EXTRACTION OF NICKEL FROM LOW GRADE HALMAHERA NICKEL LATERITIC ORE BY ATMOSPHERIC AGITATION LEACHING IN HYDROCHLORIC ACID SOLUTION

• Main Author: Irsyad, Fikri
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/81791
• Institution: Institut Teknologi Bandung

Leaching of low-grade lateritic ore with atmospheric agitation leaching at atmospheric pressure is one alternatives for hydrometallurgical extraction of nickel which has been investigated. Compared to the similar method by using sulphuric acid as a leaching agent, this method has some advantages in terms of faster reaction kinetics, higher nickel extraction percentage and a possibility of hydrochloric acid regeneration through hydrolisis of pregnant solution during iron removal stage and magnesium removal during the treatment of spent solution. In this research work, the effectiveness of leaching of lateric ore of limonitic type from Halmahera in hydrochloric acid under variations of HCl concentration, temperature, pulp density and the additions of MgCl2 as well as NaCl was studied. The possibility of magnesium precipitation in the form of magnesium sulphatehydrate was also investigated. Series of batch agitation leaching tests at atmospheric pressure were carried out to investigate the effects of HCl concentration, temperature, pulp density and the amounts of MgCl2 and NaCl additions on the extraction percentage of Ni and dissolved Fe and Mg during 8 hour leaching. X-Ray Diffraction (XRD) analysis was conducted on the residu from the leaching tests with the presences of MgCl2 and NaCl to identify the iron-bearing complex precipitate that might form during leaching. The treatments of spent solution were undertaken by introducing sulphuric acid into the spent solution in which iron and nickel removed and the precipitate formed was analyzed. The investigation results show that the highest nickel extraction percentage was at the level of 95.6% which was obtained from the leaching test using 4 molar HCl, at 100oC, under 5% pulp density using ore particle size distribution of -100 + 200 mesh for 8 hour. Under this condition, dissolved iron and magnesium are respectively 58.13% and 60.18%, while the increase of the pulp density from 5% to 15% reduces nickel extraction percentage down to 66.7%. The addition of 85 gram/liter of MgCl2 reduced the dissolved iron up to 15%. The increse of the amounts of MgCl2 added tends to decrease nickel extraction percentage. The addition of MgCl2 during leaching was found to be effectively suppress the dissolution of magnesium from ore at 0% level. The treatment of spent solution did not result in the expected Mg precipitation in the form of MgSO4.H2O due to insufficient dissolved Mg concentration in the solution and the use of CaO as neutralizing agent. Based XRD analysis it was known that the solid product obtained from the spent solution treatment was gypsum (CaSO4.2H2O) resulted fron the reaction of CaO with HCl and H2SO4.