Circular economy approach to drilling sludge management in uranium in-situ leaching: from waste to resource

Drilling sludge generated during well construction for uranium in-situ leaching (ISL) represents a major waste stream requiring sustainable management. This study develops and validates an integrated technology for converting drilling sludge into reusable materials, combining mechanical solid–liquid separation, geotextile dewatering, and cement–sludge briquetting. Stage 1 (mechanical separation on a linear-motion vibrating screen) was evaluated in a field/pilot trial at the South Karamurun site; the screening of ten geotextiles and the briquetting and permeability studies were carried out in the laboratory, with the two best geotextiles additionally tested in the field. The vibrating screen separated about 20% of the feed as sludge and yielded clarified fluid (density 1.10–1.12 g/cm³) directly reusable in drilling. Among ten geotextiles, nonwoven polypropylene fabrics gave the best filtration (visual score 10/10), reducing residual moisture to about 50%. Cement–sludge briquettes at a 1:2 sludge-to-cement ratio reached a compressive strength of 29.1 MPa and a density of 1872 kg/m³, exceeding a pure-cement reference (24.5 MPa, 1654 kg/m³); at a 1:1 ratio the compositions were water-impermeable under a hydrostatic head representative of well conditions, supporting their use as borehole-sealing material. Gamma spectrometric analysis confirmed that radionuclide levels remained within the natural background, classifying the processed sludge as non-radioactive. The proposed technology converts drilling waste into recycled drilling fluid and construction or sealing materials, demonstrating a viable closed-loop resource-management model for the uranium mining industry consistent with circular economy principles.