An upgrade of Malaysian ilmenite (FeTiO3) concentrate to synthetic rutile (TiO2) using aeration leaching was investigated in this study. Carbothermal reduction using Sarawak MukahBalingan coal and compressed National Gas (CNG) as a reductant was used to produce reduced ilmenite (RI) as an intermediate phase consisting of titanium oxide matrix with metallic iron prior to aeration leaching. Metallic iron was dissolved in ammonium chloride solution after the reduction process, separating synthetic rutile in the leaching residue. This study aims to evaluate the leaching parameters, such as concentration, temperature, and leaching time. The optimum conditions established by the design of the experiment (DOE) and the analysis of variance (ANOVA) has indicated that leaching temperature was the most significant parameter for iron dissolution. It was found that iron dissolution at a maximum value of 97.0% was achieved at an optimum condition of 0.5 M NH4Cl at 90°C for 7 hours. With an initial weight of 46 wt.%TiO2 and 37 wt.% Fe2O3, ilmenite was successfully upgraded to 80 wt.% and 8 wt.%, respectively. In conclusion, Malaysian ilmenite has a high potential value to be upgraded to synthetic rutile by aeration leaching with ammonium chloride via Becher process.
High-temperature carbothermal reduction experiments with graphite powder were conducted to assess the dephosphorization behavior of Malaysian monazite concentrate. Thermodynamic analysis of the possible dephosphorization reactions was conducted to evaluate the feasibility of the carbothermal reduction of the monazite phases. The effects of temperature, particle size, and monazite to carbon ratio were then investigated under different conditions. The carbothermal reduction experiments were conducted based on the Taguchi design method, and up to 97% of phosphorous removal was achieved under optimized conditions. The optimal conditions for dephosphorization were determined as; a reduction temperature of 1350 °C, a particle size of -75 μm, and monazite to carbon molar ratio of 0.3. Microstructural and phase characterization of the dephosphorized products revealed that CeO2, Nd2O3, La2O3, and Pr2O3 oxide phases were prominent, and no residual peaks of monazite remained in the reduced products. The information gained from the study can aid in the design of a suitable post-dephosphorization hydrometallurgical treatment for exploiting Malaysian monazite as a local source of REEs.
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