Are carbon nanotubes promising adsorbents for water treatment?

Introduction Adsorption is one of the most commonly used technologies to remove organic contaminants from aqueous solution in water treatment. The most conventional adsorbent is activated carbon (AC) – a substance which is extremely porous. However, in several recent studies, carbon nanotubes (CNTs) have been observed to be more efficient carbonaceous adsorbents than conventional ACs, with higher adsorption capacity [1-3], shorter equilibrium time [4, 5] and less weight loss in reactivation [2]. CNTs, as newly emerged carbonaceous materials, have attracted considerable interests as potential adsorbents for water treatment application due to their high specific surface area, distinct structure and modifiable surface chemistry. Therefore, a fundamental comparison between CNTs and ACs is critical and necessary in evaluating the potential environmental application of CNTs and selecting the optimal carbonaceous adsorbents in water treatment. In this review, we first summarized the physiochemical properties of CNTs and ACs, and then compared the adsorption behaviors between them in terms of adsorption capacity and kinetics.