Carbonos mesoporosos a partir do método solvent-free: avaliação dos parâmetros sintéticos e o efeito da porosidade na adsorção de contaminantes emergentes

Abstract

This work reports the synthesis of mesoporous carbons (MPCs) by solvent-free method and their application in the adsorption of emerging contaminants (ECs). First part, the synthesis of MPCs using resorcinol (carbon precursor) and F127 (surfactant) was performed. The influence of the carbon precursor/surfactant ratio (p/s), heating rate, stabilization time and self-assembly temperature on the textural properties of mesoporous carbons produced by the solvent-free method was investigated for the first time. The results indicated that the p/s ratio was the one that most influenced textural properties. MPCs with p/s 1.0 showed smaller pore size (4.8 nm) and smaller mesopore volumes (0.205-0.262 cm3 g-1). MPCs with p/s 0.50 showed larger pore diameter (5.9 nm) and larger mesopores volumes (0.459-0.525 cm3 g-1). Transmission electron micrographs indicated the formation of two types of pore ordering: wormholes (disordered pores) and honeycombs (ordered pores). MPCs-F127 were applied in the adsorption 17α-ethinylestradiol (EE2). We proved that EE2 adsorption is influenced by the pore type, pore diameter, pore volume and mesopores content of the MPCs. However, pore ordering of MPCs did not influence the adsorption. MPCs with the largest size and mesoporous content showed 99% removal in preliminary studies. One of the materials with p/s 0.50 had the highest maximum adsorption capacity (157 mg g-1) reported for EE2 at the time of publication. Furthermore, in the reuse studies, the removal capacity remained ~100% until the fourth cycle and above 85% until the tenth cycle. In the second part of this work, the use of a new surfactant, Vorasurf504 (V504), for the solvent-free method was explored. Three materials (MPCs-V504) were produced in different p/s ratios (1.0, 0.50 and 0.33). The V504 surfactant increased the pore size (5.6-29 nm) and the pore volume (0.922 cm3g-1) of the materials. CMPs-V504 were applied in the adsorption of emerging contaminants: paracetamol (PA), atrazine (AT), tenofovir (TF) and ceftriaxone (CF). In the preliminary study, MPCs with p/s 0.50 and 0.33 were able to remove more than 90% of the contaminants present in the system. However, the p/s 1.0 material removal capacity decreased for the larger contaminants. This decrease occurred because the material with p/s 1.0 has limited mesoporosity. Kinetic and isothermal studies for systems involving paracetamol and ceftriaxone proved that porosity influences the adsorption capacity. Therefore, through this work it was possible to produce efficient adsorbents for the removal of emerging contaminants, substances considered potential threats to the environment and human health. Through the variation of some synthetic parameters and the use of a new surfactant, important contributions to the area of mesoporous carbons were reported, especially for studies involving the solvent-free method.