Treated titanium dioxide pigment with high magnesium oxide addition, process of making thereof and use thereof in paper manufacture

A process for the surface treatment of titanium dioxide pigments, comprising the steps in the following order:

• (a) forming an aqueous suspension of titanium dioxide pigments;
• (b) precipitating a layer of alumina phosphate on the surface of the pigments;
• (c) precipitating a layer of alumina over the layer of alumina phosphate comprising the steps in the following order:
• (i) adding a first alumina source to the aqueous suspension;
• (ii) adding a second alumina source to the aqueous suspension, wherein the second alumina source is different from the first alumina source;
• and
• (iii) adding a third alumina source to the aqueous suspension;
• wherein steps (b), (c)(i), (c)(ii), and (c)(iii) are each followed by a maturation time;
• (d) precipitating a layer of magnesium oxide over the layer of alumina, wherein the precipitating of the layer of magnesium oxide comprises adding a magnesium source to the aqueous suspension after step (c) and adding a basic alumina source to the suspension during the addition of magnesium;
• and
• (e) recovering the titanium dioxide pigments from the suspension.