STUDY OF SULFUR SEPARATION AND IRON EXTRACTION FROM NATROJAROSITE RESIDUE OF NICKEL AS RAW MATERIAL OF IRON AND STEEL MANUFACTURING

• Main Author: Adzana, Zhahrina
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/67933
• Institution: Institut Teknologi Bandung

Environmental pollution and global warming due to the disposal of nickel ore processing residues and carbon emissions are one of the challenges for the industry. The combined pyrometallurgical-hydrometallurgical technology being developed is the processing of laterite nickel ore into an intermediate product of MHP (Mixed Hydroxide Precipitate) as raw material for electric car batteries. One of the residues of this technology is the natrojarosite, which is a product of the iron removal method through precipitation from the leach solution. Generally, natrojarosite residues contain 20-35% iron and high sulfur content. The high iron content indicates that the natrojarosite residue from hydrometallurgical nickel production may be a raw material for iron and steel manufacture. The natrojarosite residues were first prepared and characterized using Thermogravimetry/Differential Thermal Analysis (TG-DTA), X-ray Powder Diffraction (XRD), and X-ray Fluorescence (XRF) to determine the type of minerals or compounds contained in natrojarosite residues. The roasting of natrojarosite residue was carried out at a temperature variation of 500 – 1100 °C for 4 hours then reduction treatment was carried out on the sample of natrojarosite residue after roasting at a temperature of 1100 °C. The natrojarosite residue was then prepared to form briquettes. Samples were divided into two types, namely noncomposite and composite briquettes. The non-composite briquettes consisted of unroasted natrojarosite samples or roasted samples at 1100 °C. Composite briquettes contained a mixture of samples without roasting natrojarosite or roasting samples at a temperature of 1100 °C and coconut shell charcoal bioreductant as much as 20% of the sample weight. The briquettes are then placed on the coconut shell charcoal bioreductor bed. Temperature variations were reduced at 1000 °C, 1200 °C, 1400 °C for 2 hours and isothermal-temperature gradient treatment at 1000 – 1400 °C with a heating rate of 8 °C/minute for 2 hours. The roasting results characterization was carried out on the natrojarosite residue using XRD and XRF to determine the compound formed and the final composition of the natrojarosite residue. Scanning Electron Microscope-Energy Dispersive Spectroscopy (SEM-EDS) analysis to determine the elemental content in metal and slag. The data obtained were then analyzed to study the effect of roasting temperature and reduced temperature on decreasing sulfur content and increasing iron content. Increasing the roasting temperature from 500 to 1100 °C with 4 hours of removal affects reducing sulfur content from 8.94% to 3.81% and increasing iron content from 16.23% to 28.54%. The isothermal reduction temperatures and isothermal-temperature gradients, namely 1000 °C, 1200 °C, and 1400 °C, affect decreasing sulfur content and increasing iron content. In the sample without roasting the noncomposite natrojarosite, there was a decrease in the sulfur content in the metal from 19.97-2.8% to 0% or could not be detected by SEM-EDS while the iron content fluctuated with the highest iron content at 1200 °C, namely 91.79 - 98.37%. In samples with non-composite roasting, there was a decrease in the sulfur content of the metal from 1.00% to 0.43% and the highest iron content was at a temperature of 1400 °C around 91.15%. The temperature isothermal gradient has no significant effect on decreasing the sulfur content and increasing the iron content, but it does affect the fusion of metals into larger sizes and the separation of metal with slag. The initial roasting treatment at 1100 °C had no significant effect on reducing sulfur content but increased iron content at various temperatures except at 1200 °C. Composite samples in a reductive environment affect decreasing sulfur content and increasing content at various temperatures. However, it does not affect the composite temperature sample of 1200 °C. The optimal conditions of all sample variations were samples without non-composite roasting which were reduced at 1200 °C with sulfur and iron content in metals reaching 0.17 - 0.36% and 91.79 - 98.37%.