Linking Empirical Nickel Laterite Leaching Responses to Preliminary Economic Performance: Trade-Offs among Ni-Co Extraction, Acid Dosage, Fe Dissolution, and Residence Time

This revised manuscript develops a transparent metallurgical-economic screening framework for atmospheric sulfuric acid leaching of a ferruginous nickel laterite ore. The objective is not to prove a universal kinetic mechanism or a final project-level feasibility estimate, but to evaluate how experimentally observed extraction responses translate into preliminary economic ranking under clearly stated assumptions. Duplicate leaching tests were performed at 95-100 °C using sulfuric acid dosages of 700-1000 kg H₂SO₄/t ore and residence times of 30-420 min. The tables report average values used for mass-balance and screening calculations; individual duplicate results are not shown in the main text, and formal significance claims are therefore avoided. Nickel and iron responses were modeled empirically as functions of acid dosage and residence time, while cobalt was included as a revenue component in selected base-case scenarios. The results show that the highest observed Ni extraction, 74.1% at 360 min and 1000 kg H₂SO₄/t ore, also produced the highest Fe dissolution, 65.8%, and a low Ni/Fe selectivity indicator. Under the base-case economic assumptions, the most attractive evaluated scenario was 420 min and 700 kg H₂SO₄/t ore, because the lower acid-addition cost and Fe penalty offset the lower Ni and Co extraction. Sensitivity analysis confirmed that this ranking is assumption-dependent and should be interpreted as a feasibility-screening result rather than a global economic optimum. Non-monotonic extraction behavior between 360 and 420 min is discussed cautiously as a possible combination of experimental dispersion, sampling effects, and secondary Ni retention associated with Fe(III) hydrolysis and sulfate-bearing phases. The revised framework provides a practical route for converting duplicated laboratory leaching tests into auditable, assumption-sensitive screening inputs for early-stage nickel laterite project evaluation.