Physico-chemical characterization of phosphatic waste: statistical approach and efficient valorization remedies (Algeria)

Purpose. A detailed study of phosphatic dry waste from Algerian Djebel Onk mine. The ore extraction by dry process generates two wastes: coarse dry rejection +2 and +1 mm (named CDR) and fine reject from the turbo ventilate selector (named TSV). Methodology. Several techniques are used in order to characterize the representative samples taken from the study area, including X-ray fluorescence spectrometry (XRF) for chemical assessments and also advanced statistical analysis using principal component analysis, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis and differential scanning calorimetry (TGA/DSC), as well as scanning electron microscopy coupled with energy dispersive spectroscopy (SEM-EDS). Findings. The obtained results indicates that dry wastes are mostly composed of hydroxyapatite and fluorapatite associated to dolomite, calcite, quartz and muscovite. Chemical assessments using XRF and advanced statistical analysis shows that the phosphate dry wastes display a composition similar to raw phosphate, although the mineral association makes the difference: in the case of the coarse reject Na, Sr, and S are related to the apatitic phase, while for fine rejection labeled TSV, only strontium is associated, alongside the clay phase containing Ti, Fe, Cr, Zn, etc. Supporting this findings, significant levels of CaO and P2O5 content exceeding 46.33 and 25.41 % (wt.%) respectively for TSV are found. Conversely, CDR rejections contained 45.45 % CaO and 24.78 % P2O5, alongside predominant apatitic minerals (hydroxyapatite and fluorapatite) are most present in CDR 0.25 mm fraction with almost 29 (wt.%) of P2O5. Originality. The study presents valuable insights for the efficient use and valorization of phosphate dry waste materials based on statistical approach in order to predict the mineral composition. Practical value. The phosphorus-rich composition of the phosphate dry wastes suggests potential for valorization. For instance, the 0.25 mm fraction of CDR could be valorized directly with appropriate screening processes while fine TSV particles contain more than 40 % of fraction higher than sieve mesh (80 m) which need additional screening to prevent loss of concentrated ore P2O5. The potential utilization of different samples in construction materials or as soil fertilizers is also highlighted. The fixation of minor elements is linked to the liberation of the clay matrix in certain samples, offering opportunities for further processing and value extraction.