Biosorption of Cu2+, Cd2+, Pb2+, and Zn2+ using dried marine green macroalga Caulerpa lentillifera

The sorption of Cu2+, Cd2+, Pb2+, and Zn2+ by a dried green macroalga Caulerpa lentillifera was investigated. The removal efficiency increased with pH. The analysis with FT-IR indicated that possible functional groups involved in metal sorption by this alga were O-H bending, N-H bending, N-H stretching, C-N stretching, C-O, SO stretching, and S-O stretching. The sorption of all metal ions rapidly reached equilibrium within 20min. The sorption kinetics of these metals were governed by external mass transfer and intraparticle diffusion processes. The sorption isotherm followed the Langmuir isotherm where the maximum sorption capacities was Pb2+>Cu2+>Cd2+>Zn2+.     

Direct insight into insulin aggregation by 2D NMR complemented by PFGSE NMR

The aggregation of Zn(II)-bound and zinc-free human insulin was studied in solution using the H(beta)-CH(3) crosspeaks of threonine residues in 2D COSY, TOCSY, and NOESY NMR spectra which allow viewing of the oligomers in equilibrium. This is complemented by PFGSE measurements of the translational diffusion coefficient, D(i), used for monitoring the changes in equilibrium composition of aggregates on dilution of both insulins in physiological medium. The back calculation of the dilution isotherm allows establishing the association constants for oligomeric equilibria in solution and discussion of the models of association.     

Biosorption of fluoride from aqueous phase onto algal Spirogyra IO1 and evaluation of adsorption kinetics

Non-viable algal Spirogyra IO1 was studied for its fluoride sorption potential in batch studies. The results demonstrated the ability of the biosorbent for fluoride removal. The sorption interaction of fluoride on to non-viable algal species obeyed the pseudo-first-order rate equation. The intraparticle diffusion of fluoride molecules within the Spirogyra was identified to be the rate-limiting step. It was also found that the adsorption isotherm followed the rearranged Langmuir isotherm adsorption model. Fluoride sorption was dependent on the aqueous phase pH and the fluoride uptake was greater at lower pH.     

Low cost bio-sorbent 'wheat bran' for the removal of cadmium from wastewater: kinetic and equilibrium studies

Novel bio-sorbent wheat bran has been successfully utilized for the removal of cadmium(II) from wastewater. The maximum removal of cadmium(II) was found to be 87.15% at pH 8.6, initial Cd(II) concentration of 12.5 mg l-1 and temperature of 20 degrees C. The effect of different parameters such as contact time, adsorbate concentration, pH of the medium and temperature were investigated. Dynamics of the sorption process were studied and the values of rate constant of adsorption, rate constant of intraparticle diffusion and mass transfer coefficient were calculated. Different thermodynamic parameters viz., changes in standard free energy, enthalpy and entropy have also been evaluated and it has been found that the reaction was spontaneous and exothermic in nature. The applicability of Langmuir isotherm showed of monolayer coverage of the adsorbate on the surface of adsorbent. A generalized empirical model was proposed for the kinetics at different initial concentrations.     

Biosorption behavior of azo dye by inactive CMC immobilized Aspergillus fumigatus beads

The biosorption equilibria and kinetics of an azo dye (reactive brilliant red K-2BP) were examined in this study using inactive carboxylmethylcellulose (CMC) immobilized Aspergillus fumigatus beads as the biosorbent. It was found that the biosorption capacity was at maximum when dye solution pH was about 2.0, that the sorption was spontaneous and endothermic with insignificant entropy changes, and that the Freundlich isotherm model fitted well to the biosorption equilibrium data. The biosorption rates were found to be consistent with a pseudo-second-order model. An intraparticle diffusion-based Weber-Morris model was applied to evaluate rate-limiting steps of the biosorption processes. The results suggested that the diffusion controlled the overall biosorption process, but the boundary layer diffusion of dye molecules could not be neglected. External mass transfer coefficients (beta(I)S) obtained by both Mathews and Weber model and Frusawa and Smith model were consistent.     

Sorptive removal of Methylene blue from aqueous solution using palm kernel fibre: Effect of fibre dose

The use of palm kernel fibre, a readily available agricultural waste product for the sorption of Methylene blue from aqueous solution and the possible mechanism of sorption has been investigated at various fibre doses. The extent of dye removal and the rate of sorption were analyzed using two kinetic rate models (pseudo-first and pseudo-second-order kinetic models) and two diffusion models (intraparticle and external mass transfer models).

Analysis of the kinetic data at different sorbent dose revealed that the pseudo-first order kinetics fitted to the kinetic data only in the first 5 min of sorption and then deviated from the experimental data. The pseudo-second-order kinetic model was found to better fit the experimental data with high correlation coefficients at the various fibre dose used. The dye sorption was confirmed to follow the pseudo-second-order model by investigating the relationship between the amount of dye sorbed and the change in hydrogen ion concentration of the dye solution and also the dependence of dye uptake with solution temperature. It was found that the change in hydrogen ion concentration and increase in sorption temperature were directly related to the amount of dye sorbed, and activation energy was calculated to be −39.57 kJ/mol, indicating that the dye uptake is chemisorption, involving valence forces through sharing or exchange of electrons between sorbent and sorbate as covalent forces.

The intraparticle diffusion plots showed three sections indicating that intraparticle diffusion is not solely rate controlling. The intraparticle diffusion and mass transfer rate constants where observed to be well correlated with sorbent dose in the first 5 min of sorption, indicating sorption process is complex. It was found that at low sorbent dose the mass transfer is the main rate controlling parameter. However at high sorbent dose, intraparticle diffusion becomes rate controlling.     

Kinetics and mechanism of methylene blue sorption onto palm kernel fibre

The kinetics and mechanism of the sorptive removal of methylene blue dye from aqueous solution using palm kernel fibre as adsorbent have been investigated. Batch kinetic experiments were performed and system variables investigated includes pH and initial dye concentration. The kinetic data were fitted to the pseudo-first, pseudo-second, intraparticle diffusion and mass transfer models. The pseudo-first order reaction kinetics fitted to the experimental data only in the first 5 min of sorption and then deviated, while the pseudo-second order kinetic model was found to fit the experimental data for the entire sorption period with high coefficient of determination. Equations were developed using the pseudo-second order model, which predicts the amounts of methylene blue at any contact time and initial concentration within the given range. This suggests that the sorption of methylene blue onto palm kernel fibre follows a chemical activation mechanism. A mathematical relationship was also drawn between the equilibrium sorption capacity and the change in pH (ΔH⁺) at the end of the kinetic experiments with varying initial dye concentration, supporting the fact that chemical reaction (ion exchange) occurred and is important in the rate determining step. Mass transfer was found to be favoured at high concentrations while intraparticle diffusion was favoured at low concentrations.     

Removal of Astrazon Yellow 7GL from aqueous solutions by adsorption onto wheat bran

Adsorption kinetic and equilibrium of a basic dye (Astrazon Yellow 7GL) from aqueous solutions at various initial dye concentration (50-300 mg/l), pH (4-10), adsorbent dosage (2-8 g/l), particle size (354-846 microm) and temperature (30-50 degrees C) on wheat bran were studied in a batch mode operation. The result showed that the amount adsorbed of the dye increased with increasing initial dye concentration and contact time, whereas particle size and pH had no significant affect on the amount of dye adsorbed by the adsorbent. A comparison of kinetic models on the overall adsorption rate showed that dye/adsorbent system was best described by the pseudo second-order rate model. The removal rate was also dependent on both external mass transfer and intra-particle diffusion. The low value of the intraparticle diffusivity, 10(-11) cm2/s, indicated the significant influence of intraparticle diffusion on the kinetic control. The adsorption capacity (Q0) calculated from the Langmuir isotherm was 69.06 mg/g for at pH 5.6, 303 K for the particle size of 354 microm. The experimental data yielded excellent fits with Langmuir and Tempkin isotherm equations. Different thermodynamic parameters showed that the reaction was spontaneous and endothermic in nature.     

Biosorption of cadmium (II) ions by immobilized cells of Pycnoporus sanguineus from aqueous solution

Biosorption of cadmium (II) ions from aqueous solution onto immobilized cells of Pycnoporus sanguineus (P. sanguineus) was investigated in a batch system. Equilibrium and kinetic studies were conducted by considering the effect of pH, initial cadmium (II) concentration, biomass loading and temperature. Results showed that the uptake of cadmium (II) ions increased with the increase of initial cadmium (II) concentration, pH and temperature. Langmuir, Freundlich and Redlich-Peterson isotherm models were used to analyze the equilibrium data at different temperatures. Langmuir isotherm model described the experimental data well followed by Redlich-Peterson and Freundlich isotherm models. Biosorption kinetics data were fitted using pseudo-first, pseudo-second-order and intraparticle diffusion. It was found that the kinetics data fitted well the pseudo-second-order followed by intraparticle diffusion. Thermodynamic parameters such as standard Gibbs free energy (Delta G0), standard enthalpy (Delta H0) and standard entropy (Delta S0) were evaluated. The result showed that biosorption of cadmium (II) ions onto immobilized cells of P. sanguineus was spontaneous and endothermic nature.     

Removal of lead from aqueous solutions by agricultural waste maize bran

Maize bran is a low cost biosorbent that has been used for the removal of lead(II) from an aqueous solution. The effects of various parameters such as contact time, adsorbate concentration, pH of the medium and temperature were examined. Optimum removal at 20 degrees C was found to be 98.4% at pH 6.5, with an initial Pb(II) concentration of 100 mg l(-1). Dynamics of the sorption process and mass transfer of Pb(II) to maize bran were investigated and the values of rate constant of adsorption, rate constant of intraparticle diffusion and the mass transfer coefficients were calculated. Different thermodynamic parameters viz., changes in standard free energy, enthalpy and entropy were evaluated and it was found that the reaction was spontaneous and exothermic in nature. The adsorption data fitted the Langmuir isotherm. A generalized empirical model was proposed for the kinetics at different initial concentrations. The data were subjected to multiple regression analysis and a model was developed to predict the removal of Pb(II) from an aqueous solution.     

Biosorption of Nickel(II) from aqueous solution by the fungal mat of Trametes versicolor (rainbow) biomass: equilibrium, kinetics, and thermodynamic studies

This study investigates the equilibrium, kinetics and thermodynamics of Nickel(II) biosorption from aqueous solution by the fungal mat of Trametes versicolor (rainbow) biomass. The optimum biosorption conditions like pH, contact time, biomass dosage, initial metal ion concentration and temperaturewere determined in the batch method. The biosorbent was characterized by FTIR, SEM and BET surface area analysis. The experimental data were analyzed in terms of pseudo-first-order, pseudo-secondorder and intraparticle diffusion kinetic models, further it was observed that the biosorption process of Ni(II) ions closely followed pseudo-second-order kinetics. The equilibrium data of Ni(II) ions at 303, 313, and 323 K were fitted to the Langmuir and Freundlich isotherm models. Langmuir isotherm provided a better fit to the equilibrium data andthe maximum monolayer biosorption capacity of the T. versicolor(rainbow) biomass for Ni(II) was 212.5 mg/g at pH 4.0. The calculated thermodynamic parameters, ΔG^○, ΔH^○, and ΔS^○, demonstrated that the biosorption of Ni(II) ions onto the T. versicolor (rainbow) biomass was feasible, spontaneous and endothermic at 303 ～ 323 K. The performance of the proposed fungal biosorbent was also compared with that of many other reported sorbents for Nickel(II) removal and it was observed that the proposed biosorbent is effective in terms of its high sorption capacity.     

Engineered Biofilms for Metal Ion Removal

Firstly, biofilm and biosorbents are defined. Mechanisms of interactions between metal ions and biofilm are discussed in terms of diffusion, mass transfer and sorption. In a second step, different processes using biofilm to remove heavy metal in aqueous solutions are presented. The continuously stirred processes are described for metal ion removal in wastewater by biofilm coating particles. In this case, the equilibrium data obtained with isotherm curves show a good adsorption of several metal ions onto biofilm. Examples of adsorption capacities for a large number of microorganisms and heavy metal ions are presented. The fixed bed reactors packed with grains coated with a biofilm are efficient to get a sorption (adsorption or ion exchange) of cations. The pressure drop is calculated with classical equations. Some values such as adsorption capacities and breakthrough times are got from the breakthrough curves. Several models (Adams-Bohart, mass transfer, and homogeneous surface diffusion models) are applied to get design data. A new approach using neural network to model breakthrough curves is proposed and discussed.     

Study of water and oil diffusion in rape seeds with sorption-desorption and NMR techniques.

The sorption and desorption of water in rape seeds was measured. From the sorption isotherm it follows that for water content greater than about 6% the water molecules tend to form clusters. The mutual diffusion coefficient of water into and out of the seeds was determined from the time dependence of sorption and desorption. There is a pronounced hysteresis in the sorption-desorption process, desorption proceeds faster than sorption. The self-diffusion of water (at maximum humidity of the seeds) and oil within the seeds was investigated by the pulsed field gradient NMR. The measurement of oil self-diffusion shows restricted diffusion of the oil within droplets and allows the determination of the droplet radii and their distribution width.     

Equilibrium and Kinetic Studies of Cd2+ Biosorption by the Brown Algae Sargassum fusiforme

A fundamental investigation of the biosorption of Cd²⁺ from aqueous solution by the edible seaweed Sargassum fusiforme was performed under batch conditions. The influences of experimental parameters, such as the initial pH, sorption time, temperature, and initial Cd²⁺ concentration, on Cd²⁺ uptake by S. fusiforme were evaluated. The results indicated that the biosorption of Cd²⁺ depended on the initial Cd²⁺ concentration, as well as the pH. The uptake of Cd²⁺ could be described by the Langmuir isotherm model, and both the Langmuir biosorption equilibrium constant and the maximum biosorption capacity of the monolayer decreased with increasing temperature, thereby confirming the exothermic character of the sorption process. The biosorption kinetics follows the pseudo-second-order kinetic model, and intraparticle diffusion is the sole rate-limiting step for the entire biosorption period. These fundamental equilibrium and kinetic results can support further studies to the removal of cadmium from S. fusiforme harvested from cadmium-polluted waters.     

Antibody Binding Heterogeneity of Protein A Resins

Protein A affinity chromatography is a core unit operation in antibody manufacturing. Nevertheless, there is not enough understanding of in‐column antibody adsorption in the Protein A capture step. This work aims to investigate in situ the establishment of an antibody (trastuzumab) layer during Protein A chromatography both in terms of energetic contributions and uptake kinetics. Flow microcalorimetry is employed as a technique with an in situ operating detector, which provides an understanding of the thermodynamics of the adsorption process. In addition, the antibody uptake rate is also investigated in order to establish a correlation between its diffusion on the stationary phase and the associated thermodynamics. Two resins with different particle size, intraparticle porosity, and a Protein A ligand structure are studied: the synthetically engineered B‐domain tetrameric MabSelect SuRe and the synthetically engineered C‐domain hexameric TOYOPEARL AF‐rProtein A HC. The uptake rate follows a pore diffusion model at low equilibrium time, showing a slower diffusivity after a certain time because of the heterogeneous binding nature of these two resins. In addition, the microcalorimetric studies show that adsorption enthalpy is highly favourable at low isotherm concentrations and evolves toward an equilibrium with increasing surface concentration. These data suggest that the relationship between adsorption enthalpy and the establishment of the antibody layer in the Protein A chain is consistent with heterogeneous adsorption.     

Description of two-metal biosorption equilibria by Langmuir-type models

A biosorbent prepared from Ascophyllum nodosum seaweed biomass, FCAN2, was examined for its sorption capacity. Equilibrium batch sorption studies were performed using two-matal systems containing either (Cu + Zn), (Cu + Cd), or (Zn + Cd). In the evaluation of the two-metal sorption system performance, simple isotherm curves had to be replaced by three-dimensional sorption isotherm surfaces. In order to describe the isotherm surfaces mathematically, three Langmuir-type models were evaluated. The apparent one-parameter Langmuir constant (b) was used to quantify FCAN2 "affinity" for one metal in the presence of another one. The uptake of Zn decreased drastically when Cu or Cd were present. The uptake of Cd wasmuch more sensitive to the presence of Cu than to that of Zn. The presence of Cd and Zn alter the "affinity" of FCAN2 for Cu the least at high Cu equilibrium concentrations. The mathematical model of the two-metal sorption system enabled quantitative estimation of one-metal (bio)sorption inhibition due to the influence of a second metal. (c) 1995 John Wiley & Sons Inc.     

Macrokinetics of enzyme sorption on porous beads accompanied by complex formation with an immobilized ligand

A mathematical model has been proposed for enzyme sorption on porous beads accompanied by formation of a stable complex with an immobilized ligand. It has been experimentally verified by using the system trypsin (EC 3.2.21.4) - immobilized bovine basic polyvalent trypsin inhibitor on porous silica gel. The experimental results for kinetics of the non-specific/specific trypsin sorption on a carrier agree with the model. The value of the coefficient of trypsin diffusion in macroporous silica gel was calculated.     

Isotherm,Kinetic, and Thermodynamic Characteristics for Adsorption of 2,5-Xylenol onto Activated Carbon

The adsorption of the major tar compound, 2,5-xylenol, derived from the plant cell cultures of Taxus chinensis, onto activated carbon was examined at different initial 2,5-xylenol concentrations, durations, and temperatures. From the analysis of adsorption isotherms, the Langmuir isotherm model showed good fit to the equilibrium adsorption data. It was found that adsorption capacity decreased with increasing temperature, and the adsorption of 2,5-xylenol onto activated carbon was favorable. The obtained kinetic data for 2,5-xylenol adsorption with activated carbon agreed well with the pseudo-second-order kinetic model. By using intraparticle diffusion model, intraparticle diffusion and boundary layer diffusion did not play a dominant role in 2,5-xylenol adsorption. Thermodynamic parameters were calculated, which indicated that the adsorption was non-spontaneous, irreversible and exothermic nature. The isosteric heat of adsorption decreased with increase in surface loading, indicating a heterogeneous surface.