Contribution à la valorisation des fines de dépoussiérage du phosphate (DO 20%) de Djebel Onk, Wilaya de Bir El Ater (Algérie)

Abstract

The processing of Djebel Onk phosphate generates dust removal fines considered as a valuable by￾product of the phosphate industry, with potential for agricultural valorization in Saharan regions. This study aims to characterize these fines physicochemically and evaluate their effectiveness as phosphate amendments for poor soils. Analyses included particle size distribution by sieving, mineralogical analysis using X-ray diffraction (XRD), and chemical analysis for major and trace elements. Results showed that 95.79% of the fines consist of ultrafine particles (<80 µm), mainly composed of hydroxyapatite, with an average P₂O₅ content of 24.51%. The presence of calcium (40.98% CaO) and magnesium (4.45% MgO) suggests their potential as multifunctional soil amendments. Trace element analyses revealed acceptable levels of cadmium, arsenic, and lead. The direct efficiency of these fines in Saharan soils remains limited due to the alkaline nature of these soils (pH 7.7–8.2), which inhibits apatite dissolution. Composting with local organic matter, combining with acidifying fertilizers, inoculation with phosphate-solubilizing bacteria, and split applications are proposed strategies to overcome this limitation and enhance the valorization of this mining by-product. This approach contributes to reducing mining waste and improving the sustainability of Saharan agricultural systems.