Electrosorption Behavior of Carbon Nanotube and Carbon Nanofiber Film Electrodes

In this review work, the synthesis of cost-effective, large area carbon nanotube and nanofiber (CNT-CNF) film by low pressure and low temperature thermal chemical vapor deposition and its electrosorption properties in salt solutions are studied. Successful purification of water with good reproducibility by electrosorption of CNT-CNF films is achieved because of optimal pore size distribution that results in lower electrical double-layer overlapping effect. It is found that electrosorption of CNT-CNF film electrodes is mainly due to Coulombic interaction on the electrical double-layer and the ion sorption followed a Langmuir isotherm, indicating monolayer adsorption. The kinetics and thermodynamics analyses indicate that the electrosorption of NaCl onto CNT-CNF electrodes follows first order kinetics model and is driven by a physisorption process. Several experiments are conducted to study the ion removal capacity and selectivity of CNT-CNF film electrodes, showing that multivalent cations are preferentially adsorbed from the aqueous solution. For cations with same charge, the one with smaller hydrated radius will be more effectively removed.