Nevertheless, some co-existing species (e.g., citric acid) increases the arsenic adsorption efficiency of phosphorene, reaching a maximum adsorption capacity of 20 mg/g, respectively . Suitable NCl amount (0.1M) also increases the arsenic adsorption from ~40 to 95% by using graphene-oxide, without a larger competition for the adsorption sites with other co-existing anions (PO4 3-and SO4 2-) . Then, a suitable magnitude of ionic strength could be beneficial to improve the arsenic removal efficiency in layered oxides. In this regard, surface complexation modeling and vibrational spectroscopy experiments have established that ionic strength does not change the arsenic adsorption if arsenicals form innersphere surface complexes ; in opposition, outer-sphere surface complexes destabilizes at higher ionic strength values, decreasing the adsorption capacity. Therefore, phosphorene oxides are expected to retain their adsorption capacity/efficiency in the presence of coexisting anions due to the adsorption mechanism via inner-sphere surface complexation.