Green microalgae scenedesmus obliquus utilization for the adsorptive removal of nonsteroidal anti-inflammatory drugs (NSAIDs) from water samples

Abstract

In view of the valorisation of the green microalga Scenedesmus obliquus biomass, it was used for the biosorption of two nonsteroidal anti-inflammatory drugs, namely salicylic acid and ibuprofen, from water. Microalgae biomass was characterized, namely by the determination of the point of zero charge (pHPZC), by Fourier transform infrared (FT-IR) analysis, simultaneous thermal analysis (STA) and scanning electron microscopy with energy dispersive spectroscopy (SEM/EDS). Kinetic and equilibrium batch experiments were carried out and results were found to fit the pseudo-second order equation and the Langmuir isotherm model, respectively. The Langmuir maximum capacity determined for salicylic acid (63 mg g−1) was larger than for ibuprofen (12 mg g−1), which was also verified for a commercial activated carbon used as reference (with capacities of 250 and 147 mg g−1, respectively). For both pharmaceuticals, the determination of thermodynamic parameters allowed us to infer that adsorption onto microalgae biomass was spontaneous, favourable and exothermic. Furthermore, based on the biomass characterization after adsorption and energy associated with the process, it was deduced that the removal of salicylic acid and ibuprofen by Scenedesmus obliquus biomass occurred by physical interaction.