Novel zwitterionic inorganic-organic hybrids: synthesis of hybrid adsorbents and their applications for Cu2+ removal.

A series of zwitterionic hybrid adsorbents were prepared via the ring-opening polymerization of pyromellitic acid dianhydride (PMDA) and N-[3-(trimethoxysilyl)propyl] ethylene diamine (TMSPEDA), and a subsequent zwitterionic process as well as sol-gel reaction. Their applications for Cu(2+) removal by adsorption were performed. FTIR spectra confirmed the step products. TGA revealed that the initial decomposition temperature (IDT) of these zwitterionic hybrid adsorbents could arrive at near 150°C. DSC showed that T(g) values decreased with an increase in PMDA content in the hybrid matrix. Ion-change capacity (IEC) revealed that the cation-exchange capacities (CIECs) and anion-exchange capacities (AIECs) of these hybrid adsorbents were within the range of 9.13-11.49 and 4.97-6.28 mmol g(-1), respectively. Meanwhile, the CIECs and AIECs exhibit an opposite change trend as PMDA content increases. Adsorption experiment indicated that their adsorptions for Cu(2+) ions followed Lagergren second-order kinetic model, surface adsorption and intraparticle diffusion mechanisms might be the major process. These findings demonstrated that they are promising absorbents for the separation and recovery of Cu(2+) ions from contaminated water.