Beach-cast <i>Sargassum cymosum</i> macroalgae: biochar production and apply to adsorption of Acetaminophen in batch and fixed-bed adsorption processes

Abstract

In order to add value to the beach-cast <i>Sargassum cymosum</i> algae, its biomass was converted by pyrolysis process at 800°C into biochar, characterized and applied in the adsorption of Acetaminophen in batch and fixed-bed processes. Characterization by pH, Point of Zero Charge (pH_PZC), Fourier-Transform Infrared Spectroscopy (FTIR), Thermogravimetric (TG), Scanning Electron Microscopy (SEM) and Surface area (BET) showed that the biochar presents properties favourable for the Acetaminophen adsorption. High surface area was obtained of 368.1 m². g^-1, presenting the formation of pores, observed by SEM. The biochar showed basic characteristics (pH = 8.84 and pH_PZC = 9.9), inferring an adsorption involving several different mechanisms such as dispersive interactions by π electrons, electrostatic attractions, and hydrophobic interactions. The adsorption mechanism is limited by chemisorption and governed by the formation of monolayer on the biochar surface, the Pseudo-second order kinetic and Langmuir-Freundlich isotherm model described the best behaviour of batch adsorption, with equilibrium and maximum adsorption capacity <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>q</mml:mi><mml:mi>e</mml:mi></mml:msub></mml:math> = 6.93 ± 0.07 mg. g^-1 and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>q</mml:mi><mml:mrow><mml:mi>m</mml:mi><mml:mi>s</mml:mi></mml:mrow></mml:msub></mml:math> = 12.34 ± 0.45 mg. g^-1, respectively. Fixed-bed adsorption were performed varying adsorbent mass (0.3 and 0.6 g) and flow rate (2.5 and 5.0 mL. min^-1), the best <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>q</mml:mi><mml:mi>y</mml:mi></mml:msub></mml:math> = 42.33 mg. g^-1 found to adsorbent mass of 0.6 g and flow rate of 2.5 mL. min^-1. Yan model described the best behaviour of the breakthrough curves data. Thus, the results provide insights into the development of adsorbents from beach-cast of <i>Sargassum cymosum</i> to adsorption of Acetaminophen, enhancing the use of environmental waste to obtain it.