X-ray diffraction (XRD) analysis
The native DNES–CH X-ray diffractogram (as shown in Fig. 9a) exhibited sharp peaks at 2θ positions 29°, 34°, 44°, 48°, 49°, 58°, 61°, 65°, 74°, 82°, 84°, 94°, 95° and 100°. X-ray diffractogram analysis of the copper loaded DNES–CH composite (as shown in Fig. 9b) showed the amorphous nature, with sharp peaks at 2θ positions of 20°, 22°, 23°, 25°, 27°, 28°, 30°, 48° and 85°. In addition, the peaks at 43.7°, 50° and 74.2° (JCPDS copper: 04-0836) suggest the presence of copper while the peaks at 2θ positions of 32.3°, 35.2°, 38°, 46.2°, 48.6°, 51.7°, 53.4°, 56.8°, 58.1°, 65.9°, 66.1°, 68.0°, 71.5°, 72.7°, 74.7°, 82.2°, 83.0°, 83.6°, 87.6° and 89.5° (JCPDS CuO: 80-1916) indicate the formation of CuO by the reaction of the metal with the hydroxyl and the carboxyl groups present on the adsorbent. The said reaction may be due to the electron pair sharing between the copper metal and the reactive carboxyl/hydroxyl groups in the DNES–CH composite.
Fig. 9  a XRD of native DNES–CH composite. b XRD of DNES–CH composite treated with copper