External Mass Transfer Diffusion Research Articles

Mechanistic Understanding of Sieving Lithium Ions Using a Biobased Sorbent Technology for Sustainable Lithium Reclamation and Cleansing Brines.

Low-cost environmentally benign materials that can be produced in a large scale to extract lithium from brine resources could drive the lithium market toward a clean technology with high lithium recovery and production. Herein, we have investigated the utilization of a novel, environmentally benign, and low-cost biobased sorbent for the extraction of lithium from lithium-rich solutions. This biobased molecular sieving sorbent, iron(III)-tannate (Fe(III)-TA), belongs to a novel class of coordination polymer frameworks derived from a natural polyphenol-tannic acid (TA)-coordinated with iron(III) metal cations. Its lithium adsorption and kinetic isotherm studies conducted using lithium-rich aqueous solutions confirm the sorbent's dual function for lithium sieving via physisorption, chemisorption, and mass transfer diffusion processes. The adsorption equilibrium and kinetic isotherm models combined with the external and internal mass transfer diffusion models reveal a mechanistic pathway for lithium-ion adsorption. Aiding by forming a fluid film for external mass transfer diffusion of lithium ions, analytes adsorb onto the sorbent surface via physisorption and chemisorption followed by the internal mass transfer diffusion, occupying lithium ions in the sorbent's pores. The lithium adsorption efficiency studies conducted for brines with different concentrations of interference alkali and alkaline cations evidence that the sorbent's affinity for lithium ions strongly depends on the analyte concentration. The results evidence that the sorbent has the ability to lower the brine's salinity and significantly reduces the ratios of Mg/Li and Ca/Li by 4-fold and 10-fold, respectively, yielding lithium-rich solutions. Thus, implementing this innovative biobased sorbent technology as an add-in step into traditional lithium extraction and refining processes, one can design a cost-effective pathway to yield lithium-rich leachate by reducing the Mg/Li and Ca/Li ratio. Nonetheless, the present work demonstrates that Fe(III)-tannate is an effective multifunctional sorbent for sieving lithium from lithium-rich aqueous solutions as well as for desalinating brine resources to recover usable water. Thus, this biobased sorbent offers the possibility of effective application of lithium reclamation and remediation of brine, mitigating the environmental impact of brine discharge and large volume of freshwater usage for lithium extraction and refining.

Efficiency of a novel nitrogen-doped Fe3O4 impregnated biochar (N/Fe3O4@BC) for arsenic (III and V) removal from aqueous solution: Insight into mechanistic understanding and reusability potential

Worldwide, arsenic contamination has become a matter of extreme importance owing to its potential toxic, carcinogenic and mutagenic impact on human health and the environment. The magnetite-loaded biochar has received increasing attention for the removal of arsenic (As) in contaminated water and soil. The present study reports a facile synthesis, characterization and adsorption characteristics of a novel magnetite impregnated nitrogen-doped hybrid biochar (N/Fe3O4@BC) for efficient arsenate, As(V) and arsenite, As(III) removal from aqueous environment. The as-synthesized material (N/Fe3O4@BC) characterization via XRD, BET, FTIR, SEM/EDS clearly revealed magnetite (Fe3O4) impregnation onto biochar matrix. Furthermore, the adsorbent (N/Fe3O4@BC) selectivity results showed that such a combination plays an important role in targeted molecule removal from aqueous environments and compensates for the reduced surface area. The maximum monolayer adsorption (Qmax) of developed adsorbent (N/Fe3O4@BC) (18.15 mg/g and 9.87 mg/g) was significantly higher than that of pristine biochar (BC) (9.89 & 8.12 mg/g) and magnetite nano-particles (MNPs) [7.38 & 8.56 mg/g] for both As(III) and As(V), respectively. Isotherm and kinetic data were well fitted by Langmuir (R2 = 0.993) and Pseudo first order model (R2 = 0.992) thereby indicating physico-chemical sorption as a rate-limiting step. The co-anions (PO43-) effect was more significant for both As(III) and As (V) removal owing to similar outer electronic structure. Mechanistic insights (pH and FTIR spectra) further demonstrated the remarkable contribution of surface groups (OH–, –NH2 and –COOH), electrostatic attraction (via H- bonds), surface complexation and ion exchange followed by external mass transfer diffusion and As(III) oxidation into As(V) by (N/Fe3O4@BC) reactive oxygen species. Moreover, successful desorption was achieved at varying rates up to 7th regeneration cycle thereby showing (N/Fe3O4@BC) potential practical application. Thus, this work provides a novel insight for the fabrication of novel magnetic biochar for As removal from contaminated water in natural, engineering and environmental settings.

Response Surface Methodology Optimized Eriochrome Black T Dye Removal Using Alumina Beads: Isotherms and Kinetics Studies

Numerous approaches have been investigated for the development of cheaper and more effective technologies to improve the quality of industrial effluent. However, adsorption has been one of the most simplest and economical remediation technology in the treatment of wastewaters. In this study, commercial alumina beads (Al-beads) were utilized for the adsorption of Eriochrome Black T dye. The adsorption process was optimized using the RSM model by Box-Behnken Design (BBD). From the optimization result, the most influential variables are; the initial dye concentration, the interaction between adsorbent dosage with itself, and that of adsorbent dosage with initial dye concentration. The R2 value of 0.7743 implies that 77.43% on the percent dye removal could be due to the variation in the independent variable. Whereas the Adeq. precision of 6.493, and lack of fit (0.92) implies the model can be used to navigate the design space. Up to 98.28%, dye removal was attained using the Al-beads under the conditions; pH of 12.39, adsorbent dosage (1.25 g), and initial dye concentration (175 ppm). The sorption data indicated that the adsorption process was fitted to Freundlich and Temkin isotherm models, while for the kinetics study, the pseudo-second-order model was the best fit. Furthermore, the adsorption mechanism was found to be governed majorly by intra-particle diffusion with some contribution from external mass transfer diffusion.

Linearized form effect on estimation adsorption parameters of three industrial dyes by lignocellulosic sorbent.

Textile industries discharge large amounts of untreated colored wastewater into ecosystems which have adverse effects on the human, living and aquatic environment. The aims of this study were: upgrading and testing the brewery waste adsorption affinity towards BEMACID red (B-R), BEMACID yellow (B-Y) and BEZAKTIV black (B-B), verified the effect of linear form modeling on adsorption parameters values and to find the limiting kinetic step in adsorption process. The adsorption efficiency of brewery waste towards three textile dyes: B-Y, B-R and B-B is tested. The evolution between the adsorption capacity and the operating conditions such as: pH solution, adsorbent mass, contact time and initial dye concentration is determined by kinetics measurements. Effect of a form of pseudo-first order, six forms of pseudo-second order, a form of intra-particle diffusion and a form of external mass transfer diffusion are tested to the prediction of kinetic parameters and to find the limiting kinetic step. In order to modeling the equilibrium data, a form of Freundlich and five forms of Langmuir isotherms are tested. The residual concentration of dye in solution was measured by spectrophotometer. Scanning Electron Microscope (SEM) was using to investigate the structure of raw adsorbent. The results of kinetics measurements show that the perfect adsorption operating conditions are: acidic medium for all dyes (pH = 2 and pH = 3), low mass adsorbent (m = 40mg), equilibrium time t = 40min and for initial concentration of 250mg/L. Also the results prove that the adsorption mechanism is controlled by both steps of diffusions (interne and extern diffusion) and fitted well by the first and the second linearized form of pseudo-second order model with correlation coefficient R2 = 0.99. The results of isotherms modeling show that the second and the third linearized forms of Langmuir giving the best removed amount for B-Y equal 200 and 219.4mg/g respectively compared to others linearized forms. In summary, the effect of linear forms used either in the medellization of isotherms or kinetic data is significant in the prediction of adsorption parameters, also brewery waste has a significant B-Y dye adsorption affinity compared to others dyes, the descending order of maximum adsorption capacity finding is: qe = 209mg/g for B-Y, qe = 152mg/g for B-R and finally qe = 108mg/g for B-B.

Sorptive removal of phenolic endocrine disruptors by functionalized biochar: Competitive interaction mechanism, removal efficacy and application in wastewater

Sorptive removal of six phenolic endocrine disrupting chemicals (EDCs) estrone (E1), 17β-estradiol (E2), estriol (E3), 17α-ethynylestradiol (EE2), bisphenol A (BPA) and 4-tert-butylphenol (4tBP) by functionalized biochar (fBC) through competitive interactions was investigated. EDC sorption was pH dependent with the maximum sorption at pH 3.0–3.5 due to hydrogen bonds and π-π interactions as the principal sorptive mechanism. Sorption isotherm of the EDCs was fitted to the Langmuir model. Sorption capacities and distribution coefficient values followed the order E1 > E2 ≥ EE2 > BPA > 4tBP > E3. The findings suggested that EDC sorption occurred mainly through pseudo-second order and external mass transfer diffusion processes, by forming H-bonds along with π-π electron-donor–acceptor (EDA) interactions at different pH. The complete removal of ∼500 μg L−1 of each EDC from different water decreased in the order: deionised water > membrane bioreactor (MBR) sewage effluent > synthetic wastewater. The presence of sodium lauryl sulphonate and acacia gum in synthetic wastewater significantly suppressed sorption affinity of EDCs by 38–50%, hence requiring more fBC to maintain removal efficacy.

Preparation and characterization of polyethylenimine-functionalized pyroxene nanoparticles and its application in wastewater treatment

In this study, polyethylenimine-functionalized pyroxene nanoparticles were successfully prepared in-house for the removal of commercial red dye (CRD) from an industrial wastewater. The functionalization was accomplished by anchoring polyethylenimine (PEI) onto the surface of pyroxene nanoparticles without surface modifications or preliminary coating. Characterization was followed out by textural properties, X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), infrared (IR) spectroscopy, and thermogravimetric analysis (TGA). The prepared nanoparticles were successfully functionalized by the PEI and portrayed granulated-like morphologies with average crystaline domain sizes around 10nm and BET surface area (∼18m2/g) that increased reasonably to ∼119m2/g by drying using lyophilizing method instead of conventional drying of the synthesized materials. The prepared PEI-PNPs showed an excellent adsorption capacity (∼340mg/g) and fast adsorption kinetics (<15min) for the CRD from a textile wastewater in batch mode of adsorption compared with that of magnetite nanoparticles and a commercial activated carbon that had lower adsorption capacity of the dye (<50mg/g). Adsorption was not influenced by the solution pH owing to the wide range of PEI buffering capacity. The adsorption kinetics and isotherms could be well delineated using the external mass transfer diffusion and the Sips models, respectively.

Cometabolic degradation of ethyl mercaptan by phenol-utilizing Ralstonia eutropha in suspended growth and gas-recycling trickle-bed reactor

The degradability of ethyl mercaptan (EM), by phenol-utilizing cells of Ralstonia eutropha, in both suspended and immobilized culture systems, was investigated in the present study. Free-cells experiments conducted at EM concentrations ranging from 1.25 to 14.42 mg/l, showed almost complete removal of EM at concentrations below 10.08 mg/l, which is much higher than the maximum biodegradable EM concentration obtained in experiments that did not utilize phenol as the primary substrate, i.e. 2.5 mg/l. The first-order kinetic rate constant (kSKS) for EM biodegradation by the phenol-utilizing cells (1.7 l/g biomass/h) was about 10 times higher than by cells without phenol utilization. Immobilized-cells experiments performed in a gas recycling trickle-bed reactor packed with kissiris particles at EM concentrations ranging from 1.6 to 36.9 mg/l, showed complete removal at all tested concentrations in a much shorter time, compared with free cells. The first-order kinetic rate constant (rmaxKs) for EM utilization was 0.04 l/h for the immobilized system compared to 0.06 for the suspended-growth culture, due to external mass transfer diffusion. Diffusion limitation was decreased by increasing the recycling-liquid flow rate from 25 to 65 ml/min. The removed EM was almost completely mineralized according to TOC and sulfate measurements. Shut down and starvation experiments revealed that the reactor could effectively handle the starving conditions and was reliable for full-scale application.

An efficient p-tetranitrocalix[4]arene based adsorbent for the removal of carbofuran from aqueous media

Present study describes the adsorption of carbofuran (CF) from aqueous solutions using p-tetranitrocalix[4]arene based modified silica through batch and column methods. Various parameters were optimized including initial pesticide concentrations (5 mg L−1), pH (2–10), contact time (60 min) and adsorbent dosage (30 mg). Modified silica was characterized by FT-IR and scanning electron microscope. The adsorption was further explained by Langmuir, Freundlich and Dubinin–Radushkevich (D–R) models. Moreover, adsorption kinetics and adsorption thermodynamics were also investigated. Adsorption in dynamic mode was evaluated by breakthrough volumes and the Thomas model, applying batch conditions using 30 mg of modified silica at pH 5. It has been noticed that CF removal efficiency of modified silica was 98 % as compared to bare silica (48 %). Adsorption of CF on modified silica was found to be multilayer and physical in nature. Consequently, adsorption obeys pseudo-second-order kinetic equation following external mass transfer diffusion process as the rate-limiting step. Thermodynamic parameter (ΔG, ΔS, ΔH) values suggest that the adsorption of CF is spontaneous and exothermic in nature. Thomas model rate constant kTH (cm3 mg−1 min−1) and maximum solid phase concentration (qo mg g−1) was found to be 0.52 and 12.3, respectively, in dynamic mode.

Mass‐transfer processes in the adsorption of cationic dye by sawdust

AbstractAdsorption kinetic and equilibrium studies of cationic dye namely, Astrazon Yellow (AY) from aqueous solution at various initial dye concentration (15–50 mg/L), pH (2–9), particle size &lt;1600 μm on Aleppo pine‐tree sawdust were investigated in a batch mode operation.Batch adsorption studies revealed that the potential of Aleppo pine‐tree sawdust in dye removal was dependant on initial pH and initial dye concentration.To select the main rate‐limiting step in the overall uptake mechanism, a single external mass transfer diffusion model, Urano and Tachikawa model, and intraparticle diffusion model were used. The external mass transfer rate constant β was found to be 8.5 × 10−5 m−1 at initial concentration 50mg/L of AY and 1.14 × 10−4 m−1 at initial concentration 15 mg/L of AY. The multilinearity obtained in the intraparticle diffusion plot showed that both film diffusion and pore diffusion are important in controlling the overall adsorption rate. The effective diffusion coefficients Di were found to be 3.88 × 10−11 cm2/s and 4.2 × 10−11 cm2/s for initial concentration of AY of 15 mg/L and 50 mg/L, respectively, indicating that intraparticle diffusion may not be the sole dominating factor controlling the mechanism of the process into Aleppo pine‐tree sawdust. AY sorption onto sawdust was mainly located on the surface. The equilibrium isotherms were analyzed using the Langmuir, Freundlich, Temkin, and Elovich models. It was seen that the sorption data fitted to Langmuir, Freundlich, Temkin, and the Elovich isotherms, but they were very well described by the Langmuir model. © 2011 American Institute of Chemical Engineers Environ Prog, 2011

A porous vessel bioreactor for gel entrapped biocatalysts: Kinetic resolution of trans-methyl (4-methoxyphenyl)glycidate by Lecitase® Ultra in gelatin organogel (Gelozyme)

Abstract Preparation of trans-(2R,3S) methyl (4-methoxyphenyl)glycidate with enantiomeric excess (e.e.) of >99% has been carried out by enantioselective hydrolysis of the racemic glycidate ester by Lecitase® Ultra immobilized in macroporous gelatin organo-gel (gelozyme) in 47% yield. Effects of water content and particle size of the gel, different solvents, and flow rate of reaction medium on observed reaction velocity lead to optimum conditions. The reaction performed in a porous vessel bioreactor using toluene as preferred reaction medium, and gelatin-immobilized enzyme with average particle size of 1–1.2 mm, water content of 16.5% (w/w), and flow rate of 20 mL min−1, followed a typical Michaelis–Menten kinetics with apparent Vmax,app of 38 mM min−1 g−1 and apparent Km of 0.53 M. Theoretical considerations suggest that the bioreactor functions as a plug-flow reactor with complete recycle without serious pore diffusion and external mass transfer diffusion limitations. The immobilized enzyme can be used continuously for several recycles without significant loss of activity for at least two weeks.

Kinetics and modified clay thermodynamic from the Brazilian amazon region for lead removal

Modified Brazilian smectite-bearing clay samples displayed ability for lead adsorption. The structure modification of smectite were obtained through pillaring process and functionalization with [3-(2-aminoethylamino)propyl]trimethoxysilane. The chemical modification process increases the basal spacing of the natural smectite from 1.354 to 2.364 nm. The Langmuir model was fitted to experimental data in linear regression. Kinetic studies showed an equilibrium adsorption time of 700 min on the modified clay. The experimental data were correlated with two distinct kinetic models were used: (i) external mass transfer diffusion and (ii) intraparticular mass transfer diffusion. However, the intraparticle mass transfer diffusion model gave a better fit to these experimental data. The energetic effects caused by lead interactions were determined through calorimetric titration at the solid–liquid interface and gave a net thermal effect that enabled the calculation of the exothermic values and the equilibrium constant.

Synthesis and characterization of tannin-immobilized hydrotalcite as a potential adsorbent of heavy metal ions in effluent treatments

The modification of calcined hydrotalcite (HTC) by immobilizing tannin was investigated in the present work, in order to apply the modified media (TA-HTC) as an adsorbent in the removal of heavy metal ions (Cu(II), Zn(II) and Cd(II)) from industrial effluents. The adsorbent was characterized with FTIR, XRD, SEM, TG/DTG, surface area analyzer and potentiometric titrations. Batch experiments were performed as a function of process parameters such as agitation time, initial metal concentration, pH, ionic strength and adsorbent dose. The maximum adsorption was found at pH 6.0. The mechanism for the removal of metal ions by TA-HTC was based on ion exchange process. Experimental results showed that the adsorption of these metal ions was selective to be in the order of Cu(II) > Zn(II) > Cd(II). The process was very fast initially and maximum adsorption was observed with 3 h of agitation. The adsorption kinetics were investigated and kinetic parameters such as rate constant, external mass transfer diffusion and intraparticular mass transfer diffusion coefficients were evaluated. The adsorption process obeyed the intraparticular diffusion model. An increase of ionic strength of the medium caused a decrease in metal ion adsorption. Equilibrium isotherm data were analyzed by the Langmuir, Freundlich and Dubinin–Radushkevich equations using non-linear regression analysis. The best interpretation for the equilibrium data was given by the Langmuir isotherm and the maximum adsorption capacities were 81.47 mg g − 1 for Cu (II), 78.91 mg g − 1 for Zn(II) and 74.97 mg g − 1 for Cd(II). The adsorption efficiency towards heavy metal ion removal was tested using different industry wastewaters. The adsorption efficiency, regenerative and reuse capacities of this adsorbent were also assessed for four consecutive adsorption/ desorption cycles and were found to retain the adsorption capacity.

Adsorption performance of Al-pillared bentonite clay for the removal of cobalt(II) from aqueous phase

In this research, the natural bentonite clay collected from Ashapura Clay Mines, Gujarat State, India, was utilized as a precursor to produce aluminium-pillared bentonite clay (Al-PILC) for the removal of cobalt(II) [Co(II)] ions from aqueous solutions. The original bentonite clay and Al-PILC were characterized with the help of chemical analyses, methylene blue (MB) adsorption isotherm, powder X-ray diffraction (XRD), scanning electron microscopy (SEM) and infrared spectroscopy (IR), while the thermal stability of the samples were studied using thermogravimetry (TG). Surface charge density of the samples as a function of pH was investigated using potentiometric titrations. Adsorption experiments were conducted under various conditions, i.e., pH, contact time, initial concentration, ionic strength, adsorbent dose and temperature. The most effective pH range for the removal of Co(II) ions was found to be 6.0–8.0. The maximum adsorption of 99.8% and 87.0% took place at pH 6.0 from an initial concentration of 10.0 and 25.0 mg l −1, respectively. Kinetic studies showed that an equilibrium time of 24 h was needed for the adsorption of Co(II) ions on Al-PILC and the experimental data were correlated by either the external mass transfer diffusion model for the first stage of adsorption and the intraparticle mass transfer diffusion model for the second stage of adsorption. The intraparticle mass transfer diffusion model gave a better fit to the experimental data. The Arrhenius and Eyring equations were applied to the data to determine the kinetic and thermodynamic parameters for explaining the theoretical behaviour of the adsorption process. The equilibrium isotherm data were analyzed using the Langmuir, Freundlich and Scatchard isotherm equations and the adsorption process was reflected by Freundlich isotherm. The efficiency of the Al-PILC was assessed by comparing the results with those on a commercial ion exchanger, Ceralite IRC-50. The suitability of the Al-PILC for treating Co(II) solutions was tested using simulated nuclear power plant coolant samples. Acid regeneration was tried for several cycles with a view to recover the adsorbed Co(II) and also to restore the adsorbent to its original state.

Effect of agitation on removal of acetic acid from pretreated hydrolysate by activated carbon.

The effect of agitation on the adsorption of acetic acid by activated carbon was tested utilizing an external mass transfer-diffusion model. Simulated pretreated biomass was contacted with activated carbon under prescribed conditions of temperature and agitation. Adsorption isotherm studies are presented as well as batch kinetic rate studies. Use of these data enabled the determination of isotherm constants, an external mass transfer coefficient, and an effective diffusivity for each agitation rate studied. The external film coefficient results ranged from 33.62 microm/s to a complete absence of external mass transfer resistance, and the diffusivity results ranged from 0.8625 to 10.70 microm(2)/s. The optimum combination of no external film resistance, and highest diffusivity, 10.70 microm(2)/s, occurred at 250 rpm and 25 degrees C. The results of these models and the experimental parameters suggested an efficacious method and conditions for the removal of this undesirable chemical.

Kinetics of the combined sorption of copper(II) and nonionic surfactant by carboxylic acrylcationic exchanger

Kinetics of the simultaneous sorption of nonionic surfactant alkylmonoethers (ALM-10) and copper(II) cations by the hydrogen-containing form of Purolite C106 carboxylic acrylcationic exchanger has been investigated considering the possibility to control the concentration of both copper(II) and the surfactant in sewage effluents: kinetic curves were measured, coefficients of intraparticle diffusion (D) and external mass transfer diffusion (β) calculated. On increasing the acidity from pH 5 to 3 both the rate of intraparticle diffusion and the equilibrium sorption of copper(II) decrease but the corresponding parameters for ALM-10 increase. The action of copper(II) leads to an increase in the rate of ALM-10 intraparticle diffusion but results to a decrease in ALM-10 equilibrium sorption. Combined sorption of nonionic surfactant and copper(II) by hydrogen-containing form of Purolite C106 can be applicable for the purification of sewage including copper plating rinsewater from both contaminants simultaneously: accordingly to the coefficients of intraparticle diffusion for both copper(II) and the surfactant, the sorber filled with Purolite C106 would not limit the productivity if integrated into the system of sewage purification by ion exchangers.

Mass transfer and equilibrium studies for the sorption of chromium ions onto chitin

The kinetics and equilibrium of chromium sorption onto chitin were studied with respect to pH, particle size, initial metal ion concentration, sorbent concentration and stirring rate. In order to select the main rate-limiting step in the overall uptake mechanism, a single external mass transfer diffusion model and intraparticular mass transfer diffusion models were used. External film mass transfer coefficients gave a mean value of 1.16×10 −3 cm s −1. Chromium sorption onto chitin was mainly located on the surface. However, the stirring rate had no noticeable effect on the overall uptake rate of chromium. This observation led to the conclusion that external mass transfer resistance was not the major limiting phenomenon. Intraparticle diffusion coefficients gave a mean value of 2.78×10 −3 mmol g −1 s −0.5 (0.17 mmol g −1 h −0.5), indicating a poor intraparticular diffusion into the chitin or into the pores. The equilibrium isotherms were analysed using the monolayer and multilayer sorption models. Finally, the chromium binding capacity of chitin was compared with that of Rhizopus arrhizus, which possesses a high chitin content in the cell wall.