Zirconium oxide nanoparticles were prepared by precipitation from different organic acid precursors (oxalic, tartaric, citric, succinic, malic, maleic and malonic) and ignition at 750 °C. The as-prepared samples were charac-terized by XRD, FT-IR, UV–Vis and HR-TEM techniques. XRD proved the crystalline monoclinic structure of the samples with average crystal sizes ranged from 7.1 nm (for citrate) to 35.1 nm (for maleic) precursor. The FT-IR spectra of the nanooxides showed the characteristic bands due to νOH, δOH and νZr-O at 3444, 1633 and 498 cm−1, respectively. The UV–Vis spectra proved the semiconductor nature of the samples with optical energy gap ranging from 1.80 to 4.30 eV. One of the prepared samples was tested as catalyst for the photodegradation of Orange G dye in wastewater samples in presence of H2O2 where 100% removal of the dye was obtained after about 180 min.