Laravel Send::Email with "redirect" instance is not directing back to 'contact' form page

I am using Laravel for my application and I am trying to redirect to contact page after an email form. The email is sent to my mailtrap successfully though.

I have to use the "return view('contact')" rather than use redirect instance.

I want to use redirect but everytime i use the redirect instance i get an error:

Method Illuminate\Routing\Redirector::url does not exist.

My code is as below:

namespace App\Http\Controllers;
    use Illuminate\Http\Request;
    use Illuminate\Support\Facades\Route;

    use App\Http\Requests;
    use Session;
    use Mail;

    class PagesController extends Controller{

        public function getIndex(){
            return view('welcome');

        }

        public function getAbout() {

            return view('about');
        }

        public function getContact() {
            return view('contact');
        }

        public function postContact(Request $request) {
            $data = [];
            $this->validate($request, [
                'email' => 'required|email',
                'subject' => 'min:3',
                'message' => 'min:10']);

                $data = array(
                    'email' => $request->email,
                    'subject' => $request->subject,
                    'bodyMessage' => $request->message
                );

            Mail::send('emails.contact', $data, function($message) use 


($data){
                $message->from($data['email']);
                $message->to('zulfadhli.tom@gmail.com');
                $message->subject($data['subject']);
            });

            Session::flash('success', 'Your email is successfully sent!');
            return redirect()->url('/');
        }
    }

via Chebli Mohamed