Oxygen vacancy enriched SrTiO3 and NiO-based S-scheme heterojunction moored on activated carbon from exhausted water filter batteries for ameliorated photodegradation of doxycycline hydrochloride and methyl orange degradation

Background: In this research study, O-SrTiO3/NiO/AC-EWC photocatalytic heterojunction was firstly fabricated hydrothermally followed by a thermal decomposition method for aqueous doxycycline and methyl orange photodegradation. The XRD plots depict the formation of crystalline bare SrTiO3, O-SrTiO3, NiO, and amorphous activated carbon from exhausted water filter cartridges. UV-vis spectroscopy revealed improved light absorption of O-SrTiO3/NiO/AC-EWC than bare semiconductors owing to synergistic effects of present oxygen vacancies and formation of heterojunction. EIS Nyquist plots and PL spectra studies depicted that O-SrTiO3/NiO/AC-EWC heterojunction showed maximum charge isolation and migration to surface of semiconductors. Constructed S-scheme heterojunction between O-SrTiO3 and NiO supported by AC-EWC was significant to separate the photogenerated charges for the generation of active radicals with superior redox potential. Significant findings: Under 30 min of dark, O-SrTiO3/NiO/AC-EWC exhibited the highest DCHCl (39 %) and MO (35 %) adsorption from the reaction mixture. After 60 min of illumination, total DCHCl and MO degradation efficiency order was found to be O-SrTiO3/NiO/AC-EWC>O-SrTiO3/AC-EWC>O-SrTiO3>NiO>SrTiO3. Overall, O-SrTiO3/NiO/AC-EWC heterojunction has the highest degradation rate of 95.7 %, 96.2 % as well as rate constant k, 0.01513 min(-1), and 0.019 min(-1) for DCHCl and MO, respectively. A significant decrease in photoactivity of O-SrTiO3/NiO/AC-EWC on adding scavengers revealed the active role of reactive center dot O-2(-), center dot OH, h(+) for the degradation. Satisfactory reusability of effective O-SrTiO3/NiO/AC-EWC S-scheme heterojunction was demonstrated after 4 runs and found to be 91 % and 92.2 % for DCHCl and MO degradation, respectively in recycling tests. This study will shed new light on the design, and growth of integrated photocatalyst systems, and the removal of antibiotics and dyes.