Adsorption of azo dye onto nanodiamond surface

In the present work, the adsorption of azo dye acid orange 7 (AO7) onto nanodiamond (ND) surface has been investigated in order to ascertain the adsorption behavior as well as the mechanism involved in adsorption process. As control groups, another azo compound, sulfasalazine (SSZ), together with 5-aminosalicylic acid (5-ASA) and sulfapyridine (SPY), was also studied for adsorption behavior onto ND surface, respectively. Due to strong hydrogen bond interaction, ND shows high affinity with AO7 and SSZ while it only exhibits moderate and weak interaction with 5-ASA and SPY, respectively. Though the affinity is slightly lower at high pH values, the adsorption coefficients of ND with AO7 at neutral to alkaline pHs are still of the same orders of magnitude with those at low pHs, suggesting that ND could be a desirable candidate for textile wastewater treatment not only in acidic conditions but also at neutral to alkaline pHs.

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► Nanodiamond strongly interacts with azo dye through hydrogen bonds.
► Azo dye uptake higher than reported from activated carbon and carbon nanotube.
► Nanodiamond kept high affinity and uptake for azo dye even at alkaline pHs.
► Promising for dye wastewater treatment without additional cost/environmental issues.