In the case of pentavalent methylarsenicals, some interesting mechanistic features emerge because of the oxide groups and charge speciation. For neutral pollutants, the combined contribution from charge transfer and polarization effects (ECT+EPOL) accounts for up to 54% of the stabilizing energy, which is almost balanced with the electrostatic term (EELEC, 42-46%, Fig. ). Because ECT and EPOL show a strong dependence of orbitals interactions at shorter intermolecular distances, oxide groups of pentavalent methylarsenicals must covalently bind with activated phosphorous atoms of the adsorbent, in agreement with short O-P bonds in neutral PhosO-As V complexes (dO-P1.8 Å). Consequently, the innersphere surface complexation of pentavalent methylarsenicals occurs by a balanced contribution of orbital and long-range driving forces, explaining their relatively higher adsorption energies than trivalent pollutants. Note that the oxide group of pentavalent pollutants is also responsible for strong chemical bonding onto doped substrates like Al, Fe, and Si-doped graphene, denoting its key role in the low mobility of As(V) species compared to As(III) .