Triethylene Tetramine Functionalized Magnetic Graphene Oxide Chitosan Composite with Superior Capacity for the Removal of Phosphate

A novel triethylene tetramine-functionalized magnetic graphene oxide chitosan composite material (TETA-MGO/CS) with a high adsorption capacity for the phosphate was prepared by chemical coprecipitation and subsequently modified by triethylene tetramine. TETA-MGO/CS was characterized by Fourier transform infrared spectroscopy, transmission electron microscopy, vibrating sample magnetometry, X-ray diffraction, thermogravimetry, and Brunauer–Emmett–Teller analyses. The adsorption experiments of phosphate on TETA-MGO/CS were compared with MGO, MGO/CS, and TETA-MGO. Effects of pH, initial concentration of phosphate, adsorption time, and adsorption temperature were studied. The results indicated that the adsorption capacity of the four adsorbents were highly pH dependent and reached optimum at pH 3.0. Adsorption processes reached the equilibrium within 50 min. The adsorption data of the four adsorbents were well-fitted with the Langmuir isotherm. The maximum adsorption capacities of MGO, MGO/CS, TETA-MGO, and TETA-MGO/CS at 298 K calculated from Langmuir isotherm were 300.13, 314.83, 339.65, and 353.36 mg·g–1, respectively. This result is ascribed to an increase of amino after MGO functionalized by TETA and CS. The adsorption mechanism of phosphate on TETA-MGO/CS could be mainly related with electrostatic interaction. Moreover, phosphate ions adsorbed onto TETA-MGO/CS could be desorbed and can be reused three times. It indicated that TETA-MGO/CS can be used as a efficient and renewable adsorbent.