Partial pyrolysis of olive wood to improve its sorption of chlorophenols and nitrophenols

Abstract

Partial pyrolysis alters the chemical and textural properties of the lignocellulosic material. This work reports the effect of partial pyrolysis of olive wood on adsorption isotherms, kinetics and thermodynamics of chloro and nitrophenols. Shape of adsorption isotherms of the partially pyrolyzed sorbents was L3 for phenol; L2 for 2-nitrophenol and 2,4-dinitrophenol; H3 for 2-chlorophenol, 3-chlorophenol and 4-nitrophenol; and H2 for 4-chlorophenol. The pyrolyzed olive wood sorbents obeyed Langmuir and Freundlich models. Pyrolysis raised adsorption capacity, favorability and spontaneity; the adsorption became more exothermic; the randomness decreased. The adsorption was mainly physical; it occurred first by film diffusion then by pore-filling. Adsorption followed second-order rate kinetics. Adsorption of phenols on olive wood seemed to be governed by hydrophobic interaction. Washing the pyrolyzed olive wood with ethanol caused a decrease in adsorption capacity, favorability and spontaneity, and the adsorption became less exothermic. This indicated that pyrolysis produced species on the olive wood surface that played a significant role in phenols adsorption.