Carbon nanotubes as a potential adsorbent for the treatment of wastewater

Abstract

Water pollution due to heavy metal ions and organic compounds has emerged as a global concern. Among various methods for wastewater treatment such as advanced oxidation process, photodegradation, reverse osmosis etc. adsorption is an economical and effective method. Researchers have focused attention for the developement of low-cost efficient materials for the adsorption of toxic metals and organic pollutants from aqueous streams. The discovery of carbon nanotubes (CNTs) has led to a new and interesting area of research. In this context, CNTs are effectively used for the removal of various pollutants from water and wastewater. This study summarises various raw and surface modified CNTs as effective adsorbent materials for the wastewater treatment. Adsorption kinetics and mechanism are also discussed in this study. The adsorption is due to the chemical attractions between pollutants and functional groups on the surface of carbon nanotubes. The adsorption efficiency of CNTs is enhanced by oxidation with common oxidising agents such as nitric acid, potassium dichromate and sodium oxychloride. Surface oxidised CNTs have the potential to be excellent adsorbent materials for water remediation purposes. Various factors affecting the adsorption capacity of CNTs are discussed. Acid elution is reported to be an effective method for the regeneration of CNTs without affecting their adsorption capacity. Lastly, the future prospects for the development of CNTs as efficient, low-cost and nontoxic materials for remediation of water pollutants are also addressed.