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.

RESUMO ABSTRACTIn 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.

No abstract

No abstract

No abstract

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.

No abstract

Advanced oxidative processes are widely used in the degradation of organic compounds. The degradation and mineralization of the PNF was evaluated by means of an experimental factorial design, using photolysis (UV) and photo-peroxidation (UV/H2O2). With the results optimized, degradation kinetics was performed and the experimental data adjusted to mathematical models. In the UV system, it was possible to degrade just over 65% and mineralize 15% over 7 h of reaction; however, with the addition of the oxidizing agent H2O2, it was possible to obtain 100% removal of the contaminant, suggesting that there was no formation of intermediate compounds. Kinetics results fitting the first order model and the velocity constants revealed that degradation is extremely faster in the UV/H2O2 system (k1,UV/H2O2 = 0.0580 min− 1 > k1,UV = 0.0018 min− 1).