How to disable iOS 8 emoji keyboard?

Try this:

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string
{        
    if ([textField isFirstResponder])
    {
        if ([[[textField textInputMode] primaryLanguage] isEqualToString:@"emoji"] || ![[textField textInputMode] primaryLanguage])
        {
            return NO;
        }
    }
    return YES;
}

for more info see here.

EDIT :

You can hide emoji from Keyboard using this code:

txtField.keyboardType=UIKeyboardTypeASCIICapable;

EDIT :

Hide emoji selection from keyboard using Interface builder.