Remove non printable characters in input text/para field.

Hi ,

I have a set of non printable characters in DB as number and we use char function and concat function to combine in a single string and used strip function to remove it from text. Now the requirement is to replace text with space. I tried substitute function and others which is not working as expected. Please someone guide me here

a!localVariables(
  local!specialCharacterIds: rule!SUF_QueryRecordType_getSpecialCharacters(),
  local!specialCharacters: joinarray(
    a!forEach(
      local!specialCharacterIds,
      char(fv!item)
    ),
    ""
  ),
  a!paragraphField(
    label:"Comment",
    value:ri!comment,
    saveInto: {
      ri!comment,
      a!save(
        ri!comment,
        substitute(save!value,{local!specialCharacters}," ")
      )
    }
  )
)