Array
(
[0] => Array
    (
        [0] => abc@test.com
        [1] => qwrt@sometest.com
        [2] => haritha@elitesin.com
    )

[1] => Array
    (
        [0] => Kanishka.Kumarasiri@elitesin.com
        [1] => Haritha@elitesin.com
    )

[2] => Array
    (
        [0] => Kanishka.Kumarasiri@elitesin.com
        [1] => test@elitesin.com
    )

for ($i = 0; $i < count($return_arr); $i++) {

$new_value[] = explode(",", $return_arr[$i]);
}

print_r (array_unique($new_value));