Advanced oxidation processes applied to tannery wastewater containing Direct Black 38—Elimination and degradation kinetics

The application of advanced oxidation processes (H2O2/UV, TiO2/H2O2/UV and TiO2/UV) to treat tannery wastewater was investigated. The experiments were performed in batch and continuous UV reactors, using TiO2 as a catalyst. The effect of the hydrogen peroxide concentration on the degradation kinetics was evaluated in the concentration range 0–1800 mg L−1. We observed that the degradation rate increased as the hydrogen peroxide increased, but excessive H2O2 concentration was detrimental because it acted as a hydroxyl radical scavenger since it can compete for the active sites of the TiO2. In the H2O2/UV treatment, the COD removal reached around 60% in 4 h of reaction, indicating that the principal pollutants were chemically degraded as demonstrated by the results for BOD, COD, nitrate, ammonium and analysis of the absorbance at 254 nm. Artemia salina toxicity testing performed in parallel showed an increase in toxicity after AOP treatment of the tannery wastewater.