Thermochemical treatment of Moroccan rock phosphate using a zero-waste approach: phosphorus recovery and production of a binder component

Currently, the primary source of phosphorus-bearing fertilizer is phosphate ore, the processing of which generates substantial waste streams with adverse environmental consequences. The con-ventional production of phosphoric acid from rock phosphate – refined phosphate ore – typically occurs at the mining site and results in the undesired accumulation of large volumes of phos-phogypsum as a by-product. For this reason, this research investigates a thermochemical treat-ment method for rock phosphate aimed at phosphorus recovery while simultaneously generating a reactive binder component. This approach enables the production of phosphoric acid without the formation of phosphogypsum. Adding waste materials of appropriate composition to rock phos-phate can achieve dephosphorization efficiencies exceeding 92 %, even with iron-containing waste streams. By the addition of iron-free residues, even significantly higher phosphorus re-moval rates can be expected. The resulting reactive binder component exhibits favorable charac-teristics for potential application as a supplementary cementitious material, such as granulated blast furnace slag. In contrast, the direct treatment of chemically unmodified rock phosphate yields neither efficient phosphorus recovery nor a mineral fraction suitable for use as a reactive binder component. Future research will investigate the applicability of this thermochemical pro-cess to phosphorus-rich waste streams from Moroccan mines, including waste rocks and tailings.