Experimental Study on Removal of Mercury from Aqueous Solutions by Using Magnetite Carbon Nanotube (CNT) as Adsorbent

Abstract

Removal of contaminants by adsorbent is a useful and effective way to remove heavy metals from wastewater and aqueous samples. Mercury is one of the heavy metals that is toxic to humans, animals and the environment. In this study, magnetic multi-walled carbon nanotube (MMWCNT) composite was synthesized and used to remove Hg(II) from aqueous solutions. This work was conducted on a laboratory scale and based on the design of experiment by the surface response methodology (RSM) and based on Box-Behnken design, and the effects of independent variables including pH, adsorbent dose, initial concentration of Hg and contact time in different levels were evaluated with the help of Design-Expert Stat-Ease Inc software. The properties of this magnetic adsorbent were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR). The results show that the adsorption of Hg(II) on magnetic MWCNT composite is strongly dependent on contact time and adsorbent dosage. The highest efficiency of removal mercury was about 85% and that occurred when pH=6, dose of adsorbent= 0.6 g/L, initial concentration of Hg(II)=10 ppm and contact time=150 minutes. The adsorption isotherm data were better fitted by Freundlich model, while kinetic data can be characterized by the pseudo-second-order rate kinetics. In general, it can be concluded that magnetic MWCNT adsorbent has a very high ability to remove mercury.

Keywords

• adsorption
• mercury
• magnetic carbon nanotube
• adsorption isotherms
• adsorption kinetics