Sustainable Near-Infrared Reflective Blue Pigments: Recycled Aluminum from Can Seals for Cobalt Aluminates in Cool Coatings

Abstract

Inorganic cool pigments are widely used as cooling agents in residential coatings due to their ability to achieve near-infrared reflectance. These coatings can be designed to exhibit a variety of colors independent of their reflectivity and absorption properties. Recent studies have highlighted the development of novel near-infrared (NIR) blue pigments, with an increasing emphasis on environmentally sustainable options that demonstrate high NIR reflectivity. This trend highlights the importance of creating novel and eco-friendly NIR reflective blue pigments. This study presents the synthesis of cobalt aluminates with varying concentrations of coloring ions (Co2+), achieved through the recycling of aluminum can seals via chemical precipitation. The formation of the spinel phase was confirmed through X-ray diffraction (XRD), and a colorimetric analysis was performed in the CIEL*a*b* color space. The synthesized pigments exhibited high near-infrared solar reflectance, with R% values ranging from 34 to 54%, indicating their potential as energy-efficient color pigments for use in coatings.