+--------+
|some_num|
+--------+
|       3|
|      24|
+--------+

df.withColumn(
  "bucket",
  bucketFinder(
    col("some_num"),
    Array(
      (0, 10),
      (10, 20),
      (20, 30)
    )
  )
).show()

+--------+------+
|some_num|bucket|
+--------+------+
|       3|  0-10|
|      24| 20-30|
+--------+------+

def bucketFinder(col: Column, buckets: Array[(Any, Any)]): Column = {

  buckets.foreach { res: (Any, Any) =>
    when(col.between(res._1, res._2), lit(s"$res._1 - $res._2"))
  }

}

val bucket_size = 10
val floor_col = floor(df("some_num") / bucket_size) * bucket_size

df.withColumn("bucket", concat_ws("-", floor_col, floor_col + bucket_size)).show
+--------+------+
|some_num|bucket|
+--------+------+
|       3|  0-10|
|      24| 20-30|

val bucket_size1 = 5
val floor_col = floor(df("some_num") / bucket_size1) * bucket_size1

df.withColumn("bucket", concat_ws("-", floor_col, floor_col + bucket_size1)).show
+--------+------+
|some_num|bucket|
+--------+------+
|       3|   0-5|
|      24| 20-25|