The present research evaluates the adsorption of reactive dyes, Remazol Violet 5R (RV5R) and Acid Blue 25 (AB25), using Porous Clay Heterostructures (PCHs) prepared from natural bentonite. Natural bentonite, PCH with silica pillars (Si-PCH) and PCH with silica-zirconia (SiZr-PCH) were characterized by elemental analysis, XRD, N2 adsorption-desorption at −196°C, FT-IR, TG and XPS. The adsorption experiments were carried out in a stirred tank in order to evaluate the effect of pH, contact time and initial concentration. The adsorption isotherms were well fitted by Langmuir (L), Langmuir-Freundlich (LF) and Redlich Peterson (RP) models. The equilibrium data were described using the Langmuir-Freundlich model for both dyes and both materials, obtaining a maximum adsorption capacity of 209.9mgg−1 and 265.9mgg−1 for AB25 using Si-PCH and SiZr-PCH, respectively. In the case of RV5R, the maximum adsorption capacity was 127.07mgg−1 and 185.7mgg−1 for Si-PCH and SiZr-PCH, respectively. The adsorption process takes place by electrostatic interactions between the silanol groups of the PCHs with functional groups of the dyes, such as amine or hydroxyl. From the obtained results, it can be concluded that PCHs showed to be a promising material for the adsorption of dye.

O objetivo deste trabalho foi sintetizar HDL e avaliar a adsorção das proteínas IgG e HSA. O HDL foi sintetizado pelo método de co-precipitação a pH variável com a inserção dos cátions metálicos Zn e Al na razão molar 2:1. O material foi previamente analisado para a determinação das características químicas e estruturais. Foram realizados estudos em batelada utilizando tanques agitados para avaliar o efeito do pH, o tempo de contato e a concentração inicial na adsorção das proteínas. De acordo com os resultados, a adsorção da HSA ocorreu preferencialmente no pH 4,8 e da IgG no pH 7,0. A fim de favorecer a adsorção de IgG, devido a sua maior importância medicinal, utilizou-se o pH 7,0. O modelo de Langmuir se ajustou aos dados experimentais proporcionando os parâmetros de equilíbrio. As quantidades máximas de adsorção foram em torno de 100,00 mg/g tanto na adsorção de IgG como na adsorção de HSA. O parâmetro KD (constante de dissociação) foi na ordem de 10

The correlation between the adsorption capacity of commercial activated carbons and the pore size distributions in the removal of anionic dyes was investigated. We performed experimental adsorption isotherms measurements of the anionic dyes reactive red 120 (RR120), procion red MX-5B (PRMX-5B) and acid blue 25 (AB-25) in the activated carbons WV1050, Norit R1 and Maxsorb. The activated carbons were carefully characterized by N2 adsorption at 77 K and molecular simulation methods to obtain the PSDs and retention capacity of selected pores (8.9, 18.5 and 30.9 angstrom). Batch experiments were carried out in order to obtain single component dye isotherms. We found that the proposed selected pores of the PSD directly correlates with adsorption capacity when the size of the dye molecule is compatible with the carbon pore size. Between RR120 and PRMX-5B we noted that dye chemistry strongly affect the retention capacity. Based on our results, the use of N2 derived PSD and molecular simulation of dye retention in selected pores can be a useful tool to guide to the optimization of carbon-based adsorbents for dye removal. (C) 2015 Elsevier B.V. All rights reserved.

Este trabalho teve por objetivo sintetizar nanoestruturas de HDL e avaliar a adsorção da proteína BSA. O HDL foi sintetizado através do método de co-precipitação a pH variável. Logo depois o material foi analisado e caracterizado. Foram feitos estudos em batelada, utilizando tanques agitados para avaliar o efeito do pH, da cinética e as isotermas de adsorção. De acordo com os resultados, a adsorção de BSA ocorreu preferencialmente no pH 4,8 em HDL Mg/Al e em pH 6,7 em HDL Zn/Al. Os modelos de Langmuir e Langmuir –Frendlich se ajustaram bem aos dados experimentais, obtendo parâmetros de equilíbrio. As quantidades máximas adsorvidas foram em torno de 180 mg/mL em HDL Zn/Al e 139 mg/mL em HDL Mg/Al.

Natural and cross-linked chitosan spheres were used as adsorbents for oil diesel removal. Natural chitosan was cross-linked with glutaraldehyde and epichlorohydrin. The chitosan spheres were soaked in diesel oil at different concentrations using a batch adsorption system. These experiments were carried out to measure the adsorption capacity of the spheres and the percentage of oil removed from the synthetic solutions. The equilibrium data were well described by the Langmuir and Langmuir—Freundlich models, which indicates that after the chemical modification, the maximum adsorption capacity increased significantly. This increase in adsorption capacity could be explained by modifications of surface characteristics (porosity and roughness) or the formation of new bonds after the cross-linking reactions. Our study results show that bioadsorbents based on chitosan is a promising material for diesel oil removal from organic solutions, and thus can be useful in bioremediation.

Corantes aniônicos são amplamente utilizados na indústria têxtil. Sua elevada estabilidade e toxicidade são grandes causadoras de impactos em sistemas aquáticos. O presente trabalho objetiva avaliar as remoções dos corantes aniônicos reativo vermelho 120 (RV-120; MM = 1469,98 g/mol) e ácido azul 25 (AA-25; MM= 416,38 g/mol) de efluentes têxteis, utilizando um carbono (Norit-1240) como adsorvente. A caracterização do carbono foi realizada através da adsorção-dessorção de N2 a 77 K, da distribuição dos tamanhos de poros e do ponto de carga zero (ZPC). O material apresentou: área superficial de 688 m2/g; diâmetro de poro de 1,7 nm e ZPC de 7,5. Os ensaios foram realizados simulando um sistema de tanque agitado em batelada utilizando um agitador orbital com rotação constante a uma temperatura de 22ºC (±1ºC). Foram investigados o efeito do pH inicial, a cinética de adsorção e as isotermas de equilíbrio. Foram utilizados os modelos de isotermas de equilíbrio de adsorção de Langmuir (L) e Langmuir-Freundlich (LF) para estimação das capacidades máximas de adsorção (qmax), sendo melhor representado pelo modelo Langmuir, apresentando qmax de 40,19 mg/g, para o RV120, e qmax de 221,24 mg/g, para o AA-25. Concluiu-se que o adsorvente apresentou capacidades favoráveis para utilização como adsorvente de corantes têxteis.

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 N-2 adsorption at 77K 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.

In this work a non-calcined Mg-Al layered double hydroxide (Mg-Al LDH) with molar ratio of 3:1 was studied on the adsorption of IgG and HSA. Mg-Al LDH was synthesized using co–precipitation method. This material was characterized by X-ray diffraction (XRD), N2 adsorption-desorption isotherm at 77K, pHzpc, particle size and FTIR. The effects of pH, kinetic and isotherm adsorption of high purity IgG and HSA were studied by batch adsorption. Adsorption of IgG and HSA shows a dependence of solution pH. IgG was more selective for pH higher than 6.5 while HSA was low at the range of pH. The adsorption isotherms were well fitted to Langmuir and Freundlich models. The maximum IgG adsorption, achieved using 25 mmol/L sodium phosphate buffer at pH 6.5, was 164.88 mg/g obtained by Langmuir model . The maximum adsorption capacity to HSA was five times less than IgG, around 31 mg/g also Langmuir model. Studies on fixed bed in better conditions for IgG adsorption was performance to evaluate the adsorption from both proteins. The results showed the high IgG adsorbed on MgAl LDH.

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 publisher's online edition of Separation Science & Technology to view the supplemental file.