pandas to_sql : string literal cannot contain NUL (0x00) characters

I a trying to append data to a PostgreSQL database table using Pandas.DataFrame.to_sql and sqlalchemy and have received the error ValueError: A string literal cannot contain NUL (0x00) characters.

I understand this is because Postgresql does not allow UTF null characters.

this is the line of code that is creating the error:

df.to_sql(table_name,con,if_exists='append',index=False) 

How can I check where this particular character occurs in my data frame and replace it with something that will not cause this error to occur?