Microwave regeneration of spent catalyst coupled with ultrasound augmented copper impregnation as a potential adsorbent photocatalyst

The present work attempts to regenerate the spent catalyst loaded with mercuric chloride utilizing microwave heating, followed by ultrasound augmented impregnation of Cu(NO₃)₂. The ultrasound augmented impregnation as compared to conventional impregnation has resulted in adsorption capacity higher by 12.5 mg g⁻¹. The impregnated Cu(NO₃)₂ inside the carbon porous matrix was converted to copper, copper oxide, and cuprous oxide after thermal treatment. The optimal microwave regeneration process conditions were identified to microwave power 500 W, roasting temperature 800 °C and roasting duration of 25 min. The CuO loaded samples prepared at optimal regeneration conditions exhibited a MB removal capacity is 122.5 mg g⁻¹. The physico-chemical properties of Cu-spent catalyst were examined by XRF, XRD, XPS, SEM, FTIR and N₂ adsorption. Additionally, the photocatalytic effectiveness of the Cu loaded porous matrix was tested based on the MB degradation efficiency. The ultrasound augmented impregnation was found to be far superior to conventional impregnation based on the ability to photocatalytically degrade MB. (paper)