Identification and Characterization of Ti-Spheres (Titanspheres) in Cork Powder Fly Ash

Abstract

During the treatment of cork powder from different products, for example, the production of cork stoppers, cork powder is generated and used as fuel. However, the combustion of cork powder produces ash, specifically fly ash, which is the object of this study, with the aim of valorization. Previous studies showed that this ash contains, Ti-spheres (hereinafter referred to as titanspheres), among other morphotypes, which may be the most valuable ash component if they have application in ink industry as white pigment. Therefore, cork powder fly ash was sampled in the combustion unit of the champagne stoppers producer “RELVAS II”. Wet and dry sieving trials combined with ultrasound and a polycarboxylate bath were performed to obtain size fractions and concentrations of the titanspheres. A combination of analytical techniques (SEM/EDS, XRD, XRF, ICP-MS, reflected light microscopy, and Raman microspectroscopy) was used to characterize the bulk ash, size fractions, and, in particular, titanspheres. It was concluded that dry sieving is not an efficient method for cork powder fly ash size fractionating. However, with a combination of wet sieving, ultrasound, a polycarboxylate solution and acid reflux, it was possible to obtain a < 25 µm concentrate that mostly comprised amorphous aluminosilicate material, quartz, and titanspheres. The titanspheres in this concentrate have a 15–25 µm diameter, and the phases determined by XRD include rutile, perovskite and priderite.