Removal of inorganic mercury from aquatic environments by multi-walled carbon nanotubes

Abstract

BackgroundMercury is considered as a toxic heavy metal in aquatic environments due to accumulation in bodies of living organisms. Exposure to mercury may lead to different toxic effects in humans including damages to kidneys and nervous system.Materials and methodsMulti-walled carbon nanotubes (MWCNTs) were selected as sorbent to remove mercury from aqueous solution using batch technique. ICP instrument was used to determine the amount of mercury in solution. Moreover, pH, contact time and initial concentration of mercury were studied to determine the influence of these parameters on the adsorption conditions.ResultsResults indicate that the adsorption strongly depended on pH and the best pH for adsorption is about 7. The rate of adsorption process initially was rapid but it was gradually reduced with increasing of contact time and reached the equilibrium after 120 min. In addition, more than 85 % of initial concentration of 0.1 mg/l was removed at 0.5 g/l concentration of sorbent and contact time of 120 min. Meanwhile, the adsorption process followed the pseudo second-order model and the adsorption isotherms could be described by both the Freundlich and the Langmuir models.ConclusionThis study showed that MWCNTs can effectively remove inorganic mercury from aqueous solutions as adsorbent.

Removal of heavy metals and pollutants by membrane adsorption techniques

“…Jaafar (2012) used modified CNTs (HNO 3 treated) for the removal of Cu 2+ from water. Yaghmaeian et al (2015) reported that MWCNTs can effectively remove inorganic mercury from aqueous solutions as adsorbent and claimed that carbon nanotubes have high efficiency in adsorbing mercury. Mubarak et al (2016) made a comparative study of the removal of Pb 2+ ions and Cr 3+ ions to determine the efficiency of carbon nanotubes (CNTs) produced using microwave heating as an adsorbent in removing heavy metal ions from waste water.…”

Trapping Ionic Mercury Using Different Adsorbents

“…The thermodynamic studies also indicated that the process was spontaneous, feasible, and endothermic. Several other recent and relevant studies reported on mercury adsorption using different adsorbents are discussed …”

“…Nevertheless, the considerable increase in industrial activities in recent years has resulted in an unprecedented rise in trace metals in the environment at concentrations above the maximum permissible limits designed to safeguard the ecosystem . Accordingly, trace metal contamination of the aquatic environment has become a common phenomenon worldwide and has gained a lot of research attention . For instance, the outbreak of Minamata disease in Japan elicited research efforts that revealed the pathways for bioaccumulation of mercury and its compounds in the food chain.…”

Removal of Hg2+ and methylmercury in waters by functionalized multi-walled carbon nanotubes: adsorption behavior and the impacts of some environmentally relevant factors

“…The strong sorption of Hg 2+ to MWCNTs make it requires low dose of MWCNTs to remove Hg 2+ , and high (>90%) and almost equal removal efficiencies were obtained in the studied range of MWCNTs concentration (0.5−2.0 g/L) for all the four MWCNTs. Due to the relatively weak sorption of MeHg to MWCNTs, the removal efficiency four adsorbing processes in the solution: (i) NOM could combine with Hg 2+ and MeHg [25,43]; (ii) MWCNTs could adsorb Hg 2+ and MeHg [17,21,29,37,[44][45][46]; (iii) MWCNTs could adsorb NOM and form MWCNTs-NOM complexes [47]; and (iv) NOM could stabilize the dispersion of MWCNTs [26,27]. Depending on the characteristics of MWCNTs and NOM, as well as the aqueous chemistry parameters, these four processes showed different strength and therefore resulted in varied removal efficiency of Hg 2+ and MeHg.…”

“…The MWCNTs have been experimentally proven to possess cylindrical hollow micro-crystals of graphite which have strong adsorption ability, exceptional mechanical properties, unique electrical property, high chemical and thermal stability, a large specific surface area, and high adsorption capacity [13][14][15]. Researches have shown that the surface functional groups such as amino [18,19], carboxyl [20,21], hydroxy [20,21] and thiol [19,[22][23][24] on carbon nanotubes can greatly improve their adsorption capacity for metal ions. Moreover, various aqueous environment relevant factors including pH, ionic strength and natural organic matter (NOM) can affect the adsorption of metal ions onto MWCNTs [12,13,20,[25][26][27].…”