The effect of MWCNT treatment by H₂O₂ and/or UV on fulvic acids sorption

The carbon nanotubes (CNT) present in the wastewater subjected to treatment will possess altered physico-chemical properties. The changed properties will result in the unknown behavior of CNT in the environment after disposal; and it is expected to differ from their pristine analogues. In the present paper the effect of sorption of dissolved organic matter with fulvic acids (FA) as representatives onto UV and/or H₂O₂ treated CNT was tested. Both kinetics and mechanism of sorption was estimated. The chemical adsorption was a rate limiting step and a pseudo-second order kinetics described the sorption of FA onto UV and/or H₂O₂ treated CNT. The treating increased affinity towards FA and treating by UV and H₂O₂ simultaneously possessed greater impact on k₂ than UV and H₂O₂ separately. The greatest effect on CNT sorption capacity revealed H₂O₂. The sorption mechanism was described by Temkin (CNT-H₂O₂) and Dubinin-Radushkevich model. The increase in CNT surface disorder caused by UV and/or H₂O₂ treatment favored sorption of FA via π-π interactions (exfoliated surface and disordered CNT walls). FA sorption occurred between aromatic rings of FA and CNT and hydrogen bonds formed with the oxygen functional groups. The results indicate that UV and/or H₂O₂ treatment affected the sorption capacity and affinity of CNT towards FA.