Chitin/egg shell membrane@Fe 3 O 4 nanocomposite hydrogel for efficient removal of Pb 2+ from aqueous solution.

The development of adsorbents by using the byproducts or waste from large-scale industrial and agricultural production is of great significance, and is considered to be an economic and efficient strategy to remove the heavy metals from polluted water. In this work, a novel chitin/EM@Fe 3 O 4 nanocomposite hydrogel was obtained from a NaOH/urea aqueous system, where the proteins of egg shell membrane and Fe 3 O 4 nanoparticles were chemically bonded to chitin polymer chains with the help of epichlorohydrin. Due to the existence of a large number of -NH 2 , -OH, -CONH-, -COOH and hemiacetal groups, the adsorption efficiency for Pb 2+ into the absorbent was dramatically enhanced. The experimental results revealed that the adsorption behavior strongly depends on various factors, such as initial pH, initial Pb 2+ concentration, incubation temperature and contact time. The kinetic experiments indicated that the adsorption process for Pb 2+ in water solution agreed with the pseudo-second-order kinetic equation. The film diffusion or chemical reaction is the rate limiting process in the initial adsorption stage, and the adsorption of Pb 2+ into the nanocomposite hydrogel can well fit the Langmuir isotherm. Thermodynamic analysis demonstrated that such adsorption behaviors were dominated by an endothermic (Δ H ° > 0) and spontaneous (Δ G ° < 0) process.