Selective Removal of Copper(II) from Natural Waters by Nanoporous Sorbents Functionalized with Chelating Diamines

Copper has been identified as a pollutant of concern by the U.S. Environmental Protection Agency (EPA) because of its widespread occurrence and toxic impact in the environment. Three nanoporous sorbents containing chelating diamine functionalities were evaluated for Cu²⁺ adsorption from natural waters: ethylenediamine functionalized self-assembled monolayers on mesoporous supports (EDA-SAMMS), ethylenediamine functionalized activated carbon (AC-CH₂-EDA), and 1,10-phenanthroline functionalized mesoporous carbon (Phen-FMC). The pH dependence of Cu²⁺ sorption, Cu²⁺ sorption capacities, rates, and selectivity of the sorbents were determined and compared with those of commercial sorbents (Chelex-100 ion-exchange resin and Darco KB-B activated carbon). All three chelating diamine sorbents showed excellent Cu²⁺ removal (∼95−99%) from river water and seawater over the pH range 6.0−8.0. EDA-SAMMS and AC-CH₂-EDA demonstrated rapid Cu²⁺ sorption kinetics (minutes) and good sorption capacities (26 and 17 mg Cu/g sorbent, respectively) in seawater, whereas Phen-FMC had excellent selectivity for Cu²⁺ over other metal ions (e.g., Ca²⁺, Fe²⁺, Ni²⁺, and Zn²⁺) and was able to achieve Cu below the EPA recommended levels for river and sea waters.