[Code] Stripping low-ascii out of a table, slow way

I'm working on a CLR to do this considerably faster, but here's what I have for now. The purpose of this is to remove dirty data from an upstream feed. We can't make XML with it - the code that creates the XML chokes on it. Note that this isn't terribly fast, because we're brute-forcing it and having to loop through (31 * number-of-fields) times. The CLR should do it in one pass per field.

--CREATE PROCEDURE [dbo].[strip_low_ascii]  
--as  
DECLARE @columns TABLE (id INT IDENTITY, column_name sysname)  
DECLARE @odd_ascii CHAR(1),
  @ascii_value int,
  @column_start smallint, 
  @column_end SMALLINT, 
  @sql NVARCHAR(4000), 
  @field_name sysname, --to allow us to loop through all fields  
  @table_schema sysname, 
  @table_name sysname
SET @ascii_value = 31   --31 aka 0x1F.  Space is 32/0x20.  0-30 is our "low-ascii" range
SET @table_schema = 'dbo'
SET @table_name = 'yourtablename'

CREATE TABLE #list_of_id (id bigint primary key)
  
INSERT INTO @columns  
      SELECT COLUMN_NAME FROM INFORMATION_SCHEMA.COLUMNS   
      WHERE TABLE_SCHEMA = @table_schema 
  AND TABLE_NAME = @table_name
  AND DATA_TYPE IN ('char','varchar','nchar','nvarchar')  
  
SELECT @column_start = MIN(id), @column_end = MAX(id) FROM @columns  
  
WHILE @ascii_value >= 0 --look for all low ascii  
BEGIN  
      SET @odd_ascii = NULL  
      SET @column_start = 1  
      SELECT @odd_ascii = CHAR(@ascii_value)  
  
      WHILE @column_start <= @column_end  
      BEGIN  
   TRUNCATE TABLE #list_of_id
            SET @field_name = NULL  
            SET @sql = NULL   
            SELECT @field_name = column_name FROM @columns WHERE id = @column_start  
            SELECT @sql = 'insert into #list_of_id 
                  SELECT id FROM ' + QUOTENAME(@table_schema) + '.' + QUOTENAME(@table_name) + '
                  WHERE insert_datetime >=CONVERT(CHAR(8),GETDATE(),112)  
                  AND ' + @field_name + ' LIKE ''%'' +  @oddascii  + ''%''  
      IF @@rowcount >0   --( select count from @list_of_id )
            update ' + @table_name + ' set ' + @field_name + ' =  REPLACE(' + @field_name + ',  @oddascii, '''')   
            WHERE insert_datetime >=CONVERT(CHAR(8),GETDATE(),112)  
   and id in (select id from #list_of_id)
            AND ' + @field_name + ' LIKE ''%'' + @oddascii + ''%'''  
            
  
--PRINT @sql  
  
            EXECUTE sp_executesql @sql, N'@oddascii char(1)', @oddascii = @odd_ascii  
  
            SET @column_start = @column_start + 1  
      END  
  
      SET @ascii_value = @ascii_value-1  
END