Iranian Journal of

Background and Objective: Dyes are important pollutants that lead to producing serious hazards to human, other animals and organisms. Dyes are not biodegradable by aerobic treatment processes. Therefore, their removal from industrial effluents before discharging into the environment requires extreme and great attention. The aim of this research was to evaluate removal efficacy of methyl orange dye from aqueous solutions using NiFe₂O₄ nanoparticles.

Materials and Methods: This study was an empirical investigation in which NiFe₂O₄ nanoparticles were synthesized by co-precipitation method and were used as an adsorbent for the removal of methyl orange from aqueous solution. NiFe₂O₄ nanoparticles were characterized using X-Ray Diffraction (XRD), Transmission Electronic Microscopy (TEM), pH_pzc and SEM-EDX elemental analysis methods. Experiments were conducted discontinuously using 20 mL methyl orange solution of 40 mg/L. The effect of variables such as pH (2-8), amount of adsorbent (0.009-0.07 g) and contact time (2-70 min) on the efficacy of dye removal was studied. Finally, experimental data were compared by Langmuir, Freundlich, and Temkin isotherms and pseudo-first-order and pseudo-second-order kinetic models.

Results: TEM images showed that the NiFe₂O₄ nanoparticles had spherical shapes with the size of 12 nm. The results indicated that removal efficiency increased up to 0.04 g adsorbent and 20 min contact time. The optimum pH for methyl range removal was 2. Moreover, under these conditions, the adsorption process followed the Langmuir adsorption isotherm with a correlation coefficient of 0.995 and pseudo-second-order kinetic model with a correlation coefficient of 0.999. Also, the maximum adsorption capacity of the prepared adsorbent was 135 (mg/g) for Langmuir isotherm.

Conclusion: The NiFe₂O₄ nanoparticles are effective and available adsorbents for the removal of methyl orange from industrial wastewater.

Background and Objective: Owing to the extended usage in the safekeeping of environments, the photocatalytic materials have been widely applied. The purpose of the present study was to investigate the photocatalytic activity of ZnO and SnO₂ nanoparticles in removal of methyl orange from aqueous media.

Materials and Methods: ZnO and SnO₂ nanoparticles were synthesized through sol-gel and chemical precipitation respectively. Methyl orange was selected as model pollutant. The effect of weight fraction on the removal of pollutant was investigated in the range of 0.25, 0.5, and 1 weight percent. Meanwhile, for investigating the effect of radiation time, the suspension containing pollutant and nanoparticles was irradiated. The obtained results were analyzed by MSTATC, Ver 1.42 software and Duncan’s multiple range test.

Results: The analysis of variance results of removal efficiency of methyl orange showed that in the suspension involving ZnO and SnO₂, radiation time, weight fraction and the combined effect of them have a significant effect on the removal of methyl orange at 5% level of probability. Meanwhile, by increasing irradiation time from 5 to 25 min, the removal efficiency in suspensions containing ZnO and SnO₂ reached 97.42 and 65.55% respectively. Investigation on the effect of concentration on the removal of methyl orange shows that the removal of methyl orange increases with respect to the weight fraction.

Conclusion: According to the obtained results, it was observed that the photocatalytic activity of ZnO is higher than that of SnO₂. Therefore, the application of ZnO is more effective for removal of methyl orange from aqueous media.