Sorption of ofloxacin and chrysoidine by grape stalk. A representative case of biomass removal of emerging pollutants from wastewater

Emerging pollutants, as antibiotics or dyes, in aquatic ecosystems are a crucial concern and numerous techniques have been developed for their removal. Efficiency, cost effectiveness, and biodegradability reveal biomass sorption as one of the most appealing methods. This study aims to evaluate the effectiveness of grape stalk as a sorbent for ofloxacin (a fluoroquinolone antibiotic) and chrysoidine (an azo-dye). The kinetic and the thermodynamic aspects of the sorption were studied. A pseudo first-order kinetic behavior is shown by both substances, though the kinetic constants of ofloxacin are almost double than those of chrysoidine. The sorption isotherms, which strictly follow the Langmuir model, show remarkable differences as a function of pH and of biomass size. The trend of Langmuir parameters, Q_max and K, as a function of pH and size, is discussed, and different binding mechanisms are proposed. Kinetic and thermodynamic parameters prefigure grape stalk as a potential biomass for scavenging toxic substances from wastewater.