STUDY OF SCANDIUM EXTRACTION FROM PREGNANT SOLUTION OF RED MUD LEACHING IN HYDROCHLORIC ACID BY SOLVENT EXTRACTION METHOD USING D2EHPA

• Main Author: RUMONDANG HARLAND, RONALDO
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/62752
• Institution: Institut Teknologi Bandung

Indonesia is one of the countries with the largest bauxite reserves in the world. According to the Mineral Commodity Summaries 2021 report, United State Geological Survey (USGS), Indonesia's bauxite reserves in 2020 amounted to 1.6 billion tons, which ranks 6th in the world after Guinea, Australia, Vietnam, Brazil and Jamaica (Mineral Commodity Summaries USGS, 2021). In bauxite, it is identified that there is a content of rare earth elements (REE) in various concentrations. Among the rare earth metals contained in red mud, scandium (Sc) is reported to have the highest value (price) representing ±95% of the LTJ value contained in red mud (Borra et al., 2015). Among the rare earth metals contained in red mud, scandium (Sc) is reported to have the highest value (price) representing ±95% of the REE value contained in red mud (Borra et al., 2015). In this study, the effectiveness of the solvent extraction of scandium from the solution produced by the leaching of red mud in hydrochloric acid solution using D2EHPA with the addition of Tributhyl Phosphate (TBP) as a modifier and kerosene as a diluent. The solvent extraction experiment studied the effect of extractant concentration (D2EHPA), extraction time, temperature, and the ratio of the volume of organic solution to the volume of aqueous solution (O/A ratio) on extraction percentage of Sc and co-extraction of impurity metals (namely Fe, Ti and Al) as well as the separation factor of Sc with these impurity metals. The optimum experimental conditions were determined in the range of variables varied by the Taguchi Method and the significance of the influence and contribution of the solvent extraction process variables on the extraction percentage of Sc and the separation factor of Sc with metal impurities using the ANOVA method. Research activities in the laboratory began with the preparation and characterization of red mud samples. The characterizations of red mud samples were conducted with X-ray Fluorescence (XRF) analysis to determine the chemical composition of red mud samples from PT. ICA and X-ray Diffraction (XRD) analysis to identify the dominant compound in red mud. The next step was preparation of a scandium-rich solution obtained from leaching the red mud sample v in 6M HCl, EDTA 7 g/l, red mud size fraction -200 mesh (P100 75 ????m), temperature 60oC, solid-liquid ratio 17 g/L for 4 hours which refers to the best conditions obtained in the previous research done by Chandrasari, 2021. The concentrations of Sc, Fe, Ti and Al in the pregnant leach solution were determined by performing an Inductively Coupled Plasma Mass Spectrometry (ICP-MS) analysis. After knowing the composition of the initial aqueous solution, then a series of solvent extraction experiments were carried out using a mixture of D2EHPA and TBP. The variables that were varied in the experiment included D2EHPA concentration, extraction time, temperature, A/O ratio and pH. This series of solvent extraction experiments was carried out with a limited factorial design where only 1 variable changed with other variables being fixed and a series of experiments designed with the Taguchi Method. Experiments with the limited factorial method were carried out to determine the effect of each variable on the percent extraction of Sc, coextraction of Fe, Ti and Al and the separation factor (????x-y) between Sc and the three impurities, which were obtained from the comparison of the distribution coefficient of Sc (DSc) with the distribution coefficient of the impurity metals (Dm). Meanwhile, the Taguchi method was used to determine the optimum conditions of the experiment. Furthermore, the significance of the experimental variables and their contribution (in percent) to the extraction percentage of Sc and the separation factor of Sc with metal impurities was determined. Based on the experimental results and data analysis carried out, increasing the concentration of D2EHPA from 0.05M to 0.10M increased the percent extraction of Sc, but further increasing the concentration of D2EHPA to 0.20M tended to no longer increase the extraction of Sc. Increasing the extraction time from 3 minutes to 9 minutes, increased the extraction percent of Sc, but further increasing the extraction time up to 12 minutes apparently decreased the extraction of Sc. In addition, the increase in temperature only has a positive effect on Sc extraction up to 40oC where a further increase in temperature tends to decrease Sc extraction. This is in accordance with thermodynamic calculations which indicate that the solvent extraction process of Sc is exothermic. Analysis using the Taguchi method showed that the optimum experimental conditions were obtained at a concentration of 0.20M D2EHPA; extraction time of 3 minutes with 99.4% Sc extraction percentage. In this condition, the separation factor of Sc to Al (????Sc-Al) is 199.3; Sc- Fe 380; and Sc-Ti 76.3. The results of ANOVA showed that the variable that contributed the highest influence on the separation of Sc with other impurities in the range that was varied in the study was pH, namely 41.40%, 41.96% and 27.75% for the separation of Sc-Al, Sc-Fe and Sc-Ti, respectively.