Prevent visual editor remove tags

I’m using custom styles in my post/pages using text editor.

The problem i’m having when i’m trying to use a “empty” tag in text editor and when I switch between “Visual” & “Text” is removed by Visual editor.

Ex:

I want to add fontawesome in my post “<i class=”fa fa-pencil” aria-hidden=”true”></i>” in text editor and switch to visual and back again to text is removed.

How i can prevent not removed? or how i can use fontawesome in my posts/pages?