Estudo da capacidade de adsorção de hidrocarbonetos policíclicos aromáticos presentes em solução aquosa utilizando resinas poliméricas reticuladas

Abstract

Polycyclic aromatic hydrocarbons (PAHs) represent a class of hydrophobic compounds formed from the incomplete combustion of organic material and can interact with DNA promoting mutagenic and carcinogenic responses. Monitoring water systems contaminated by the presence of these substances is one of the main challenges faced by researchers who have been investigating the adoption of new methodologies and materials for the extraction and/or pre-concentration of these pollutants in matrices of environmental samples. In the present work, the ability to remove phenanthrene (PHE) (model HPA) from aqueous solutions by adsorption on different cross-linked polymeric resins was studied. Cross-linked resins with different monomeric compositions and morphological properties were selected for this study. These resins were prepared by combining the crosslinkers divinylbenzene (DVB) or ethylene glycol dimethacrylate (EGDMA) with the comonomers chloromethyl styrene (CMS), glycidyl methacrylate (GMA), methacrylic acid (MAA) or styrene (Sty). Preliminary batch adsorption tests were carried out by adding the adsorbents in PHE solutions (1.0 mg L‒1). These solutions were quantified after the adsorption process using the spectrofluorimetry technique and subsequently the removal capacity of each resin was calculated. In the study of adsorption kinetics, two resins were chosen that showed high removal efficiencies (>90%) in preliminary tests. For the modeling of the adsorption kinetics, reaction models (pseudo-first order, pseudosecond order and Elovich) and diffusion models (external diffusion, intraparticle diffusion of Weber-Morris and Urano-Tachikawa) were tested to adjust the experimental data. The performance of the resin with greater efficiency was evaluated in a column study (continuous flow) and the data obtained were used for the construction of the breakthrough curve, determination of the saturation point, work capacity and total adsorption capacity. In general, the results obtained in the preliminary tests showed that most of the resins containing the Stymonomer or crosslinked with DVB showed satisfactory PHE removal values in water (≥92.9%), except for the resin composed of CMS and DVB (70.3%). The kinetic data obtained a better fit by the pseudo-second order reaction model for poly(DVB) and poly(Sty/DVB) resins (R²>0.999) and the amount of solute adsorbed at equilibrium calculated (qe,calc) was of 0.313 ± 0.002 and 0.273 ± 0.001 mg g‒1, respectively. Among the diffusional models, the UranoTachikawa equation best fitted the data obtained for poly(DVB) (R² = 0.956) and poly(Sty/DVB) (R² = 0.906). Column adsorption studies indicated that the saturation point was reached when 11.8 L of PHE solution (1.0 mg L‒1) was eluted through the column packed with 15 mg of poly(DVB) resin at an approximate flow of 10 mL min‒1. This resin showed a working capacity and total adsorption capacity of 0.152 g cm‒3 and 0.0289 g cm‒3, respectively.