One-pot synthesis of magnetic iron oxide nanoparticle-multiwalled carbon nanotube composites for enhanced removal of Cr(VI) from aqueous solution.

Magnetic nanoparticle-multiwalled carbon nanotubes composites (MNP/MWCNTs) were prepared using 1,6-hexanediamine functionalized Fe3O4 nanoparticles (MNP) linked to carboxylic MWCNTs by facile one-pot solvothermal synthesis for highly efficient removal of Cr(VI) from aqueous solution. The easily obtained magnetic nanocomposites were systematically characterized, and several major factors affecting the adsorption-based removal were investigated, including solution pH, adsorbent dosage, temperature and contact time. The removal efficiency was highly dependent on solution pH; low pH facilitated removal with the maximum efficiency at pH 2.0. The adsorption isotherm was well fitted with the Langmuir isotherm model and the adsorption capacity increased with the temperature increasing. The adsorption kinetic data could be well described by the pseudo-second-order and the intraparticle diffusion models, indicating that the intraparticle diffusion was not the only rate-limiting step. The MNP/MWCNTs displayed excellent selectivity and high anti-interference ability toward Cr(VI) when confronted with commonly coexisting ions. By using an external magnetic field, the exhausted MNP/MWCNTs could be readily separated from the solution after adsorption of Cr(VI) and well regenerated, and could keep about 80% removal efficiency in the fifth adsorption-desorption cycle. The simple, rapid and reliable MNP/MWCNT-based method proved to be a cost-effective, convenient and potentially applicable way to targeted pollutant removal and wastewater treatment.