ia <- as.data.frame(sapply(ia,gsub,pattern="#",replacement=""))

d <- data.frame(x = as.character(1:5),y = c("a","b","#","c","d"))
> d[] <- lapply(d,gsub,pattern = "#",replace = "")
> d
  x y
1 1 a
2 2 b
3 3
4 4 c
5 5 d

d <- data.frame(x = as.character(1:5),
                y = c("a","b","#","c","d"),
                z = rep("#",5))
> d[,!sapply(d,function(x) all(x == "#"))]
  x y
1 1 a
2 2 b
3 3 #
4 4 c
5 5 d

df <- df[,-1]