Potential Application of Alternative Materials for Organic Pollutant Removal

Abstract

The work aims to synthesize and characterize vegetal charcoal (or biochar) from Syzygium cumini (AC-SC), evaluating the adsorption capacity for dexamethasone drug (DEX) removal, using the kinetic and equilibrium adsorption. The samples were characterized by N₂ porosimetry, X-ray diffraction, scanning electron microscopy with energy-dispersive spectroscopy, zeta potential, and zero charge point. Adsorption equilibrium was carried out applying the Langmuir, Freundlich, Redlich-Peterson, Sips, and Toth models, and kinetic adsorption applied the pseudo-first order, pseudo-second order, Elovich, Avrami, and Weber-Morris models. AC-SC showed a heterogeneous and porous surface, negatively charged, crystalline structure, specific surface area of the 2.14 m² g^-1 and pH_ZCP = 7.36. About the effect of the AC-SC concentration, 5.0 g L^-1 showed the best DEX removal (53.02%), about the others' concentration (2.0 and 7.5 g L^-1). About the equilibrium and kinetic adsorption, the Sips model and pseudo-second order showed the best experimental data adjusted, indicating that the adsorption monolayer was dependent on the ions onto the biosorbent, with a maximum adsorption capacity of 0.744 mg g^-1 after 180 min. Therefore, AC-SC can be used as an alternative material in the removal of organic pollutants, such as drug removal.

Keywords: Adsorption; Biochar; Biosorption; Dexamethasone; Syzygium cumini.

Fig. 1

Schematic representation of the AC-SC preparation process

Fig. 2

XRD pattern diffractogram of the AC-SC

Fig. 3

a SEM micrograph at 710 × magnification and b elementary composition (% weight) obtained by EDS analysis for the AC-SC.

Fig. 4

N₂ adsorption/desorption isotherms of the AC-SC

Fig. 5

Zero charge point (pH_ZCP) of the AC-SC