Perpustakaan Digital ITB

The increasing demand for nickel-based products, particularly nickel sulfate for electric vehicle (EV) batteries, necessitates the development of sustainable and efficient processes for Mixed Hydroxide Precipitate (MHP) refining. Nitric acid leaching represents a promising approach due to its strong oxidizing properties, which may enhance nickel recovery. However, conventional nitric acid production via methane-based steam reforming is unsustainable due to its high carbon emissions. Non-thermal plasma (NTP) nitrogen fixation provides a potential alternative, enabling the oxidation of nitrogen gas into nitric acid without the reliance on fossil fuels. In this study, the performance of Plasmapps’ Plasma Nitrate Generator was evaluated for nitric acid production and subsequent application in MHP leaching. Nitric acid was produced from deionized water using non-thermal plasma with O?, N?, and ozone as reactant gases under varying parameters of volume, anode and cathode geometry, cooling system, gas ratio, voltage, and ozone flow. The weak nitric acid obtained was further concentrated through enrichment using a rotary evaporator and subsequently applied for the leaching of mixed hydroxide precipitate (MHP), which had been previously dried and manually ground. Leaching experiments were conducted at controlled conditions of temperature (60 °C and 80 °C), nitric acid concentration (0.5 M and 1 M), slurry density (1/10 and 1/5), and rotation speed (500 rpm) for four hours. The resulting pregnant leach solution (PLS) was separated by filtration and analyzed for dissolved metal contents using Atomic Absorption Spectroscopy (AAS), while the solid residue underwent further digestion prior to characterization. This systematic approach enabled evaluation of nitric acid production efficiency and its effectiveness for MHP leaching. Process optimization of plasma-assisted nitric acid generation identified optimal conditions (300 mL water, 5-needle anode with plate cathode, 0.4 LPM gas flow at N?:O? = 4:1, 20 kV, with added ozone) producing up to 12,000 ppm nitric acid in 2 hours, further enriched to 63,000 ppm via rotary evaporation. Despite high energy consumption (129 kWh/mol) and low single-pass nitrogen conversion (4%), the acid proved effective for MHP leaching, achieving dissolution rates of 98% Ni, 88% Co, and 36% Mn under 1 M acid, 80 °C, and 1:10 slurry density. Statistical analysis showed nickel recovery was mainly influenced by acid concentration (58%), followed by slurry density (30%) and temperature (9%), with kinetics fitting the shrinking particle model controlled by the surface chemical reaction (R² = 0.9088). These results demonstrate the potential of plasma-generated nitric acid as a selective, sustainable leaching agent, though efficiency improvements (100-fold) are needed for industrial feasibility. Studi Produksi Asam Nitrat melalui Fiksasi Nitrogen Plasma Non-Thermal untuk Proses Pelindian Mixed Hydroxide Precipitate (MHP)