Preparation and characterization of chitin/magnetite/multiwalled carbon nanotubes magnetic nanocomposite for toxic hexavalent chromium removal from solution

Natural organic polymer; chitin, was physically mixed with magnetite nanoparticles and the well-known adsorbent; multiwalled carbon nanotubes (MWCNTs), in order to enhance its adsorption ability and obtain magnetic nanocomposite. Morphological, chemical and physical properties of the prepared chitin/magnetite/MWCNTs (CMM) were investigated using various characterization techniques. The TEM revealed that MWCNTs and magnetite nanoparticles were homogenously dispersed over the chitin surface. Also, the prepared CMM magnetic nanocomposite showed higher surface area and significant magnetic properties compared with the natural chitin. Removal of Cr(VI) by CMM magnetic nanocomposite was explored, and it was found that significant enhancement in the %Cr(VI) removed by increasing the removal time, CMM mass, and by decreasing the temperature of solution, were observed. Moreover, Cr(VI) removal was explored kinetically and thermodynamically, and the results showed that pseudo-second-order kinetic model was the most appropriate model for describing the removal process, and the removal was spontaneous, exothermic, and accompanied with a decrease in the degree of randomness. Finally, the results showed the significant enhancement of the removal ability of natural chitin upon its modification and the preparation of the CMM magnetic nanocomposite, which is a potential and promising adsorbent for environmental remediation. (C) 2017 Elsevier B.V. All rights reserved.