Selective Photodegradation on Dual Dye System by Recoverable Nano SnO₂ Photocatalyst

Abstract

A facile co-precipitation technique was developed to prepare SnO₂ nanoparticles using stannous chloride dihydrate (SnCl₂⋅2H₂O) and characterized. The photocatalytic efficiency of nano SnO₂ was tested for degradation of Rhodamine B: C₂₈H₃₁ClN₂O₃ + (nano SnO₂/λ = 254 nm) + reactive species (^•O₂^{−, •}OH, ^•OOH) → H₂O + CO₂. In addition, mixture of Rhodamine B (RhB) and malachite green oxalate (MGO) were selected as the dual dye system (model pollutants) and their influencing factors such as concentration of mixtures (RhB + MGO), catalyst dosage, intensity of light source (254 and 365 nm), pH were also studied. Blank experiment (without catalyst) and surface adsorption indicates that Rhodamine B degrades at relatively very slow rate with k = 2.30 × 10⁻³ min⁻¹ and k = 2.4 × 10⁻³ min⁻¹ respectively. However, nano SnO₂ induces a large increment in degradation rate corresponding with k = 4.0 × 10⁻³ min⁻¹ (RhB = 8.69 × 10⁻⁶ M, catalyst 50 mg/100 mL, λ = 254 nm) and mixed dyes k_RhB = 18.96 × 10⁻³ min⁻¹ and k_MGO = 26.5 × 10⁻³ min⁻¹ were obtained. Further, the reusability of the catalyst was sustained up to three cycles and verified with XRD pattern.