Visible light water disinfection using [Ru(bpy)2(phendione)](PF6)2·2H2O and [Ru(phendione)3]Cl2·2H2O complexes and their effective adsorption onto activated carbon

Abstract Water soluble Ru(II) polypyridyl complexes [Ru(bpy) 2 (phendione)](PF 6 ) 2 ·2H 2 O (complex1) and [Ru(phendione) 3 ]Cl 2 ·2H 2 O (complex2) (bpy = 2,2′-bipyridine, phendione = 1,10-phenanthroline-5,6-dione) showed complete photoinactivation of Gram positive and negative bacteria on photolysis using light emitting diode array as visible light source. Photoinactivation of Escherichia coli was not observed in presence of mannitol, which indicated that hydroxyl radicals attack cells and lead to cell damage. Fluorescence microscopy and SEM analysis revealed loss of cell integrity due to membrane damage and emphasise that complexes have the ability to cause complete photoinactivation of E . coli . Activated carbon and silica were employed as adsorbents to remove these photoactive complexes from water. Freundlich adsorption capacity, K F , values of complex1 and complex2 for adsorption by activated carbon were determined to be 22.74 and 8.26, respectively. K F , values of complex1 and complex2 for adsorption by silica were determined to be 3.62 and 0.57, respectively. The study reveals that complex1 and complex2 are promising candidates for visible light inactivation of bacteria and can also be effectively removed from water by adsorption onto activated carbon, and imply that these complexes are potential photosensitizers for visible light water disinfection.