I want to remove special characters from an array field using SQL Query.

SELECT
  dbo.ROOTCAUSEM1.ID,
  convert(char(4000),convert(varbinary(4000), rca4))
create function dbo.RemoveSpecialChars (@rca4 varchar(256)) returns varchar(256)
begin
   if @rca4 is null
      return null
   declare @s2 varchar(256)
   set @s2 = '' "
   declare @l int
   set @l = len(@rca4)
   declare @p int
   set @p = 1
   while @p <= @l
   begin
      declare @c int
      set @c = ascii(substring(@rca4, @p, 1))
      if @c between 48 and 57 or @c between 65 and 90 or @c between 97 and 122
         set @s2 = @s2 + char(@c)
      set @p = @p + 1
      end
   if len(@s2) = 0
      return null
   return @s2
   end
FROM
  dbo.ROOTCAUSEM1
WHERE
( dbo.ROOTCAUSEM1.OPEN_TIME > '10-10-2015'  )
 
END