can sodium persulfate etch or damage a titanium heater?
If the surface of the immersed element is all titanium, the answer appears to be that it won't get corroded unless the temperature is much higher than 50$^\circ$C; see http://www.azom.com/article.aspx?ArticleID=1336

The case is changed if there are joints or parts made of something else, as in this illustration: http://www.saltwatereddies.com/content-popup_image/pID-2199/popup_image.html

I would think that would not be so safe.  

Of course, if you've been breaking glass heating elements right and left, you have little to lose by trying the titanium one...