function obtenermail() {
    //console.log($('#destinatario').val());
    var ced = $('#destinatario').val();
    $.ajax({
        type: "POST",
        data: { 'cedula': $('#destinatario').val()},
        url: "<?php echo site_url();?>"+"/roles/obtenercorreo",
        success : function(data) {
            console.log(data);

        }
    });
}

public function obtenercorreo(){
    if($this->session->userdata('logueado')){
        $ced = $this->input->post('cedula');
        $data = $this->persona_model->getPersonaced($ced);
        echo json_encode($data);
    }else{
        redirect('','refresh');
    }
}

[{"cedula":"1100253986","nombres":"SOTO CASTILLO LAURO HERNAN","mod_laboral":"CONTRATO COLECTIVO","email":""}]

console.log(data[0])
console.log(data.cedula)
console.log(data['cedula'])

$.ajax({
    type: "POST",
    data: { 'cedula': $('#destinatario').val()},
    url: "<?php echo site_url();?>"+"/roles/obtenercorreo",
    success : function(data) {
        var datos = JSON.parse(data);
        console.log(datos[0].cedula);
        console.log(datos[0].email);
    }
});

$.ajax({
    type: 'POST',
    dataType: 'json',
    data: { 'cedula': $('#destinatario').val() },
    url: "<?php echo site_url(); ?>/roles/obtenercorreo",
    success : function(data) {
        console.log(data[0].cedula);
        console.log(data[0].email);
    }
});

header('Content-Type: application/json');
echo json_encode($data);

success : function(data) {
        console.log(data.cedula);
        console.log(data.email);
    }