[eluser]TheFuzzy0ne[/eluser]
That's not the right function for what you're trying to do. You should be using the [url="http://ellislab.com/codeigniter/user-guide/libraries/sessions.html"]sessions[/url] library for that.
Code:
$this->session->set_userdata('lang_id', $id); // Sets the data
$lang_id = $this->session->userdata('lang_id'); // Gets the data
Hope this helps!