Inorganic oxide systems as platforms for synergistic adsorption and enzymatic conversion of estrogens from aqueous solutions: Mechanism, stability and toxicity studies

Synthetic hormones constitute a dangerous class of pollutants as they impose risks on the reproductive health of ecosystem life and humans via the water, including drinking water. Traditional methods of wastewater treatment seem to be inefficient. In this work, design and fabrication of a new biosystem made of CaSiO₃ and laccase is reported and its application for removal of 17α-ethynylestradiol (EE2) from aqueous systems is demonstrated. EE2 is a synthetic estrogen, which is known to resist degradation. The effect of treatment time, pH, temperature, estrogen concentration and mass of the biocatalytic system was investigated. Treatment of EE2 solution (0.1mg/L) with 100mg of the biosystem for 12h at pH 5, 25 °C resulted in 100% removal efficiency. The data confirmed a synergistic degradation of estrogen resulting from simultaneous adsorption and biocatalytic conversion with a significant predominance of enzymatic conversion. The efficiency of estrogen removal by the biosystem varied depending on type of cations and anions present in the solution. After 10 cycles of repeated use, and 20 days of storage, the CaSiO₃-laccase biosystem retained ~40% of its initial activity. Application of the CaSiO₃-laccase biosystem significantly reduced toxicity and estrogenic activity of the solution. Finally, it was also possible to remove more than 40% of EE2 from samples of real wastewater using the CaSiO₃-laccase biosystem. The method may pave the way for new efficient approaches for removal of pharmaceuticals and hormones from wastewater.