Effect of Borax-, KOH-, and NaOH-Treated Coal on Reducing Carbon Waste and Activated Carbon Production in Synthetic Rutile Production from Ilmenite

William Spencer, Don Ibana, Pritam Singh and Aleksandar N. Nikoloski ()
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William Spencer: Harry Butler Institute (Centre for Water, Energy and Waste), Extractive Metallurgy Hub, Murdoch University, 90 South Street, Murdoch, WA 6150, Australia
Don Ibana: Harry Butler Institute (Centre for Water, Energy and Waste), Extractive Metallurgy Hub, Murdoch University, 90 South Street, Murdoch, WA 6150, Australia
Pritam Singh: Harry Butler Institute (Centre for Water, Energy and Waste), Extractive Metallurgy Hub, Murdoch University, 90 South Street, Murdoch, WA 6150, Australia
Aleksandar N. Nikoloski: Harry Butler Institute (Centre for Water, Energy and Waste), Extractive Metallurgy Hub, Murdoch University, 90 South Street, Murdoch, WA 6150, Australia

Clean Technol., 2025, vol. 7, issue 4, 1-25

Abstract: Coal is commonly used as both fuel and reducing agent in producing synthetic rutile from ilmenite (FeTiO 3 ) via the Becher process, which upgrades ilmenite to high-purity TiO 2 (>88%). However, coal-based reduction generates significant carbon waste. This study investigated the effect of adding 1–5% w / w potassium hydroxide (KOH), sodium hydroxide (NaOH), and sodium tetraborate (borax) to coal during ilmenite reduction to improve metallisation and reduce carbon burn-off. Results showed that 1% w / w additives significantly increased metallisation to 96% (KOH), 95% (NaOH), and 93% (borax), compared to 80% without additives, while higher concentrations (3–5% w / w ) decreased metallisation. Scanning electron microscopy (SEM)analysis showed cleaner particle surfaces and optimal metallisation at 1% w / w , whereas higher additive levels caused agglomeration or sintering due to elevated silica and alumina activity. Additive type also influenced TiO 2 quality, with KOH enhancing TiO 2 at low concentrations but causing negative effects at higher levels, while NaOH and borax reduced TiO 2 quality via sodium-based compound formation. All additives reduced carbon burn-off, with KOH producing the greatest reduction. The iodine number of the carbon residue increased with higher additive concentrations, with KOH achieving 710 mg/g at 1% w / w and 900 mg/g at 5% w / w , making the residue suitable for water treatment. Overall, KOH is the most effective additive for producing high-quality synthetic rutile while minimising carbon waste.

Keywords: cleaner technology; high-value carbon; coal reduction; critical minerals; sustainable mineral processing; titanium minerals (search for similar items in EconPapers)
JEL-codes: Q2 Q3 Q4 Q5 (search for similar items in EconPapers)
Date: 2025
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