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A B S T R A C TKinetics study of atmospheric pressure acid leaching (APAL) process is indispensable for extractor design in an industrial scale. So far, the kinetic model used for this process is the shrinking core model. In this study, the shrinking core model was evaluated against experimental data for laterite leaching process using a solution of low concentration nitric acid (0.1 M). Variations in temperature and particle size were carried out at 303–358 K and <75–250 microns. Other operating conditions, such as pulp density, stirring speed, and time were kept at 20% w/v, 200 rpm, and 120 minutes, respectively. The model evaluation results showed that the shrinking core model was not suitable for this process because the process controlling stage is not just one stage only.Keywords: kinetics; laterite; leaching; shrinking core.A B S T R A KStudi terkait kinetika proses atmospheric pressure acid leaching (APAL) sangat diperlukan untuk proses perancangan ekstraktor dalam skala industri. Selama ini, model kinetika yang digunakan untuk proses tersebut adalah model shrinking core. Dalam studi ini, model shrinking core dievaluasi terhadap data percobaan proses leaching bijih laterit dengan menggunakan larutan asam nitrat konsentrasi rendah, 0,1 M. Variasi suhu dan ukuran partikel dilakukan pada 303–358 K dan <75–250 mikron. Kondisi operasi lainnya, seperti densitas pulp, kecepatan pengadukan, dan lama proses dijaga tetap pada 20%b/v, 200 rpm, dan 120 menit, secara berurutan. Hasil evaluasi model menunjukkan bahwa model shrinking core tidak cocok untuk proses ini karena tahapan pengendali proses tidak hanya satu tahapan saja.Kata kunci: kinetika; laterit; leaching; shrinking core

Abstract. Nickel laterite ore contains oxide of iron, aluminum or both with nickel, cobalt and chromium which can be leached out using hydrometallurgical process. For the purpose of meeting the world's increasing demand of nickel, there is a need to invent environmentally friendly process to efficiently leach nickel. This experiment used nickel laterite ore obtained from Pomalaa, South Sulawesi. The leaching agent is metabolic citric acid produced by Aspergillus niger under optimum condition. Leaching process was done in three-necked flask in atmospheric temperature and constant stirring speed of 200 rpm. The variable examined in the experiment was pulp density and particle size of nickel laterite ore. Samples were taken at 3, 7, 10, 14, and 17 minutes and then filtered and diluted to be analyzed using ICP-AES. The result of the experiment showed the maximum recovery of metals increase with the decrease of the pulp density. The maximum recovery for varying pulp density were at 5% solid/liquid ratio and the recovery were Ni at 1.63%, Al at 0.47%, Fe at 0.23% and Mg at 1.09%. The effect of particle size on leaching process showed that the leaching process follows the shrinking core model. The maximum recovery of metals at particle size were at 100-120 mesh with Ni at 1.37%, Fe at 0.10%, Al at 0.72% and Mg at 0.62%.

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