[Preparation of Nanocomposite Hydrogel and Its Adsorption of Heavy Metal Ions]

An acylamino and hydroxyl functionalized hydrogel [p(HMAm/HEA)] was newly prepared by the ⁶⁰ Co-γ-induced polymerization of N-hydroxymethyl acrylamide (HMAm) and 2-hydroxyethyl acrylate (HEA). Then the copolymer p(HMAm/HEA) hydrogel was utilized for in situ nanosized hydrous manganese dioxide (HMO) loading to prepare nanocomposite hydrogel HMO-p(HMAm/HEA) for Pb²⁺ and Cu²⁺ removal. The nanocomposite hydrogel was characterized by SEM, TEM and FTIR, showing that p(HMAm/HEA) hydrogel was indeed a copolymer of HMAm and HEA monomers, and the loading of HMO nanoparticles onto p(HMAm/HEA) was successful. Various influencing parameters on heavy metal ions removal by HMO-p(HMAm/HEA), such as initial pH, temperature, initial heavy metal concentration, contact time and competing Ca²⁺ and Na⁺, were estimated. The results showed that the adsorption process was temperature-independent, pH-sensitive, Langmuir monolayer adsorption and followed a pseudo-second-order rate equation. The presence of high concentrations of competing Ca²⁺ and Na⁺ had no significant effect on the adsorption process. The XPS spectra analyses further indicated that Pb²⁺ and Cu²⁺ were adsorbed via the ion exchange of -OH groups. Moreover, HMO-p(HMAm/HEA) could be regenerated by 0.05 mol·L^-1 of HCl, and obtained excellent repeated use.