There is no such thing as "junk characters" or "junk values" -- period. Each and every character has a valid value in the collating sequence. The characters may not be printable but that does not mean they are "junk".
You should browse or edit the data set in hex mode so you can see precisely what the non-printing characters actually are. Once you know what they are, you can devise a way to remove them.
An old saying " I couldn't repair your brakes, so I made your horn louder".
Being said, Correct your bad SQL (I assume query means SQL here ) , NOT to add anything you don't want than correcting anything later. If you can't do it yourself then add a new topic to DB2 section and share the problem.