Multiwalled carbon nanotubes to remove mercury from industrial wastewater

Iranian researchers from Tarbiat Modarres University produced a sorbent made of multiwalled carbon nanotubes functionalized with sulfuric groups and studied its performance in the removal of mercury from industrial wastewater. The sorbent has applications in the recovery of wastewater produced by various industries that release hazardous toxic metals in the environment, including petrochemical (containing chloralkali unit), plating and electronic industries as well as battery manufacturing, etc. The most important objective of the researchers was to introduce a high-performance sorbent to remove mercury from aqueous solutions, even in the presence of other ions existing in industrial wastewater. In order to achieve their goal, the researchers functionalized multiwalled carbon nanotubes with amine and thiol functional groups. Next, they studied and investigated thermodynamic and kinetic parameters of mercury sorption process by the synthesized sorbent in continuous and batch systems by using the existing models. The research was carried out through the following steps. Firstly, carbon nanotubes were functionalized through five successive stages, including purification, oxidation, amination, melamination and thiolation. Adsorption of mercury ions from aqueous solution was carried out, and parameters effective in the adsorption were studied as well. Finally, the researchers optimized the process of mercury removal from synthetic wastewater and real wastewater obtained from chloralkali industry by using functionalized carbon nanotubes as the sorbent. The sorbent produced by the researchers can be used for the removal of metallic ions, specifically mercury, from industrial wastewater and also from drinking water. It can also be used as the immobile phase of SPE cartridges in pre-concentration and measurement of very small amounts of mercury and methyl-mercury ions in aqueous solutions. Results of the research have been published in details in Chemical Engineering Journal, vol. 237, October 2014, pp. 217-228.