Binary Competitive Adsorption Research Articles

Adsorption-desorption characteristics of typical heavy metal pollutants in submerged zone sediments: a case study of the Jialu section in Zhengzhou, China.

In recent years, the accumulation ability of heavy metals in sediment has become a key indicator for sediment pollution prevention and control. The adsorption-desorption processes of typical heavy metal pollutants in sediments under different conditions were explored and relied in this article. In addition, different binary competitive adsorption systems were designed to study the competitive adsorption properties of heavy metal contaminants, The quasi-secondary kinetic model simulated the adsorption kinetic process. The sediment adsorption rates for heavy metals were (in descending order) Cu, Pb, Cd, Zn. The Elovich equation simulated the desorption kinetics process better, and the sediment desorption rates for heavy metals were (in descending order) Cd, Cu, Zn, Pb. The average free adsorption energy E of heavy metals was within the range of 8-16 kJ∙mol-1. After the removal of organic matter, the ability of the sediment to sequester heavy metals decreases, The binary competitive adsorption results showed that the presence of interfering ions had the greatest effect on Cd and the least effect on Pb. The adsorption and desorption of the four heavy metals by the sediments in the submerged zone increased with the increase of temperature, and the ratio of desorption to adsorption also increased therewith: the adsorptions of heavy metals by the sediments were all spontaneous processes (under heat absorption reactions). The presence of organic matter can increase the ability of the sediment to sequester Cd, Pb, Cu, and Zn. Additionally, heavy metals exhibited significant selective adsorption properties.

Breaking binary competitive adsorption in the domino synthesis of pyrroles from furan alcohols and nitroarenes over metal phosphide

Herein, an efficient domino synthesis for N-aryl pyrroles and tetrahydropyrroles from biomass-derived furan alcohols (i.e., 5-methyl furfuryl alcohol, and 2,5-bis(hydroxymethyl)furan) and nitrobenzenes was reported for the first time over metal phosphides. Dual active sites, including metal sites for nitro hydrogenation, acid sites for furan alcohol ring-opening determine the catalytic performance. Different from traditional tandem catalysts of Pd/C and HZSM-5 or Amberlyst-15 that suffer from binary competitive adsorption of furan and nitro groups on metal sites, as well as hydroxyl and hydrogenated amino groups on the acidic sites, metal phosphides show unexpected cooperative catalytic properties with the oriented synthesis of pyrroles over NiCoP and tetrahydropyrroles over Ni2P. Furthermore, the catalyst displays outstanding stability and recycling performance after 4 runs. This work demonstrates an effective strategy for governing reaction routes by selective activation and shows the powerful synergistic effect of hydrogenation and acid catalysis.

Adsorption of cadmium ions from simulated battery wastewater by polyethylene polyamine-modified activated carbon.

The objective of this work was to study the treatment of wastewater containing cadmium ions (Cd2+). Activated carbon (AC) was modified with potassium hydroxide (KOH) and polyethylene polyamine (PEPA). The structure and morphology of the modified AC was characterized. The effect of pH on adsorption was investigated, and the binary competitive adsorption and the reusability of the modified AC were studied. Subsequently the modified AC was used as an adsorbent for the removal of Cd2+ from wastewater. The adsorption capacity of optimized modified AC was 9.7 times that of unmodified AC. Kinetic adsorption curves were in accordance with pseudo-second-order kinetics, and the isothermal curves were in accordance with the Langmuir equation. The results indicate that the AC has potential in the treatment of the wastewater containing Cd2+ discharged from chemical plants during battery manufacturing.

Competitive kinetics of Ni(II)/Co(II) and Cr(VI)/P(V) adsorption and desorption on goethite: A unified thermodynamically based model

Predicting the dynamic behavior of coexisting ions on mineral interface is essential to understanding their lability in soil matrix, but a mechanical kinetic model for predicting competitive adsorption is lacking. In this study, the thermodynamic and kinetic adsorption behaviors of Ni(II), Co(II), Cr(VI), and P(V) on goethite under various condition were investigated by batch and stirred-flow experiments, respectively. The equilibrium model CD-MUSIC was developed to describe their equilibrium behavior, followed by the development of a multi-rate kinetic model constrained by the equilibrium model to describe their kinetic behavior. Ni(II) and Co(II) exhibit similar adsorption affinities, while the adsorption of P(V) was stronger and faster than that of Cr(VI). The two surface species of Cr(VI) and P(V) differed in dynamic features, a finding confirmed by in-situ ATR-FTIR spectroscopy. The kinetic model was successfully used to predict the binary competitive adsorption of Ni(II)-Co(II) and Cr(VI)-P(V), and especially the overshooting of Cr(VI) induced by P(V). Our results showed that an integrated thermodynamic-kinetic model obtained from a single-ion experiment can be extended to describe complex multi-ion interactions, indicating the robustness and scalability of the model’s parameters. This approach can be used to construct more comprehensive equilibrium and dynamic models of the actual soil environment.

Deformation and swelling of coal induced from competitive adsorption of CH4/CO2/N2

The deformation and swelling coal macromolecules could be induced from the adsorption of the CH4, CO2, and N2, however, their microscopic mechanisms have been minimally reported to date. Here, the binary competitive adsorption and the induced differential swelling ratio of the coal matrix were simulated through the molecular simulation and the poromechanical model. The swelling ratios of coal matrix in CO2 + CH4 competitive systems increase with the increasing CO2 mole fraction. However, those in the N2 + CH4 competitive systems decrease with the increasing N2 mole fraction. The swelling of the coal matrix is more significant at the high pressures than at the low pressures. The reduction rates are higher at N2 mole fraction of 0.4–0.8 than those at N2 mole fraction of 0–0.4 and 0.8–1.0. Under the geological conditions, almost half of the differential swelling ratios could be achieved for CO2 mole fraction of 0.25 and CH4 mole fraction of 0.40 respectively independent of the burial depth. These two differential swelling ratios increase with the increasing burial depth. Our results indicated that the swelling effects are significant at the shallowest sites (especially at the injection sites > 1200 m), leading to the low permeability for the deep ECBM engineering.

Single and Binary Competitive Adsorption of Cobalt and Nickel onto Novel Magnetic Composites Derived from Green Macroalgae

Easily separated novel magnetic composite, derived from a kind of green macroalgae—Enteromorpha prolifera, was employed for effective adsorption of radioactive cobalt (60Co) and nickel (63Ni). The ...

A cost-effective β-cyclodextrin polymer for selective adsorption and separation of acetophenone and 1-phenylethanol via specific noncovalent molecular interactions

To separate acetophenone (AP) and 1-phenylethanol (PE), a kind of cost-effective β-cyclodextrin based polymeric sorbent (CE-CDP) was constructed by crosslinking β-cyclodextrin with toluene-2,4-diisocyanate trimer. According to the characteristic results, the structure of the CE-CDP consisting of β-cyclodextrin cavity, aromatic urethane bond and unique isocyanurate ring was proved substantially. It was shown that crosslinking process would enhance the thermal stability, and the incorporation of the unique crosslinking units into CE-CDP's network potentially improved the selective adsorption performance compared to analogous polymer with non-isocyanurate ring structure. The static adsorption performance of CE-CDP in single solute system was investigated. The adsorption capacity of AP was much higher than that of PE, indicating that CE-CDP exhibits much stronger affinity toward AP over PE. Based on the results, we found that the spontaneous adsorption processes of AP and PE onto CE-CDP could be well described by pseudo-second order kinetics, Langmuir and Freundlich isotherm models. And the preferential AP adsorption over PE (selectivity≈6) was further verified through binary competitive adsorption. In addition, the density functional theory calculations showed that the coexistence of β-cyclodextrin cavity, aromatic urethane bond and isocyanurate ring endows CE-CDP with high AP adsorption capacity and selectivity. The theoretical results also indicated that the noncovalent interactions involving the intermolecular hydrogen bonding, π-π interactions and electrostatic interaction are favorable for binding AP rather than PE. In conclusion, CE-CDP was proved to be a good adsorbent for selective separation of AP and PE with mass producibility, low cost, high reusability and wide application prospect.

Sensitive and label-free quantification of cellular biothiols by competitive surface-enhanced Raman spectroscopy

A label-free surface-enhanced Raman spectroscopy (SERS)-based method for the rapid quantification detection of cellular biothiols at picomolar levels was developed by using a mechanism of binary competitive adsorption to regulate the plasmon coupling behavior of gold nanoparticles (Au NPs). 4,4′-Dipyridyl (Dpy), a small organic ligand with two symmetrically located pyridine rings, was used to shorten the inter-particle space and generate a multitude of “hot spots”, which in turn amplified the fingerprint signals of Dpy molecules. When biothiols were introduced into the Dpy-containing solution of Au NPs, they competitively adsorbed to the metal surface through the much stronger S–Au linkage, leading to the disaggregation of Au NPs and SERS quenching of Dpy molecules. The change of SERS responses was quantitatively related to biothiols added to the solution, and the detection limit down to 0.14pM for GSH was facilely achieved without any pre-concentration. The total assay time, including data analysis was within 8min. Finally, the SERS-based method was successfully applied to measure cellular biothiols, indicating its potential applicability in biological and biomedical research.

Adsorption of Pure and Binary CO2, CH4, and N2 Gas Components on Activated Carbon Beads

The adsorption equilibriums of CO2, CH4, and N2 pure gases on pitch-based activated carbon beads have been studied using a magnetic suspension microbalance at (293, 303, 333, and 363) K within a pressure range of 0 kPa to 4000 kPa. It is found that experimental adsorption capacities can be successfully described with both the Sips and Multisite Langmuir (MSL) isotherm models. Afterward, binary competitive adsorption breakthrough experiments (CO2/CH4 and CH4/N2) at 303 K and adsorption isotherms of gas mixtures under different conditions have been measured. Theoretical calculations from Sips model-based ideal adsorbed solution theory are found to have better agreement with experimental data of competitive binary adsorption than that from MSL model. Promising adsorption selectivity (5.5) between CH4 and N2 is obtained at 303 K as the pressure of a binary gas mixture is 100 kPa with yCH4 = 0.5 in the feed. Therefore, the activated carbon beads reported in this study can be considered as a promising adsorbent...

A situ co-precipitation method to prepare magnetic PMDA modified sugarcane bagasse and its application for competitive adsorption of methylene blue and basic magenta

Magnetic pyromellitic dianhydride (PMDA) modified sugarcane bagasse (SCB) was prepared by a situ co-precipitation method. Results showed that the magnetic modified SCB could be recycled easily by an applied magnetic field. Adsorption capacities of the magnetic sorbent for cationic dyes: methylene blue and basic magenta were 315.5 and 304.9mgg−1, respectively. Competitive adsorption in the binary system showed that concentration percentages (CP) and initial concentration (C0) both had good linear relationship with adsorption capacities of the magnetic sorbent (qe′) in the investigated range. The linear equations between CP and qe′ almost did not affect by the variation of total initial concentration of the dyes (CT), whereas that between C0 and qe′ changed greatly with it. CP was the main factor that impacted qe′ in the binary competitive adsorption system. Similar linear equations between CP and qe′ demonstrated that the magnetic sorbent had similar adsorption affinity toward the two dyes.

Displacement mechanism of binary competitive adsorption for aqueous divalent metal ions onto a novel IDA-chelating resin: Isotherm and kinetic modeling

Adsorptive properties for Cu (II), Pb (II) and Cd (II) onto an iminodiacetic acid (IDA) chelating resin were systematically investigated at the optimal pH-value in both single and binary solutions using batch experiments. The Langmuir isotherm model and the pseudo second-order rate equation could explain respectively the isotherm and kinetic experimental data for sole-component system with much satisfaction. The maximum adsorption capacity in single system for Cu (II), Pb (II) and Cd (II) was calculated to be 2.27mmol/g, 1.27mmol/g and 0.65mmol/g individually. The initial adsorption rate followed the order as Cu (II)>Pb (II)>Cd (II) at the fixed initial concentration, and for each metal the initial sorption rate increased as the initial concentration increased. In addition, the modified Langmuir model could describe the binary competitive adsorption behavior successfully, with which the interaction coefficient was obtained to follow the order as Cu (II)<Pb (II)<Cd (II). Furthermore, in every case of the investigated three binary systems, the reduction in both the uptake amounts and distribution coefficients testified the antagonistic competitive phenomena. Obviously, this novel IDA-chelating resin possessed of a good selectivity toward Cu (II) over Pb (II) and Cd (II) for the obtained highest separation factor values were up to 21.30 and 133.91 in the range of tested. This interaction mechanism between the favorable component and other metal ions could mainly contribute to the direct displacement impact which be herewith illustrated schematically.

Single-component and competitive adsorption of levulinic/formic acids on basic polymeric adsorbents

The adsorption equilibria of single-component and binary mixtures of levulinic/formic acids in the aqueous solution on three different types of basic polymeric adsorbents were experimentally measured at 30 °C. Adsorption isotherms such as Langmuir, Freundlich and Sips were applied to correlate the single-solute adsorption data. Results demonstrated that the adsorption isotherms of both acids on all three adsorbents were best described by the Sips model, and that formic acid has higher adsorption capacity and stronger affinity on all three resins. The adsorption of binary mixtures of formic/levulinic acids reveals that formic acid is preferentially adsorbed and levulinic acid can be competitively displaced by formic acid. Binary Sips model and the ideal adsorbed solution (IAS) theory were employed to simulate the binary competitive adsorption data. The binary Sips model cannot predict the competitive adsorption behavior. The IAS model was successfully coupled with Sips isotherm parameters determined from single-component adsorption data to predict the binary competitive adsorption behavior of levulinic/formic acids on all three resins.

Determination of competitive adsorption isotherm parameters of pindolol enantiomers on α 1-acid glycoprotein chiral stationary phase

In this paper, inverse method (IM) was used to determine the binary competitive adsorption isotherm of pindolol enantiomers by a least-square fitting of the proposed model to the experimentally measured elution curves of racemic pindolol. The isotherm parameters were determined by minimizing the least-square error using an adaptation of genetic algorithm, non-dominated sorting genetic algorithm with jumping genes (NSGA-II-JG). An equilibrium dispersive (ED) model combined with bi-Langmuir isotherm was used in predicting the elution profiles. The determined parameters show good agreement with the experimental profiles at various experimental conditions such as sample volume, concentration and flow rates of the racemic mixture. Robustness and validity of the isotherm parameters were also verified by frontal analyses at various step inputs. Results from both the pulse tests and the frontal analysis indicate that adsorption isotherm derived from the inverse method is quite reliable. This method requires relatively less number of experiments to be performed and therefore, lower experimental costs confirming that inverse method is an attractive alternative approach of experimental technique in determining the competitive adsorption isotherm for binary systems.

Synthesis and characterization of creatinine imprinted poly(4-vinylpyridine- co-divinylbenzene) as a specific recognition receptor

In this study, molecularly imprinted poly(4-vinylpyridine- co-divinylbenzene) (poly(4-VP- co-DVB)) as the specific receptor of creatinine was prepared by heated polymerization. 4-Vinylpyridine (4-VP) was used as the functional monomer. Creatinine was used as the template and divinylbenzene (DVB) was the cross-linking agent. After polymerization, water was applied to remove the imprinted creatinine from the polymer. Approximately 72% of the imprinted creatinine template was extracted. Solid-state 13C NMR was used to analyze qualitatively the imprinting effect of the synthetic polymer. Adsorption results of creatinine by the imprinted poly(4-VP- co-DVB) and the corresponding non-imprinted polymer were compared. Maximum imprinting ratio of 4.56, defined as the maximum binding capacity of the MIP to that of non-MIP, was achieved. The adsorption kinetics could be precisely described by Langmuir isotherms. The kinetic parameters, Q m and K m, with the respective values of 11.95 mg/g and 0.11 dL/g were obtained. Imprinting ratio of the creatinine imprinted poly(4-VP- co-DVB) was also obtained. Selectivity factors of the imprinted poly(4-VP- co-DVB) defined as the binding of creatinine with respect to the other analogs ranging from 2.0 to 4.0 were obtained. The major detection interference of creatinine for clinical applications may come from creatine. Therefore, the creatinine/creatine binary competitive adsorption experiment was also carried out to evaluate the specific recognition ability of the polymer. The binding specificity of the imprinted poly(4-VP- co-DVB) toward creatinine was thus confirmed.

Equilibrium Adsorption of Single Component and Binary Mixtures of Aromatic Compounds onto a Polyfunctional Hypercrosslinked Polymeric Adsorbent

A polyfunctional hypercrosslinked polymeric adsorbent, LA-8, was synthesized and characterized. It was first used to investigate the adsorption properties of 1-amino-2-naphthol-4-sulphonic acid (1,2,4-acid), including the corresponding adsorption isotherms, thermodynamics and binary competitive adsorption with 2-naphthol. The Freundlich model gave good fits to both the single and binary adsorption isotherms, indicating an endothermic and favourable adsorption process. The positive value of ΔH0 for the single solute system was in the range of 30-60 kJ/mol showing the existence of integrated processes involving chemical interaction. The values of ΔG0 demonstrated the spontaneous nature of the adsorption process while the value of ΔS0 showed increased randomness at the solid-solution interface, thereby indicating the presence of stoichiometric displacement. Both ΔH0 and ΔS0 appeared to vary linearly with increased solid loading, qe. Pre-adsorbed 2-naphthol molecules supplied another adsorption site for 1,2,4...

Modeling chromatographic chiral separations under nonlinear competitive conditions

AbstractThe chromatographic separation of Tröger's base enantiomers with ethanol as eluent on microcrystalline triacetate cellulose (CTA) was studied. Binary competitive adsorption equilibrium data measured were interpreted using ideal adsorbed solution and real adsorbed solution (RAS) theory. Both models were used to simulate a set of column breakthrough experiments. The competitive behavior of the two enantiomers is quantitatively discussed and the reliability of the two models is assessed. The results show that the RAS model can describe with good accuracy the complex competitive adsorption behavior exhibited by the CTA/Tröger's base model system. This conclusion is expected to apply to the adsorption of the other enantiomeric mixtures on chiral stationary phases.

Comparison between the hodograph transform method and frontal chromatography for the measurement of binary competitive adsorption isotherms

Frontal analysis is an accurate method of isotherm determination. However, for the study of binary competitive isotherms, it requires a large number of measurements, it is time consuming and it needs excessive amounts of pure chemicals. The hodograph transform method is of considerable interest because it uses much smaller amounts of chemicals. It requires validation. In this work, the potential precision and accuracy of the two methods were compared and the optimum experimental conditions for each were determined on the basis of simulation study.