Evaluation of adsorbend prepared from eucalyptus pruning wood fro quinoline removal in aqueous media via adsorptive processes

Evaluation of adsorbend prepared from eucalyptus pruning wood fro quinoline removal in aqueous media via adsorptive processes

• Autor
• Matheus Leonardo Gomes da Silva
• Co-autores
• Jean Heliton Lopes dos Santos , Alex Leandro Andrade de Lucena , Raíssa Aguiar de Freitas , Marta Maria Menezes Bezerra Duarte
• Resumo

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  Evaluation of adsorbend prepared from eucalyptus pruning wood fro quinoline removal in aqueous media via adsorptive processes

   

  Matheus Leonardo Gomes da Silva, Jean Heliton Lopes dos Santos, Alex Leandro Andrade de Lucena, Raíssa Aguiar de Freitas, Marta Maria Menezes Bezerra Duarte

  Federal University of Pernambuco (UFPE), Department of Chemical Engineering, Av. dos Economistas, S/N, Recife, 50740-590, Brazil

  Abstract

  During the processing of petroleum, liquid toxic effluents are generated, such as quinoline. In view of the above, this work aims to evaluate the kinetic evolution and equilibrium adsorption of quinoline, in an aqueous medium, using activated carbon from eucalyptus pruning wood as an adsorbent. The adsorption kinetic evolution was rapid, reaching equilibrium in the first minutes. Both the pseudo-first order and pseudo-second order models well represented the experimental data, indicating that adsorption depends on both the available sites and the concentration of the adsorbate in solution. The Sips model presented the best fit to the experimental data, indicating adsorption in mono and multilayers, in addition to a heterogeneous surface and with a maximum adsorption capacity of 123 mg·g^-1. The values of R², Sr² and n suggests that adsorption is favorable, and the active sites have different energy levels. In this way, the adsorbent prepared from biomass residue proved to be effective in removing quinoline.

  Keywords: Adsorption; Agro-industrial waste; Biomass.

   

  1. Introduction

  Oil refineries play an important role in the production of goods for use, thus contributing to the structuring of Society. Oil goes through several processing stages (atmospheric distillation and vacuum distillation) and conversion (catalytic cracking and catalytic reforming). It is in these stages where a significant number of liquid effluents are generated, generally containing hydrocarbons, phenols, sulfur compounds, nitrogen compounds, oxygen compounds, as well as heavy metals [1, 2].

  Among the nitrogenous aromatic compounds, quinoline stands out for being commonly found in fossil fuels. The removal of quinoline from effluents is crucial to avoid harm to fauna, flora and humans if it is discarded in receiving bodies without proper treatment [3].

  Conventional effluent treatment methods (physical, chemical and biological) are inefficient for removing quinoline from aqueous media. Therefore, it is necessary to apply a process such as adsorption. This process stands out for its operational simplicity, as it does not require qualified labor, and for the possibility of using waste to produce the adsorbent, in addition to allowing the recovery of the quinoline after desorption [4, 5].

  In view of the above, this work aimed to evaluate the kinetic evolution and equilibrium adsorption for the removal of quinoline in an aqueous medium using activated carbon prepared from eucalyptus pruning wood as an adsorbent.

  2. Methodology

  2.1 Preparation and quantification of the working solution

  Quinoline stock solutions (NEON, 96%) were prepared at a concentration of 1000 mg·L^-1. Working solutions were obtained by diluting the stock solution. All reagents used to adjust pH and carry out the tests were of analytical grade. The quinoline contents were quantified before and after conducting the adsorption experiments using the ultraviolet-visible (UV-Vis) molecular absorption spectrophotometry technique (TermoScientific, Genesys 10S UV-Vis).

  A spectral scan was performed in the range of 200-800 nm to identify the quinoline characteristic wavelength (?). Based on it, na analytical curve was built and the limits of detection and quantification were calculated, as well as the methods precision.

  Blank assays were conducted for each experiment. The calculation fo the absorbed amount per mass of adsorbent (adsorptive capacity, q) was carried out using Equation (1).

  

  In which: C₀ and C_f are the initial and final concentrations of the adsorbate (mg·L^-1); V the volume of the solution (L) and m the adsorbent mass in gram (g).

  2.2 Adsorbent preparation

  Eucalyptus pruning wood charcoal was provided by Elephant LTDa company. Those were carbonized in a metal oven with an internal heating source for 4 h at 500°C. The chemical activation was carried out using phosphoric acid (H₃PO₄ 85%, Vetec brand), in a 5:3 (M/V) ratio, in a refractory container, and homogenized using a glass rod. Then, the mixture was placed in a muffle furnace (Quimis brand) with a hating ramp (10°C·min^-1 at 100°C/30 min, 200°C/1 h and 350°C/1h). 

  After cooling, the activated carbon was washed by immersion in a 1% NaHCO₃ solution (FMaia) to remove residual acid until the pH of the solution reached between 6 and 7. It was then washed with distilled water and dried in an oven at 105ºC for 24 hours. The prepared adsorbent was called eucalyptus activated carbon (EAC) and classified using a series of Tyler sieves.

  2.3 Kinetic Evolution of the adsorptive process

  Based on the parameters established in previous studies (pH of the solution equal to 5, granulometry less than 0.09 mm, stirring speed of 200 rpm and mass ratio of the adsorbent and volume of the solution equal to 1 g·L^-1), studies were carried out to evaluate the kinetic evolution of adsorption.

  The tests consisted of placing the adsorbent in contact with solutions containing quinoline at 30 mg·L^-1 at time intervals ranging from 0 to 360 minutes. Pseudo-first order (Equation 2) and pseudo-second order (Equation 3) kinetic models were fitted to experimental data [5].

  

  In which: k₁ the pseudo-first order adsorption rate constant (min^-1); q_e and q_t the adsorptive capacities at equilibrium and at time t; k₂ the pseudo-second order adsorption rate constant (g·mg^-1·min^-1).

   

  The model adjustments to experimental data were performed using Origin 8.5 software using nonlinear adjustment methods. The quality of model adjustments was assessed by calculating the residual values ??left by the models (Sr²) and the linear regression coefficients (R²).

  2.4 Adsorptive equilibrium

  The adsorption equilibrium tests were conducted within the equilibrium time established in the previous study and under the operating conditions previously defined and used in the study of the kinetic evolution.

  Quinoline solutions with concentrations ranging from 1 to 250 mg·L^-1 were added to the EAC adsorbent, maintaining the temperature at 30 ± 2°C. To evaluate the adsorption process, the Langmuir (Equation 4), Freundlich (Equation 5) and Sips (Equation 6) models were applied.

  

  In which: q is the adsorption capacity of the material (mg·g^-1); K_L is the Langmuir model equilibrium adsorption constant (adsorbate/adsorbent interaction constant in L·mg^-1); q_máx is the maximum adsorptive capacity; K_F is the adsorption constant of the Freundlich model [mg·g^-1(L·mg^-1) n^-1]; q_e is the adsorption capacity at equilibrium (mg·g^-1) Palavras-chave

• Keywords: Adsorption; Agro-industrial waste; Biomass.
• Área Temática
• Adsorção aplicada ao meio ambiente