Synthesis of magnetic graphene/nylon 6 nanocomposite and its application for removal of lead ions from aqueous solutions: isotherm and kinetic studies

摘要

A magnetic graphene/nylon 6 composite is presented as a novel adsorbent. The materials were synthesized successfully through chemical methods. Graphene oxide was synthesized by Hummers and Offeman's method, and then magnetized by precipitation of Fe3O4. The nanocomposite was dispersed in a solution of nylon 6, and simultaneously graphene oxide was reduced to graphene. The characterization of the sorbent was carried out by X-ray diffraction, scanning electron microscopy, Brunauer-Emmett-Teller, a vibration-sample magnetometer and Fourier-transform infrared spectroscopy. Graphene has a high surface area, and oxygen and nitrogen in the nylon 6 increase the active sites of the sorbent to adsorb cations. Also, the sorbent can be magnetically separable. Accordingly, the sorbent was utilized for the removal of lead ions from aqueous solutions. To achieve the maximum recovery, the effects of various parameters such as solution pH, adsorbent dosage, and adsorption time on the removal process were investigated. The optimal conditions for removal of Pb(II) ions from aqueous solutions were found at pH 7, adsorbent dosage of 20 mg, and adsorption time of 20 min. The reproducibility and stability of the sorbent were successfully investigated, but the sorbent is not reusable. Furthermore, Freundlich and Langmuir isotherm models were used in the equilibrium studies. The results showed that the Freundlich isotherm was fitted well with the experimental data. In the kinetic studies, pseudo-first-order and pseudo-second-order models were evaluated, and the pseudo-second-order equation showed the optimal correlation with the obtained data.