Removal of a mixture of veterinary medicinal products by adsorption onto a Scenedesmus almeriensis microalgae-bacteria consortium

The adsorption of the veterinary medicinal products (VMP) tetracycline (TET), ciprofloxacin (CIP), sulfadiazine (SDZ) and sulfamethoxazole (SMX) onto a dried Scenedesmus almeriensis microalgae-bacteria consortium was studied at several equilibrium concentrations (20 to 1000 mu g/L). Scanning electron microscopy (SEM) and Fourier-transform infrared spectroscopy (FTIR) analysis were performed to investigate the surface morphology of the microalgae and to identify the effect of the antibiotics functional groups on the surface of the consortium of S. almeriensis and bacteria. Ultra-high performance liquid chromatography tandem mass spectrometry (UHPLCMS/MS) was used to determine the feasibility of this consortium for the removal of antibiotics via biosorption. Freundlich and Langmuir adsorption models were used for the mathematical description of the adsorption equilibrium. Pseudo-first order and pseudo-second order kinetic models were applied to fit the biosorption experimental data. Relative antibiotic removal was higher at low equilibrium concentrations. In the range of the initial VMP concentration studied, ciprofloxacin and tetracycline exhibited the highest removal efficiency of 43-100% and 75-82%, respectively. Likewise, ciprofloxacin and tetraciclyne presented the highest adsorption rates of 0.11-26.66 and 1.78-27.09 mg.mu g(-1).h(-1), respectively. This study revealed that the S. almeriensis-bacteria consortium has a high biosorption power and proved that biosorption is an important mechanism in the removal of ciprofloxacin and tetraciclyne using a microalgae-based water treatment process. However, sulfadiazine and sulfamethoxazole removals did not exceed 32%.