SHORT COLUMN TESTS FOR NICKEL HEAP LEACHING: CRITICAL REVIEW OF TEST DESIGN, HYDRAULIC ARTIFACTS, AND SCALE-UP RELIABILITY

Short-column tests are routinely used to bridge laboratory bottle-roll experiments and industrial heap leaching, particularly for nickel laterite ores; however, their predictive value is often overstated because simplified hydraulic conditions do not replicate the transport and flow phenomena that govern heap performance at scale. This review critically examines the assumptions underlying short-column testing, focusing on the coupling among reaction kinetics, mass-transfer limitations, and fluid distribution, and identifies systematic sources of bias, including preferential flow, wall-confinement effects, non-representative irrigation regimes, and artificially saturated conditions that distort leaching kinetics and produce non-representative recovery trends. A comparative analysis of reported protocols reveals substantial inconsistencies in column geometry, particle-size distribution, agglomeration practices, and control of solution chemistry, limiting reproducibility and cross-study comparisons. The common interpretation of short-column data as intrinsically kinetic leads to overestimating recoveries when extrapolated to heap scale. A scale-aware conceptual framework is proposed to link intrinsic reaction kinetics to transport constraints and structural evolution in real heaps, showing that short-column tests are suitable for comparative and mechanistic evaluation but cannot be used as standalone predictors of industrial performance.