Cícero Wellington Brito Bezerra

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.

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.

Complexação de íons de metais por matéria orgânica dissolvida: modelagem e aplicação em sistemas reais

Os ions de metais pesados sao conhecidos tanto pela sua importância fisiologica e industrial, bem como pelo risco ambiental e a saude humana. Para elucidar o comportamento dessas especies nos corpos hidricos, os quais recebem grande parte da descarga de metais, seja de origem antropica ou por fontes naturais, e necessario entender as interacoes que elas apresentam com o meio, principalmente a especiacao quimica. Um dos mais importantes processos pelos quais passam as especies metalicas em corpos aquaticos naturais e a interacao com a materia orgânica dissolvida (MOD), que pode ser por adsorcao, reacoes de troca ionica ou por complexacao. Neste trabalho foram realizados varios experimentos com o objetivo de descrever o comportamento da complexacao de tres importantes cations Cu(II), Cd(II) e Pb(II) com a materia orgânica (acido humico comercial), sob condicoes diversas de forca ionica em meio tamponado. Os resultados foram avaliados de acordo com o modelo de van den Berg e Kramer para a complexacao de metais. O modelo foi aplicado na determinacao da capacidade de complexacao dos ions em amostras reais, oriundas de tres rios maranhenses que integram a Amazonia legal: Itapecuru, Bacanga e Pericuma. Nas aguas dos rios utilizou-se o parâmetro carbono orgânico dissolvido (COD) para expressar a MOD. Os resultados confirmaram forte interacao entre a MOD e ions de metais pesados e que o modelo de van den Berg e Kramer e satisfatorio para se estimar a constante de complexacao (K) e a concentracao de sitios de complexacao (Lt). Nas amostras simuladas em laboratorio a ordem de complexacao dos metais foi Cu(II) > Cd(II) > Pb(II) e a capacidade de complexacao mostrou ser linear em funcao da concentracao de acido humico comercial. Acredita-se que por ter menor raio ionico, o ion Cu(II) possui maior afinidade com os sitios de complexacao. Nas amostras retiradas dos corpos aquaticos, observou-se que o rio com maior concentracao de COD (rio Bacanga) apresentou maior capacidade de complexacao; entretanto, a ordem foi Pb(II) > Cu(II) > Cd(II) provavelmente devido a presenca de ions Cu(II) em maior quantidade nas aguas dos rios.

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.

Uso de sílica e sílica-titânia organofuncionalizadas para a remoção de Cu(II) em aguardentes

Palavras-chave: SUMMARY THE USE OF ORGANOFUNCIONALIZED SILICA AND SILICA-TITANIA FOR Cu (II) REMOVAL IN SPIRITS. The high levels of copper in Brazilian spirits is a problem of prominent importance, taking into account the relevance of this metal. This work investigates the efficiency of two solids: silica organofunctionalized with thimethoxysil(propil) ethylenediamine (Si-Dia) and silica-titania modified with the same organofunctionaling agent (Si-Ti-Dia) as copper sequestrating agents in a Brazilian spirit obtained from sugar cane. It was verified that the matrices Si-Dia and Si-Ti-Dia are very good sequiestrating agents, reducing the concentrations of Cu, Zn and Fe in the studied spirit sample in 82, 83 and 64% and 88, 31 and 22%, respectively at 25 ± 1.0°C and pH 4.0. alcoholic beverage; copper; adsorption; modified silica; atomic absorption spectometry.

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.

Electrochemical behavior of ruthenium-hexacyanoferrate modified glassy carbon electrode and catalytic activity towards ethanol electrooxidation

3- ion and three ruthenium forms (Ru(II), Ru(III) and Ru(IV)), characteristic of ruthenium oxide compounds. The modified electrode displayed excellent electrocatalytic activity towards ethanol oxidation in the potential region where electrochemical processes Ru(III)-O-Ru(IV) and Ru(IV)-O-Ru(VI) occur. Impedance spectroscopy data indicated that the charge transfer resistance decreased with the increase of the applied potential and ethanol concentration, indicating the use of the RuHCF modified electrode as an ethanol sensor. Under optimized conditions, the sensor responded linearly and rapidly to ethanol concentration between 0.03 and 0.4 mol L -1 with a limit of detection of 0.76 mmol L -1 , suggesting an adequate sensitivity in ethanol analyses.

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

Removal of the Textile Dye Indanthrene Olive Green from Aqueous Solution Using Chitosan

The kinetics and equilibrium of the adsorption of Indanthrene Olive Green (IOG) from aqueous solution onto chitosan have been investigated. The chitosan was characterised in terms of its average degree of de-acetylation (DD) and by XRD, TGA/DTG, IR, SEM and specific BET surface area methods. Batch adsorptions experiments were carried out at different pH values and dye concentrations. It was found that the adsorption process was favoured by acidic pH conditions (4.0–6.0). The adsorption followed second-order rate kinetics and the experimental equilibrium data followed the Langmuir isotherm, thereby suggesting that chemisorption might be the major adsorption mode. Such adsorption also occurred on chitosan fibres, although to a significantly lower extent than on crushed chitosan. The corresponding thermodynamic parameters (ΔG0, ΔH0 and ΔS0) were calculated. The positive values obtained for ΔH0 (161.7 kJ/mol) and ΔS0 [559.9 J/(mol K)] suggest that the adsorption process was endothermic, with the randomness of the system increasing during the adsorption process. A simplified adsorption model has also been proposed.