Use of an industrial by-product phosphogypsum in the production of white textured paints

Phosphogypsum (PG) is the main by-product of fertilizer and phosphoric acid production. Currently, over 21 million tonnes of phosphogypsum are accumulated in Lithuania. About 5500 tonnes of PG are added to these 'hills' every day; thus, they are getting replenished at a rate of 2 million tonnes per year. Currently, the area of phosphogypsum occupies ca. 84 ha, and their height reaches 60 m. Phosphogypsum is stored in the open areas, thereby discharging such toxic contaminants as fluorine and various water-soluble and insoluble oxides into the environment. As a result, it inflicts harm on all living organisms, and there is reasonable concern regarding the arising environmental issues. This has led to profound interest in using phosphogypsum as an alternative raw material for a variety of purposes. The paint industry is continuously trying to reduce its harmful environmental impact. This is especially related with titanium dioxide which is one of the most common materials used in white paint manufacturing; yet, at the same time, a large amount of TiO2 goes to waste.Considering these challenges, a study of the possibility of using phosphogypsum in the preparation of water -emulsion acrylic white paint with partial replacement of TiO2 was performed. The investigation has shown that titanium dioxide cannot be completely replaced with PG; however, as a filler, it can still account up to 32% of their total content. It is noteworthy that acidic impurities in phosphogypsum must be neutralised before use. Lime-modified phosphogypsum reduces the TiO2 content and contributes to superior properties of the paint, i.e., it leads to a higher whiteness index, better wet abrasion resistance, faster film formation in comparison with the widely applied industrial water-emulsion acrylic paint.