White background with dodge tool
A simple way to make a white background is using the dodge tool. First duplicate the image, than we select Layer - New Adjustment Layer - Curves. Than we drag the lower left graph from the lower right corner to the corner. We select the duplicate image and after select the dodge tool - range - highlight and exposure about 10 - 20 and we begin to erase the edges. You can also work with the midtones and shadows. Hope this will work for you :)
Here is an example :
Photo credits: Atenuant.