Ivanildo Silva

Modeling of the fixed - bed adsorption of carbon dioxide and a carbon dioxide - nitrogen mixture on zeolite 13X

In this study, the fixed-bed adsorption of carbon dioxide and a carbon dioxide-nitrogen mixture on zeolite 13X was investigated. The adsorption equilibrium and breakthrough curves were determined at different temperatures - 301-306 K, 323 K, 373 K and 423 K. A model based on the LDF approximation for the mass transfer, considering the energy and momentum balances, was used to describe the adsorption kinetics of carbon dioxide and a carbon dioxide-nitrogen mixture. The model acceptably reproduced all of the breakthrough curves and can be considered as adequate for designing a PSA cycle to separate carbon dioxide- nitrogen mixtures.

Adsorption of Anionic and Cationic Dyes from Aqueous Solution on Non-Calcined Mg-Al Layered Double Hydroxide: Experimental and Theoretical Study

Non-calcined Mg-Al layered double hydroxide (LDH) with Mg/Al molar ratio of 3:1 was synthesized using the co-precipitation method. Sorption of anionic (acid blue 25 - AB25, reactive blue 4 - RB4), and cationic (methylene blue - MB) dyes by Mg-Al LDH form aqueous solution was investigated. The effect of solution pH, initial concentration, and contact time were investigated by batch adsorption experiments. The adsorbed amount increases with decrease in pH solution for AB25 and RB4. The cationic dye (MB) solution was insensitive to pH variation and also exhibited a low performance in the kinetic equilibrium studies. While anionic dyes were almost completely extracted from the solution, 90% of the methylene blue remained in solution. The equilibrium data were well described using the Langmuir-Freundlich model for RB4, AB25, and MB dyes with maximum adsorption capacity of 328.90, 246.10, and 43.48 mg/g, respectively. Finally, the mechanism of adsorption involving the dyes and LDH was evaluated using the Monte Carlo approach in the NVT ensemble. The results suggest that molecular simulation can be used to preview quantitatively the dye uptake. Supplemental materials are available for this article. Go to the publishers online edition of Separation Science & Technology to view the supplemental file.

Dye Ligand Epoxide Chitosan/Alginate: A Potential New Stationary Phase for Human IgG Purification

Cibacron Blue F3GA immobilized as ligand onto epoxide chitosan/alginate composite was prepared and evaluated for the purification of human immunoglobulin G (IgG) isolated from human serum by dye-ligand affinity chromatography. The effect of buffer pH on IgG adsorption, kinetic and isothern adsorption of high-purity IgG were studied by batch adsorption. The adsorption isotherm data were well fitted (using 25 mmol/L sodium phosphate buffer at pH 6.0) by the Langmuir–Freundlich model with a maximum adsorption capacity of 99 mg/g, apparent dissociation constant of 1.2 × 10−6 mol/L and n equal to 4.86. Fixed-bed experiments were performed using high-purity IgG, achieving a recovery rate of 53%. Human serum diluted ten times was also injected into the column. An enrichment of IgG in the elution fraction with traces of human serum albumin was observed. According to the study results, this material can be applied in the purification of human IgG under optimized conditions.

Human IgG adsorption using dye-ligand epoxy chitosan/alginate as adsorbent: influence of buffer system

The aim of this work was to evaluate the ability of Cibacron Blue F-3GA dye-ligand chitosan/alginate epoxide on human IgG adsorption under different buffer systems at 25xa0mmolxa0L−1: Morpholinoethane sulfonic acid, morpholinopropane sulfonic acid, hydroxyethylpiperazine ethanesulfonic acid and tris-hydroxymethyl aminomethane (Tris–HCl). Batch adsorption studies were performed in order to evaluate the effect of buffer pH and nature on IgG uptake as well the equilibrium isotherms. Chromatographic experiments were performed with both human IgG (high purity) and human serum and each buffer with NaCl 1.0xa0M was used in the elution step. Best results (maximum equilibrium adsorption capacity of 110.9xa0mgxa0g−1) were found at pH 7.8 with Tris–HCl buffer. The Langmuir–Freundlich model provided a good fit for the adsorption isotherm. In chromatographic experiments with high purity IgG and Tris/HCl buffer, IgG dynamic adsorption capacity onto E-Ch/Al-Cibacron was 13.4xa0mgxa0g−1, which accounted for 60xa0% of IgG injected into the column. Chromatographic experiments with diluted (tenfold) human serum were conducted and it was found by electrophoresis that IgG is preferentially adsorbed with respect to other proteins using all buffers systems, especially with Tris–HCl. The amount of desorbed protein from E-Ch/Al-Cibacron was around 7.0xa0mgxa0g−1 for all buffers. The new stationary phase showed high affinity for IgG and may be a potential adsorbent for human IgG purification.

Adsorption behavior of bovine serum albumin on Zn–Al and Mg–Al layered double hydroxides

In this work, non-calcined Mg–Al and Zn–Al layered double hydroxides (LDHs) with molar ratio of 3:1 were investigated for the adsorption of bovine serum albumin (BSA). Both LDHs were synthesized using the co-precipitation method and were characterized by X-ray diffraction, N2 adsorption–desorption isotherm at −196xa0°C, elemental analysis and X-ray photoelectron spectroscopy. The adsorption of BSA was evaluated in a batch adsorption system to assess the influence of buffer solution and buffer pH, contact time and initial concentration. Fixed-bed adsorption experiments were also performed in order to evaluate the dynamic adsorption behavior of BSA on the LDH as well as the regenerability of this material. In the batch adsorption experiments, the maximum amount of BSA adsorbed was reached at its isoelectric point (pIxa0=xa04.8) with 50xa0mM acetate buffer for Mg–Al LDH and pH 6.7 with 50xa0mM 2-(N-morpholino)ethanesulfonic acid (MES) buffer for Zn–Al LDH. The Langmuir and Langmuir–Freundlich models provided maximum equilibrium adsorption capacity of 338.74 and 346.54xa0mgxa0g−1for Zn-Al LDH, respectively, and 196.12 and 197.80, respectively,xa0for Mg-Al LDH. Column experiments were carried out with a constant flow of 1xa0mLxa0min−1, varying the feed concentration of BSA solutions from 1.0 to 2.0xa0mgxa0mL−1. An average of 98xa0% of BSA injected into the column was retained, and a completely elution was reached using 50xa0mM sodium phosphate with pH 12.Graphical Abstract

Improvement in the Adsorption of Anionic and Cationic Dyes from Aqueous Solutions: A Comparative Study using Aluminium Pillared Clays and Activated Carbon

The aim of this work was to evaluate the adsorption properties of anionic dye Reactive Black 5 (RB5) and cationic dye Methylene Blue (MB) from salted aqueous solution using natural clay, aluminum pillared clay (Al-PILC), and activated carbon. The textural properties of the materials were obtained by N2 adsorption at 77 K and the structural properties of natural and pillared clays were determined by X-ray diffraction. The effect of pH, contact time, initial concentration of dye, and influence of the addition of NaCl were evaluated by batch adsorption. Adsorption isotherms of Al-PILC, in different salt concentration were compared with natural clay and activated carbon. The adsorption isotherms were well fitted by the Langmuir and Langmuir-Freundlich models. The process of pillaring only improved the adsorption of the anionic dye RB5. Depending on the system adsorbent/adsorbate analyzed, the salt concentration can either help or hinder dye adsorption. We found that a special morphology formed during the process of pillaring greatly increased adsorption of the MB cationic dye in the range of high salt concentrations. This unexpected result may help in developing new pillarization strategies to treat effluents with high salt content.

Adsorption of Cellulase Isolated from Aspergillus Niger on Chitosan/Alginate Particles Functionalized with Epichlorohydrin:

This work investigates the adsorption of cellulase (isolated from Aspergillus niger) in a fixed-bed column using chitosan/alginate particles functionalized with epichlorohydrin (Cs/Ag–E) as the adsorbent. The particles were prepared and characterized with respect to apparent density, particle porosity, particle size, surface chemistry and thermal stability. Cellulase solutions were prepared in sodium citrate buffer (20 mM) at pH 5. Several breakthrough curves were obtained by varying the flow rate and feed concentrations in order to evaluate the suitable bed height and determine the adsorption isotherm, respectively. The adsorption isotherm fitted well with Langmuir equation with maximum adsorption capacity of about 11 mg of cellulase/g of adsorbent. Successive cycles (adsorption/washing/elution) were performed and the results demonstrate the reversibility of the process and its potential for enzyme purification and separation. However, cellulase activity in the eluted fraction is only 29% of that of the fresh enzyme fed to the column.

Removal of Reactive Turquoise Blue Dye from Aqueous Solution Using a Non-Conventional Natural Adsorbent

Batch and fixed bed experiments were carried out for the removal of Reactive Turquoise Blue Q-G125% (TB) dye from aqueous solution using cashew apple bagasse (CAB) as non-conventional adsorbent. CAB, a lignocellulosic material, used in this study contained 20.56% ± 2.19% cellulose, 10.17% ± 0.89% hemicellulose, and 35.26% ± 0.90% lignin and was characterized as nonporous material and its surface area cannot be determined by nitrogen adsorption at 77 K. Kinetic and equilibrium study were performed in batch systems, evaluating the effects of pH, contact time, initial concentration, adsorbent loading, and temperature on the adsorption. The pseudo-second-order model best described the adsorption kinetic data. The adsorption isotherms of TB onto CAB were well fitted by the Freundlich model. The maximum adsorption capacity of the biomass was 145.10 mg/g and high levels of dye removal (> 90%) at 60°C. According to thermodynamic results, the adsorption of TB onto CAB is a spontaneous endothermic process. Dynamic adsorption behavior was studied in fixed bed system. The highest bed adsorbed quantity of 32 mg/g with 100 mg/L TB initial concentration at 1 mL/min flow rate and 1.4 cm bed-height was obtained. The results showed that CAB is a promising adsorbent for the adsorption of the dye.

Separation of Lactic Acid Produced by Hydrothermal Conversion of Glycerol Using Ion-Exchange Chromatography

Production of lactic acid by hydrothermal conversion of glycerol is an option to add value to the large amounts of glycerol that is being generated during the production of biodiesel. This work aimed to separate lactic acid by ion-exchange resins in a fixed-bed column. Adsorption isotherms were obtained from the breakthrough curves using different initial concentrations of lactic acid (60–302 g/l) and temperatures (30, 40 and 60 °C). Maximum adsorption capacities were estimated by the Langmuir model. Adsorption and desorption cycles for a binary and a real mixture were performed. The methodology proposed for the separation of lactic acid in a fixed-bed column presented high values of adsorptive capacity for both Amberlite IRA-96 and Amberlite IRA-67 resins at 30 °C. Lactic acid was more strongly adsorbed by Amberlite IRA-96 than the IRA-67 resin with maximum adsorption capacity of 544 and 341 g/l, respectively. Chromatographic experiments for the single-component solution (lactic acid), binary mixture (lactic acid and glycerol) and real mixture showed high values of recovery (29.2%, 31.3% and 23.5%, respectively) and productivity (3.14, 7.00 and 2.43 kg of lactic acid/kg resin. day).