Carvão ativado de capim annoni (Eragrostis plana Nees) produzido por pirólise convencional e ativação química aplicado ao processo de remoção de fármacos

Abstract

The present study describes the synthesis, characterization and application of Annoni Grass (Eragrostis Plana Nees) activated charcoal by conventional pyrolysis method and chemical activation for removal of two pharmaceutical compounds, acetylsalicylic acid (AAS) and sodium diclofenac (DFC) of aqueous solution. The Capim Annoni activated carbon synthesis process (CA-EPN 700) consisted of three main steps: chemical activation of the activating agent precursor biomass (ZnCl2), pyrolysis in a conventional tubular furnace with 10ºC min -1 heating ramp and maintained for 1 hour at 700 °C in an inert atmosphere and acid leaching of inorganic compounds. CA-EPN 700 was characterized by Elemental Analysis (CHN), Scanning Electron Microscopy (SEM), N2 Adsorption/Desorption Isotherms, Fourier Transform Infrared Spectroscopy (FTIR-ATR), Boehm Titration Method techniques. and Zero Charge Point (pHPCZ). Drug adsorption assays (AAS and DFC) on CAEPN 700 were performed by batch adsorption procedure at 25 °C. Important parameters that influence the adsorption capacity of drugs (AAS and DFC) in CA-EPN 700 were investigated as amount of adsorbent mass, solution pH, contact time between adsorbent and adsorbate, and initial concentration of adsorbate. The maximum adsorption capacity for AAS and DFC in CA-EPN 700 were obtained at pH 5. The minimum amount of CA-EPN 700 mass required to obtain the maximum adsorption capacities for AAS and DFC was 60 mg CA -EPN 700 in 20 mL of adsorbate (AAS and DFC). Equilibrium condition was satisfied within 60 minutes for both pharmaceutical compounds studied. The nonlinear equilibrium models Langmuir, Freundlich and Sips were used to describe the mechanism of interaction between adsorbentadsorbate. The Sips equilibrium model was the best fit for the experimental data set. Based on the Sips model the maximum adsorption capacity (Qmax) was 221.22 mg g-1 for AAS and 356.78 mg g-1 for DFC. Adsorption kinetics of pharmaceutical compounds (AAS and DFC) in CA-EPN 700 were investigated using the nonlinear kinetic models of Pseudo-first order, Pseudo-second order and Elovich. The Pseudo-second order kinetic model was the model that best described the adsorption kinetics for both pharmaceutical compounds studied in this work presenting high values of adjusted coefficient of determination (R2 adj) closer to the corresponding unit and low values for standard deviation (SD). The results show the viability of Capim Annoni application as precursor biomass for activated carbon synthesis and also show that CA-EPN 700 can be used for AAS and DFC adsorption studies of aqueous solution.