Removal of mercury (II) from aqueous solutions by multiwalled carbon nanotubes coated with manganese oxide

Abstract

Background and aims: Water pollution by heavy metals is one of the most important environmental problems. Among the heavy metals, mercury (Hg) is a very toxic metal and its high concentration can lead to impaired pulmonary and renal dysfunction. The aim of this study was to determine the amount of Hg removal by carbon nanotubes coated with manganese (Mn) oxide from aqueous solutions. Methods: In this study, multi-walled carbon nanotubes coated with Mn oxide were prepared and used to remove Hg from aqueous environments. In addition, the physical and structural characteristics of the nanotubes were determined by the X-ray diffraction (XRD). The impact of diverse variables was further investigated, including the initial concentration of Hg, the initial pH of the solution, contact time, mixing rate, as well as the amount of nano-composite and the impacts of confounders (nitrate and chloride). Finally, optimum conditions for each of these parameters were obtained by the Taguchi statistical method. Results: The XRD analysis showed that the nanotubes were properly coated with Mn oxide. Furthermore, the results demonstrated that under pH 7, the rate of mixing of 150 rpm, the contact time of 60 minutes, the amount of nano-composite of 60 mg, and the initial density of Hg 80 mg/L can be achieved by removing 95% Hg. Moreover, the confounder factors of nitrate and chloride reduced the amount of Hg removal by 4 and 5%, respectively. Conclusion: Based on the results, the nanotubes coated with Mn oxide can be used as easy and strong absorbents for the rapid absorption of Hg from drinking water and industrial wastewater.

Evaluation of Pb (II) Removal by Tea Pulp Modified with Magnetite Nanoparticle

“…technique has been used to prepare particles with homogeneous composition and narrow size distribution [20,26,27]. Tis technique is probably the most common and efcient method to obtain magnetic particles.…”

“…TWMNPs adsorbent were separated through an external magnetic feld and washed three times with double distilled water (DDW) and ethanol and dried at 60 °C [20,28]. Te reactions that occur in the production of magnetic nanoparticles TWMNPs are as shown in equations ( 1) and ( 2), [20,26,27].…”

“…According to Figure 8(a), with increasing the initial concentration of Pb (II) (Cp) from 0.1 to 2 g L − 1 , the amount of Pb (II) removal and the response surface increased. One of the most important causes for the increase in Pb (II) adsorption is the increasing pressure gradient and driving force in mass transfer and as a result Pb (II) adsorption by magnetite nanoparticles increases [26]. In a research project by Zhang et al, the deletion of Pb (II) by SiO 2 -Fe 3 O 4 and AlOOH was examined, their results showed that lead removal increased with increasing initial Pb (II) concentration [37].…”

A comprehensive review of the application of modified carbon nanotubes (CNTs) for the removal of metals from wastewater

“…There are three different types of mercury (Hg): metallic element, inorganic salt, and organic salt [107]. These substances can be found in soil, freshwater, and ocean, and industrial waste processes and products all contain mercury [121]. Due to the harmful consequences of mercury, even at very low concentrations, WHO has set a maximum acceptable mercury concentration in water at 1 mg l −1 [39].…”

Removal of Natural Organic Matter (NOM) from Aqueous Solutions by Multi-Walled Carbon Nanotube Modification with Magnetic Fe3O4 Nanoparticles

“…Separating the sorbent by a simple magnetic process is another advantage of this combination. Also, previous studies found that MWCNTs can decrease the pollutants from aqueous solutions and sediments [18][19][20]. Due to the presence of NOM in drinking water and its related problems, diferent methods have been used and proposed to remove these substances.…”