Recycling of copper contaminants from wastewater as new hybrid catalysts for the synthesis of valuable pharmaceutical intermediates

The recycling of heavy-metals contaminants from wastewater as a source of valuable products perfectly fits in the principles of Circular Economy in view of restoring pollutants back into the system with new social and economic value. [1] To limit the release of heavy metals into the environment, national regulatory bodies impose effective wastewater treatments. Unfortunately, conventional methods, i.e. precipitation, coagulation, complexation, outcome often as inefficient or very expensive when contaminants are present in low concentrations. Biosorption, conversely, mediated by EPS (extracellular polymeric substances) [2-3] , produced by several bacterial cells strains, is gaining a great deal of attention as an economic, efficient and sustainable green depolluting approach of wastewater from metal cations such as copper. Serratia plymuthica strain SC5II [4] proved as the best bacterial strain displaying copper adsorbing properties with a maximum Cu specific removal of 21.6 mg/g. Copper coordination to EPS components in both its oxidation states was thus deeply investigated by 1H NMR titration, DLS, FT-IR analysis and SEM spectroscopy. The so obtained hybrid catalysts, merging the reactivity of copper with the stereoselectivity arising from EPS structures, were preliminarily applied to enantioselective β-borylation of α,β-unsaturated chalcones as useful intermediates in the synthesis of pharmaceutically related compounds. [5-6]