Natural mineral-supported green nanotechnology for oil-water separation and environmental remediation: surface engineering, separation mechanisms and scale-up perspectives

Natural mineral-derived nanomaterials offer a credible route to lower the cost and environmental burden of treating oil-contaminated water, yet their performance is often reported without a common framework linking mineral chemistry, surface modification, wetting state, pore architecture, operating conditions, and end-of-life risk. This Review critically examines quartz, zeolites, vermiculite, bentonite, kaolin, halloysite, attapulgite, and iron-bearing minerals as granular media, coatings, adsorbents, and membrane building blocks for oil-water separation and broader environmental remediation. Particular attention is given to quartz because of its abundance, mechanical stability, and modifiable silanol-rich surface, while comparisons with layered and fibrous minerals reveal complementary advantages in ion exchange, nanoscale channel formation, and interfacial adsorption. The evidence shows that high laboratory rejection can arise through fundamentally different pathways: underwater oleophobic hydration layers, oil-affine sorption, size exclusion, droplet coalescence, electrostatic repulsion, and catalytic degradation. Consequently, percentage removal alone is insufficient for material selection. Meaningful comparison requires feed oil concentration and chemistry, droplet-size distribution, surfactant content, flux or hydraulic loading, pressure, bed depth or membrane thickness, regeneration protocol, coating retention, and mass-normalised capacity. Green modification is strongest when it reduces hazardous reagents, anchors a minimal functional layer to an abundant mineral, and preserves regeneration without releasing nanoparticles or secondary contaminants. Persistent barriers include inconsistent testing, swelling and compaction of clays, coating loss, fouling under real wastewater matrices, energy-intensive calcination, and limited pilot-scale evidence. A decision framework is proposed that connects mineral structure and wettability to process configuration, durability, safety and local resource availability. South African quartz illustrates how regionally abundant minerals can support decentralised pre-treatment and water-reuse systems when mineral beneficiation, coating chemistry and life-cycle verification are developed together. Future research should prioritise harmonised performance reporting, continuous-flow trials with real effluents, coating-leachate analysis, regeneration over multiple cycles, techno-economic assessment and safe-by-design mineral nanocomposites. These measures are necessary to move natural mineral nanotechnology from impressive batch demonstrations to reliable and responsible remediation infrastructure.