Thermal treatment of rock phosphate: Phosphorus recovery and production of an alternative binder component

Phosphorus, classified as a critical raw material by the European Commission, is an essential component of global food security through its role in the fertilizer industry. However, the current processes for producing mineral fertilizers, especially from phosphate ores, lead to environmental problems. Heavy metal residues are spread on arable fields and tailings that are not further processed due to low phosphate content are landfilled. Therefore, the experimental approach in this study consists of chemically modifying processed phosphate rock with other industrial residues, so-called corrective materials. These mixtures are treated thermochemically with a subsequent rapid cooling of the molten material. The aims are to obtain phosphorus via the gas phase and to produce a slag fraction that can be used as an alternative binder component in the cement or construction material industry. In addition, valuable metals should be recovered if they are contained in the corrective materials. Preliminary results indicate that the high-temperature process can remove phosphorus from the system, enabling further utilization, such as producing phosphoric acid. In addition, the chemical composition of the slag fraction obtained is within the desired limits for use as an alternative binder component. Initial investigations into binder suitability, such as latent hydraulic activity, are promising. Furthermore, the reduction reaction during the thermochemical treatment enabled the separation of a metallic fraction after the material had been processed. The research results indicate that the proposed approach offers an alternative process route to produce mineral fertilizers using low-grade ores and by-products from phosphate ore processing. This strategy enables the treatment of tailings with lower phosphorus content, improving material efficiency and significantly reducing the environmental footprint of mineral fertilizer production. The proposed method not only facilitates phosphorus recovery but also generates an alternative binder component, which helps mitigate emissions in the cement industry. Moreover, the approach aligns with a zero-waste concept by providing a recycling option for industrial residues as corrective materials. To summarise, it can be said that research into cross-sectoral topics is becoming increasingly important in order to achieve climate targets through the more efficient use of primary raw materials on the one hand and the recycling of industrial waste on the other.