Font awesome icons disable getting square only

Question

I have added font awesome icons in my html page for data table plugin UI using css

<link rel="stylesheet" type="text/css" href="/js/datatable/pratik/font-awesome.min.css"/>
<link rel="stylesheet" type="text/css" href="/js/datatable/font-awesome.css" />

But due to some errors I changed all symbols into special escape characters. May be that's why it's showing blank square.Any trick to resolve this error. My code for font awesome icon is:

 text: '<i class="fa fa-list-ol-3x" aria-hidden="true" style="color:#81ad30"></i>',

Thanks.