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The adsorption kinetics of adenine and adenosine on a ligand-exchange matrix, carboxymethyl diaminoethane poly(vinyl chloride) in cobalt form (cobalt-CMEDA-PVC), have been studied in a fixed-bed column system. The initial ligand concentrations ranged between 1.25x10-5 and 2.0x10-4 mol L-1. The kinetic studies were carried out spectrophotometrically, in order to determine the rate-controlling step of the adsorption. The kinetic data of the single-component systems were acquired from the breakthrough curves of the ligands on the basis of the equivalent points method. In this study, the homogeneous diffusion model was adapted to a fixed-bed column system to describe the differentiation in the ligand concentration of the effluent, beginning from breakthrough point as a function of time. The results obtained for the adsorption kinetics indicated that the diffusion step plays a significant role in the adsorption kinetics of the ligands, due to the fact that the adsorption performance was strongly affected by the initial concentration of ligands. [ABSTRACT FROM AUTHOR]

The article presents a study which demonstrates the use of the dynamic method known as stepwise frontal analysis (SFA) to obtain the equilibrium sorption data of copper and aniline on a carboxylated diaminoethane sporopollenin (CDAE-S) solid phase. The Langmuir model for copper and the Freundlich model for aniline have been used to model the derived data. Furthermore, the Scatchard plot analysis was also used to analyze the equilibrium binding data of the two chemicals. The study reveals that the sorption of copper was primarily attributed to specific interactions, with carboxyl groups as the main binding sites, while sorption of aniline was attributed to nonspecific interactions. The role of aminocarboxylic acid functionalities in the sorption of copper and aniline is also examined.

Abstract: Single component adsorption of phenol and 2-, 3- and 4-nitrophenol from water was studied under dynamic column conditions by using a carboxymethyl diaminoethane sporopollenin in a cobalt ion-loaded form, Co(II)-CDAE-S, as solid phase. Adsorption isotherm data were acquired by frontal analysis for five plateau concentrations ranged from 1.25×10−5 to 2.00×10−4 mol l−1. The studied ligand-exchange sporopollenin resin showed a selective adsorptive nature within the group of studied nitrophenols, and the nature of phenols'' adsorption on the Co(II)-CDAE-S was analyzed in terms of specific bindings by using Scatchard plot analysis. In light of the Scatchard plot analysis, the adsorption of examined compounds was mainly attributed to the specific bindings based on the ligand-exchange matrix of the studied adsorbent. The nitro-substituted phenols were found to be less strongly adsorbed than the phenol, and both binding strength and theoretical saturation capacity had an obvious relationship with the position of nitro substituent: The theoretical saturation capacities calculated from applied isotherm models exhibited an increase in the order of phenol <4-nitrophenol <3-nitrophenol <2-nitrophenol, whereas a reverse order was showed for binding strengths. [Copyright &y& Elsevier]

The adsorption phenomena of Methylene blue (MB) and Methyl orange (MO) on a carboxylated diaminoethane sporopollenin (CDAE-S) solid phase were investigated in a column arrangement by using breakthrough technique. The adsorption phenomena were evaluated using some common adsorption isotherm models and Scatchard plot analysis, and obtained results were interpreted for evaluating the usability of CDAE-S for removal, recovery and preconcentration of the studied dyes both at the laboratory and industrial scales. On the basis of Scatchard plot analysis, the interaction types between the CDAE-S and the studied dyes were criticized in terms of affinity phenomena. Thus, the usability of a biomacromolecule-derived material, CDAE-S, as a cheap, environmentally-friendly and effective solid-stationary phase exhibiting both cation-exchange and anion-exchange characteristics at the same time, is discussed through the present study. Besides, from the obtained results, the protonated CDAE-S, which functionally resembles an amino acid structure, are presented as a two-in-one solid-stationary phase, and its adaptability to common processes performed under column conditions is also drawn in detail. [Copyright &y& Elsevier]

Abstract: The interactions of ligands, such as adenine, adenosine, uracil and uridine with Co(II) ions immobilized by carboxylated diaminoethyl matrix on sporopollenin were investigated as a function of temperature by the breakthrough technique. The adsorption characteristics of ligands on Co(II)-carboxylated diaminoethyl sporopollenin [Co(II)-CDAE-S] were investigated by Scatchard plot analysis under optimized conditions of flow rate and temperature. Equilibrium binding data used in Scatchard plot analysis for adenosine gave rise to a linear plot, indicating the presence of specific interaction and Langmuirean behavior. However, the adsorption of uracil on this ligand-exchange stationary phase was affected by the electrostatic or hydrophobic interaction in the whole concentration range. In the case of adenine and uridine, the adsorption performance was strongly affected by the initial ligand concentration. At high concentration, adenine and uridine were adsorbed specifically to the ligand exchanger matrix exposed on the adsorbent. At lower concentrations, the binding to the second sets of adsorbent was appeared because of nonspecific interaction such as hydrophobic and electrostatic. [Copyright &y& Elsevier]

In this work, adsorption kinetics of nucleic acid bases and nucleosides as ligands on cobalt(II)–carboxylated diaminoethyl sporopollenin (CDAE-sporopollenin) have been performed using continuous column runs. Adsorption rate measurements were carried out by using a UV-Vis spectrophotometer, and rate control step of the adsorption process was determined. The adsorption of nucleic acid bases and nucleosides from solutions of different initial concentrations onto resin was measured as a function of time at 25 °C. The results show that type of ligand has a great effect on ligand adsorption behaviour. External ligand concentrations play a significant role on adsorption rate of nucleic acid bases. The homogeneous diffusion model (HDM) is applied to the experimental breakthrough data. In all of the concentration range of adenine and uracil (nucleic acid bases), the graphs of −ln[1−U(α)] versus t were a straight line, which suggests that fractional attainment of equilibrium adsorption under film diffusion control is observed. On the contrary, adenosine and uridin (nucleosides), the graphs were not a straight line and have underwent adsorption under particle diffusion control. [Copyright &y& Elsevier]

This study was conducted to confirm the possibilities of determining the binding constants of ligands in metal–ligand complexes containing carboxylic groups bound polymer by using breakthrough technique. Aniline and o-anisidine were selected as model ligands. A mini column apparatus was used to study sorption of ligands onto ligand exchange resin. The experiments were conducted in a constant temperature at 25 °C. The equilibrium sorptions of aniline and o-anisidine were measured in order to determine the part of the sorption on Co(II)-CDAE-sporopollenin resin. The sorption of aniline is seen to be higher than that sorption of o-anisidine. The characteristics of the sorption process were investigated using Scatchard plot analysis (q/C vs. q). In the sorption of o-anisidine, deviation from linearity in the plot of q/C versus q was observed, indicating the presence of multi-model interaction and non-Langmuirean behavior. Furthermore, in high concentration of aniline deviation from linearity in the plot of q/C versus q was appeared. Particularly for o-anisidine, divergence from the Scatchard plot was evident, consistent with the participation of secondary equilibrium effects in the adsorption process. However, Scatchard plot analysis of the equilibrium binding data for aniline onto ligand exchanger gave rise to a linear plot. The ligand binding constants of aniline and o-anisidine were determined as 0.071 and 0.156 mol mol−1 Co2+, respectively. [Copyright &y& Elsevier]

Abstract: Sorption behavior of Cu(II) ions on a humic acid-based solid phase, insolubilized humic acid (IHA), were investigated under continuous column conditions. The quantitative data were derived on the basis of breakthrough curves obtained at different experimental conditions. For the studied experimental conditions, the highest and lowest observable capacities of IHA toward Cu(II) were found as 48.34 and 0.84μmolg−1, respectively. In order to evaluate the pH dependence of Cu(II) binding on IHA, the effect of influent concentration was investigated at three different pH values (1.0, 2.0 and 3.0), and adsorption isotherms were derived for each acidic condition. The characteristics of Cu(II) bindings were evaluated by using Scatchard plot analysis, and it was observed that under strongly acidic condition, pH 1.0, nonspecific and/or multi-type interactions between Cu(II) and IHA were the prevailing effects causing the Cu(II) sorption. On the other hand, at pH 2.0 and 3.0, the role of specific interactions was more clearly observed, and so at pH(s) 2.0 and 3.0, the binding of Cu(II) on IHA was mainly attributed to specific interactions rather than nonspecific ones. For pH 2.0 and 3.0, the binding types of Cu(II) on IHA were sub-classified according to different affinities observed between Cu(II) and IHA, and thus two main types of specific bindings were proposed for the studied influent concentration range (1.0×10−3 to 1.0×10−1 moll−1): Type-1, high-affinity/low capacity and Type-2, low-affinity/high capacity bindings. Finally, probable benefit of each specific binding type in separation of Cu(II) from acidic aqueous media has been discussed in detail. [Copyright &y& Elsevier]

Abstract: The adsorption behavior of Crystal Violet (CV) on a sporopollenin-based solid phase, carboxylated diaminoethane sporopollenin (CDAE-S), was investigated under column conditions, and the obtained breakthrough profiles were used in evaluations and quantifications. The adsorption capacity of the CDAE-S was observed to be considerably higher than that of diaminoethane sporopollenin (DAE-S), revealing the importance of electrostatic interactions and carboxyl groups in the adsorption of CV on the CDAE-S. The binding of CV on the DAE-S was found to be a typical nonspecific adsorption, whilst cation-exchange was proposed as the main mechanism for monolayer adsorption of CV on the CDAE-S. Hence in the present study, the cation-exchange is suggested as an effective process for removal and recovery of CV from aqueous effluents, and in view of the pH point of zero charge matter, multifunctionality of the CDAE-S is discussed in detail, and various application possibilities based on “aminocarboxylic acid” functionality are also drawn. [Copyright &y& Elsevier]

Abstract: The adsorption behaviors of Methylene Blue and Methyl Orange on a diaminoethane sporopollenin (DAE-S) solid phase were investigated in a column arrangement, and breakthrough profiles were used in evaluations and quantifications. The adsorption behaviors were evaluated using some common adsorption isotherm models and Scatchard plot analysis. The results showed that the DAE-S was useful for abstracting anionic dyes from cationic dyes. Thus, the usability of a biopolymer derived material (DAE-S) as a cheap, environmentally friendly and effective solid/stationary phase is discussed through the present study, and the adaptability of the DAE-S to common processes performed under column conditions is also drawn in detail. [Copyright &y& Elsevier]

Kinetic studies of chlorinated anilines as ligands on the cobalt(II)-carboxylated diaminoethyl-sporopollenin (CDAE-sporopollenin) have been performed using continuous column runs. Adsorption rate measurements were carried out by using a UV–visible spectrophotometer, and rate control step of the reaction was determined. The adsorption of chlorinated anilines from solutions of different initial concentrations onto resin was measured as a function of time at 25 °C. The initial ligand concentrations ranged from 6.0×10−4 to 2.5×10−3 mol l−1. The results concerning the influence of the external solution concentration of the ligands upon the fractional attainment of equilibrium prove that the diffusion of the ligands into the resin beads plays an important role in the mechanism of the exchange reaction, although the exchange rate is chemical in its ultimate mechanism. A very fast initial adsorption resulting in an almost instantaneous attainment of the bulk of the equilibrium adsorption was followed immediately by a very slow rate of adsorption. In the case of 4- and 2,5-dichloroaniline, in all of the concentration range, the graphs of −ln[1−U(α)] versus t were a straight line, which suggests that fractional attainment of equilibrium adsorption under film diffusion control is observed. On the contrary, 2- and 3-chloroaniline, the graphs were not a straight line and have underwent adsorption under particle diffusion control. [Copyright &y& Elsevier]

Abstract: The adsorption of aniline from aqueous solutions onto cobalt(II)-poly(vinyl chloride)-carboxylated diaminoethane (PVC-CDAE) resin has been studied using a mini-column apparatus at 25±0.1°C. First of all, experimental data obtained from the breakthrough curves were tested by using the Scatchard plot analysis, to have a preliminary prediction about the types of interaction of the resin with aniline. Our aim was to determine the model which best describes the experimental data. The aspect of the Scatchard plot indicated that the aniline adsorption did not follow the Langmuir model and the presence of two types of binding sites for aniline on the resin. However, the dynamics of aniline uptake were represented by the Freundlich model reasonably well. The kinetics of aniline adsorption from aqueous solution on the cobalt(II)-PVC-CDAE have also been tested using continuous column runs and rate-controlling step of the process was determined. In this study, homogeneous diffusion model was adapted to a column system to describe the change in the aniline concentration at the column exit beginning from breakthrough point as a function of time. Kinetic studies revealed that the rate-controlling step of the aniline adsorption was predominately film diffusion controlled rather particle diffusion. [Copyright &y& Elsevier]

The adsorption of indole and its 2-methyl derivative from aqueous solutions onto cobalt(II)-carboxylated diaminoethane sporopollenin (CDAE-sporopollenin) was studied using a fixed-bed column at 25±0.1 °C. Minicolumn adsorption studies showed that the breakthrough and the total adsorption capacities of CDAE-sporopollenin in the concentration range we have studied increased with increasing external ligand concentration. The characteristics of the adsorption process were investigated using Scatchard plot analysis, where the equilibrium binding data for indole on ligand exchanger gave rise to a linear plot. However, for 2-methylindole, divergence from the Scatchard plot was evident, consistent with the participation of secondary equilibrium effects in the adsorption process. The adsorption behaviors of ligands on CDAE-sporopollenin were expressed by both the Langmuir and Freundlich isotherms. The adsorption isotherm data for these ligands on the resin can be satisfactorily fitted to the Freundlich isotherm within the concentration range studied. However, in the case of 2-methylindole, the experimental data did not fit the Langmuir model, especially when a high ligand concentration range is used; this is probably due to the nonspecific interactions between the ligand exchange matrix and the methyl group present. Ligand adsorption constants and correlation coefficients for the ligands were calculated from the Langmuir and Freundlich isotherms. [Copyright &y& Elsevier]

Ligand adsorption of adenine and adenosine has been studied by using cobalt(II)–poly(vinyl chloride) carboxylated diaminoethyl (PVC–CDAE) resin. Column runs were conducted to study the performance of the ligand exchanger. The adsorption of adenine and adenosine from solutions of different initial concentrations onto resin was measured using by breakthrough technique at 25 °C. The ligand concentration was chosen to be 0.0125–0.2 mmol l−1. The characteristics of the adsorption process were investigated by using Scatchard plot analysis (q/C versus q). And the adsorption behaviour of these ligands on cobalt(II)–PVC–CDAE is expressed by the Langmuir and Freundlich isotherms. The adsorption data with respect to all ligands provide an excellent fit to the Freundlich isotherm, giving correlation coefficients in the range of 0.95–0.99 for the Freundlich isotherm. On the contrary, when the Langmuir isotherm model was applied to these data, a good fit was not obtained for the high ligand concentrations. [Copyright &y& Elsevier]