Recovery and reuse of TiO2 and other pigments from paint waste

Licentiate thesis, 2014

Titanium dioxide (TiO2) has numerous applications in our society, most notably as a white pigment in products such as paint, paper and plastic. Since 2010 there has been a sharp increase in the demand for and price of TiO2. As a result new and innovative ways of TiO2 production are needed. One potential source for recovering of TiO2 could be from waste paint. Not only could a recycling or recovery process for paint residues give paint manufacturers a new source of pigment, it would also give the industry a way of handling production waste and leftover paint products. In this work the possibility of replacing virgin pigments with inorganic residues from a waste paint pyrolysis process has been investigated. TiO2 and commonly used extender pigments were characterised using thermogravimetric analysis (TGA), X-ray diffraction (XRD) and specific surface area measurements (BET-N2) before and after the pyrolysis process. The inorganic residues from the pyrolysis were used in two different types of paint formulations as pigment replacement. The properties of the paints based on the pyrolysis residues were compared to the properties of paints based on virgin material. Results showed the crystal structures of the major pigments were left intact following the pyrolysis recovery process. Additionally, the recovery process had a negligible effect on the surface areas of all pigments except TiO2. The paints made from recycled material had acceptable opacity and gloss, but also showed surface defects due to poorly dispersed pigments and a decrease in whiteness.