Abstract: In this paper, titanium-containing paper sludge was utilized as the raw material for the recovery of titanium dioxide (TiO₂) through a combined process of sodium carbonate mixed roasting-two stage acid leaching-ammonium hydrogen fluoride (NH₄HF₂) leaching. The effects of key parameters such as roasting temperature, mass ratio of Na₂CO₃ to paper sludge, H₂SO₄ concentration and NH₄HF₂ concentration on the recovery rate and purity of TiO₂ were systematically investigated. The results show that under the roasting temperature of 850 ℃, mass ratio of Na₂CO₃ to paper sludge of 0.7∶1.0 and roasting time of 120 min, the optimal recovery effect of TiO₂ is achieved through a first acid leaching (acid leaching temperature is 70 ℃, H₂SO₄ concentration is 3.0 mol/L, liquid-to-solid ratio is 5∶1, acid leaching time is 60 min), second acid leaching (acid leaching temperature is 50 ℃, H₂SO₄ concentration is 1.5 mol/L, liquid-to-solid ratio is 5∶1, acid leaching time is 60 min), and NH₄HF₂ leaching (NH₄HF₂ concentration is 90 g/L, liquid-to-solid ratio is 5∶1, leaching time is 60 min, leaching temperature is 60 ℃). Under these conditions, the TiO₂ recovery rate is 81.20%, and the purity is 94.85%. The process destroys the phase structure of titanium-oxygen compounds and silicates by high-temperature roasting of sodium carbonate. Combined with acid leaching and NH₄HF₂ leaching, the efficient separation of titanium is realized, which provides a theoretical reference for the resource utilization of titanium-containing paper sludge.

Key words: titanium-containing paper sludge, TiO₂, recovery rate, purity, roasting, leaching