Intraparticle Model Research Articles

Potential of waste pumice and surface modified pumice for hexavalent chromium removal: Characterization, equilibrium, thermodynamic and kinetic study

The sorption potential of natural (NP) and surface modified pumice using MgCl2 (MGMP) as an abundant and low cost geo-material for the removal of Cr(VI) ion was investigated. The influence of contact time, solution pH, initial metal concentration, amount of absorbents and solution temperature was studied. Natural and modified adsorbents were characterized by means of XRD, XRF, SEM and FTIR technologies. Maximum sorption was observed at pH 1 and 100mg/L metal concentration. Equilibrium data were accurately fitted onto Langmuir, Freundlich and Temkin isotherms, showing the heterogeneous nature of the adsorbents; maximum sorption capacity according to the Langmuir isotherm were 87.72mg/g and 105.43mg/g for NP and MGMP, respectively, showing a high sorption potential if compared to adsorbents used for Cr(VI) removal. Intra-particle model demonstrated that film diffusion was the rate-limiting step instead of intra-particle diffusion, as confirmed from the analysis of pseudo-second order rate constants, showing an absence of limitation due to pore diffusion. Relevance of pumice was confirmed since high regeneration yields were obtained, 94.3% in acidic conditions (1M HCl) for spent non-modified pumice and 91.3% in alkaline conditions (4M NaOH) for spent modified pumice.

Equilibrium and kinetic study of the adsorption of reactive blue, red, and yellow dyes onto activated carbon and barley husk

Batch adsorption of reactive blue H3R (B), red 3BF (R), and yellow FG (Y) dyes onto activated carbon (AC) and barley husk (BH) was studied. Various experiments were carried out to find the effect of initial dye concentration (5–100 mg/l), adsorbent dosage (0.1–1 g), contact time (15–420 min), pH solution (2.5–8.5), and temperature 30°C. The experimental data showed that the increasing uptake at decreasing pH with respect to (AC) was with B and R dyes while in comparison with (BH) was showed increased uptake at pH increasing for all dyes. Adsorption capacity increased with increasing initial concentration of all dyes with (AC) and (BH). The experimental data were analyzed using Langmuir, Freundlich, and Sips isotherm models. The adsorption of B, R, and Y dyes with (AC) was well fitted with all above models with R2 (0.925–1), while adsorption onto (BH) for B dye showed R2 (0.87–0.96) for above models, while for other dyes showed low R2 values. Pseudo-first-order, pseudo-second-order kinetic, and intraparticle diffusion models were used to analyze the kinetic data. The data were well fitted at dye concentration 10 ppm with the pseudo-first order when R2 values for B, R, and Y dyes were (0.88, 0.97, and 0.982) and (0.98, 0.947, and 943) for (AC) and (BH), respectively, while intraparticle models with R2 values were (0.97, 0.9, and 0.818) and (0.932, 0.8, and 0.947) for each of (AC) and (BH), respectively. Pseudo-second-order model showed well fitting for (AC), when R2 values were (0.77, 0.965, and 0.998) for B, R, and Y dyes, respectively.

Adsorption kinetics of some textile dyes onto granular activated carbon

Adsorption kinetics of Acid Blue 113 (AB), Basic Red 5 (BR) and Reactive Yellow 81 (RY) textile dyes were studied. The investigations were essentially conducted to determine the influence of the initial dye concentration of aqueous solutions on the adsorption kinetics. The experiments, carried out in a batch reactor, allowed the determination of the equilibrium times (≤1h for RY and AB and ≈4h for BR). The experimental data were analyzed according to the surface reaction and intra-particle models. In effect, the adsorption results were perfectly fitted to the pseudo-second order, with very high regression coefficients (r2), predicting a significant intra-particle diffusion stage in the controlling of the adsorption process. Moreover, the fitting to Elovich equation, confirms that the process is ensured by chemisorption on a highly heterogeneous material.

Nanoclay-Supported Zero-Valent Iron as an Efficient Adsorbent Material for Arsenic

The release of arsenic to aqueous environment imposes threats to human health. Montmorillonite supported zero-valent iron (ZVI-MMT) is a material with capability of immobilizing arsenic from aqueous environment. The arsenic adsorption efficiency of ZVI-MMT was obtained. In addition, adsorption kinetics of arsenic contaminated water on the material was determined. Arsenic and iron content was quantified by an inductively coupled plasma mass spectrometer (ICP-MS), interplanar distance of the adsorbent was measured by x-ray diffractometer (XRD), and the morphology of the adsorbent was obtained from a transmission electron microscope (TEM). Isotherm data were analyzed using the Langmuir and Freundlich isotherms. The data fitted well to Langmuir isotherm with derived adsorption capacity of 20.1 mg/g. Kinetics data were analyzed using intra-particle model, Elovich equation, pseudo first-, and pseudo second-order models. Elovich equation and pseudo second-order equation fitted the experimental data with pseudo second-order rate constant of 61.2 x 10-4 g/mg-min.

Adsorption of 60Co on natural and dithizone-modified chitin

Immobilization of dithizone onto natural biopolymer chitin to enhance the ability of chitin to adsorb 60Co was performed. Natural and dithizone-modified chitin was characterized using surface area analyzer and infrared spectroscopy. The sorption was studied in relation to the contact time, pH, initial 60Co concentration, and adsorbent dosage. Batch adsorption models based on the assumption of the pseudo-first-order, pseudosecondorder, and intraparticle models were applied to examine the adsorption kinetics. The results showed that kinetic data followed closely the pseudo-first-order model. The Freundlich, Langmuir, and Redlich-Peterson isotherms were used for the mathematical description of the adsorption equilibrium, and the best fitting was attained using the Freundlich model. Sorption studies were also performed at different temperatures to obtain the thermodynamic parameters of the process. The quantity ΔG0 decreases with an increase in temperature, indicating that the sorption is more favorable at higher temperatures. The positive value of ΔH0 indicates that the sorption is endothermic.

Comparison of Adsorptive Removal of Total Nitrogen (T-N) and Total Phosphorous (T-P) in Aqueous Solution using Granular Activated Charcoal (GAC)

The present study is to explore the possibility of utilizing granular activated charcoal (GAC) for the removal of total phosphorous (T-P) and total nitrogen (T-N) in aqueous solution. Batch adsorption studies were carried out to determine the influences of various factors like initial concentration, contact time and temperature. The adsorption data showed that GAC has a similar adsorption capacity for both T-N and T-P. The adsorption degree of T-N and T-P on GAC was highly concentration dependent. It was found that the adsorption capacity of GAC is quite favorable at a low concentration. At concentrations of 1.0 mg L-1 of T-P and 2.0 mg L-1 of T-N, approximately 97 % of adsorption was achieved by GAC. The equilibrium data were fitted well to the Langmuir isotherm model. The pseudo-second-order kinetic model appeared to be the better-fitting model because it has higher R2 compared with the pseudo-first-order and intra-particle kinetic model. The theoretical adsorption equilibrium qe,cal from pseudo-second-order kinetic model were relatively similar to the experimental adsorption equilibrium qe,exp. To evaluate the effect of thermodynamic parameters at different temperatures, the change in free energy ΔG, the enthalpy ΔH and the entropy ΔS were estimated. Except for adsorption of T-P at 278 K, the ΔG values obtained were all negative at the investigated temperatures. It indicates that the present adsorption system occurs spontaneously. The adsorption process of T-N by GAC was exothermic in nature, whereas T-P showed endothermic behavior. In addition, the positive values of ΔS imply that there was the increase in the randomness of adsorption of T-N and T-P at GAC-solution interface.

Synthesis and characterization of zinc sulfide nanoparticles loaded on activated carbon for the removal of methylene blue

In the first part of this research, zinc sulfide nanoparticle loaded activated carbon was synthesized by a simple and low cost procedure. Zinc sulfide nanoparticles were prepared, characterized and loaded on commercially available activated carbon. The zinc sulfide nanoparticle was characterized by UV–vis, SEM and XRD analysis. The objective of this study was to assess the suitability and efficiency of zinc sulfide nanoparticle loaded activated carbon (ZnS‐NP‐AC) for the removal of Methylene blue (MB) from aqueous solution. Adsorption studies were conducted in a batch mode and the influences of various operating parameters including pH, contact time, initial dye concentration, ZnS‐NP‐AC amount on the extent of MB adsorption were investigated in details. The adsorption equilibrium data were fitted well to the Langmuir model. The maximum MB adsorption capacity was found as 100 mg g−1 of adsorbent. To investigate the kinetic of adsorption, the time dependency of removal percentage of MB on ZnS‐NP‐AC was analyzed by various models such as, pseudo‐first‐order, pseudo‐second‐order, Elovich, and intraparticle diffusion kinetic. It was found that the adsorption follows pseudo‐second‐order kinetic with involvement of intraparticle model. © 2012 American Institute of Chemical Engineers Environ Prog, 32: 535–542, 2013

Multi-scale modeling of fixed-bed thermo-chemical processes of biomass with the representative particle model: Application to pyrolysis

Modeling fixed-bed thermo-chemical processes of biomass should be considered as a multi-scale problem. The molecular, particle and reactor level should be considered together in the models. A framework for a multi-scale model for dynamic fixed-bed/ moving-bed thermo-chemical conversion processes and the respective numerical solution method is introduced: the Representative Particle Model (RPM). In the RPM approach an intra-particle model is solved for each finite volume element of the reactor. All particles within a finite volume element are assumed to obey the same characteristics as the one for which the intra-particle model is solved, which is why it can be considered as representative. The particle level is then considered, as opposed to quasi-continuous models, that are just appropriate when intra-particle gradients of temperatures and concentrations are negligible. And compared to the Discrete Particle Model (DPM), where a model for each particle in the bed (up to 105–106 particles in technical scale fixed-bed gasification) is solved simultaneously with the fluid-phase balances in the reactor domain, the computational effort is significantly smaller. The RPM is applied to fixed-bed pyrolysis and compared to experimental results available in the literature. The RPM is able to predict the experimental results, describing intra-particle gradients, in a much more feasible time compared to the DPM. The importance of intra-particle gradients in fixed-bed pyrolysis is also highlighted, showing differences in the conversion time of more than 30% when the particle size is doubled, from a particle diameter of 1.24–2.48cm. Therefore the RPM is a feasible way to include the particle level in a multi-scale description of fixed-bed pyrolysis.

Adsorptive performance of penta-bismuth hepta-oxide nitrate, Bi5O7NO3, for removal of methyl orange dye

The adsorption of methyl orange dye from aqueous solution onto penta-bismuth hepta-oxide nitrate, Bi(5)O(7)NO(3), synthesized by precipitation method, was studied in a batch adsorption system. The effects of operation parameters such as adsorbent dose, initial dye concentration, pH and temperature were investigated. The adsorption equilibrium and mechanism of adsorption was evaluated by Langmuir and Freundlich isotherm and different kinetic models, respectively. The results indicate that adsorption is highly dependent on all operation parameters. At optimum conditions, the adsorption capacity was found to be 18.9 mg/g. The adsorption data fits well with the Langmuir isotherm model indicating monolayer coverage of adsorbate molecules on the surface of Bi(5)O(7)NO(3). The kinetic studies show that the adsorption process is a second-order kinetic reaction. Although intra-particle diffusion limits the rate of adsorption, the multi-linearity plot of intra-particle model shows the importance of both film and intra-particle diffusion as the rate-limiting steps of the dye removal. Thermodynamic parameters show that the adsorption process is endothermic, spontaneous and favourable at high temperature.

Electrochemically assisted coagulation for the removal of boron from water using zinc anode

The present work provides a critical study on the adsorption of boron by electrochemically generated zinc hydroxide. The various operating parameters on the removal efficiency of boron were investigated, such as initial pH, current density, electrode configuration, inter-electrode distance, co-existing ions and temperature. The results showed that the optimum removal efficiency of 93.2% was achieved at a current density of 0.2A dm−2, at pH of 7.0 with the energy consumption of 1.007kWh m−3. First- and second-order rate equations, Elovich and intraparticle models were applied to study adsorption kinetics. Adsorption isotherms of boron on Zn(OH)2 were determined and correlated with isotherm equations such as Langmuir, Freundlich and D-R models. Thermodynamic parameters, such as standard Gibb's free energy (∆Go), standard enthalpy (∆Ho), and standard entropy (∆So), were also evaluated by Van't Hoff equation. The adsorption process follows second-order kinetics. The adsorption of boron preferably fits with Langmuir adsorption isotherm suggesting monolayer coverage of adsorbed molecules for all current densities and concentration. The adsorption of boron onto Zn(OH)2 was found to be spontaneous and endothermic thermodynamically.

EQUILIBRIUM AND KINETICS STUDY OF NITRATE REMOVAL FROM WATER BY PUROLITE A520-E RESIN

Equilibrium and kinetics of nitrate removal from aqueous solutions of pH = 6.8 were investigated using the strong base anion exchange resin (Purolite A-520E) in the batch method. The experimental equilibrium data were analyzed by means of the Langmuir, Freundlich and Dubinin-Radushkevich sorption isotherm models. The Langmuir model describes sorption isotherm of nitrates with high correlation coefficients and better than Dubinin-Radushkevich and Freundlich models. The effect of temperature on the nitrates ion exchange process onto resin was also investigated, and various thermodynamic parameters, such as .G, .H and .S have been calculated. The thermodynamic parameters indicate the spontaneous and endothermic nature of the ion exchange process. The experimental curves q t have bee confronted with three kinetic models, and the corresponding kinetic constants have been identified. The best fit of experimental sorption data was obtained by means of the pseudo-second order and intra-particle models.

Evolution of adsorption kinetics and isotherms of gallic acid on an activated carbon oxidized by ozone: Comparison to the raw material

The evolutions of both adsorption kinetics and isotherms of gallic acid on a commercial activated carbon (AC), initially submitted to ozone in water for 4 h were studied. The microporous properties were investigated by N 2 physisorption at 77 K and the surface oxygen groups created on the surface of the carbon by oxidation were characterized by Fourier Transform Infrared Spectroscopy (FTIR). The studies of the adsorption kinetics and the isotherms of gallic acid on the ozonated and non ozonated AC were carried out at several temperatures (between 5 °C and 50 °C). Four models (pseudo-first order, pseudo-second order, Elovich and the intraparticle model) were used in order to determine kinetic parameters of adsorption. The best results were obtained with the pseudo-second order model. Moreover, a decrease in both the rate constant and the activation energy of adsorption with the ozone exposure time of AC was evidenced. However, no modification appeared in the adsorption mechanism rate limited by the intraparticle diffusion both for ozonated and for non ozonated AC. Two models (Langmuir and Dubinin–Radushkevich) were tested from experimental isotherms and compared. The Langmuir model provided the best correlation under all the temperatures. Results showed that ozonation of AC for 4 and 8 h led to an increase in surface oxygen groups, which can be considered as acid groups, without microporous modification. The adsorption capacity of the oxidized material was increased by a value up to 28% under all the experiments. The Langmuir and the DR models showed that the surface occupied increases and the process of micropores filling proves to be favoured when the AC is oxidized by ozone.

Electrochemical removal of boron from water: Adsorption and thermodynamic studies

AbstractThe present work provides an electrochemical removal of boron from water and its kinetics, thermodynamics, isotherm using mild steel and stainless steel as anode and cathode respectively. The various operating parameters on the removal efficiency of boron were investigated, such as initial boron ion concentration, initial pH, current density and temperature. The results showed that the optimum removal efficiency of 93.2% was achieved at a current density of 0.2 A dm−2 at pH of 7.0. First‐, second‐order rate equations, Elovich and Intraparticle models were applied to study adsorption kinetics. Adsorption isotherms of boron on Fe(OH)3 were determined and correlated with isotherm equations such as Langmuir, Freundlich and D‐R models. Thermodynamic parameters, such as standard Gibb's free energy (ΔG°), standard enthalpy (ΔH°) and standard entropy (ΔS°), were also evaluated by Van't Hoff equation. The adsorption process follows second‐order kinetics. The adsorption of boron preferably fits with Langmuir adsorption isotherm suggesting monolayer coverage of adsorbed molecules. The adsorption of boron onto Fe(OH)3 was found to be spontaneous and endothermic. © 2011 Canadian Society for Chemical Engineering

Adsorption characteristics of the hazardous dye Brilliant Green on Saklıkent mud

In this work, the adsorption capacity of Saklıkent mud as low-cost adsorbent, for the removal of hazardous dye, Brilliant Green, from aqueous solution was studied. The adsorptive properties of Saklıkent mud was investigated in terms of temperature, initial dye concentration and contact time. The results obtained from the experiments were compared for kinetic and thermodynamic parameters. The kinetic data for the adsorption of Brilliant Green on Saklıkent mud supports the pseudo-first-order kinetic model and the intra-particle model at 25 °C. However, the highest values of r 2 (>0.99) were obtained from the second order adsorption model for the adsorption of Brilliant Green at higher temperatures. From the kinetic data it was found that the calculated values of the maximum adsorption capacity ( q e,calc) are very close to the maximum adsorption capacity ( q e,exp) obtained experimentally. The experimental adsorption capacity of the Saklıkent mud changed from 9.2 mg g −1 to 9.7 mg g −1 by increasing temperature from 25 °C to 55 °C. The equilibrium adsorption data were discussed using the Langmuir isotherm model. To reveal the adsorptive capacity of Saklıkent mud the BET surface area and the pore volume were found and its chemical composition was analyzed by X-ray fluorescence spectrometry.

Adsorption of polycyclic aromatic hydrocarbons from aqueous solutions by modified periodic mesoporous organosilica

A novel procedure was developed for the synthesis of a periodic mesoporous organosilica (PMO), which was used to remove polycyclic aromatic hydrocarbons (PAHs) from aqueous solutions. Adsorption equilibrium isotherms and adsorption kinetics experiments were carried out in solutions of PAHs (2–60mgL−1), using the PMO as adsorbent. Adsorption models were used to predict the mechanisms involved. The adsorption kinetics data best fitted the pseudo-first-order kinetic model for naphthalene, and to the pseudo-second-order model for fluorene, fluoranthene, pyrene, and acenaphtene. The intraparticle model was also tested and pointed to the occurrence of such processes in all cases. The isotherm models which best represented the data obtained were the Freundlich model for fluoranthene, pyrene, and fluorene, the Temkin model for naphthalene, and the Redlich–Peterson model for acenaphtene. PAHs showed similar behavior regarding kinetics after 24h of contact between adsorbent and PAHs. FTIR, XRD, BET, and SEM techniques were used for the characterization of the adsorbent material.

Equilibrium and kinetics studies of 2,4,5-trichlorophenol adsorption onto organophilic-bentonite

The adsorption of 2,4,5-trichlorophenol (2,4,5-TCP) from aqueous solutions onto the crude bentonite modified with hexadecyltrimethylammonium-bromide (HDTMAB) have been studied. The parameters that affect the 2,4,5-TCP adsorption onto modified bentonite (BHDTMA), such as contact time, solution pH, and temperature have been investigated and optimized conditions determined. Three kinetic models have been evaluated in order to attempt to fit the experimental data, namely the pseudo-first order, the pseudo-second-order and the intraparticle model. The results show that the pseudo-second-order kinetic model generates the best agreement with the experimental data for the adsorption system. Adsorption equilibrium data of 2,4,5-TCP on BHDTMA were analyzed by Langmuir, Freundlich and Langmuir-Freundlich isotherm models. The results indicate that the Langmuir-Freundlich model provides the best correlation of experimental data. The maximum capacity of BHDTMA at 293 K was founded around 72 mg/g. The thermodynamic parameters such as a free energy, enthalpy and entropy of adsorption was calculated. The negative values of ΔG° and ΔH° indicate the spontaneous and exothermic nature of the process.

Adsorption of copper on amine-functionalized SBA-15 prepared by co-condensation: Kinetics properties

Amino-functionalized SBA-15 prepared by co-condensation was tested for the removal of copper ions from aqueous solutions under different temperatures, pH, initial concentrations and agitation speeds. The obtained results indicated that the amino-functionalized SBA-15 was very efficient and equilibrium was achieved in less than 30 min at room temperature. The kinetic data was analyzed using four models, namely the first-order, the pseudo first- and second-order and the intraparticle diffusion model. Within the conditions used, the pseudo second-order kinetic model provided the best fit to the experimental data. Applying the intraparticle model showed that the adsorption involved three different stages.

Adsorption of ammonium from an aqueous solution by fly ash and sepiolite: Isotherm, kinetic and thermodynamic analysis

This study aimed to remove ammonium from paper mill industry (4500 m 3 h −1) wastewater, which is discharged to sea from a plant located in the western Turkey. As adsorbent, fly ash, raw sepiolite and thermal activated sepiolite (TAS) were used. The effect of factors such as; particle size, temperature and pH on adsorption process was investigated. From kinetic studies, equilibrium time was found as 1 h for both adsorbents. From experiments carried out at different pHs, it was observed that pH plays an important role in the ammonium adsorption process, both ionizating the compounds and modifying sorbent surfaces. It was also observed that fly ash is more effective than raw sepiolite and TAS to remove ammonium and in addition, adsorption increases with decreasing particle size. The kinetic data support pseudo-second-order model ( r 2 ⩾ 0.99) but show very poor fit for pseudo-first order model ( r 2 < 0.90). Intra-particle model also shows that there are two separate stages in sorption process, namely, external diffusion and the diffusion of inter-particle. Adsorption isotherms for fly ash and TAS were fitted to Freundlich models more effectively than Langmuire models ( r 2 ⩾ 0.999). Thermodynamics parameters such as; free energy (Δ G 0), enthalpy (Δ H 0) and entropy (Δ S 0) were also calculated. Based on the results, it can be concluded that the sepiolite and fly ash have potential of being used as a sorbent for removal of ammonium in wastewater treatments from Bleached Kraft Mills Effluent (BKME).

Multiparametric investigation of competitive and noncompetitive sorption characteristics of SMP fractions (carbohydrate and protein) on activated carbon

Sorption characteristics of soluble microbial products (SMPs) as carbohydrate and protein on activated carbon were investigated. Batch experiments were conducted to evaluate the sorption kinetics and the equilibrium conditions. The parameters studied included initial SMP concentration (50–200 mg/L), activated carbon dosage (0.25–50 g/L), contact time (0.02–4 h), particle size of activated carbon used (5–75 μm, 75–850 μm, and 850–1000 μm), and presence of one or both SMP fractions. The equilibrium sorption of carbohydrate and protein were significantly affected by the presence of the second SMP fraction in the solutions. Adsorption isotherms were expressed by the Langmuir and Freundlich models. The adsorption rates under noncompetitive and competitive conditions were analyzed with kinetics-based Lagergren pseudo-first order and pseudo-second order models; and diffusion-based external diffusion and Weber–Morris intraparticle models. Both SMP fractions were removed effectively, however, sorption of protein was significantly better than that of carbohydrate in all cases. The relatively significant effect of particle size on sorption of protein indicates that protein is most likely adsorbed as a single layer on the carbon surface. For the carbohydrate, the increase in particle size did not decrease the sorption significantly indicating that carbohydrate may be adsorbed in multiple layers or may diffuse into the porous matrix more effectively.

Comparison study of ammonia and COD adsorption on zeolite, activated carbon and composite materials in landfill leachate treatment

Chemical oxygen demand (COD) and ammoniacal nitrogen have always been the crucially problematic parameters in landfill leachate treatment. This study was conducted to investigate the adsorption properties of ammoniacal nitrogen and COD in semi-aerobic leachate from the Pulau Burung landfill site on zeolite, activated carbon and a new composite media in terms of adsorption isotherm and kinetic. The results show that all adsorbents fitted well with both Langmuir and Freundlich isotherms (R 2 > 0.9) for ammonia adsorption. A comparison study indicated that the adsorption capacity of composite adsorbent towards ammoniacal nitrogen was higher than zeolite and activated carbon and comparable to activated carbon for COD. Findings from a kinetic study indicated that the adsorption of ammonia on new composite adsorbent and zeolite follow almost all kinetic models such as pseudo-first-order, pseudo-second-order, Elovich and intra-particle diffusion model, although pseudo-second-order was the most dominant. COD adsorption fitted well with the pseudo-second-order kinetic model, while activated carbon obeys the pseudo-first-order and intra-particle models.