Lanthanum oxide-based nanomaterials synthesized by using carbon aerogel template for efficient phosphate capture

Abstract

Phosphate is a chemical compound that contains phosphorus, an essential nutrient for the growth of all organisms on Earth. However, the overuse of fertilizers has created a serious environmental problem worldwide, because the discharge of wastewater containing excess phosphate leads to eutrophication. Therefore, proper management of phosphate from wastewater is very important. In this study, lanthanum oxide-based nanomaterials (LONs) were synthesized by a hard-template method using porous carbon aerogels, and their potential as adsorbents for efficient phosphate removal was evaluated. The use of carbon aerogels offers facile production of porous adsorbents because simple calcination under air can remove the template, which is more suitable for environmental and industrial applications than the use of toxic chemicals for conventional silica template removal. The morphology and porosity of the LONs were controlled by adjusting the synthesis conditions, including calcination and oxidation. The phosphate removal capacity of LONs strongly depends on the porous structure and surface area because the adsorption process is governed by monolayer adsorption of phosphate-forming lanthanum phosphate. LONs with an optimized structure exhibited a high adsorption capacity of 135.14 mg P g−1 at 28 °C (qm by the Langmuir isotherm model). LON adsorbents have great potential for efficient phosphate removal to meet increasingly stringent discharge standards and to prevent the pollution of water resources.