One of the important minerals for a raw material of titanium dioxide is ilmenite (FeTiO3). A model p — Physical Chemistry — Thermodynamics Chemistry Question
Synthesis of titanium dioxide
One of the important minerals for a raw material of titanium dioxide is ilmenite (FeTiO3). A model process of the synthesis of titanium dioxide (sulfate process) is divided into the following processes, (A) - (D).
(A) Iron(II) sulfate and titanyl sulfate (TiOSO4) aqueous solution is prepared by dissolving ilmenite in a concentrated sulfuric acid with heating.
(B) Iron(II) sulfate heptahydrate is precipitated by controlling the concentration of the solution and cooling it.
(C) After the precipitate of iron (II) sulfate heptahydrate is filtered out, titanium hydroxide (TiO(OH)2) is precipitated by heating the filtered solution and subsequently carrying out hydrolysis reaction.
(D) Titanium dioxide is prepared by the calcination of titanium hydroxide.
The obtained iron(II) sulfate is utilized as the source of some ferrite. The surplus sulfate acid is neutralized with limestone (calcium carbonate). The obtained gypsum (calcium sulfate dihydrate) is utilized as a by-product.
Natural ilmenite ore contains lots of impurities. Assuming that the titanium content is 35.0 mass % in the natural ilmenite ore when titanium is converted into titanium dioxide and that the impurities in the ore contain no titanium component except for ilmenite, calculate the mass of ilmenite, m, in 1000 kg of the natural ilmenite ore.
Model Answer
Molar mass of ilmenite: M(FeTiO3) = 151.7 g mol–1, and that of TiO2: M(TiO2) = 79.9 g mol-1
1000 kg × 0.350 (TiO2) / 79.9 g mol-1 × 151.7 g mol-1 = 664.518 kg
m(FeTiO3) = 665 kg
Show the chemical reaction which proceeds through the processes (A) and (B) described above as the form of one chemical formula.
Model Answer
Processes (A) and (B):
FeTiO3 + 2 H2SO4 + 5 H2O → FeSO4 ⋅7 H2O↓ + TiOSO4(aq)
Show the chemical reaction through all of the processes (A) – (D) described above as the form of one chemical formula.
Model Answer
(C) TiOSO4(aq) + 2 H2O → TiO(OH)2 + H2SO4
(D) TiO(OH)2 → TiO2 + H2O
From the answer 12.2:
(A) and (B), FeTiO3 + 2 H2SO4 + 5 H2O → FeSO4 ⋅7 H2O↓ + TiOSO4(aq)
Processes (A) – (D):
FeTiO3 + H2SO4 + 6 H2O → FeSO4 ⋅ 7 H2O + TiO2
In a laboratory, 25.0 cm3 of concentrated sulfuric acid (18.0 mol dm-3) was used in order to obtain titanium dioxide from 10.0 g of pure ilmenite. Calculate the minimum mass of calcium carbonate that is necessary for neutralizing the surplus sulfuric acid when all of the processes (A) – (D) proceed completely.
Model Answer
Chemical formula of the neutralization:
H2SO4 + CaCO3 → CaSO4 ⋅2 H2O + CO2
M(H2SO4) = 98.08 g mol-1; M(CaCO3) = 100.1 g mol-1
The necessary amount of sulfuric acid for the reaction:
n(H2SO4) = m(FeTiO3) / M(FeTiO3) × 2 = 10.0 g / 151.7 g mol-1 × 2 = 0.132 mol
The amount of surplus sulfuric acid:
n(H2SO4) = 18.00 mol dm-3 × 0.025 dm3 – 0.132 mol = 0.318 mol
The necessary amount of calcium carbonate for the neutralization:
m(CaCO3) = 0.318 mol × 100.1 g mol-1 = 31.8 g