OPTIMASI EKSTRAKSI BIJIH NIKEL DENGAN METODE ATMOSPHERIC ACID LEACHING MENGGUNAKAN ASAM SULFAT

(STUDI KASUS PENAMBANGAN KOLAKA UTARA)

Abstrak

Nikel laterit kadar rendah (<1,5% Ni) kurang ekonomis diolah dengan proses pirometalurgi sehingga memerlukan teknologi hidrometalurgi, salah satunya Atmospheric Acid Leaching (AAL) menggunakan asam sulfat (H₂SO₄). Penelitian ini bertujuan menganalisis pengaruh serta menentukan kondisi optimum variasi konsentrasi H₂SO₄, temperatur, dan waktu pelindian terhadap persen ekstraksi nikel dari bijih limonit Kolaka Utara dengan kadar awal 1,53% Ni dan 42,20% Fe. Metode penelitian menggunakan One-Factor-at-a-Time (OFAT) dengan variasi konsentrasi H₂SO₄ sebesar 1, 3, 5, dan 7 M, temperatur 50, 70, 90, 100, 110, dan 120 °C, serta waktu pelindian 60, 120, 180, dan 240 menit. Parameter tetap meliputi kecepatan pengadukan 300 rpm, rasio padat-cair (S/L) 0,2 g/cm³, ukuran partikel <200 mesh, dan pra-kalsinasi pada 550 °C selama 2 jam. Karakterisasi kadar residu dilakukan menggunakan X-Ray Fluorescence (XRF). Hasil penelitian menunjukkan bahwa peningkatan konsentrasi H₂SO₄ hingga 7 M meningkatkan persen ekstraksi nikel menjadi 92,32% karena bertambahnya ion H⁺ yang berperan dalam proses pelindian. Persen ekstraksi tertinggi berdasarkan variasi temperatur diperoleh pada 100 °C, yaitu 95,86%, sedangkan peningkatan temperatur hingga 110–120 °C menurunkan ekstraksi akibat pembentukan lapisan pasivasi dan pengendapan senyawa besi. Berdasarkan variasi waktu, ekstraksi tertinggi sebesar 96,69% diperoleh pada 240 menit, namun 120 menit ditetapkan sebagai waktu optimum operasional karena telah mencapai kondisi mendekati kesetimbangan dengan persen ekstraksi 95,23%. Dengan demikian, kondisi optimum proses AAL diperoleh pada konsentrasi H₂SO₄ 7 M, temperatur 100 °C, dan waktu pelindian 120 menit.

Low-grade nickel laterite (<1.5% Ni) is uneconomical to process by pyrometallurgical methods, making hydrometallurgical technologies such as Atmospheric Acid Leaching (AAL) using sulfuric acid (H₂SO₄) a promising alternative. This study aimed to evaluate the effects of H₂SO₄ concentration, leaching temperature, and leaching time and to determine the optimum operating conditions for nickel extraction from North Kolaka limonite ore containing 1.53% Ni and 42.20% Fe. A One-Factor-at-a-Time (OFAT) method was employed by varying the H₂SO₄ concentration (1, 3, 5, and 7 M), temperature (50, 70, 90, 100, 110, and 120 °C), and leaching time (60, 120, 180, and 240 min). Constant parameters included a stirring speed of 300 rpm, a solid-to-liquid ratio (S/L) of 0.2 g/cm³, a particle size of <200 mesh, and pre-calcination at 550 °C for 2 h. Residual nickel content was characterized using X-Ray Fluorescence (XRF). The results showed that increasing the H₂SO₄ concentration to 7 M improved nickel extraction to 92.32% due to the greater availability of H⁺ ions during leaching. The highest extraction based on temperature was achieved at 100 °C, reaching 95.86%, whereas increasing the temperature to 110–120 °C reduced extraction because of iron-bearing precipitate formation and passivation layer development. The highest extraction based on leaching time was 96.69% at 240 min; however, 120 min was selected as the optimum operational time because the extraction efficiency (95.30%) had reached a near-equilibrium condition controlled by diffusion through the product layer. Therefore, the optimum AAL operating conditions were 7 M H₂SO₄, 100 °C, and 120 min.