Advancing Cleaner Technologies for Production of Synthetic Rutile and Activated Carbon

William Spencer

Titanium is a critical element essential for everyday applications, including titanium dioxide (TiO2) for pigments in paints, plastics, and paper, as well as in surgical implants (Ti). It is also essential for producing advanced materials in aerospace, including components for aircraft, spacecraft, and space exploration. Australia is a leading global producer of key mineral commodities like ilmenite and rutile, which are essential for producing titanium dioxide. Owing to limited natural rutile reserves, the increasing demand for titanium requires converting ilmenite into synthetic rutile. Upgrading ilmenite (FeO.TiO2) with coal is critical in synthetic rutile production via the Becher process. Ilmenite (> 52 % w/w TiO2, < 47 % w/w FeO) is reduced with coal in a kiln and leached to produce synthetic rutile with > 88 % w/w TiO2. The Becher process is a common process for producing synthetic rutile, relying on coal, which leads to the generation of carbon waste. This study investigate the minimisation of carbon waste and the development of cleaner technologies to produce synthetic rutile and activated carbon. The research focuse on optimising process efficiency and reducing carbon emissions in the production of synthetic rutile and activated carbon, aiming to lower the environmental impact of these processes. Three Australian ilmenite and three coal samples were characterised using inductively coupled plasma optical emission spectrometry (ICP OES), Fourier transform infrared spectroscopy (FTIR), X-ray fluorescence (XRF), X-ray diffraction (XRD), and scanning electron microscopy (SEM) instruments. The research provided four findings on optimising ilmenite reduction and minimising carbon waste, and two findings on improving activated carbon yield and quality. Three ilmenite samples, varying in surface areas, sizes, and compositions, were reduced at 1100°C and leached with diluted HCl. The results indicate that larger surface areas improve the reduction process and enhance synthetic rutile quality. A linear correlation was established between ilmenite surface area and metallisation, highlighting surface area as a key variable in the reduction process. Three coal samples from Western Australia, differing in surface area, were subjected to KOH activation at 800°C for two hours. The study concludes that larger surface areas led to higher yields and increased active sites, improving carbon activation. The surface area of coal significantly impacts both the iodine number and yield of activated carbon, underscoring its importance in optimising production and minimising waste. Renewable materials like wood and gumtree sticks were effective in reducing ilmenite at 1100°C while producing less carbon waste. These materials, containing alkaline components such as calcium, enhanced the reduction process and yielded higher-grade synthetic rutile. Furthermore, the residual carbon exhibited activated carbon properties, making it a valuable by-product for water treatment. Alkaline-based additives, including borax, KOH, and NaOH, were used to improve ilmenite reduction. These additives enhanced coal porosity, accelerating gas–solid reactions, reducing reaction times, and minimising carbon burn-off. This approach also increased the yield of activated carbon as a by-product, reducing overall waste. Low-grade iron ore, specifically goethite, was successfully used to produce activated carbon from waste wood. A one-step activation process at 1100°C increased the iodine number and carbon yield, making the resulting activated carbon suitable for commercial applications such as wastewater treatment. Metallic iron was produced as a by-product of this process. Hydrogen (H₂) was demonstrated to effectively reduce ilmenite without carbon, thereby eliminating carbon emissions. The results conclude that, as hydrogen has a smaller molecular diameter, it diffuses more efficiently through smaller pores, enhancing ilmenite reduction and resulting in high-quality ‘green’ rutile. The study findings support the potential of hydrogen for zero-emission, sustainable rutile production. Future research should aim to optimise hydrogen reduction conditions for various ilmenite types, focusing on blending combinations and integrating low-grade ores to improve product quality and sustainability. Conducting pilot-scale studies is important to validate laboratory findings and assess the economic viability of these methods. Additionally, the activated carbon industry should explore using low-grade iron ores like goethite to improve production and quality. Collectively, these efforts will contribute to developing sustainable practices in both the rutile and activated carbon sectors, aligning with broader environmental goals.

Advancing Cleaner Technologies for Production of Synthetic Rutile and Activated Carbon

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