Pandas Replace NaN with blank/empty string

I have a Pandas Dataframe as shown below:

    1    2       3
 0  a  NaN    read
 1  b    l  unread
 2  c  NaN    read

I want to remove the NaN values with an empty string so that it looks like so:

    1    2       3
 0  a   ""    read
 1  b    l  unread
 2  c   ""    read