Combined system of natural pomegranate as heterogeneous bioadsorbent and photocatalysis for removal of textile dye herbicide in presence of heavy metals: Effect of operating parameters and reaction monitoring

The photocatalytic degradation of acid orange II (AOII), which is a toxic dye effluent for textile applications, has been studied using natural pomegranate as heterogeneous bioadsorbent in the presence of TiO2 activated by an external ultraviolet radiation under various conditions. Powder of pomegranate rind and leaves has been tested for heavy metals adsorption. A special attention has been paid to the treatment efficiency of a real dye effluent in the presence of heavy metal, namely zinc (Zn). The experimental results showed that for low values of Zn2+ in the solution (40 mg/L), AOII removal kinetics fastened until reaching an optimum, then slowed down for higher concentrations (100 mg/L). This behavior could be explained by the fact that at low zinc concentrations, Zn2+ could be incorporated in the photocatalytic process because of its photonic character. At high concentrations, zinc is more susceptible of consuming radicals due to competition effect. On the other hand, results showed that no photocatalytic activity of Zn2+ was recorded. The degradation rate was strongly influenced by the presence of heavy metals, initial concentrations of AOII, and amount of crushed powder of pomegranate rind and leaves. Moreover, different ways of adding natural pomegranate in the photocatalytic reactor have been tested in order to keep Zn2+ concentration in optimal conditions. © 2017 Desalination Publications. All rights reserved.