Photocatalytic decomposition of Congo red dye by black paste@TiO2 as an efficient recyclable photocatalyst

Abstract Manufacturing active and economical catalysts and using them in water treatment is one of the most important challenges facing researchers. Spent batteries signify a source of harmful materials when discarded without suitable treatment. In this work, a black paste as one of the main components of spent battery doped with different ratios of TiO 2 nanocomposites (0, 1, 3, 7, and 10 %) were manufactured using the sol–gel method. The characterization of the paste@TiO 2 nanocomposites has been investigated by SEM, XRD, DRS, FTIR, and BET analysis. The results show formation of anatase phase of TiO 2 in all doped samples. While the XRD of black paste indicates the presence of Mn 3 O 4 as a main phase. Photocatalytic properties of black paste@TiO 2 nanocomposites have been investigated using Congo red dye. The results showed that the presence of TiO 2 in the paste could increase the specific surface area and the composites’ photocatalytic efficiency. A higher percentage of TiO 2 (10 %) added to the black paste resulted in higher black paste@TiO 2 nanocomposite catalytic activity. The experimental photodegradation data were found to be consistent with the Lagergren kinetics model. The recyclability of the photocatalysts was examined for reuse in the industrial sector. Signifying that the black paste dopped with 10 % of TiO 2 (PTO4) photocatalyst in this study had high reusability.