Sorption of naphthalene and its hydroxyl substitutes onto biochars in single-solute and bi-solute systems with propranolol as the co-solute

Abstract The sorption of naphthalene and its hydroxyl-substituted compounds onto two biochars that were produced at different temperatures was studied. The influences of propranolol as a co-solute and solution pH on the sorption were investigated. The sorption capacities of 1-naphthol and 4-nitro-1-naphthol on the biochar with a pyrolytic temperature of 200 °C (BC200) were greater compared to naphthalene. This occurred because the substitution of hydroxyl- and nitro-groups on the aromatic ring enhanced surface adsorption, e.g. hydrogen bond and π-π electron donor-acceptor interaction, while the hydroxyl in 1-naphthalenemethanol did not show the promoting effect. The sorption on the biochar with a pyrolytic temperature of 700 °C (BC700) followed a different sequence of 4-nitro-1-naphthol