Filtration of sodium chloride from seawater using carbon hollow tube composed of carbon nanotubes

Abstract

The present article deals with filtration of seawater to remove sodium chloride (NaCl) using filter made from organized structures of carbon nanotubes (CNTs). The filter consists of hollow carbon cylinder (length ~10 cm, diameter ~1 cm), which is composed of radially aligned CNTs. This carbon hollow cylinder has been synthesized by continuous spray pyrolysis of ferrocene–benzene solution in argon atmosphere. The hollow cylinder has been turned into a water filter by closing one end and keeping a small funnel at the other. Filtration of seawater (Marina Beach, Chennai, India) has been obtained both under the self pressure of seawater column in the hollow cylinder and under the difference of pressure created by enclosing the filter in a vacuum tight container. It has been found that the efficiency of filtration is about two times higher under partial vacuum (~10–2 torr) created on the filtrate (water) side. After filtration of seawater, a deposit in the inner surface of hollow cylinder has been found. This deposit has been characterized by X-ray diffraction, transmission electron microscopy and energy dispersive X-ray analysis, and it has been found that the deposit was NaCl. The filtration leads to almost complete removal of NaCl from the seawater.