Synthesis and characterization of Fe0/TiO2 nano-composites for ultrasound assisted enhanced catalytic degradation of reactive black 5 in aqueous solutions.

In the present study, nanocomposites (NCs) of zero valent iron nanoparticles (Fe0 NPs) and titanium dioxide nanoparticles (Fe0/TiO2 NCs) were prepared by coating Fe0 NPs onto the surface of TiO2 NPs through borohydride reduction of Fe(II) salt for the ultrasound assisted removal/ degradation of reactive black 5 (RB5) dye from aqueous solutions. Morphological and structural characterizations of the Fe0/TiO2 NCs were performed by FE-SEM, HR-TEM, XRD, XPS and Brunauer-Emmett-Teller (BET) method. The Fe0/TiO2 NCs exhibited highly efficient ultrasonic degradation/decolourization of RB5, compared to TiO2 NPs counterpart. In the presence of ultrasonic irradiation, 0.25g/L of Fe0/TiO2 NCs showed complete removal of 100mg/L RB5 dye within 10min of reaction. An increase in RB5 removal efficiency was obtained with decrease in initial concentration and solution pH, whereas it was decreased with decrease in the amount of Fe0/TiO2 NCs. The rate of RB5 degradation was in good agreement with the pseudo-first-order kinetic model. Higher RB5 removal efficiency was observed at a higher ultrasonic power level. Coexisting NO3- and SO42- ions had only a minor impact on the removal of RB5, whereas, CO32- ions considerably affected the% removal of RB5 using Fe0/TiO2 NCs. Regeneration/reusability experiments revealed that Fe0/TiO2 NCs could be reused efficiently up to 7th removal cycle without considerable loss of their original RB5 removal performance. Liquid chromatography-mass spectrometry (LC-MS) study, used for the detection of the RB5 degradation products showed that the degradation mechanism proceeds via the reductive cleavage of the azo linkage of the dye which produced 1-sulfonic, 2(4-aminobenzenesulfonyl) ethanol as the stable end product.