Photocatalytic degradation of Congo red dye using La(OH)3 nanoparticles under visible light irradiation

Lanthanides are an attractive class of elements and have unique optical, catalytic, and magnetic properties because of their unique electron configuration (4f electrons). Lanthanide hydroxides Ln(OH)3 are of great importance because they represent a straightforward approach toward oxides or sulfides through dehydration or sulfuration. Hydroxyl groups may also act as active sites for surface grafting through condensation reactions of organic and/or biological reagents [1]. Lanthanum, the lightest element in the lanthanide series, has been widely studied in its oxide, hydroxide, phosphate, or oxychloride form and has been extensively applied in optoelectronic devices, phosphors, solid electrolyte, catalysis, sorbent, and a gas sensor [2,3]. Especially, lanthanum hydroxide (La(OH)3) is one of the novel rare earth compounds, and has been used in many field, such as ceramic, superconductive materials, hydrogen storage materials, electrode materials, etc, especially in catalyst and sorbent materials. The study of one-dimensional La(OH)3 has also been of growing interest owing to the promising applications in lanthanum hydroxide nanowires modified carbon paste electrode (LNW/CPE), catalyst, sorbent materials, sensors, multiplex materials, and the procedure for the collection of As(III) [4,5]. In the present study, La(OH)3 nanoparticles were prepared by the sol-gel method. The synthesized Lanthanum hydroxide nanoparticles were characterized by powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy, scanning electron microscopy and energy dispersive X-ray analysis (EDX). The X-ray powder diffraction (XRD) analysis revealed the formation of hexagonal phase La(OH)3 with average crystallite size of 29 nm. The present photocatalyst displays notable catalytic activity for the removal of Congo red dye in water under visible light irradiation. It was established that the catalyst could remove ca. 90% of the Congo red dye. The effects of initial dye concentration, photocatalyst dose, and visible light irradiation on dye degradation were evaluated.