Green synthesis of La2O2CO3 nanoparticles using tragacanth gel and its use as photocatalyst in the degradation of Black WNN dye

Lanthanum oxide is used to make optical glasses, which increases their density, refractive index, and hardness. In combination with oxides of tungsten, tantalum, and thorium, La2O3 improves the resistance of the glass against alkali compounds and is known as one of the ingredients for production of piezoelectric and thermoelectric materials. It is also used as a catalyst for the oxidative coupling of methane. Owing to its excellent physical and chemical properties, La(OH)3 has been extensively used as high-potential oxide ceramic, hydrogen storage materials, superconductive materials and, etc. Until quite recently, the catalytic and sorbet properties of La(OH)3 have been concerned intensively for their potential applications. Different metal oxides, hydroxides and carbonates were examined as photocatalysts for wastewater treatment. The effluents of textile and dye industries are the main pollutants in wastewater. This causes serious environmental problems such as increase of toxicity of environment, chemical oxygen demand (COD), biochemical oxygen demand (BOD), bad smell, and color of the wastewater. The colored organic dyes are heavily polluted the water system. The complete remediation of these dyes into less harmful chemicals is required to overcome these problems. Among various dye remediation process, the heterogeneous photocatalytic process is well known method for the decomposition of hazardous waste materials especially organic compounds into less harmful chemicals [1-4]. The use of natural gel is generating interest of researchers toward cost effective, nontoxic, economic viability and eco-friendly green synthesis of nanoparticles. In this work, lanthanum oxy-carbonate nanoparticles were synthesized using tragacanth gel as biotemplate by the sol–gel method without using any organic chemicals. The sample was characterized by powder X-ray diffraction, fourier transform infrared spectroscopy and scanning electron microscopy. Thereupon, La2O2CO3 NPs as an efficient photocatalyst was used for the degradation of Black WNN dye under visible light irradiation. The results display that the catalyst could remove ca. 90% of the Black WNN dye. The effects of initial dye concentration, photocatalyst dose, and visible light irradiation on dye degradation were evaluated.