MODELING ERYTHROMYCIN ADSORPTION TO THE MACROPOROUS RESIN SEPABEAD SP825

We examined the adsorption of aqueous erythromycin (EM) to the macroporous resin Sepabead SP825 in a series of batch experiments. The equilibrium data were well described by a Langmuir isotherm. The free energy, enthalpy, and entropy of adsorption were calculated, and a film and pore diffusion model was used to simulate the mass transfer mechanism, taking into account diffusion across the liquid film surrounding individual particles and diffusion within the resin particle. The model predictions were consistent with the experimental data and consequently were used to determine the mass transfer coefficients.     

Adsorption of Lignosulfonate Compound from Aqueous Solution onto Chitosan-Silica Beads

The main objective of this study is to investigate the possibility of crosslinked chitosan-tetraethoxy orthosilane (TEOS) (chitosan-silica) beads to be used as an adsorbent material to adsorb the lignosulfonate compound in solution. Different parameters affecting the adsorption capacity such as contact time, adsorbent dosage, initial concentration, pH, ionic strength, and temperature have been investigated. Adsorption isotherms of lignosulfonates onto chitosan-silica beads were also studied. Batch adsorption experiments were carried out and the optimum lignosulfonate adsorption onto chitosan-silica beads occurred at contact time of 30 minutes, the adsorbent dosage of 40 g/L, initial concentration of 50 mg/L, pH 5, and a temperature of 45°C. Adsorption isotherms studied through the use of graphical methods revealed that the adsorption of lignosulfonates onto chitosan-silica beads follows the Langmuir model, with the maximum adsorption capacity being 238.3 mg/g at pH 7. Adsorption is dependent on the ionic strength. The adsorption of lignosulfonate on chitosan-silica beads was best described with the pseudo-second-order kinetic model with a rate constant of 0.32 g · mg^?1 · min^?1, while intra-particle-diffusion was the main rate-determining step in the lignosulfonate adsorption process. The chitosan-silica beads investigated in this study were thus exhibited as a high potential adsorbent for the removal of lignosulfonate from solution.     

Performance of Unmodified Paper Solid Waste for Cadmium Removal From Aqueous Phase: Equilibrium and Kinetic Studies

The reuse of paper solid waste (PSW) as a low-cost sorbent for Cd removal from aqueous phase was investigated. Batch experiments were conducted to study the effects of pH (3.5, 5.5, 7.5), contact time (10–360 min), PSW dose (2.5–20 g L^?1), and Cd concentration (5–50 mg L^?1) at an ionic strength of 0.01 M NaNO₃ on adsorption efficiency and capacity. Cd removal of ～96% occurred in 20 mg L^?1 Cd solution at pH 5.5 containing 20 g L^?1 PSW. Equilibrium was attained after 120 min and the equilibrium adsorption capacity of PSW increased with increasing Cd concentration from 5 to 50 mg L^?1. The kinetic process of Cd adsorption obeyed the pseudo-second-order kinetic model. Langmuir and Freundlich models described equally well the experimental data and the maximum adsorption capacity was 4.89 mg g^?1. PSW can be used for reducing Cd concentration in Cd-contaminated water systems.     

Removal of Copper (II) Ions from Aqueous Solutions using Na‐mordenite

Abstract

The potential to remove copper (II) ions from aqueous solutions using Na‐mordenite, a common zeolite mineral, was thoroughly investigated. The effects of relevant parameters solution pH, adsorbent dose, ionic strength, and temperature on copper (II) adsorption capacity were examined. The sorption data followed the Langmuir, Freundlich, and Dubinin‐Radushkevich (D‐R) isotherms. The maximum sorption capacity was found to be 10.69 mg/g at pH 6, initial concentration of 40 mg/dm³, and temperature of 40°C. Different thermodynamic parameters viz., changes in standard free energy (ΔG⁰), enthalpy (ΔH⁰), and entropy (ΔS⁰) have also been evaluated and the results show that the sorption process was spontaneous and endothermic in nature. The dynamics of the sorption process were studied and the values of rate constant of adsorption, rate constant of intraparticle diffusion were calculated. The activation energy (E_a) was found to be 11.25 kJ/mol in the present study, indicating a chemical sorption process involving weak interactions between sorbent and sorbate. The interaction between copper (II) ions and Na‐mordenite is mainly attributable to ion exchange. The sorption capacity increased with the increase of solution pH and the decrease of ionic strength and adsorbent dose. The Na‐mordenite can be used to separate copper (II) ions from aqueous solutions.     

A novel lanthanum-modified bentonite,Phoslock, for phosphate removal from wastewaters

Phoslock^®, a lanthanum-modified bentonite, has been investigated for phosphate uptake from synthetic and real wastewaters in laboratory and field. In laboratory tests, equilibrium and kinetics were studied at various temperatures, ionic strength, and pHs. The investigation indicated that phosphate adsorption occurs through a chemisorption process. The activation energy of the adsorption process was calculated based on pseudo-second order rate constant. The maximum adsorption capacity of Phoslock was unaffected at pH 5–7, but decreased at higher pHs. The monovalent phosphate anion, H₂PO₄⁻, had the greatest affinity for the adsorbent surface. Furthermore, it was also shown that the activation energy was lower at a higher solution pH attributed to the loss of adsorption sites at the higher pHs while it remained unaffected by the ionic strength of the solution. A field test also demonstrated that the Phoslock works well for phosphate uptake in polluted waters.     

Mass transfer mechanisms in fixed-bed adsorption of erythromycin

The equilibrium and kinetic characteristics of the adsorption of erythromycin to Sepabeads SP825 were determined. The equilibrium data in a batch system was well described by a Langmuir isotherm. The separation performance was investigated in a fixed-bed system with respect to the adsorption superficial velocity, ionic strength and pH. A mathematical model was used to simulate the mass transfer mechanism, taking film mass transfer, pore diffusion and axial dispersion into account. The model predictions were consistent with the experimental data and were consequently used to determine the mass transfer coefficients.     

Mass transfer mechanisms in fixed-bed adsorption of erythromycin

The equilibrium and kinetic characteristics of the adsorption of erythromycin to Sepabeads SP825 were determined. The equilibrium data in a batch system was well described by a Langmuir isotherm. The separation performance was investigated in a fixed-bed system with respect to the adsorption superficial velocity, ionic strength and pH. A mathematical model was used to simulate the mass transfer mechanism, taking film mass transfer, pore diffusion and axial dispersion into account. The model predictions were consistent with the experimental data and were consequently used to determine the mass transfer coefficients.     

COMPARISON OF ION EXCHANGE AND DONNAN EQUILIBRIUM MODELS FOR THE PH-DEPENDENT ADSORPTION OF SODIUM AND CALCIUM IONS ONTO KRAFT WOOD PULP FIBERS

ABSTRACT

Management of nonprocess element (NPE) accumulation in pulp washing operations requires equilibrium models that predict the distribution of metals between the wash liquor and the pulp fibers. The overall goal of this study was to assess models for predicting the multi-component adsorption of hydrogen ions (H⁺), sodium ions (Na⁺), and calcium ions (Ca⁺²) onto bleached and unbleached kraft pulp fibers over a pH range of 2.7–11. As part of this study, binary equilibrium constants for hydrogen and metal ion exchange on carboxylate sites in bleached pulp (0.041 meq/g dry pulp) were measured at 25°C, with log K ^Na/Ca = ?1.604 ± 0.119, log K ^H/Ca = 0.633 ± 0.087, and intrinsic dissociation constant pK _io of 3.64 ± 0.46. Ion exchange and Donnan equilibrium models adequately predicted the multi-component equilibrium data for competitive adsorption of H⁺, Na⁺, and Ca⁺² onto bleached kraft wood pulp fibers. The ion exchange model was fully predictive, whereas the Donnan model required that the solution pH be known. At pH 2.7–6, the Donnan model predicted the adsorption of Na⁺ and Ca⁺² onto both bleached and unbleached wood pulp fibers better than the ion exchange model. The ion exchange model assumed that residual carboxylate in the pulp served as the only site for the competitive binding of hydrogen and metal ions. In contrast, the Donnan model assumed a non site-specific distribution of metal ions between charged fiber and external solution phases and a carboxylate site specific adsorption of hydrogen ions. Above pH 6, both models failed to predict that the calcium adsorption on unbleached brownstock pulp increased beyond the carboxylate site capacity, suggesting that other functional groups within the brownstock pulp with intrinsic dissociation constant values higher than carboxylate were providing additional binding sites for calcium.     

p-Sulphonatocalix[8]arene functionalized silica resin for the enhanced removal of methylene blue from wastewater: equilibrium and kinetic study

ABSTRACT

The present investigation represents the synthesis of new p-sulphonatocalix[8]arene-based silica resin, p-SC8SR (5) and its application for the enhanced removal of methylene blue (MB) dye from contaminated water. The new p-SC8SR (5) resin was characterized by FT-IR, SEM, and EDX spectroscopy. The adsorption of MB on p-SC8SR (5) was investigated systematically by evaluating the effects of adsorbent dosage, initial pH, contact time, dye concentration, and ionic strength. Excellent adsorption (94%) of MB on p-SC8SR (5) was achieved at pH 9.5, contact time 10 min by using 0.2 mol L^?1 ionic strength and 2 × 10^?5 M initial MB dye concentration. Kinetic behavior of MB dye adsorption process on the newly synthesized p-SC8SR (5) adsorbent follows the pseudo-second-order rate model (R² = 0.998 and 0.999 for 2 × 10^?5 M and 1 × 10^?4 M, respectively). Adsorption isotherms were fitted well by the Freundlich model with excellent value of coefficient of determination (R²) = 0.995 which demonstrated that the adsorption of MB follows multilayer mechanism. Wastewater samples contaminated with MB were used to assess efficiency of the p-SC8SR (5) adsorbent. Results indicated that newly synthesized p-SC8SR (5) was found to be efficient adsorbent. During the removal process, the role of different functional groups’ cyclic structure was scrutinized and found that the ionic property as well as π–π interaction of host molecules played imperative role in the extent of adsorption.     

Usability of activated carbon with well-developed mesoporous structure for the decontamination of malachite green from aquatic environments: kinetic,equilibrium and regeneration studies

This study examines the potential use of activated carbon (TAC) produced under optimized conditions from tomato processing waste (TW) as an adsorbent for the removal of malachite Green (MG) dye from aqueous solution. Batch experiments tested the effects of TAC dosage, initial concentration, contact time, ionic strength and temperature on adsorption property of TAC at the natural pH of TAC-MG in the aqueous medium. The adsorption kinetics could be expressed well by the pseudo-second order model. Intra-particle diffusion model process shows that it is governed by several mechanisms. Equilibrium data fitted well to the Langmuir isotherm. The maximum adsorption capacity was found as 526.32 mg/g at pH 4.0 and 328 K. Thermodynamic studies indicated that the process was endothermic and spontaneous.     

Adsorption Characteristics of Chromium(VI) Ions onto Fe(III)-Coordinated Amino-Functionalized Poly(glycidylmethacrylate)-Grafted TiO2-Densified Cellulose

An investigation was conducted with a newly developed adsorbent, iron(III)- coordinated amino-functionalized poly(glycidylmethacrylate)-grafted TiO₂-densified cellulose (Fe(III)-AM-PGDC) on the removal of chromium(VI) from aqueous solution. Batch experiments were performed under various conditions of time, pH, concentration, dose, ionic strength, and temperature. Adsorption of Cr(VI) on Fe(III)-AM-PGDC was dominated by ion exchange or outer-sphere complexation. The maximum adsorption capacity was found to be 109.76 mg g^?1. Thermodynamic study showed that adsorption of Cr(VI) onto Fe(III)-AM-PGDC is more favored. The complete removal of Cr(VI) from electroplating wastewater was achieved by the adsorbent. The adsorbent did not lose its adsorption capacity even after the fourth regeneration.     

CORROSION INHIBITION AND ADSORPTION BEHAVIOR OF MALACHITE GREEN DYE ON ALUMINUM CORROSION

Malachite green dye (MG) was studied as a corrosion inhibitor for aluminum in 1.0 mol dm^?3 HCl and 0.5 mol dm^?3 KOH using the gravimetric technique. The results revealed an inhibiting effect of MG, which was highly restrained in 0.5 M KOH and pronounced in 1.0 M HCl. MG inhibited the corrosion reaction in the acidic medium by adsorption on the metal/solution interface following the Flory-Huggins isotherm. Inhibition efficiency increased with MG concentration and synergistically increased in the presence of iodide ions, but decreased with a rise in temperature. The local reactivity of the MG molecule was analyzed theoretically using the density functional theory to explain the adsorption characteristics, while molecular dynamics simulations were performed to illustrate the adsorption structure of MG at a molecular level. The theoretical predictions showed good agreement with experimental results.     

Separation of salidroside from the fermentation broth of engineered Escherichia coli using macroporous adsorbent resins

Salidroside (8-O-β-D-glucoside of tyrosol), a plant-derived natural product, is used for treatment of hypoxia, fatigue and aging diseases. The availability of salidroside is restricted since it is extracted from 3-5 years old Rhodiola roots, which grow very slowly in the cold region of northern hemisphere of Earth. Our laboratory has constructed an engineered Escherichia coli and established a fermentation process to produce salidroside from glucose. In this article, nine macroporous resins from polarity to non-polarity, including NKA-9, S-8, AB-8, SP825, D101, LSA-8, LX-12, LX-18 and LX-68 resins, were tested to separate salidroside from fermentation broth. After static and dynamic experiments, the weakly polar SP825 resin had a better separation efficiency among nine resins. The adsorption kinetic and isotherm of salidroside on the SP825 resin were determined, and the pseudo-second-order kinetic model and Langmuir model could be fitted well. The effects of the pH on adsorption and ethanol concentration on desorption were investigated, and an optimal separation process was established. The adsorption for salidroside in the SP825 resin column was conducted with loading 150 ml at pH 7, and desorpted by washing 50 ml of 80% ethanol solution. Under the best process conditions, the purity and yield of salidroside in the final product were 91.6% and 74.0%, respectively. The results showed that the macroporous SP825 resin would be feasible and effective to prepare salidroside and has promising application in the downstream process of microbial fermentation.     

Dye Attached Nanoparticles for Lysozyme Adsorption

In this work, Reactive Blue 15 dye functionalized poly(HEMA) nanoparticles were synthesized for reversible adsorption of lysozyme from its aqueous solution. For this, nano-sized poly(HEMA) nanoparticles were synthesized by the surfactant free emulsion polymerization. Reactive Blue 15 dye then covalently attached to the polymeric structure. These novel dye attached poly(HEMA) nanoparticles were used for the adsorption of lysozyme. Characterization of dye attached nanoparticles was carried out by using FTIR, AFM, and elemental analysis. Incorporation of the dye onto the polymeric structure was demonstrated by FTIR and elemental analysis, while the size and the shape of the nanoparticles were shown by AFM. The incorporated amount of the dye was found to be 70.3 μmol/g nanoparticle with sulphur stoichiometry and it was found that the prepared nanoparticles were in a spherical form and were about 100 nm diameter. Lysozyme adsorption studies were carried out with different conditions (pH, lysozyme concentration, temperature, and ionic strength) and maximum lysozyme adsorption was found to be 630.7 mg/g nanoparticle at pH 7.0 in 25°C medium temperature. Adsorbed lysozyme was desorbed by 1.0 M of NaCl with 96% recovery and synthesized dye-attached nanoparticles were used 10 times without any decrease in their adsorption capacity.     

SYNTHESIS OF ACTIVATED CARBON FROM JATROPHA SEED COAT AND APPLICATION TO ADSORPTION OF IODINE AND METHYLENE BLUE

This article provides evidence that jatropha seed coat residues can be used as a carbon source for preparing activated carbons that have good adsorption properties for iodine and methylene blue. Activated carbons were prepared using three different methods of activation, physical, chemical, and physico-chemical, for a range of activation temperatures (600°, 700°, 800°, and 900°C) and activation hold times (1, 2, and 3 h). The highest BET surface area (1479 m² g^?1) and the highest iodine adsorption (1511 mg g^?1) were obtained with physico-chemical activation at a temperature of 900°C and a hold time of 2 h. This activated carbon gave higher BET surface area and iodine adsorption than commercial activated carbon (1169.1 m² g^?1 and 1076 mg g^?1). The activated carbons prepared by physico-chemical activation at 900°C and 2 h were then tested for adsorption of methylene blue at a range of concentrations of methylene blue (100, 200, 300, 400, and 500 mg L^?1). It was found that a Langmuir isotherm gave a better fit (R ² = 0.999) to the observed adsorptions than a Freundlich isotherm (R ² = 0.884). For the adsorption kinetics, a pseudo-second-order model gave a better fit (R ² > 0.998, Δq _e  = 3.7%) than a pseudo-first-order model (R ² ≈ 0.95, Δq _e  = 85.6%). These results suggest that chemisorption is the rate-controlling step for the adsorption of methylene blue. The experimental results show that jatropha seed coat is a lignocellulosic waste precursor for preparation of activated carbon that is an alternative source for preparation of commercial-grade activated carbons.     

Removal of Basic Dye Crystal Violet from Aqueous Solution by Cu(II)-Loaded Montmorillonite

The effects of contact time, reaction temperature, and ionic strength on crystal violet adsorption onto Cu(II)-loaded montmorillonite were studied. The kinetic experimental data were analyzed using pseudo-first-order, pseudo-second-order, and Elovich equations to examine the adsorption mechanism. The result suggested that the adsorption was best represented by the pseudo-second-order equation. The suitability of the Langmuir, Freundich, and Temkin isotherms to equilibrium data was also investigated at 25°C. The maximum adsorption capacity was 114.3 mg dye/g Cu(II)-loaded montmorillonite at adsorbent concentration 1 g/L. The differential heat of adsorption was evaluated and the result showed that adsorption of crystal violet onto the Cu-loaded sample was chemical in nature. The ionic strength and reaction temperature exhibited an insignificant impact on the crystal violet adsorption. The Cu(II)-loaded montmorillonite could serve as low-cost adsorbents for removing crystal violet from aqueous solution compared to the data reported in the literature.     

Synthesis and application of nanocomposite Fe3O4@SiO2@CTAB–SiO2 as a novel adsorbent for removal of cyclophosphamide from water samples

ABSTRACT

We present a way of synthesizing nanocomposite Fe₃O₄@SiO₂@CTAB–SiO₂ by employing simple sol–gel technique with selective etching for extreme selectivity adsorption of cyclophosphamide (CP). The transmission electron microscopy (TEM); scanning electron microscopy (SEM); X-ray diffraction (XRD); Fourier transform infrared (FT-IR); vibrating sample magnetometer (VSM); pH_PZC; and Brunauer, Emmett and Teller (BET) techniques were used for nanocomposite characterization. These nanoparticles have an S_BET of 157.8 m² g^?1 and a high saturation magnetization of 67.5 emu g^?1. First, the adsorption system was examined as a function of contact time under various initial CP contents, ionic strength, initial solution pH, adsorbent dose and temperature in batch test. The optimum dose, pH and contact time were obtained to be 0.01 g, 7.0 and 30 min, respectively. Ultimately, experimental isotherm and kinetics data of adsorption of CP onto nanocomposite Fe₃O₄@SiO₂@CTAB–SiO₂ were fitted to classical models. Additionally, it was found that the maximum adsorption process capacity of CP on adsorbent was 342.8 mg g^?1.     

Analysis of statistical thermodynamic model for binary protein adsorption equilibria on cation exchange adsorbent

A study of nonlinear competitive adsorption equilibria of proteins is of fundamental importance in understanding the behavior of preparative chromatographic separation. This work describes the nonlinear binary protein adsorption equilibria on ion exchangers by the statistical thermodynamic (ST) model. The single-component and binary protein adsorption isotherms of bovine hemoglobin (Hb) and bovine serum albumin (BSA) on SP Sepharose FF were determined by batch adsorption experiments in 0.05 mol/L sodium acetate buffer at three pH values (4.5, 5.0 and 5.5) and three NaCl concentrations (0.05, 0.10 and 0.15 mol/L) at pH 5.0. The ST model was found to depict the effects of pH and ionic strength on the single-component equilibria well, with model parameters depending on the pH and ionic strength. Moreover, the ST model gave acceptable fitting to the binary adsorption data with the fitted single-component model parameters, leading to the estimation of the binary ST model parameter. The effects of pH and ionic strength on the model parameters are reasonably interpreted by the electrostatic and thermodynamic theories. Results demonstrate the availability of the ST model for describing nonlinear competitive protein adsorption equilibria in the presence of two proteins.     

Adsorption of uranium on phosphoric acid-activated peanut shells

ABSTRACT

Phosphoric acid-activated peanut shells (PS) were prepared by hydrothermal treatment at 200–800 °C and denoted as peanut shell-activated carbons (PACs). The PACs were characterized as adsorbent for removing U(VI) from aqueous solutions. The U(VI) adsorption on PACs follows the pseudo-second-order kinetic equation and the Langmuir model. The adsorption capacity depends on solution pH and ionic strength and PAC-800 exhibits the highest adsorption capacity. The increasing U(VI) adsorption could be attributed to C = OOH groups and delocalized π electrons as sorption sites by surface complexation and ion exchange. Therefore, PACs as economic adsorbents could potentially remove U(VI) from aqueous solutions.     

EQUILIBRIUM,KINETICS, AND BREAKTHROUGH STUDIES FOR ADSORPTION OF Cr(VI) ON CHITOSAN

Wastewater containing low levels of pollutants can be effectively treated by the adsorption technique. In the present work, an adsorption study was carried out using chitosan as adsorbent in a fixed-bed column for the removal of Cr(VI) from wastewater solutions. The column performance of Cr(VI) adsorption onto chitosan was studied at different bed heights (3–9 cm), flow rates (50–200 mL/min), initial metal concentrations (2–10 mg/L), pH values (2–7), and temperatures (30°–60°C). The equilibrium data for the batch adsorption of Cr(VI) on chitosan were tested using the Langmuir, Freundlich, and BET isotherm models. The Langmuir model was found to be the most suitable, with a maximum adsorption capacity of 35.7 mg/g and a correlation coefficient (R ²) = 0.952. The experimental data were found to fit well with the pseudo-second-order kinetic model, with R ² = 0.999. The dynamics of the adsorption process was modeled using the Adams-Bohart, Thomas, and mass transfer models. The models were used to predict the breakthrough curves of adsorption systems and to determine the characteristic design parameters of the column. The adsorption data were observed to fit well with all three models. The model parameters were derived using MATLAB software. In order to compare quantitatively the applicability of adsorption dynamic models in fitting to experimental data, the percentage relative deviation (P) was calculated and found to be less than 5, confirming that the fit is good for all three models.