Contributing factors on the removal of Azo-dyes from industrial wastewater: A comparison of the efficiency of sonocataysis and photocatalysis process

The influence of the number of operating parameters on photocatalytic and sonocatalytic Acid Red 88 degradation from an aqueous solution was investigated in this paper. The experimental results indicated that the sonocatalytic process with Ni-TiO2 was far more effective for the degradation of high concentration azo dyes, regardless of the process condition. In order to achieve a larger surface area of the catalyst, Ni-TiO2 was suspended in the aqueous solution. The optimum experimental conditions obtained as catalyst dosage of 0.6mg L-1, pH of 7 and dye concentration of 30 mg L-1. The COD value of the solution after photodegradation showed a significant decrease to 59 mg L-1 from 1573 mg L-1 while this value decreased to 34 mg L-1 after sonocatalytic degradation. The catalyst performance was evaluated by SEM and XRD techniques. Dye removal efficiency of 88% was obtained by sonocatalysis process with a dye concentration of 300 mg L-1 and within a pH range of 2-11. However, the efficiency was only 28% after photocatalytic degradation with the same dye concentration and within a more limited pH range of 3-9. Therefore, a specific method was proposed in this article for azo dye degradation.