Solar-driven photodegradation of 17-β-estradiol and ciprofloxacin from waste water and CO₂ conversion using sustainable coal-char/polymeric-g-C₃N₄/RGO metal-free nano-hybrids

Herein, we report the synthesis of a metal-free coal-char supported polymeric g-C₃N₄/RGO (RPC) nano-photocatalyst for the efficient solar powered degradation of the noxious emerging pollutants ciprofloxacin (CIF) & β-estradiol (ESD) and conversion of CO₂ into CH₄, CO & O₂. RPC shows good photocatalytic and adsorption activity owing to its high surface area and reduced charge recombination rate. The photodegradation results of the treated water sample were investigated in terms of reaction kinetics, active species trapping experiments, high resolution mass spectrometry (HR-MS) and Chemical Oxygen Demand (COD) analysis. The higher solar photoactivity is attributed to the higher surface area, higher visible absorption, charge transfer, and reduced recombination. The superoxide radical anions were found to be the major active species in photodegradation, which is also supported by the band structure analysis. The catalytic activity is highly enhanced by the addition of H₂O₂, O₂ and O₃ as they facilitate the formation of radicals. The possible degradation pathways for the degradation of CIF and ESD have been proposed. This work shows promising solar-active metal-free photocatalysts for efficient environmental remediation and CO₂ conversion to fuels.