A sustainable adsorbent for phosphate removal: modifying multi-walled carbon nanotubes with chitosan
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Phosphorus, a major culprit for eutrophication of aquatic environments, is dissolved in water primarily in the form of phosphate; hence, it is difficult to remove, and different materials are being investigated, aiming at high removal capabilities. Meanwhile, recovery capability must also be considered, since phosphorus present in wastewater may serve as a potential alternative resource for the mineral phosphorus. Carbon nanotubes are promising for the treatment of phosphate pollution; however, studies about their removal potential are limited. Herein, multi-walled carbon nanotubes were modified with chitosan through simply cross-linking to obtain a novel adsorbent for phosphate removal. Our data show that a maximum adsorption as high as 36.1 ± 0.3 mg P g−1 was achieved in 30 min at pH 3 and 293 K. The adsorption capacity of the composite (chitosan/multi-walled carbon nanotubes) could be maintained at 94–98% even after 5 adsorption–desorption cycles. An exothermic process was obtained, according to the Freundlich isotherm model. Based on the reported performance, the composite has a great advantage compared with other novel adsorbents for phosphate removal, indicating that the composite is a highly potential material to treat phosphorus-induced eutrophication of water bodies.
This work was supported by the State Scholarship Fund sponsored by the China Scholarship Council (Y. H.), National Natural Science Foundation of China (U1612441), Sino-Israeli Intergovernmental Scientific and Technological Cooperation Project (2015DFG92450), and the 2014 Cooperative Project Between the Chinese Academy of Sciences and the Xinjiang Autonomous Region (X.L.). The authors would also like to thank the United States National Science Foundation, under award number 1561427 (M.G., F.C.M., and S.D.M.), for financial support.
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Conflict of interest
The authors declare that they have no conflict of interest.