential extraction and diffusive gradients in thin films (DGT) techniques.

Much attention has been paid to the availability of arsenic (As) in soils, while few studies were carried out on the comparison between the dry and flooded soils using different methods. In this study, chemical sequential extraction and diffusive gradients in thin films (DGT) techniques were employed to study the availability of As in soils amended with a range of exogenous As followed by one-year incubation under dry and flooded conditions, respectively. The results showed that the proportions of available solid As pools, including non-specifically adsorbed As (F1) and specifically adsorbed As (F2), had consistent increases with the increase of As amendment. The concentration of DGT-measured As (C DGT) and dissolved As in soil solution (C SOL) also increased up to 2573 (dry) and 1823 (flooded) times and 4067 (dry) and 3105 (flooded) times of the control, respectively, while their ratios (R) showing the extent of C SOL sustained from solid resupply decreased from 0.17 to 0.10 (dry) and 0.35 to 0.21 (flooded). Modelling with DGT-induced fluxes in soils (DIFS) further showed an increase of T c (the characteristic time to reach equilibrium from DGT perturbation) and decreases of desorption and adsorption rate constants (k 1 and k -1) with the increase of As amendment, reflecting a decrease in kinetic exchange rate of As between available solid As pool and soil solution. The flooded soils had greater values of R, k -1 and k 1 and lower value of T c in comparison with the dry soils, indicating a greater availability of As under the flooded condition.

Oxygen adsorption and desorption characteristics of LSCF5582 membranes for oxygen separation applications

This study examines the oxygen adsorption and desorption characteristics of La0.5Sr0.5Co0.8Fe0.2O3−δ (LSCF5582) membranes prepared at sintering temperatures of 1200–1300°C, with the aim of gaining an insight into their performance in the surface reaction limited regime for oxygen separation applications. The findings of this work are then compared with our experimental data on Ba0.5Sr0.5Co0.8Fe0.2O3−δ (BSCF5582) membranes. It is demonstrated that the adsorption rate constants of both membranes are two orders of magnitude greater than their respective oxygen desorption rate constants as the oxygen adsorption occurs in less than 24s whilst the oxygen desorption takes approximately one hour to reach equilibrium. The activation energy for oxygen adsorption of LSCF5582 reduced to a quarter of its value with increasing the sintering temperature from 1200°C to 1300°C. This is attributed to the oxygen exchange occurring more rapidly along the grain boundaries resulting in a lower activation energy. The LSCF5582 grain sintered at 1200°C is the optimum selection for oxygen separation applications at an operating temperature of 850°C and oxygen partial pressure of 0.21bar.

Current at a Rotating Disk Electrode under Electrosorption and Surface Diffusion Limitation

Following a model for the current limited by adsorption and surface diffusion at a rotating disk electrode (rde), the case is analyzed when surface diffusion is preceded by adsorption with charge transfer. The electrode surface consists of a distribution of reaction sites embedded in a supporting phase where electrosorption and surface diffusion take place. Electrosorption is described by five parameters, an equilibrium potential (E0ad), a microscopic partial charge transfer (zad), a charge transfer coefficient (βad), and the rate constants for desorption and adsorption (k1 and k2, respectively). Analytical expressions for the current – overpotential (j vs ηad) and the Koutecký – Levich (KL) relation (1/j vs 1/ω1/2) are provided as a function of electrosorption parameters and surface diffusivity (Ds). The KL relation is linear, with the same slope as for a classical rde, whereas the intercept (1/ jK) depends on electrosorption parameters and Ds. Tafel relations for the intercept current (log jK vs. η) are provided for the general and limiting cases. Effects of the radial convective transport in the electrolyte over reaction sites, and of the overlapping of surface diffusion areas are included in the model. The analytical expressions can be used to determine surface diffusion kinetics parameters from rde results.

Desorption rate of glyphosate from goethite as affected by different entering ligands: hints on the desorption mechanism

Environmental contextGlyphosate is a heavily used herbicide that is mobilised in soil and sediments through adsorption–desorption processes from the surface of mineral particles. We demonstrate that the desorption rate of glyphosate from goethite, a ubiquitous mineral, is nearly independent of the concentration and nature of the substance that is used to desorb it. The results elucidate the desorption mechanism and are relevant to understand and predict the environmental mobility of glyphosate. AbstractThe desorption kinetics of glyphosate (Gly) from goethite was studied in a flow cell using attenuated total reflectance Fourier-transform infrared spectroscopy. Because Gly forms an inner-sphere surface complex by coordinating to Fe atoms at the goethite surface, the desorption process is actually a ligand-exchange reaction, where Gly is the leaving ligand and water molecules or dissolved substances are the entering ligands. A series of possible entering ligands that can be found in nature was tested to evaluate their effect on the desorption kinetics of Gly. Contrarily to expectations, the desorption rate was quite independent of the entering ligand concentration. Moreover, the identity of this ligand (phosphate, citrate, sulfate, oxalate, EDTA, thiocyanate, humic acid, water) had only a small effect on the value of the desorption rate constant. By analogy with the reactivity of transition metal complexes in solution, it is concluded that the rate is mainly controlled by the breaking of the Fe–Gly bond, through a dissociative or a dissociative interchange mechanism. The results are relevant in understanding and predicting the environmental mobility of Gly: irrespective of the identity of the entering ligand, Gly will always desorb from iron (hydr)oxides in nature at nearly the same rate, simplifying calculations and predictions enormously. The importance of studying desorption kinetics using mineral surfaces and environmentally relevant molecules is also highlighted.

Pairing micropollutants and clay-composite sorbents for efficient water treatment: Filtration and modeling at a pilot scale

Organically modified clay minerals have been widely developed, tested and employed as sorbents for organic pollutants. However, the process of pollutant-composite pairing is not commonly addressed, which would be valuable for efficient pollutant filtration by such sorbents. This study presents an approach for achieving efficient pollutant removal by large-scale composite filters, based on pairing chemically compatible pollutants and composites and by employing a predictive filtration model. The removal of three organic pollutants, simazine, sulfentrazone and diclofenac by lab-scale filtration columns containing one of three sorbents, a polymer-, micelle- or liposome-clay composite, was measured. Understanding the factors governing pollutant-organic modifier interactions enabled to pair an efficient sorbent to each pollutant. The high removal (80%) of simazine by the polymer composite, was attributed to hydrogen bonds and π-π interactions, compared to less than 20% removal by the surfactant composites. The removal of the anionic diclofenac (pKa=4.1) was mainly governed by electrostatic attraction, explaining its high removal by the most positively charge sorbent, the liposome composite. Sulfentrazone (pKa=6.5) removal was mostly affected by micellar solubilization and upon its removal, the zeta potential of the micelle-composite was not reduced as obtained for diclofenac removal. The filtration of the successful pairs was modelled to determine sorbent capacity and adsorption and desorption rate constants. The pilot filtration experiments were well described by the model and demonstrated efficient removal of paired pollutants and sorbents. Model simulations predicted promising treatment at environmental pollutant concentrations in the μgL−1 range. This pairing approach along with model calculations can be a strong and valid tool for efficient pollutant-sorbent filtration.

Theoretical investigation of crystallographic orientation effect on the chemical etching rate

The chemical etching of boron-doped p-Si(100) and p-Si(111) substrates in Br2+Ar mixture is considered. The experimentally measured dependences of silicon etching rate on partial pressure of Br2 molecules are compared with those theoretically calculated. It is found that at the same temperature desorption rate constant for SiBr2 molecules on p-Si(100) substrates is more than twice higher than on p-Si(111) substrates. The difference in desorption rate constants is caused by higher concentration of dangling bonds on Si(100) surface. The averaged desorption activation energy of SiBr2 molecules is equal to Ed±ΔEd=(2.02±0.11)eV. The influence of crystallographic orientation on the rate constant for Si+Br2→SiBr2 reaction is negligible.

Organic Acids Regulation of Chemical-Microbial Phosphorus Transformations in Soils.

We have used an integrated approach to study the mobility of inorganic phosphorus (P) from soil solid phase as well as the microbial biomass P and respiration at increasing doses of citric and oxalic acid in two different soils with contrasting agronomic P status. Citric or oxalic acids significantly increased soil solution P concentrations for doses over 2 mmol kg-1. However, low organic acid doses (<2 mmol kg-1) were associated with a steep increase in microbial biomass P, which was not seen for higher doses. In both soils, treatment with the tribasic citric acid led to a greater increase in soil solution P than the dibasic oxalic acid, likely due to the rapid degrading of oxalic acids in soils. After equilibration of soils with citric or oxalic acids, the adsorbed-to-solution distribution coefficient (Kd) and desorption rate constants (k-1) decreased whereas an increase in the response time of solution P equilibration (Tc) was observed. The extent of this effect was shown to be both soil and organic acid specific. Our results illustrate the critical thresholds of organic acid concentration necessary to mobilize sorbed and precipitated P, bringing new insight on how the exudation of organic acids regulate chemical-microbial soil phosphorus transformations.

Hydrogen Recombination Rates on Silica from Atomic-Scale Calculations

A combined molecular dynamics (MD) and Monte Carlo approach was used to bridge time scales, enabling calculations of surface recombination rates for hydrogen on silica. MD was used for temperatures between 10 and 600 K at a high pressure of 10 atm, yielding recombination coefficients between 0.1 and 1. For the lower pressures more common in applications, low recombination rates make the corresponding calculations intractably expensive. A Monte Carlo technique, informed by the MD simulations, was designed to bridge the essential time scales. Distinct weak and strong surface binding sites for atomic hydrogen with densities of approximately 10 nm–2 were found using grand canonical Monte Carlo (GCMC) simulations, which, in turn, were used to obtain Eley–Rideal rate constants based on semiequilibrium theory. Monte Carlo variational transition state theory (MCVTST) was used to calculate Langmuir–Hinshelwood and thermal desorption rate constants for hydrogen atoms in strong and weak adsorption sites. Calculated reaction rates were used in a Langmuir kinetics model to estimate the recombination coefficient γ for T = 10–2000 K at gas-phase radical densities between 1012 and 1016 cm–3, yielding values of γ = 10–4–0.9.

Surface PEGylation of Silver Nanoparticles: Kinetics of Simultaneous Surface Dissolution and Molecular Desorption.

A quantitative study of the stability of silver nanoparticles (AgNPs) conjugated with thiolated polyethylene glycol (SH-PEG) was conducted using gas-phase ion-mobility and mass analyses. The extents of aggregation and surface dissolution of AgNPs, as well as the amount of SH-PEG adsorption and desorption, were able to be characterized simultaneously for the kinetic study. The results show that the SH-PEG with a molecular mass of 6 kg/mol (SH-PEG6K) was able to adsorb to the surface of AgNP to form PEG6K-HS-AgNP conjugates, with the maximum surface adsorbate density of ∼0.10 nm(-2). The equilibrium binding constant for SH-PEG6K on AgNPs was calculated as ∼(4.4 ± 0.9) × 10(5) L/mol, suggesting a strong affinity due to thiol bonding to the AgNP surface. The formation of SH-PEG6K corona prevented PEG6K-HS-AgNP conjugates from aggregation under the acidic environment (pH 1.5), but dissolution of core AgNPs occurred following a first-order reaction. The rate constant of Ag dissolution from PEG6K-HS-AgNP was independent of the starting surface packing density of SH-PEG6K on AgNP (σ0), indicating that the interactions of H(+) with core AgNP were not interfered by the presence of SH-PEG6K corona. The surface packing density of SH-PEG6K decreased simultaneously following a first-order reaction, and the desorption rate constant of SH-PEG6K from the conjugates was proportional to σ0. Our work presents the first quantitative study to illustrate the complex mechanism that involves simultaneous aggregation and dissolution of core AgNPs in combination with adsorption and desorption of SH-PEG. This work also provides a prototype method of coupled experimental scheme to quantify the change of particle mass versus the corresponding surface density of functional molecular species on nanoparticles.