Upgrading　copper　slag　into　value-added　products　provides　an　untapped　opportunity　to　address　arsenic　pollution　in　the　environment　and　promote　waste　recycling,　but　the　problem　of　excessive　arsenic　in　products　remains　a　huge　engineering　challenge.　Herein,　we　employ　DFT　calculations　to　explore　the　dissociation　mechanism　of　AsMA　and　propose　a　universal　descriptor　for　screening　As　removal　agents　for　the　first　time.　The　dissociation　of　AsMA　is　related　to　the　disturbance　of　the　Mo-As　bond　by　Ba　and　follows　the　＇Perturbation　–　Re-stabilization　–　Dissociation＇　mechanism.　The　BΨ　value　of　Ba　is　near　the　minimum　value　of　−0.1058　in　the　universal　descriptors,　which　renders　it　potential　candidates　for　As　removal　agents.　As　expected,　Ba　can　increase　As　removal　efficiency　by　approximately　45　%　when　employing　the　Si-Ca-Ba　alloy　compared　to　other　Ca-based　alloys.　This　work　offers　contributions　to　the　As　removal　technology　for　copper　slag　value-added　products　while　also　highlighting　the　DFT　calculations　used　in　guiding　engineering　practices.　©　2024　Elsevier　B.V.