Rapid enhanced photocatalytic degradation of dyes using novel N-doped ZrO2

• A novel N–ZrO2 is synthesized by a thermal decomposition method.
• Complete removal of amaranth and methylene blue is obtained by UVA/N–ZrO2.
• N–ZrO2 is photostable and reusable.
• Band gap narrowing is mainly responsible for enhanced activity.
• N doping extends the spectral response up to the NIR region.

A novel N-doped ZrO2 (N–ZrO2) photocatalyst is synthesized through thermal decomposition of zirconium hydroxide-urea complex and is characterized using various techniques, including XRD, FTIR, TGA, SEM, TEM, UV-DRS, XPS, XANES, and BET. The N–ZrO2 possesses pure monoclinic structure with high crystallinity. By using the proposed facile route of synthesis, both interstitial and substitutional N doping with high dopant stability can be realized. The optical properties of the catalyst are significantly altered after N doping, giving an optical response in the visible and near infrared regions and an additional strong absorption peak in the UVA region. The N–ZrO2 showed a higher photocatalytic activity than pristine ZrO2 for the degradation of amaranth (AM) and methylene blue (MB) under visible or UV light irradiation, which could be attributed to the band gap narrowing, higher specific area, smaller crystalline size, and higher availability of surface hydroxyl groups. Due to its molecular structure and light absorption characteristics, MB is easier to degrade than AM. Overall removal efficiencies, including adsorption and photolysis, for AM and MB by N–ZrO2 at pH 7 with initial dye concentration of 10 mg/L, catalyst concentration of 1 g/L, and visible light irradiation of 144.7 W/m2 are 67.2 and 96%, respectively. Using UVA light of only 3.5 W/m2 under identical experimental conditions, complete removal of MB and AM is obtained. The photocatalytically treated solution of either AM or MB is nontoxic against Bacillus cereus, an agriculturally important soil microorganism.