Sirlane Aparecida Abreu Santana

Kinetics and thermodynamics of textile dye adsorption from aqueous solutions using babassu coconut mesocarp

Extracted babassu coconut (Orbignya speciosa) mesocarp (BCM) was applied as a biosorbent for aqueous Blue Remazol R160 (BR 160), Rubi S2G (R S2G), Red Remazol 5R (RR 5), Violet Remazol 5R (VR 5) and Indanthrene Olive Green (IOG) dye solutions. The natural sorbent was processed batchwise while varying several system parameters such as stirring time, pH and temperature. The interactions were assayed with respect to both pseudo-first-order and second-order reaction kinetics, with the latter the more suitable kinetic model. The maximum adsorption was obtained at pH 1.0 for all dyes due to available anionic groups attached to the structures, which can be justified by pH(pzc) 6.7 for the biosorbent BCM. The ability of babassu coconut mesocarp to adsorb dyes gave the order R S2G>VR 5>BR 160>IOG>RR 5, which data were best fit to Freundlich model, but did not well-adjusted for all dyes. The dye/biopolymer interactions at the solid/liquid interface are all spontaneous as given by free Gibbs energy, with exothermic enthalpic values of -26.1, -15.8, -17.8, -15.8 and -23.7 kJ mol(-1) for BR 160, R S2G, RR 5, IOG and VR 5, respectively. In spite of the negative entropic values contribution, the set of thermodynamic data is favorable for all dyes removal. However, the results pointed to the effectiveness of the mesocarp of babassu coconut as a biosorbent for removing textile dyes from aqueous solutions.

Immobilization of ethylenesulfide on babassu coconut epicarp and mesocarp for divalent cation sorption

A new synthetic methodology route consisted in reacting the natural babassu coconut mesocarp (BCM) and babassu coconut epicarp (BCE) with ethylenesufide, for adding basic sulfur centers in pendant chains that possess high potential activity for coordinating divalent cations from aqueous solution. All biomaterials were characterized by elemental analysis, infrared (IR), (13)C NMR and thermogravimetry. The sulfur elemental analysis gave 2.00+/-0.05 and 8.67+/-0.01% for BCES and BCMS, which correspond to 0.60+/-0.01 and 2.71+/-0.01 mmol of this element per each gram of BCE and BCM, to confer a degree of functionalization of 20.2+/-0.07 and 86.7+/-0.01 mg g(-1). This synthesis enabled from IR weak SH band at 2544 cm(-1) due to the incorporation of the reagent into the structure. The basic centers favor copper sorption with increasing pH from 2 to 6 observed by a batchwise methodology and the data obtained from the chosen pH 6 were adjusted to Freundlich and Langmuir models, favoring fit for the latter equation. The kinetics of sorption was established at 30 min for both biopolymers with a pseudo-second-order model.

Immobilization of ethylene sulfide in aminated cellulose for removal of the divalent cations

Cellulose (Cel) was first chemically modified with thionyl chloride to increase its reactivity. In the next step CelCl was reacted with ethylenediamine (CelEn) and subsequently reacted with ethylene sulfide to obtain a solid substance, CelEnEs. The modification reactions were confirmed by elemental analysis, TG, XRD, (13)C NMR and FTIR. The chemically modified biopolymer CelEnEs had an order of divalent metal sorption of Pb(2+)>Cd(2+)>Ni(2+)>Co(2+)>Cu(2+)>Zn(2+), and the maximum adsorption capacities were found to be 6.282±0.023, 5.783±0.015, 5.561±0.017, 4.694±0.013, 1.944±0.062 and 1.733±0.020 mmol g(-1), respectively. The equilibrium data were fitted to Langmuir, Freundlich and Temkin models, and in general, the experimental data best fit the Freundlich model. This newly synthesized biopolymer proved to be a chemically useful material for cations removal from aqueous solution.

Exploring the favorable ion-exchange ability of phthalylated cellulose biopolymer using thermodynamic data.

A phthalylated ion-exchange biopolymer was obtained by adding cellulose to molten phthalic anhydride in a quasi solvent-free procedure. Through this route 2.99+/-0.07 mmolg(-1) of pendant groups containing ester and carboxylic acid moieties were incorporated into the polymeric structure that was characterized by elemental analysis, solid-state carbon nuclear magnetic resonance (CP/MAS), infrared spectroscopy, X-ray diffraction, and thermogravimetry. The chemically modified polysaccharide is able to exchange cations from aqueous solution as demonstrated by batchwise methodology. The data were adjusted to a modified Langmuir equation to give 2.43+/-0.12 and 2.26+/-0.11 mmolg(-1) for divalent cobalt and nickel cations, respectively. The net thermal effects obtained from calorimetric titration measurements were also adjusted to a modified Langmuir equation, and the enthalpy of the interaction was calculated to give endothermic values of 2.11+/-0.28 and 2.50+/-0.31kJmol(-1) for these cations, respectively. The spontaneity of this ion-exchange process is reflected in negative Gibbs energy and with a contribution of positive entropic values. This set of thermodynamic data at the solid-liquid interface suggests a favorable ion-exchange process for this anchored biopolymer for cation exchange from the environment.

Epicarp and mesocarp of babassu (Orbignya speciosa): characterization and application in copper phtalocyanine dye removal

The mesocarp and epicarp components of the babassu palm tree were applied as novel alternative biosorbents for copper phtalocyanine textile dye removal from aqueous solutions. The natural biopolymers were characterized by elemental analyses, solid state 13C NMR, infrared spectroscopy, thermogravimetric analysis and X-ray diffractometry. Results demonstrated that the compositions of the mesocarp and epicarp are similar to those of other lignocellulosic materials, and that they were very effective for removal of the textile dye Turquoise Remazol. A pseudo second-order kinetic model resulted in the best fit with experimental data for both epicarp and mesocarp (R2 = 0.999), providing rate constants of sorption, k2, of 0.31 and 1.43 g mg-1 min-1, respectively. The Langmuir and Freundlich isotherm models were employed for adsorption analysis of the experimental data in their linearized forms. The second model resulted in the better fit for Turquoise Remazol dye, which presented maximum adsorption of 1.44 and 2.38 mg g-1 at pH 6.0 for mesocarp and epicarp, respectively.

Chitosan-edible oil based materials as upgraded adsorbents for textile dyes

Biopolymer chitosan is a low cost, abundant, environmentally friendly, very selective and efficient anionic dyes adsorbent, being a promising material for large-scale removal of dyes from wastewater. However, raw chitosan (CS) is an ineffective cationic dyes adsorbent and its performance is pH sensitive, thus, CS modifications that address these issues need to be developed. Here, we report the preparation and characterization of two new CS modifications using edible oils (soybean oil or babassu oil), and their adsorption performance for two dyes, one anionic (remazol red, RR) and one cationic (methylene blue, MB). Both modifications extended the pH range of RR adsorption. The babassu oil modification increased adsorption capacity of the cationic dye MB, whereas the soybean oil modification increased that of RR. Such improvements demonstrate the potential of these two new CS modifications as adsorbent candidates for controlling dyes pollution in effluents.

REMOÇÃO DE COMPOSTOS FENÓLICOS DE SOLUÇÕES AQUOSAS UTILIZANDO CARVÃO ATIVADO PREPARADO A PARTIR DO AGUAPÉ (Eichhornia crassipes): ESTUDO CINÉTICO E DE EQUILÍBRIO TERMODINÂMICO

Activated carbon was produced from the water hyacinth (CAA) by impregnation with ZnCl2 (1:2), followed by pyrolysis at 700 oC, under N2. CAA was used for the adsorption of phenol, m-cresol and o-cresol from aqueous solutions, using batch adsorption. The effects of contact time, pH, temperature and concentration on sorption were investigated. Adsorption capacity, calculated using the Langmuir model proved to be dependent on temperature, reaching values of 163.7, 130.2 and 142.3 mg g-1 for phenol, m-cresol and o-cresol, respectively, at 45 oC. Thermodynamic data at the solid-liquid interface suggests an endothermic, spontaneous and environmentally-friendly process.

Casca de arroz Quimicamente Tratada como Adsorvente de Baixo Custo para a Remoção de Íons Metálicos (Co2+ and Ni2+)

Rice husk is an agricultural byproduct and its final disposition has been a serious environmental problem. However, it can be conveniently applied to the sorption of undesirable species from aqueous medium. This work investigated the sorption characteristics for Co 2+ (aq) and Ni 2+ (aq) ions and the best conditions of the sorption processes onto in nature (IN) and modified rice husks. Chemical treatments were performed by treating rice husk with phosphoric acid (AF) and phosphoric acid/urea (AFU). The experiments were conducted in aqueous solution, pH 4.8, and under constant temperature (28 ± 1 °C) and stirring. Kinetics and isotherms models were applied to the experimental data. The observed order for the maximum adsorption capacities (mmol.g -1 ) were: Co 2+ : 0.10 IN 2+ : 0.08 IN DOI: 10.5935/1984-6835.20160045

High performance maleated lignocellulose epicarp fibers for copper ion removal

Abstract - Natural lignocellulosic fiber epicarp extracted from the babassu coconut ( Orbignya speciosa ) was chemically modified through reaction with molten maleic anhydride without solvent, with incorporation of 189.34 mg g -1 of carboxylic acid groups into the biopolymer structure. The success of this reaction was also confirmed by the presence of carboxylic acid bands at 1741 and 1164 cm -1 in the infrared spectrum. Identically, the same group is observed through 13 C NMR CP/MAS in the solid state, via high field signals in the 167 pm region. Both the precursor and the immobilized maleated biopolymers presented nearly the same thermal stability and similar crystallinity to cellulose. However, the pendant carboxylic groups have the ability to remove copper with maximum sorption through a batchwise process at pH 6.0, as expected from the point of zero charge, determined to be 6.45. The sorption kinetic data were fitted to pseudo-first order, pseudo-second order, Elovich-chemisorption and intra-particle diffusion models and the equilibrium data were fitted to the Langmuir, the Freundlich and Tenkim isotherm models. Taking into account a statistical error function and determination coefficients, the data were fit to the pseudo-first and pseudo-second order kinetic and Langmuir isotherm models, with a maximum sorption capacity of copper ions of 55.09 mg g

Wood (Bagassa guianensis Aubl) and green coconut mesocarp (cocos nucifera) residues as textile dye removers (Remazol Red and Remazol Brilliant Violet)

In this work the efficiency of two lignocellulosic waste materials, wood residues and coconut mesocarp, were investigated as adsorbents towards two representative textile dyes (Remazol Red, RR and Remazol Brilliant Violet, RBV). The moisture, carbohydrate, protein, lipid, ash and fiber contents of both natural matrices were characterized. The materials were also characterized by infrared spectroscopy, X-ray diffractometry, scanning electron microscopy, specific surface area analysis and thermogravimetry. The adsorption of dyes was monitored by using UV-Vis spectrophotometry. It was verified that both, coconut mesocarp (CM) and wood residues can act as effective adsorbents towards the investigated dyes. It is verified that the maximum adsorption capacity ΓM (mg g-1) for RBV and RR are 7.28 and 3.97 towards CM and 0.64 and 0.71 towrads SD. Furthermore, it was verified that the adsorption is strongly pH dependent and, as a general behavior, an increase in the pH value is associated with a decrease of the total amount of adsorbed dye. The adsorption of violet dye onto coconut mesocarp is well described by the Langmuir model, while all the remazol red fitted better with the Freundlich equation.