How to select and replace last occurrence of column value in postgres query

Question

Database structure is as follow -

Table : account_name

id | string_name
1  | "110\u001F121\u001FHELLO"
2  | "110\u001F121\u001FBYE"
3  | "110\u001F122\u001FTAP"

I want to select uniq string_name from table account_name as follow expected output -

string_name
"110\u001F121\u001FNOTHING"
"110\u001F122\u001FNOTHING"

here record with id=2 cannot be selected as after adding NOTHING it will be the same as record with id=1. Also, \u001F this is a special character, it prints this character on rails console but shows blank space in pgadmin output and the format of string_name is not fixed as there may be any number of chunks connected by \u001F. We only want to replace text after last occurrence of \u001F.