How do I remove a column from a txt file?

Text files don't have columns: the only way to remove anything is to create a new file, then read the old file copying the data you do want and not copying the data you don't.
So use a loop, read each line from the file as a string, then modify the string to remove the data you don't want. Write the changed line to the new file, and repeat.
After the loop, either delete or rename the original file, then rename the new file to the original file name.