Study on the removal of heavy metal ions from industry waste by carbon nanotubes: Effect of the surface modification: a review

Removal of noxious materials such as heavy metal ions (which are hazardous above certain ppm concentration) from wastewater is one of the biggest environmental challenges that suffers the economy nowadays. On the basis of their versatility, environmental friendliness, the adsorption was proved to be a most economical and efficient technology, which is used extensively for their removal from the aqueous media. Among the various developed adsorbents used so far, carbon nanotubes (CNTs) show a unique impact on the fast adsorption and rapid removal of noxious impurities from the aqueous source. CNTs festooned on the sources like activated carbon, nanoparticles, and nanocomposities enhanced the efficiency and potential of the adsorbent. Due to their unique structural, electronic, optoelectronic, semiconductor, as well as mechanical, chemical, and physical properties, they have been extensively used to remove heavy metals in wastewater treatment. The adsorption mechanisms are majorly contributed by the chemical interactions between the metal ions and the functional groups present on the surface of the CNTs. Greater the surface area more will be the number of reducing groups hence more attributable to better CNT sorption performances.