Ibuprofen and acetylsalicylic acid biosorption on the leaves of the knotweed Fallopia x bohemica

Abstract

Surface water contamination by pharmaceuticals is a serious environmental problem which must be solved by the purification of waste water, for example by sorption on different kinds of sorbents. The aim of this study is to verify the possibility of the utilization of crushed knotweed (Fallopia x bohemica) leaves as a cheap biosorbent for ibuprofen (IBU) and acetylsalicylic acid (ASA) sorption and to compare the sorption capacities with those of natural bentonite and active carbon. The time dependence of the selected pharmaceuticals’ sorption on the knotweed leaves was studied. The sorption equilibrium was reached after 6 hours. Subsequently, the sorption isotherms for selected pharmaceuticals were measured. The obtained experimental data correspond to the Langmuir model for all studied sorbents and for both pharmaceuticals. The maximal adsorbed amounts (calculated from the Langmuir model) on the knotweed leaves were 185.2 μmol g⁻¹ (38.2 mg g⁻¹) for IBU and 96.2 μmol g⁻¹ (17.3 mg g⁻¹) for ASA. These sorption capacities are lower compared to that of the active carbon and comparable to that of the studied bentonite. The mechanism of the pharmaceuticals’ sorption on the knotweed leaves can be explained by interactions among the nitrogen and oxygen bearing groups and by π–π interactions between the aromatic parts of the IBU and ASA molecules and the aromatic parts of the knotweed leaves’ structure. It was found that knotweed leaves represent an interesting alternative biosorbent usable for water purification.