Management of a ciprofloxacin as a contaminant of emerging concern in water using microalgae bioremediation: mechanism, modeling, and kinetic studies

Pharmaceutical residues which are labeled as a new class of environmental contaminants have potentially negative environmental and human health effects. Recently, biosorption is one of the most appealing choices to manage these pharmaceutical wastes in water. However, the environmental limitations of the adsorbent material are an obstacle to the development of this process. Hence, the current study suggested two biosorbents; Chlorella vulgaris and Synechocystis sp. microalgae to manage Ciprofloxacin (CIP) in water. The experimental results showed that the optimal adsorption conditions are an initial CIP concentration of 4.0 mg L ^− 1 and pH 5 and 3 for Synechocystis sp. and C. vulgaris , respectively. The adsorption process fitted well with the pseudo-second-order kinetic model. The main mechanism of biosorption is the complexation of CIP with carboxyl, hydroxyl, carbonyl, and amido groups which was confirmed by Fourier-transform infrared spectroscopy (FTIR), Scanning electron microscopy (SEM), and energy-dispersive X-ray spectrometry (EDX) analyses which represent the presence of CIP on the cyanobacterial cell surface and intracellularly. These results revealed that the adsorption mechanism of CIP by Synechocystis sp. PCC6803 and C. vulgaris provide theoretical guidance for insight into the biosorption mechanisms of pharmaceutical residues by other strains.