Synthesis of polyamide grafted carbon microspheres for removal of rhodamine B dye and heavy metals

Polyamide branches grafted onto carbon microspheres (CMS) was successfully synthesized by interfacial polymerization of 1,3,5-trimesoyl chloride and 1,3-phenylene diamine in situ with CMS. The obtained CMS-polyamide was characterized by Fourier transform infrared spectroscopy, thermogravimetric analyzer, scanning electron microscopy and Energy-dispersive X-ray spectroscopy. The sorption efficiency of the CMS-polyamide was evaluated by using rhodamine B (RhB) dye-polluted solutions. It exhibited excellent adsorption performance for the removal of RhB with adsorption capacity of 19.9 mg/g. The pseudo-second-order equation and the Langmuir model exhibited a good correlation with the adsorption kinetics and isotherm data with R² of >0.99. Tests of adsorption/desorption were performed, and the results showed that dye loaded CMS-polyamide could be regenerated (97%) using acetone. Possible adsorption mechanisms have been proposed, where electrostatic attraction, π-π stacking interactions and complexation interaction with metal dominate the adsorption of RhB. The excellent removal rate (≃100%) of RhB, even in the presence of heavy metals (Pb, Cd, Hg, Cr, Ni, and Cu) in single and binary systems, endowed the CMS-polyamide with the potential for applications in water treatment.