Investigation of NiO/Pd/Al2O3, CuO/Pd/Al2O3 and CoO/Pd/Al2O3 as catalysts for ozone decomposition and as photocatalysts

Abstract

Ozone decomposition over nanosized catalysts Pd/α-Al₂O_3, NiO/Pd/α-Al₂O₃, CuO/Pd/α-Al₂O₃ and CoO/Pd/α-Al₂O₃ was investigated, the catalytic systems were characterized using XRD, SEM, XPS, EPR, IR, (DR) UV–Vis and BET methods. The active NiO, CuO and CoO (10 wt%) phases of the supported catalysts were synthesized using deposition method on precursor Pd/α-Al₂O₃ (Pd content – 0.15 wt%). Activity of NiO/Pd/α-Al₂O₃ towards ozone decomposition is highest reaching almost 100 % within 20 min under working conditions. The precursor, containing only Pd shows lowest catalytic activity. The contact surface between catalyst and ozone increase in correlation with the reached activity due to deposition of transition metal oxides over Pd/α-Al₂O₃. Photocatalitic decoloration of three model wastewater textile dyes under UV light was also tested. The initial concentration of Reactive Orange 16 (Yellow), Reactive Blue 19 (Blue) and Reactive Red 180 (Red) dyes in water solutions was 20 ppm. The rate constants of NiO/Pd/Al₂O₃ photocatalysts decreased in the row: 30.4 (Blue) > 19.0 (Yellow) > 7.6 (Red). For CuO containing samples the rate constants are: 22.6 (Blue) > 17.4 (Yellow) > 6.7 (Red). For CoO/Pd/Al₂O₃ catalysts the values of rate constant are: 13.1 (Blue) > 9.1 (Yellow) > 2.5 (Red). We can conclude that NiO/Pd/Al₂O₃ has superior performance for all of the three used model contaminates, folowed by CuO/Pd/Al₂O₃ and CoO/Pd/Al₂O₃.