While switching between text editor mode or updating post fontawesome icon vanishes.Please do not refer to use any plugin.I think i tag is stripped by editor,how can I overcome this?
My code in editor text mode

```
<span><i class="fa fa-user"></i></span>

```

or

```
<i class="fa fa-user"></i>

```

As long as I am in text mode everything is well but when I switch to visual mode all of my code gets vanish.