Photocatalytic kinetics of 2,4-dichloroaniline degradation by NiO-clinoptilolite nanoparticles.

The ball-mill clinoptilolite nanoparticles (CNP) was ion-exchanged in Ni(II) solutions and calcined to obtain NiO-CNP catalysts with various NiO loadings. The resultant CNP was ion-exchanged in 0.1, 0.2, 0.3, and 0.4 M Ni(II) solutions and then calcined at 450 °C. The resultant NiO-CNPs contained 1.9, 2.3, 3.0, and 3.2% NiO, respectively. The XRD, FTIR, and DRS characterization techniques were applied. By applying the Scherrer equation on the XRD results, the average crystallite size for the NiO-CNP samples was estimated in the range of 42-65 nm. The pHpzc of the NiO-CNP species was slightly changed from 6.8 to 7.6 by an increase in the loaded NiO. The band gap energy of the samples was calculated by applying the Kubelka-Munk equation on the DRS results. The band gap energies of 3.81, 4.05, and 3.63 eV were estimated for the direct electronic transitions of the CN2, CN2.3, and CN3.2 samples, respectively. The boosted photoactivity was obtained in 2,4-dichloroanilyne (DCA) degradation when NiO supported onto both micronized clinoptilolite and its nanoparticles. The effects of the most important experimental variables on DCA photodegradation rate were kinetically studied by applying the Hinshelwood model on the results. The faster rate for the DCA photodegradation was achieved at the optimal conditions, including the catalyst dose: 0.5 g/L, C: 5 ppm, and the initial pH: 3. Some new peaks were observed in the HPLC chromatograms for the photodegraded DCA solutions after 180 min and 300 min, which showed 84% and 95% DCA photodegradation.