Intraparticle Diffusion Control Research Articles

Extraction Kinetics of Rare Earth Elements from Ion-Adsorbed Underclays

Citric acid has been identified as an environmentally sustainable organic acid capable of leaching up to ~30% of easily accessible REEs from underclay material. An analysis of the leaching profiles was performed to discern the reaction rates, extraction efficiencies, and potential leaching mechanisms of REEs and cations of interest from ion-adsorbed underclays. The initial leaching stage follows a slow intraparticle diffusion mechanism followed by a second stage controlled by a mixed diffusion regime. The leaching profiles of Ca and P were similar to those of REEs, suggesting that REEs are most likely derived from mineral surfaces such as hydroxyapatite or crandallite rather than predominately from underclays. Fitting to a modified diffusion control model found diffusion-controlled leaching to be the primary mechanism whereas non-diffusive mechanisms made up about 22% of the extracted REEs. Gangue cations associated with underclays had less non-diffusive leaching than REE species, indicating that their leaching kinetics may be dominated by diffusion from within the material or potentially from product layer formation. Fitting to Boyd plots further indicated that REEs were leached following intraparticle diffusion control. These results have important implications for the development of more efficient and sustainable methods for extracting REEs or critical minerals from alternative feedstocks.

Novel slow-release nanohybrid from zinc hydroxysalt intercalated with dicamba herbicide

Dicamba was intercalated by co-precipitation into a zinc-layered hydroxide salt (LHS) to create a slow-release nanohybrid weed control without leaching. The X-Ray Powder Diffractometry (XRPD) patterns of the LHS intercalated with dicamba showed a basal spacing of 20.48 Å and 26.10 Å, confirming its allocation as a monolayer and bilayer interdigitated arrangement, respectively. The Fourier Transformant Infrared (FTIR) spectrum showed bands typical of dicamba and provided information about its bridging bidentate coordination to the matrix layer. The thermogravimetric analysis (TGA) estimated the compound's formula as Zn5(OH)8(dicamba)2·4.14H2O. The thermal stability of the LHS/dicamba system, the stages of mass loss, the characterization of the compounds released in the pyrolysis, the activation energy (Ea), and the kinetics were all analyzed. The average activation energy for decomposition of intercalated dicamba indicates that the thermal degradation occurred with the breakage of covalent bonds. Controlled release of dicamba from its nanohybrid in water was observed for 962 h (40 days). The pseudo-second-order model described the release process satisfactorily from its linear fitting, suggesting intraparticle diffusion or surface diffusion control. In summary, the intercalation of dicamba in the zinc LHS produced a slow-release material that can aid in weed control.

Impact of the Non-Uniform Catalyst Particle Size on Product Selectivities in Consecutive Reactions

The analysis of consecutive reactions A→B→C in porous catalyst particles, where the simultaneous processes of diffusion and chemical reactions take place and both reactant and products are subjected to diffusion limitations, was performed for catalyst particles with non-uniform sizes, a fact that has not been considered so far. The system comprises first-order consecutive irreversible reactions that proceed on spherical catalyst particles with a log-normal volume particle size distribution (PSD), which is typical in many catalytic applications. Regardless of the prevailing diffusion regime (chemical control, transition situation or intraparticle diffusion control), the yield of the intermediate product (B) reaches a maximum value as a function of the conversion of reactant (A), then decreases as a consequence of the prevalence of the secondary reaction that converts it into the secondary product (C). If intraparticle diffusion resistances affect the reactant species, given the relationship between the kinetic constants and the mean particle size, the selectivity to the intermediate product is negatively affected by the dispersion in PSD. The larger the dispersion in PSD, the stronger the negative impact.

Efficient Water Softening in Heavy Oil Steamflood Operations

Summary Pigging of once through steam generators (OTSGs) has indicated various types of scales, the most predominant of these being silicates of hardness causing ions. It was noted that scaling propensity can potentially go up with higher steam quality (SQ) as the reject stream gets concentrated with ions. However, models suggested that there are benefits of higher SQ in enhancing fuel savings (8%) and electricity savings (2%) when SQ was increased by 20%. The challenges of higher SQ were noted in terms of increased scaling tendency and therefore the need for improved softening. In Field D, the service cycle, the backwash cycle, and the brining cycle were optimized leading to a gain in throughput and reduction in salt consumption. Service cycle improvement gained 30 to 130% in throughput between two regenerations, backwash cycle improvement by fluidizing the bed to nearly 35% helped gain 10% in throughput, and reduction of brining cycle from 75 to 48 minutes helped reduce salt consumption by 56% without impacting the throughput. In Field B, a 6-month pilot revealed that shallow shell resins where ion exchange is more efficient due to inert core (better intraparticle diffusion control) can enhance the throughput by 30 to 80% and simultaneously reduce the number of regenerations by 15 to 30%. Resin fouling is still a major challenge to contend with as oil can foul the resin and throughput can decline by 0.5 to 3 folds. In a plant operation, where there are multiple softener and brine vessels, there is a need to optimize them as a system. Reliability, availability, and maintainability (RAM) models are used in Field C to (a) address equipment configuration optimization with impact on capital capacity expansion project scope, (b) understand how net soft water delivery capacity was affected by increases in inlet hardness, and (c) assess through a comparison scenario if the large cost of addressing the valve issue in an upstream nutshell filter was worth the lost production opportunity related to unplanned downtime.

Hydration kinetics of K2CO3, MgCl2 and vermiculite-based composites in view of low-temperature thermochemical energy storage

Thermochemical energy storage (TCES) may store heat for a theoretically indefinite amount of time at high energy storage density. It is an ideal means to achieve seasonal thermal energy storage (TES). Hydration at atmospheric pressure of inorganic hygroscopic salts has attracted much attention from the scientific community: TES in the range 30 °C-150 °C is achievable and suitable for domestic heating applications such a space-heating. While progress at both material and reactor scales have been made, there is still a lack of fundamental understanding of the relationships connecting the two, which is necessary in order to enable full TCES potential and develop technical solutions. We investigated inorganic salts K2CO3 and MgCl2, and composites consisting in these salts impregnated into vermiculite. Experimental measurements (dynamic vapour sorption) and numerical optimization of known solid-state kinetic models relevant for sorption were used to derive kinetic coefficients for different solid-state reaction kinetic models and to shed light on the possible rate-limiting mechanisms of the hydration of each material. Potassium carbonate (K2CO3) hydration was found to be kinetically hindered by what appears to be a diffusion barrier at the interparticle level. Impregnation of K2CO3 lead to a significantly improved hydration, controlled at 25 °C by nucleation and 40 °C by phase-boundary control according to the best fitting kinetic models. MgCl2 hydration was best modelled by first-order model and diffusion-type models, pointing towards intraparticle diffusion control. Finally, the hydration of MgCl2 impregnated into vermiculite was best modelled by phase-boundary control models, with no notable rate-limiting step change at different temperatures.

Experiment and regeneration kinetic model study on CO2 adsorbent prepared from fly ash

• Loaded potassium-based CO 2 adsorbent was prepared from fly ash. • Temperature programmed desorption of adsorbent was performed. • Experiment and model fitting were combined to study desorption regeneration. • Avrami fractional kinetic model was used to simulate regeneration kinetics. • Diffusion models were used to analysis desorption mechanism. Using power plant fly ash to prepare CO 2 adsorbent can not only realize low-carbon power in power plants, but also effectively use solid waste to achieve the objective of treating the waste with waste. Regeneration characteristic is an important performance of adsorbent. Through the temperature programmed desorption experiment, the influence of different regeneration conditions on performance and regeneration kinetics can be studied, and the optimal calculation of regeneration conditions can be carried out, so as to realize the recycling of adsorbent with economic benefits. The optimal regeneration temperature and heating rate were 150 °C and 10 °C/min, respectively. Under these conditions, the desorption capacity was 1.7454 mmol/g, and the desorption efficiency was 86.38%. Avrami fraction kinetic model was used to simulate and calculate the regeneration kinetics of adsorbent. The results showed that the regeneration temperature affected the regeneration mechanism. High regeneration temperature and high heating rate could promote the desorption kinetic rate to increase. When the regeneration temperature was 90 °C and 190 °C, k a was 0.000885 min −1 and 0.001318 min −1 respectively. Three kinds of diffusion were used to study the regeneration mechanism. It was concluded that after the regeneration temperature was higher than the chemical desorption temperature, the desorption regeneration could be divided into early, middle and final stages, and the rate controlling steps were respectively: intraparticle diffusion control, joint control of surface chemical reaction and intraparticle diffusion, and membrane diffusion control. Physical desorption occured when the regeneration temperature was lower than 110 °C. The desorption time was longer and CO 2 concentration released was always low.

Mercury vapor adsorption and sustainable recovery using novel electrothermal swing system with gold-electrodeposited activated carbon fiber cloth

A novel electrothermal swing (ETS) system with gold-electrodeposited activated carbon fiber cloth (GE-ACFC) was developed to adsorb and sustainably recover low-concentration Hg0. GE-ACFC with an Au growth time of 1200 s displayed the largest Hg0 adsorption capacity and >90% removal efficiency. The Hg0 adsorption of GE-ACFC was dominated by physisorption via Au amalgamation. In contrast, Hg adsorption of untreated ACFC (RAW-ACFC) was mainly controlled by physisorption and chemisorption related to carbonyl groups. Nevertheless, both ACFCs could reach 100% ETS Hg0 regeneration. The Hg re-adsorption of GE-ACFC was stable, with efficiency >90% at different regeneration temperatures in three-cycle ETS experiments, but the Hg re-adsorption efficiencies of RAW-ACFC greatly decreased to only 60% after 250 ℃ regeneration, due to the formation of electrothermal hot spots in the ACFC. Because the thermal and electrical conductivity of GE-ACFC increased due to Au electrodeposition, the presence of electrothermal hot spots in GE-ACFC-1200s was minor. Simulation results showed that both pseudo-first-order and pseudo-second-order models fitted well to the desorption patterns of the GE-ACFC. Mass transfer model further suggested that intraparticle diffusion control was the rate-limiting step, with diffusion coefficients increased from the first to the third cycle for GE-ACFC.

A new method of characterizing mass transfer controlling mechanism in pollutant adsorption from aqueous solutions

Pollutant adsorption from aqueous solutions is usually controlled by diffusion or mass transfer which can be external film diffusion or intraparticle diffusion or both, depending on the relative magnitude of the film and intraparticle mass transfer resistances. Traditionally the Biot number is used to characterize mass transfer controlling mechanism in adsorption. In this work a new quantitative characterization method is proposed. Specifically the average fractional film mass transfer resistance is defined and used as an indicator of the relative importance of film and intraparticle mass transfer resistances. The average fractional film mass transfer resistance varies from 0 to 1, corresponding respectively to complete intraparticle diffusion control and complete film diffusion control. Numerical simulations of batch adsorption processes are performed and the corresponding average fractional film mass transfer resistance calculated for a wide range of process parameters. Based on the simulation results a correlation is obtained between the average fractional film mass transfer resistance and the Biot number, the adsorbate partition ratio and the separation factor. It is shown that the Biot number alone is not sufficient to characterize mass transfer controlling mechanism in adsorption.

Pore-resolving simulation of char particle gasification using micro-CT

Understanding the interaction between transport, reaction and morphology at the scale of individual char particles is important for optimizing solid fuel gasification and combustion processes. However, most particle-scale models treat porous char particles as an effective porous continuum, even though the presence of large, irregular macropores, voids and fractures render such upscaled treatments mathematically invalid, and the models non-predictive. A new modeling framework is therefore proposed to elucidate the impact of morphology on char particle gasification and combustion. A pore-resolving, transient, three-dimensional simulation for gasification of a realistic coal char particle is developed based on X-ray micro-computed tomography (micro-CT). The large macropores and voids resolved by micro-CT are explicitly represented in the particle’s geometry and conservation equations based on first principles are solved in those regions. Upscaled, effective-continuum equations are applied only within the micro- and meso-porous grains surrounding the voids, where such equations are mathematically appropriate. To assess the impact of the realistic particle morphology, a second model which employs effective-continuum equations everywhere and assumes spherical symmetry is also developed for a particle having the same initial mass, volume, porosity, surface area and equivalent diameter as the pore-resolving model. The results indicate that large, irregular voids enhance mass transport throughout the particle and affect its overall conversion behavior when reactions occur under intra-particle diffusion control.

Dynamics of trace metal sorption by an ion-exchange chelating resin described by a mixed intraparticle/film diffusion transport model. The Cd/Chelex case

The time-evolution of Cd2+ ion sorption by Chelex 100 resin was studied in batch experiments as a function of time, pH, ionic strength, stirring rate, mass of resin and initial metal ion concentration. In the experimental conditions, the amount of resin sites are in excess with respect to the amount of metal ion, leading to extensive depletion of metal in bulk solution when equilibrium is reached. The data were described using a mixed control mass transport model in finite volume conditions (MCM) that includes explicitly both intraparticle and film diffusion steps. Exact numerical computations and a new approximate analytical expression of this model are reported here. MCM successfully predicts the influence of pH and ionic strength on the experimental Cd(II)/Chelex kinetic profiles (which cannot be justified by a pure film diffusion controlled mechanism) with a minimum number of fitting parameters. The overall diffusion coefficient inside the resin was modelled in terms of the Donnan factor and the resin/cation binding stability constant. The values of the latter coefficient as a function of pH and ionic strength were estimated from the Gibbs-Donnan model. Even though MCM is numerically more involved than models exclusively restricted to film or intraparticle diffusion control, it proves to be accurate in a wider range of values of the mass transfer Biot number and solution/resin metal ratios.

Adsorptive Removal of As(III) from Aqueous Solution by Raw Coconut Husk and Iron Impregnated Coconut Husk: Kinetics and Equilibrium Analyses

AbstractAs(III) removal from aqueous solution was conducted using low-cost adsorbents like unmodified raw coconut husk (RCH) and modified iron impregnated coconut husk (IICH). Prepared both adsorbents was characterisation by using elemental analyses, FTIR, TGA, SEM and EDX. The analysis behaviour indicates, both adsorbents are highly suitability for As(III) removal. The effects of operational parameters, such as pH, adsorbent dose and initial concentration on these adsorbents were investigated and compared with other agriculture based adsorbent. The result reveals that the As(III) removal capacity is effective in the pH range of 6.2–7.8 and the optimum pH and adsorbents dose was found as 7.0 and 40 g l−1, for RCH and IICH, respectively. Kinetic and equilibrium studies over a wide range of operating conditions are tested to evaluate the effectiveness of RCH and IICH to remove As(III) from water. The values of bothkf1andks2values are found to be nearly same and same trend was observed at higher 50 mg l−1and lower arsenic concentration 25 mg l−1for RCH and IICH. But the kinetic data is fitted better in the pseudo-second-order kinetic model than the pseudo-first order model. The effective intraparticle diffusion coefficient of As(III) ions in RCH and IICH is observed to be 2.145×10−9 cm2s−1and 1.838×10−10 cm2s−1, which indicates that the overall As(III) adsorption on both adsorbents are intraparticle diffusion control. Equilibrium isotherms for the adsorption of As(III) on RCH and IICH were analyzed at different dose and different initial concentration. At different concentration system, Freundlich isotherm and Redlich-Peterson are best fitted followed by Langmuir and Temkin isotherm models and for varying doses, all equilibrium models give almost similar fitness.

The kinetic studies of the cobalt ion removal from aqueous solutions by dolomite-based sorbent

The kinetics of Co(II) ions adsorption on thermally activated dolomite was studied with respect to the calcination temperature of natural dolomite. The sorption of Co(II) onto all samples is reasonably fast: The first 30–35 min accounts for approximately 70–80 % of Co(II) removal from feed solutions. In order to select the main rate-determining step in the overall uptake mechanism, a series of experiments were performed and data obtained were interpreted in terms of film diffusion control, intraparticle diffusion, pseudo-first-order and pseudo-second-order models. From the modeling of kinetic data, it can be concluded that adsorption of Co(II) ions from aqueous solution by heat-treated dolomite is a complex phenomenon and occurs in a mixed diffusion mode—the kinetic data are well described by the pseudo-second-order equation. The possible multistage sorption mechanism involving film diffusion and intraparticle diffusion control steps as well as chemical interaction between Co(II) ions and calcined dolomite is proposed.

Evaluation of thiol-modified vermiculite for removal of Hg(II) from aqueous solutions

Aiming the removal of Hg(II) from waters, Na+ exchanged vermiculite (Na-VT) was modified with l-cysteine (CYS-VT), cysteamine hydrochloride (CTA-VT) and (3-mercaptopropyl) trimethoxysilane (3-MPS-VT). Modification with CTA and CYS was made at pH6.0±0.1 to facilitate ion exchange of Na+ in the interlayer with the protonated amines. Modification with 3-MPS was made by silylation, covalently binding the modifier to the silanols. Initial adsorption rate (μmolg−1min−1) on Na-VT and 3-MPS-VT was very fast and obeyed a pseudo second order kinetics. Intraparticle diffusion controlled the initial adsorption rate in CTA-VT and CYS-VT. Adsorption isotherms constructed at pH6.0±0.1 and 25.0±0.5°C fitted to Langmuir and Freundlich equations. The adsorption capacities of CTA-VT, CYS-VT, 3-MPS-VT and Na-VT were 83±30, 57±4, 21±2 and 18±1μmolg−1 (n=3), respectively. The adsorption capacity in columns followed the order: 3-MPS-VT>CTA-VT>CYS-VT>Na-VT, which is consistent with the instantaneous adsorption on 3-MPS-VT and the intraparticle diffusion control in CTA-VT and CYS-VT. The modifications afforded materials with adsorption capacities less affected by variation of ionic strength and pH as a consequence of the strong binding of Hg(II) to the incorporated thiols.

Combination of Na-modified zeolite and anion exchange resin for advanced treatment of a high ammonia–nitrogen content municipal effluent

In this study, the exchange equilibrium and kinetic experiments of ammonia–nitrogen on the Na-form zeolite were conducted. The results indicated that the presence of humic acid have a negative effect on the equilibrium exchange capacity but have limited influence on the equilibrium time except shorten the sole intra-particle diffusion control time. The exchange equilibrium data could be well fitted by Freundlich model in the absence of humic acid but Langmuir model in the presence of humic acid. While the exchange kinetic data could be well described by pseudo-second-order kinetic model in both situations. An anion exchange resin exhibited high removal efficiency to humic acid and dissolved organic matter through kinetic results and fluorescence excitation-emission matrix (EEM) spectroscopy results. The use of the anion exchange resin prior to the Na-form zeolite improved the ammonia–nitrogen removal efficiency from 78% to 95% and increased the treatment volume of the Na-form zeolite from 51 BV (bed volume) to 76 BV. Both the resin and the Na-form zeolite could be successfully regenerated by the combination of alkaline and sodium chloride. Complete elution of ammonia–nitrogen was achieved when the mass percentage of sodium chloride and alkaline was 10% and 0.6% respectively.

Transient effectiveness factors in the dynamic analysis of heterogeneous reactors with porous catalyst particles

A model to calculate the actual transient effectiveness factor in spherical porous catalyst particles in gradientless reactors, where a first order reaction takes place under isothermal conditions, linear equilibrium adsorption and intraparticle diffusion control, was developed. After a certain time has elapsed following a change in the feed׳s reactant concentration, the transient effectiveness factor can be approximated as a linear combination of the steady state effectiveness factor and the relative rate of change of the concentration in the fluid phase. Oppositely to the well-known steady state effectiveness factor, which depends only on the Thiele modulus ϕ, related to intrinsic properties of the catalysts, the transient effectiveness factor also depends on other two dimensionless numbers: α, the relationship between the capacity of accumulation of reactant in the fluid and solid phases, and ϕf, a relationship between the convective flow and the intraparticle diffusion rate. In this way, the catalyst load, the reactor volume and the volumetric flow do impact on the effectiveness factor. The coefficients defined as Ia and If are the Diffusion–Adsorption–Reaction Factor and the Flow Factor, respectively, which are complex functions of the Thiele modulus, the convective modulus ϕf and the system׳s adsorption capacity α, and which can be used to correct the steady state effectiveness factor to yield the approximated transient effectiveness factor, which is more exact. In the case of a pulse perturbation in the reactant׳s concentration, the transient effectiveness factor reaches a constant value which is larger than that from the steady state effectiveness factor and, the larger the catalyst mass and the flow, the larger the difference. Results show the existence of a pseudo-equilibrium state in gradientless reactors.

CO2 Gasification Kinetics of Algal and Woody Char Procured under Different Pyrolysis Conditions and Heating Rates

This paper presents the results on gasification kinetic data, influence of the different models on predicted gasification rates, reaction order and comparison of gasification reactivity of the chars prepared in different conditions as well as that among the feedstock (algal and woody chars). A fresh water alga, Chlorococcum humicola and three types of woody biomass were pyrolyzed separately in a thermogravimetric analyzer (TGA) and in an entrained flow reactor (EFR), and the resultant chars were then gasified in the temperature range 700–1000 °C under CO2 to compare their intrinsic kinetics and to determine the transition temperatures between kinetic control and intraparticle diffusion control. The transition temperature was dependent on both sample and pyrolysis condition. Activation energy and frequency factor were determined using three kinetic models (volumetric, grain and random pore). The activation energy of different chars was determined to be in the range of 180–307 kJ/mol. Among the models, the random pore model was found to be predicting the weight loss profile most accurately except for the algal and a woody char from EFR. The reaction order and reactivity were found to be varying significantly with the pyrolysis condition of the chars.

The Investigation of Phenol Removal from Aqueous Solutions by Water Hyacinth

The potential of water hyacinth ash for phenol adsorption from aqueous solution was studied. Batch kinetic and isotherm studies were carried out under varying experimental conditions of contact time, pH, phenol concentration, and solution temperature. The adsorption of phenol was studied at pH 7. Batch adsorption models, based on the assumption of the pseudo-first-order, pseudo-second-order, and Elovich models, were applied to examine the kinetics of the adsorption. The results showed that kinetic data followed closely to the Elovich kinetic model. The experimental data were further analyzed by the expression of Boyd and the intraparticle diffusion model to determine the actual rate controlling steps. The overall rate of phenol uptake was found to be controlled by external mass transfer at the beginning of adsorption; then it gradually changed to intraparticle diffusion control at a later stage. Various adsorption models were used for the mathematical description of adsorption equilibrium and it was found that the experimental data fitted very well to the Langmuir model. Different thermodynamic parameters such as free energy, enthalpy, and entropy have been calculated and it was concluded that with the increase in temperature adsorption decreases, indicating the exothermic nature of the process.

Surface Modification of Hydrophobic Resin with Tricaprylmethylammonium Chloride for the Removal of Trace Hexavalent Chromium

Chromium(VI) is one of the most toxic contaminants in the environment, even at low concentration. The conventional chemical precipitation process for Cr(VI) wastewater treatment becomes less effective at low Cr(VI) concentration. By a two-step solvent–nonsolvent method, tricaprylmethylammonium chloride (Aliquat 336) can be immobilized onto the surface of porous Amberlite XAD resin with good stability, giving Aliquat 336-modified resins (AMRs). Furthermore, the exposure of the cationic ammonium functional group facilitates the adsorption and stripping efficiency of Cr(VI). The amount of immobilized tricaprylmethylammonium chloride was 2.0 mmol/g of resin. A kinetic study showed that the adsorption of Cr(VI) was under film-diffusion control followed by intraparticle-diffusion control. The Cr(VI) adsorption capacity was as high as 1.37 mmol/g. More than 99% of the adsorbed Cr(VI) could be stripped during regeneration. For stability and reusability, the AMRs maintaine da high level of Cr(VI) adsorption even after four cycles of adsorption/stripping. The experimental results for actual wastewater demonstrated that the AMRs can be used effectively for the treatment of trace Cr(VI)-containing wastewater.

Study of sodium tripolyphosphate-crosslinked chitosan beads entrapped with Pseudomonas putida for phenol degradation

This study was aimed to investigate the efficiency of phenol degradation by Pseudomonas putida entrapped within the beads prepared by chitosan crosslinked with sodium tripolyphosphate. The efficiency of phenol degradation was optimized by changing various processing parameters, such as the amount of cells, beads washing medium as well as acclimatization strategy. These entrapped cells were found to be superior to the free suspended ones in terms of improving the toleration to the environmental loadings (e.g., high pH, low ionic strength and high phenol concentration) and repeating usage for an extended period. Diffusion coefficient calculation has indicated that phenol degradation by the entrapped cells varied from the intraparticle diffusion control to the reaction control as the beads were used repeatedly. In the bead-packed column test, with the addition of hydrogen peroxide to increase the dissolved oxygen level for cell metabolism, phenol in the influent was almost completely degraded.

Kinetics and mechanism of adsorption of methylene blue from aqueous solution by nitric-acid treated water-hyacinth

Kinetics adsorption experiments were conducted to evaluate the adsorption characteristics of a cationic dye (methylene blue, MB) onto nitric-acid treated water-hyacinth (N-WH). Results showed that N-WH can remove MB effectively from aqueous solution. The loading of MB onto N-WH was found to increase significantly with increasing the initial MB concentration, but the residual concentration of MB in solution also increased. A complete removal of MB from solution was only achieved at the lower range of initial MB concentration (less than 286 mg/L). Temperature had a slight effect on the amount adsorbed at equilibrium. The adsorption rate was fast and more than half of the adsorbed-MB was removed in the first 15 min at room temperature, which makes the process practical for industrial application. The adsorption kinetics at room temperature could be expressed by the pseudo second order model, while at higher temperatures (45–80 °C) and low MB concentration (97 mg/L) both Lagergren's model and the pseudo second order model can be used to predict the kinetics of adsorption. The overall rate of dye uptake was found to be controlled by external mass transfer at the beginning of adsorption, then gradually changed to intraparticle diffusion control at a later stage. The initial period where external mass transfer is the rate controlling step was found to increase with increasing initial MB concentration and decrease with increasing temperature. The increase in temperature was also found to increase the rate of adsorption and reduce the time required to reach equilibrium. The initial rate of adsorption, h o, was calculated, it was found to increase with increasing temperature, while the increase in MB concentration decreased h o at the lower concentration range then increased h o again at high concentration. The value of the activation coefficient, E, was found to be 8.207 kJ/mol, which indicates a diffusion controlled process.