The present invention is drawn to a method for removing colloidal titanium
dioxide and titanium oxychloride from by-product hydrochloric acid. The
method includes adding phosphate ion source and quaternary amine to the
by-product acid to cause the titanium dioxide and the titanium
oxychloride to form a precipitate. The precipitate can then be separated
from the acid, thus producing a decontaminated hydrochloric acid product
with reduced levels of titanium.