Carbon micro- and nanofibrous materials with high adsorption capacity for water desalination

Abstract

This work demonstrates the adsorption capacity of carbon micro- (CF) and nanofibrous (CNF) adsorbents differing in specific surface area, fiber diameter and open porosity in the removal of NaCl from water. The effect of the adsorption conditions, i.e. contact time, initial salt concentration, and oxidative surface treatment on the adsorption kinetics and equilibrium salt uptake capacity was investigated. Adsorption experiments were carried out by batch-mode experiment at room temperature. The study showed that activated CNF exhibit high adsorption capacity for NaCl, namely 827.5 mgNaCl/gCNF, and this value is over 40 times higher than that of activated carbon and exceeds the values reported for CNT and GO. The adsorption kinetics followed the pseudo-second-order kinetic model and was largely controlled by the intramolecular diffusion rate. The equilibrium data showed a good correlation with the Langmuir and Freundlich isotherms, which supported the complex interaction of salt with the carbon surface. It was shown that salt ions can be attached to the fibrous surface both by ion-exchange mechanisms and electrostatic interactions. The carbon fibrous adsorbents present a new approach to water desalination through the mechanism of adsorption and continuous crystallization, and may be used for the elaboration of new type membranes for water purification and desalination.