use this
<i class="icon glyphicon glyphicon-search" aria-hidden="true"></i>
in drupal bootstrap theme ckeditor 4, usually remove
check follow
https://www.drupal.org/node/2369415
https://www.drupal.org/node/1908696
this way is ok, on
site/all/modules/ckeditor/ckeditor.config.js
put
config.protectedSource.push( /<i[^>]*><\/i>/g );
in CKEDITOR.editorConfig = function(config) { OOXXOO }
then ckeditor can put <i> on source mode, but can not show on edit, change source again, code not remove.
so save, then show on page...... I think it ...ok
just try