Open terminal. Type this and hit enter:
cupsctl WebInterface=yes
Then:
1) Open a browser window and type http://localhost:631
2) On the CUPS screen select the Administration tab
3) Click Manage Printers
4) Select the Canon device by IP address (or name if you can find it on the list)
5) Click Administration drop down box and select Set Default Options
6) Click General
7) Select 1-sided Printing from Print Style drop down box. Select Set Default Options (bottom of page)