Polymorphic LiZnSbO4 with orthorhombic and monoclinic phases for the efficient photocatalytic degradation of RhB and tetracycline in wastewater

Abstract

In this work, polymorphic LiZnSbO₄ powders have been synthesized via the solid-state reaction route, and their photocatalytic performances have been investigated under ultraviolet (UV) light illumination. XRD analysis discloses that a phase transition from the orthorhombic (α-LiZnSbO₄) to monoclinic (β-LiZnSbO₄) crystal system occurs while sintering above 1100 °C. Under UV light illumination for 90 min, α-LiZnSbO₄ exhibits a higher degradation ratio (92%) for RhB (5 mg L⁻¹) compared with that for β-LiZnSbO₄ (27%), which is due to its relatively high crystal symmetry and surface area and thus effectively increasing the carrier mobility. The α-LiZnSbO₄ catalyst also displays remarkable recyclability even after four successive cycles. On the basis of the scavenging and electron paramagnetic resonance (EPR) trapping measurement results, the confirmed active radicals are ˙OH and ˙O₂⁻ in the photocatalytic reaction. The degradation routes of RhB have been elucidated according to the intermediates detected. Besides RhB, tetracycline (TC) can also be efficiently degraded by α-LiZnSbO₄.