Síntese e caracterização de materiais carbonáceos e hidróxido duplo lamelar (HDL) para aplicação na adsorção dos contaminantes emergentes ibuprofeno e paracetamol

Abstract

Emerging contaminants (ECs) are chemical compounds that are inserted into water bodies by society, which cause serious consequences to the aquatic ecosystem, in addition to the production of compounds harmful to human health when effective treatment methods are not implemented. Ibuprofen (IBU) and paracetamol (PAR) are drugs that are included in the group of ECs, classified as non-steroidal anti-inflammatory drug (NSAID) and analgesic, respectively. Activated carbons (ACs) from biomass have been sources of studies in the field of drug adsorption. Lamellar double hydroxides (LDHs) are anionic synthetic clays capable of adsorbing these pollutants from the aqueous medium. The synthesis of AC, composites of LDH and AC are studied as an environmental remedy. In this work, carbonaceous adsorbents and lamellar double hydroxide were used to remove IBU and PAR from the aqueous medium in a batch system. AC was produced from Brazil nut shells (Bertholletia excelsa H.B.K.) and chemically activated using H3PO4 (55% m/v, in mL). LDH and LDH-AC composite were synthesized by coprecipitation method; cationic ratio 3:1 (Mg/Al). The results of chemical and textural characterizations showed that AC has an acid character, point of zero charge (pHPCZ 3.2), hydrophobic (hydrophobicity index, HI of 0.93), high surface area value (SBET 1651.31 m2 .g-1 ) and pore volume (VTOTAL 1194 cm3 .g-1 ). The composite LDH-AC and LDH have a basic character and pHPCZ values (9.2 and 8.2, respectively), HI values (0.35 and 0.44 respectively); the LDH-AC and LDH materials showed SBET and VTOTAL values lower than the AC values: LDH-AC (SBET 79.9781 m2 .g-1 ; VTOTAL 0.067211 cm3 .g-1 ) and LDH (SBET 2.1179 m2 .g-1 ; VTOTAL 0.004648 cm3 .g-1 ). The optimal experimental conditions for adsorption defined in this study were: initial pH of the solution (pH of 3.0), mass of adsorbent (m of 0.015 g) and initial concentration of adsorbate (C0 of 20 mg.L-1 ). The pseudo-second order kinetic model (PSO) showed the best fit to the experimental data of the studied adsorptive processes. The Freundlich isotherm was well suited to the experimental data of the adsorptive processes (AC_IBU) and the Sips isotherm best described the experimental data of the adsorptive processes (LDHAC_IBU and LDH_IBU), at temperatures of 26, 45 and 55 °C. The thermodynamic configurations confirmed that the adsorption process for both systems (AC_IBU, LDHAC_IBU, LDH_IBU) is favorable at low temperatures, exothermic (LDH-AC_IBU and LDH_IBU) and endothermic (AC_IBU) and with greater accuracy of the CA adsorbent by IBU .The adsorbents in this study were classified as potential materials under development for adsorption of the emerging contaminants investigated.