O‐carboxymethyl chitosan entrapped by silica: preparation and adsorption behaviour toward neodymium (III) ions

Abstract BACKGROUND: The recovery of neodymium from dilute solutions has become important because of its wide application in industry. This work reports the preparation of novel carboxymethyl chitosan adsorbents entrapped by silica (SiO 2 /CMCH) and their application for adsorption of neodymium(III) ions from aqueous solution. RESULTS: The effect of the CMCH content, equilibrium pH (pH e ), contact time, initial concentrations of Nd(III) and temperature on the adsorption was investigated. The amount of Nd(III) adsorption increases with increasing pH e , which can be explained by the pH‐titration curve of CMCH. Temperature has a positive effect on Nd(III) adsorption, and the amount adsorbed is 53.04 mg g −1 dry adsorbent or 434.75 mg g −1 CMCH at 328 K. Adsorption kinetics and isotherm can be described by the pseudo‐second‐order model and Langmuir equation. Both complexation and ion exchange mechanisms are believed to play an important role in Nd(III) adsorption, and possible coordination between CMCH and Nd(III) is speculated. Complete desorption can be reached when the concentration of HCl is more than 0.1 mol L −1 . CONCLUSION: A novel method was developed to prepare SiO 2 /CMCH adsorbents through a one‐step sol‐gel strategy. The prepared adsorbents were biocompatible and non‐toxic with a good adsorption ability for Nd(III), and could be used for adsorptive recovery of Nd(III) from aqueous solutions. © 2012 Society of Chemical Industry