Kinetic modeling of the adsorption and desorption of metallic ions present in effluents using the biosorbent obtained from Syagrus romanzoffiana.

In this study, the kinetic mechanism of adsorption and desorption, as well as the equilibrium isotherms, of four metallic ions (Cd2+, Cu2+, Ni2+, and Zn2+) mono and multicomponent were investigated. The biosorbent used was produced from Jerivá (Syagrus romanzoffiana-commonly known as queen palm) coconut. A kinetic model that considers macropore diffusion as a control step was solved. The finite volume method was used in the discretization of the equations, and the algorithm was implemented in the Fortran programming language. The equilibrium time for monocomponent adsorption was 5 min; for the multicomponent tests, equilibrium occurred instantly (less than 2 min of adsorption). The pseudo-second-order model presented the lowest mean of the sum of normalized errors (SNE) and represented the experimental data of mono and multicomponent adsorption and desorption. Single and multicomponent Langmuir model represented the adsorption isotherms. The maximum capacity of adsorption of metallic ions, both mono and multicomponent, was higher for copper, and the multicomponent adsorption proved to be antagonistic; the presence of co-ions in the solution reduced the removal of metals due to competition between these contaminants. The capture preference order was justified by the physicochemical properties of the ions, such as electron incompatibility and electronegativity. All these situations justified the maximum adsorption of Cu2+, followed by Zn2+, Cd2+, and Ni2+ in the mixture.

Electrocoagulation applied for textile wastewater oxidation using iron slag as electrodes.

The indigo blue dye is widely used in the textile industry, specifically in jeans dyeing, the effluents of which, rich in organic pollutants with recalcitrant characteristics, end up causing several environmental impacts, requiring efficient treatments. Several pieces of research have been conducted in search of effective treatment methods, among which is electrocoagulation. This treatment consists of an electrochemical process that generates its own coagulant by applying an electric current on metallic electrodes, bypassing the use of other chemical products. The purpose of this study was to evaluate the potential use of iron slag in the electrocoagulation of a synthetic effluent containing commercial indigo blue dye and the effluent from a textile factory. The quantified parameters were color, turbidity, pH, electrical conductivity, sludge generation, phenol removal, chemical oxygen demand (COD), and total organic carbon (TOC). The electrocoagulation treatment presented a good efficiency in removing the analyzed parameters, obtaining average removal in the synthetic effluent of 85% of color and 100% of phenol after 25 min of electrolysis. For the effluent from the textile factory, average reductions of 80% of color reaching 177.54 mg Pt CoL-1, 91% of turbidity reaching 93.83 NTU (nephelometric turbidity unit), 100% of phenol, 55% of COD with a final concentration of 298.8 mg O2 L-1, and 73% of TOC with a final concentration of 56.21 mg L-1, in 60 min of electrolysis. The reduced time for removal of color and phenolic compounds in synthetic effluent demonstrates the complexity of treating the real effluent since to obtain removals of the same order a 60-min period of electrolysis was necessary. The results obtained demonstrate the potential of using iron slag as an electrode in the electrocoagulation process in order to reuse industrial waste and reduce costs in the treatment and disposal of solid waste. Thus, the slag can be seen as an alternative material to be used in electrocoagulation processes for the treatment of effluents from the textile industry under the experimental conditions presented, its only limitation being the fact that it is a waste and therefore does not have a standardization in the amounts of iron present in the alternative electrodes.

Tratamento numérico e ensaios experimentais da remoção de fenol em reator batelada e coluna de leito fixo utilizando carvão ativado / Numerical treatment and experimental tests of phenol removal in batch and fixed bed column using activated carbon

RESUMO Neste estudo, foram obtidas as cinéticas e isotermas de adsorção do fenol presentes em efluentes sintéticos em reator batelada e coluna de leito fixo, utilizando como adsorvente carvão ativado de casca de coco. O objetivo foi a obtenção dos parâmetros cinéticos e de equilíbrio do processo para simular diferentes condições operacionais em uma coluna de adsorção em leito fixo. Foram avaliadas a influência do pH, a massa de adsorvente, a concentração inicial de fenol e três diferentes temperaturas para os testes em reator batelada. Foi possível trabalhar no pH natural da solução e o aumento da temperatura indicou adsorção exotérmica, favorável e espontânea. Os dois modelos de isoterma (Langmuir e Freundlich) representaram bem os dados experimentais (R2 ≈ 0,9). Valores aproximados de capacidade máxima de adsorção foram encontrados para o reator batelada e para a coluna de leito fixo (qmáx = 41,69 mg.g-1 para o reator batelada e qmáx = 41,98 mg.g-1 para a coluna de leito fixo). O método de Volumes Finitos foi utilizado na discretização das equações matemáticas e um algoritmo computacional foi implementado em linguagem FORTRAN. O código computacional foi validado com dados experimentais deste trabalho (erro médio de 13%), podendo-se assim simular diferentes condições operacionais do sistema de adsorção em coluna de leito fixo com vista a futuras aplicações industriais.

ABSTRACT In this study, the kinetics and adsorption isotherms of phenol present in synthetic effluents were obtained in a batch reactor and fixed bed column, using adsorbent coconut shell activated carbon. The objective was to obtain the kinetic and equilibrium parameters of the process to simulate different operating conditions in a fixed bed adsorption column. The influence of the pH, adsorbent mass, initial phenol concentration, and three different temperatures for the batch reactor tests were evaluated. It was possible to work on the natural pH of the solution and the temperature increase indicated exothermic, favorable, and spontaneous adsorption. Both isotherm models (Langmuir and Freundlich) represented the experimental data (R2 ≈ 0.9). Approximate values of maximum adsorption capacity were found for the batch reactor and for the fixed bed column (qmax = 41.69 mg g-1 for the batch reactor and qmax = 41.98 mg g-1 for the fixed bed column). The Finite Volume method was used in the discretization of the mathematical equations and a computational algorithm was implemented in FORTRAN programming language. The computational code was validated with experimental data of this work (mean error of 13%) and it was possible to simulate different operational conditions of the fixed bed column adsorption system for future industrial applications.

Study of phenol biodegradation in different agitation systems and fixed bed column: experimental, mathematical modeling, and numerical simulation.

Phenol degradation was studied in two different agitation systems in a batc h reactor (mechanical agitation and orbital agitation) and the support of the most efficient system was used for fixed bed bioreactor studies. The support used was coconut shell charcoal. The results showed that the mechanical agitation bioreactor was more effective in phenol removal, due to the amount of biomass adhered to the support (8.56 mg gsupport-1), running at approximately 100% of the phenol biodegradation in 300 min. The toxicity analysis of the waters was moderate, because the EC50,48h values in the analyzed samples are higher than 50%. Within the experimental data obtained from the batch system, it was possible to find the parameters of the kinetic model of Michaelis-Menten, which was used to simulate the bioreactor in a fixed bed. A mathematical model of a one-equation, which considers the effects of dispersion, convection, and reaction in the liquid phase, and diffusion and reaction inside the biofilm was used and the results obtained through numerical simulation were compared with the experimental results of the bioreactor in a fixed bed, and new operational conditions in the bed were simulated with good accuracy.

Combined microfiltration and adsorption process applied to public water supply treatment: water quality influence on pesticides removal.

Granular activated carbon (GAC) fixed bed adsorption technology was applied to remove carbamates carbaryl, methomyl and carbofuran from public water supply. In order to minimize the effect of clogging and to evaluate adsorbent saturation for carbamates, the microfiltration (MF) was previously used to adsorb and the backwash procedure of the GAC bed was carried out. The determination and quantification of the carbamates were performed by analytical technique in high performance liquid chromatography with post-column derivatization and fluorescence detector. The MF of the water previously adsorbed in the GAC fixed bed allowed the greater removal of 100% of the carbamates pesticides with an initial concentration of 25 µg L-1 during the first 48 h of operation. The saturation of the GAC fixed bed occurred in 240 h, due to the partial removal of the natural organic matter by the MF, consequently the competition for adsorptive sites of the GAC was smaller. The backwashing procedure contributed to the partial recovery of the performance of the hydraulic filtration and allowed to identify the saturation of the adsorption column, since the sealing phenomenon preceded the saturation. Finally, the use of public water supply was considered a relevant and positive aspect, since it allowed the identification of the performance of this technology in the removal of carbamates pesticides considering the presence of substances inherent to the public water supply.

Bioethanol Production From Hydrolyzed Lignocellulosic After Detoxification Via Adsorption With Activated Carbon and Dried Air Stripping.

Bioethanol production has been presented as an alternative for supplying energy demand and minimizing greenhouse gases effects. However, due to abrasively conditions employed on the biomass during pretreatment and hydrolysis processes, inhibitors for fermentation phase such as acetic acid and others can be generated. Based on this problem, the aim of this work was to evaluate the adsorption of acetic acid on microporous activated carbon and investigate the stripping of the same component with dried air. For adsorption process, three concentrations of acetic acid (5, 10, and 20%) were analyzed by adsorption kinetics and adsorption isotherms (Langmuir and Freundlich models). Pseudo-second order model showed to fit better when compared to Pseudo-first order model. The Intraparticle Diffusion model presented the first phase of the adsorption as the regulating step of the adsorption process. The Langmuir model showed the best fitting, and the maximum capacity of adsorption was found as 128.66 mg.g-1. For stripping procedure an apparatus was set in order to insert dried air by a diffusor within the solution in study. Increasing temperature showed to be determinant on augmenting acetic acid evaporation in 2.14 and 6.22 times for 40 and 60°C when comparing it to 20°C. The application of the pickling process for removal of fermentation inhibitors in sugarcane bagasse hydrolyzed allowed the production 8.3 g.L-1 of ethanol.

Biosorption of metal ions using a low cost modified adsorbent (Mauritia flexuosa): experimental design and mathematical modeling.

Buriti fibers were subjected to an alkaline pre-treatment and tested as an adsorbent to investigate the adsorption of copper, cadmium, lead and nickel in mono- and multi-element aqueous solutions, the results showed an increase in the adsorption capacity compared to the unmodified Buriti fiber. The effects of pH, adsorbent mass, agitation rate and initial metal ions concentration on the efficiency of the adsorption process were studied using a fractional 2(4-1) factorial design, and the results showed that all four parameters influenced metal adsorption differently. Fourier transform infrared spectrometry and X-ray fluorescence analysis were used to identify the groups that participated in the adsorption process and suggest its mechanisms and they indicated the probable mechanisms involved in the adsorption process are mainly ion exchange. Kinetic and thermodynamic equilibrium parameters were determined. The adsorption kinetics were adjusted to the homogeneous diffusion model. The adsorption equilibrium was reached in 30 min for Cu(2+) and Pb(2+), 20 min for Ni(2+) and instantaneously for Cd(2+). The results showed a significant difference was found in the competitiveness for the adsorption sites. A mathematical model was used to simulate the breakthrough curves in multi-element column adsorption considering the influences of external mass transfer and intraparticle diffusion resistance.

Simulação numérica e ensaios experimentais da remoção de Fe (III) da água para utilização nas indústrias alimentícias / Numerical simulation and experimental tests of removal of Fe (III) from water for use in food industry

RESUMO Neste estudo foram realizadas as cinéticas e isotermas de adsorção dos íons Fe (III) presentes em afluentes sintéticos utilizando como adsorvente carvão ativado de casca de coco. O objetivo foi a obtenção dos parâmetros cinéticos e de equilíbrio do processo para assim simular diferentes condições operacionais em uma coluna de adsorção em leito fixo. Foram avaliadas a influência de três diferentes temperaturas na adsorção de Fe (III), sendo que o aumento da temperatura indicou adsorção exotérmica. A isoterma de Freundlich representou melhor os dados experimentais. Também foi realizado o estudo cinético e o modelo que apresentou melhor os dados experimentais foi o modelo de Pseudo-Primeira Ordem para as três concentrações estudadas. O método de Volumes Finitos foi utilizado na discretização das equações matemáticas e um algoritmo computacional foi implementado em linguagem FORTRAN. O código computacional foi validado com dados experimentais encontrados na literatura (erro máximo de 6,2%) podendo-se assim simular diferentes condições operacionais do sistema de adsorção com aplicação na indústria alimentícia.

ABSTRACT In this study were performed the kinetics and isotherms of adsorption of the ions Fe (III) from synthetic affluent using activated carbon from coconut shell as adsorbent. The objective was to obtain the equilibrium and kinetic parameters of the process and thereby simulating different operating conditions in a adsorption column fixed bed. It was evaluated the influence of three temperatures different on the adsorption of Fe (III), in which the temperature increase indicated adsorption exotherm. The Freundlich isotherm showed the best fit to the experimental data. At the kinetic study the model that best fit to the experimental data was the model Pseudo-First Order for the three concentrations studied. The finite volume method was used for discretization of the mathematical equations and a computational algorithm was implemented in FORTRAN. The computational code was validated with experimental data found in the literature (maximum error of 6.2%) can thus simulate different operating conditions of the system.