Photocatalytic Removal of Acid Blue 113 Dye from Aqueous Solutions Using Zinc Oxide-Kaolin Nanocomposite under Visible Light Irradiation

Textile industries produce huge amounts of colored wastewater. Synthetic dyes cause serious problems to human health and aquatic organisms due to their toxic and carcinogenic properties. In this study, Acid Blue 113 (AB113), which is stable and persistent against conventional treatment methods was selected as the target contaminant.

The synthesis of the ZnO-Kaolin nanocomposite was performed by simple co-precipitation approach. The crystalline structure, functional groups, morphology, and elemental composition of the prepared samples were characterized using XRD, FT-IR, SEM and EDX analyses, respectively. Next, the photocatalytic response was evaluated via degradation of AB113 dye under visible irradiation. Also, the influences of operating parameters, including pH, catalyst value, initial AB113 concentration, various gases, organic compound types, and catalyst recycling on the photocatalytic performance were studied in a batch reactor.

The SEM analysis confirmed the ZnO-Kaolin spherical structure. Presence of organic compounds in the aqueous medium decreased AB113 removal efficiency. The highest removal efficiency (84.33%) was obtained at catalyst loading=0.4 g.L-1, initial dye concentration=20 mg.L-1, and pH=7. Compared with ZnO and Kaolin nanoparticles, the resulting catalyst (ZnO-Kaolin) exhibited significantly improved photocatalytic activity in AB113 degradation. The degradation of AB113 was found to follow the first order kinetic (Kobs: 0.122 min-1 and R2: 0.9516) and the Langmuir-Hinshelwood model (KC: 0.278 mg.L-1.min-1 and KAB113: 0.128 L.mg-1).

The proficient performance of the LED/ZnO-Kaolin system illustrated that it can be used for practical applications in water treatment.