Background and purpose: Textile dye effluents have some potential risks which require effective treatment before discharging into the environment. Advanced oxidation processes can remove pollutants faster than other processes due to active hydroxyl radical production; therefore, increase the efficiency of dye removal. This study was aimed at investigating dye removal process using UVA/ZnO and UVA/TiO₂ nanocatalysts.

Materials and methods: This study was done in a batch reactor on synthetic and real samples and the effects of initial dye concentrations, TiO₂ and ZnO nanoparticles dosage, time, pH  and interference compounds on efficiency of dye removal was investigated. The Daphnia Magna was used for bioassay test.

Results: The removal rates of dye in optimum conditions were 69% and 95.5% by UVA/ZnO and UVA/TiO₂ processes, respectively and the optimum pH in the process was 9 and 2, respectively. In this study, the initial concentration of dye and COD were found to have adverse relation with removal rate of dye in two processes (p<0.05, r²_ZnO= 0.99, r²_TiO2= 0.94). With increasing the catalyst and exposure time at both processes the dye removal rate increased. In this study, LC50 96 h decreased from 96.7 to 44.7 mg/l.

Conclusion: The current study showed that TiO₂/UVA process with effective optimization of operational factors, has high performance in R.B 86 dye decolorization and reducing toxicity.