Characterizations and potential recovery pathways of phosphate mines waste rocks

• Published in: Journal of cleaner production 2022-11, Vol.374, p.134034, Article 134034
• Main Authors: Safhi, Amine el Mahdi, Amar, Hicham, El Berdai, Yahya, El Ghorfi, Mustapha, Taha, Yassine, Hakkou, Rachid, Al-Dahhan, Muthanna, Benzaazoua, Mostafa
• Format: Article
• Language: English
• Subjects: carbonates; concrete; dolomitic limestone; Linear attenuation coefficient; lithology; medicine; Mining circular economy; Morocco; Ore sorting; Phosphate mine waste rocks (PMWR); phosphates; phosphorus; remediation; road construction; Valorization; Waste management
• ISSN: 0959-6526; 1879-1786
• DOI: 10.1016/j.jclepro.2022.134034

The phosphate ore production is steadily increasing due to its high demand for agriculture, medicine, and others. Ore extraction generates a considerable quantity of waste rocks that are generally stocked in piles. The current research aims to investigate the characterization of phosphate mine waste rocks (PMWR) generated in Benguerir, Morocco mine site. As a part of a wide project aiming to recycle those stockpiles, sensor-based ore sorting will be employed to separate the different lithologies. As a prior investigation before implementing this technology, two samples of 25 tons from the destoning and screening PMWR piles were sampled and submitted to manual sorting. The latter operation revealed the presence of different lithologies including indured phosphate, different types of siliceous, carbonate, phosphorus, and marly rock types. Those waste rocks were characterized physically, chemically, and mineralogically. Their potential uses for recycling or upcycling was investigated and addressed. About 25% of indured phosphate was found, which can be first recovered by ore sorting. This reserve of residual phosphate could be recovered using beneficiation methods. The flintstone, phosphated flintstone, and dolomitic limestone exhibit good physical and mechanical properties that meet the requirements to produce concrete. The silexite and siliceous marls have a low density and could be used as lightweight aggregate for non-structural concrete blocks production. The investigation on tender marls corroborates the literature and their suitability as alternative binders or as supplementary cementitious materials. Those marls could be used as well as lime binder for repairing historical buildings or as hydraulic lime binder for road construction. PMWR valorization as road construction materials was already proved. However, studying this remediation pathway after the recovery of phosphate and other lithologies by ore sorting is highly recommended. The recycling of those by-products will decrease the natural resources consumption in the civil engineering field alongside with resolving their environmental problems.