Turning waste into wealth: Process optimization as a pathway to mercury-free artisanal gold mining in Suriname

Interventions in artisanal gold mining (AGM) to reduce environmental impacts, such as mercury pollution, must prioritize economic gold losses, a primary motivation for miners. We systematically sampled feeds and tailings from two AGM operations in Northeastern Suriname processing secondary ores (alluvial, colluvial and eluvial) in zigzag sluice boxes with unbacked vinyl carpets. Miners discharge concentrates for amalgamation after one to three weeks of operation. This delayed cleanup causes severe bed overloading and hydrodynamic scouring, physically ejecting previously trapped gold into tailings. Consequently, operational gold recovery for eluvial/colluvial ore was only 34% (feed: 0.29 ppm Au), while a dry alluvial operation recovered 84.2% (feed: 0.62 ppm Au). Grain size analyses of tailings revealed major losses in coarse fractions (+2 mm) driven by a combination of hydrodynamic carry-over and unliberated gold locked in quartz. To mitigate this, we recommend size classification followed by targeted comminution of the coarse fraction. Additionally, significant fine gold losses (<0.063 mm) occur because particles fail to settle under the sluices' high turbulent kinetic energy. Introducing centrifugal concentrators overcomes these flow barriers, improving recovery and facilitating the transition to mercury-free production. Crucially, time-series economic simulations demonstrate that a proposed US$ 630,000 mercury-free plant achieves capital payback within 21 months under targeted baseline conditions. This proves that process optimization, even when accounting for operational cost fluctuations, is a financially resilient prerequisite for environmental mitigation in the AGM sector.