Hmmm. Typically users are trying to do the opposite. That is to say have footnotes appear in one column when the text is in two columns. There's no way I can think of to do this. The footnote will always be inserted into the frame in which the footnote reference is inserted. You can have the footnotes span two columns but not split the footnotes into two columns of a single column frame.
After two years, is there still no answer in relation to this issue: two column footnotes in a single column text page?