Rapid synthesis of tetragonal zirconia nanoparticles by microwave-solvothermal route and its photocatalytic activity towards organic dyes and hexavalent chromium in single and binary component systems

Abstract In this paper, tetragonal zirconia nanoparticles (ZrO2 NPs) were synthesized via rapid microwave mediated solvothermal method in just 10 min reaction time. A combination of X-ray diffraction, Raman, Scanning Electron Microscopy (SEM), High Resolution Transmission Electron Microscopy (HRTEM) and XPS analysis confirmed the formation of single phase tetragonal ZrO2 with average crystallite size ∼ 10 nm. The band gap energy of the synthesized ZrO2 was measured to be 3.67 eV. The photocatalytic behaviour of synthesized ZrO2 NPs was examined for the degradation of two anionic dyes (Eosin Yellow and Bromophenol Blue) and the reduction of Cr(VI) under UV light irradiation. ZrO2 adsorbed and degraded both the dyes within 120 min. At 20 mg/L concentration, more than 96 % of Cr(VI) was reduced to Cr(III) within 60 min. Under the operating conditions, both the degradation of dyes and reduction of Cr(VI) followed pseudo first-order kinetics and rate constant values were inversely dependent on the initial dye concentration. The probable mechanism for the degradation has been proposed through advanced oxidation process. ZrO2 NPs was also found efficient for simultaneous remediation of dye and Cr(VI). The photoreduction of Cr(VI) to Cr(III) was further confirmed from XPS analysis of ZrO2 NPs after chromium reduction.