{"references": ["S. Bernard, a Enayati, L. Redwood, H. Roger, and T. Binstock, \"Autism:\na novel form of mercury poisoning.,\" Med. Hypotheses, vol. 56, no. 4,\npp. 462\u201371, Apr. 2001.", "\"U.S. EPA, Mercury Study Report to Congress, EPA 452, Executive\nSummary, EPA OAQPS/ORD, 1997, pp. R97\u2013R105.\"", "W. F. Fitzgerald, D. R. Engstrom, R. P. Mason, and E. A. Nater, \"The\ncase for atmospheric mercury contamination in remote areas,\" Environ.\nSci. Technol., vol. 32, no. 1, pp. 1\u20137, 1998.", "P. L. Bidstrup, \"Toxicity of Mercury and its Compounds.\" Toxic.\nMercur. its Compd., 1964.", "K. Kadirvelu, M. Kavipriya, C. Karthika, N. Vennilamani, and S.\nPattabhi, \"Mercury (II) adsorption by activated carbon made from sago\nwaste,\" Carbon, vol. 42, no. 4, pp. 745\u2013752, 2004.", "\"U.S. Environmental Protection Agency (EPA) and Environment\nCanada. 1999. Update: Binational Toxics Strategy \u2013 Mercury Sources\nand Regulations.\"", "\"U.S. EPA. 2005. Great Lakes Pollution Prevention and Toxics\nStrategy. Background Information on Mercury Sources and\nRegulations.\"", "C. F. Forster and D. A. Wase, \"Biosorbents for metal ions,\" 1997.", "J. C. a. de Wuilloud, R. G. Wuilloud, R. a. Olsina, and L. D. Martinez,\n\"Separation and pre-concentration of inorganic and organo-mercury\nspecies in water samples using a selective reagent and an anion\nexchange resin and determination by flow injection-cold vapor atomic\nabsorption spectrometry,\" J. Anal. At. Spectrom., vol. 17, no. 4, pp. 389\u2013\n394, Apr. 2002.\n[10] J. L. Capelo, C. D. Dos Reis, C. Maduro, and a Mota, \"Tandem focused\nultrasound (TFU) combined with fast furnace analysis as an improved\nmethodology for total mercury determination in human urine by\nelectrothermal-atomic absorption spectrometry\" Talanta, vol. 64, no. 1,\npp. 217\u201323, Sep. 2004.\n[11] D. P. Torres, M. A. Vieira, A. S. Ribeiro, and A. J. Curtius,\n\"Determination of inorganic and total mercury in biological samples\ntreated with tetramethylammonium hydroxide by cold vapor atomic\nabsorption spectrometry using different temperatures in the quartz cell,\"\nJ. Anal. At. Spectrom., vol. 20, no. 4, pp. 289\u2013294, 2005.\n[12] B. Welz, \"Atomic Absorption Spectrometry (2nd edn.) VCH,\" New\nYork, p. 279, 1985.\n[13] L. Malachowski, J. L. Stair, and J. A. Holcombe, \"Immobilized\npeptides/amino acids on solid supports for metal remediation,\" Pure\nAppl. Chem., vol. 76, no. 4, pp. 777\u2013787, 2004.\n[14] S. Dutta, A. Bhattacharyya, P. De, P. Ray, and S. Basu, \"Removal of\nmercury from its aqueous solution using charcoal-immobilized papain\n(CIP).,\"J. Hazard. Mater., vol. 172, no. 2\u20133. pp. 888\u201396, 30-Dec-2009.\n[15] I. Ghodbane and O. Hamdaoui, \"Removal of mercury (II) from aqueous\nmedia using eucalyptus bark: kinetic and equilibrium studies,\" J.\nHazard. Mater., vol. 160, no. 2, pp. 301\u2013309, 2008.\n[16] K. Anoop Krishnan and T. S. Anirudhan, \"Removal of mercury(II) from\naqueous solutions and chlor-alkali industry effluent by steam activated\nand sulphurised activated carbons prepared from bagasse pith: kinetics\nand equilibrium studies.,\" J. Hazard. Mater., vol. 92, no. 2, pp. 161\u201383,\nMay 2002.\n[17] M. B. Lohani, A. Singh, D. C. Rupainwar, and D. N. Dhar, \"Studies on\nefficiency of guava (Psidiumguajava) bark as bioadsorbent for removal\nof Hg (II) from aqueous solutions.,\" J. Hazard. Mater., vol. 159, no. 2\u2013\n3, pp. 626\u20139, Nov. 2008.\n[18] F. Di Natale, a Lancia, a Molino, M. Di Natale, D. Karatza, and D.\nMusmarra, \"Capture of mercury ions by natural and industrial\nmaterials.,\" J. Hazard. Mater., vol. 132, no. 2\u20133, pp. 220\u20135, May 2006.\n[19] S. W. Al Rmalli, A. a Dahmani, M. M. Abuein, and A. a Gleza,\n\"Biosorption of mercury from aqueous solutions by powdered leaves of\ncastor tree (Ricinuscommunis L.),\" J. Hazard. Mater., vol. 152, no. 3,\npp. 955\u20139, Apr. 2008.\n[20] M. Velicu, H. Fu, R. P. S. Suri, and K. Woods, \"Use of adsorption\nprocess to remove organic mercury thimerosal from industrial process\nwastewater.\" J. Hazard. Mater.,vol. 148, no. 3. pp. 599\u2013605, 30-Sep-\n2007.\n[21] T. Masciangioli and W. Zhang, \"Environmental nanotechnology:\nPotential and pitfalls,\" Environ. Sci. Technol, vol. 37, p. 102A\u2013108A,\n2003.\n[22] N. Savage and M. S. Diallo, \"Nanomaterials and water purification:\nopportunities and challenges,\" J. Nanoparticle Res., vol. 7, no. 4\u20135, pp.\n331\u2013342, 2005.\n[23] R. Saito, M. Fujita, G. Dresselhaus, and u M. S. Dresselhaus,\n\"Electronic structure of chiral graphene tubules,\" Appl. Phys. Lett., vol.\n60, no. 18, pp. 2204\u20132206, 1992.\n[24] C. Dekker, \"Carbon nanotubes as molecular quantum wires,\" Phys.\nToday, vol. 52, pp. 22\u201330, 1999.\n[25] M. Meyyappan and D. Srivastava, \"Carbon Nanotube: A Big Revolution\nin a Technology that Thinks Very, Very, Very Small,\" IEEE Potentials,\nvol. 19, no. 3, pp. 16\u201318, 2000.\n[26] C. P. Nanseu-Njiki, S. R. Tchamango, P. C. Ngom, A. Darchen, and E.\nNgameni, \"Mercury (II) removal from water by electrocoagulation using\naluminium and iron electrodes,\" J. Hazard. Mater., vol. 168, no. 2, pp.\n1430\u20131436, 2009.\n[27] Y.-H. Li, S. Wang, J. Wei, X. Zhang, C. Xu, Z. Luan, D. Wu, and B.\nWei, \"Lead adsorption on carbon nanotubes,\" Chem. Phys. Lett., vol.\n357, no. 3\u20134, pp. 263\u2013266, May 2002.\n[28] J. Li, S. Chen, G. Sheng, J. Hu, X. Tan, and X. Wang, \"Effect of\nsurfactants on Pb(II) adsorption from aqueous solutions using oxidized\nmultiwall carbon nanotubes,\" Chem. Eng. J., vol. 166, no. 2, pp. 551\u2013\n558, Jan. 2011.\n[29] Y.-H. Li, S. Wang, X. Zhang, J. Wei, C. Xu, Z. Luan, and D. Wu,\n\"Adsorption of fluoride from water by aligned carbon nanotubes,\"\nMater. Res. Bull., vol. 38, no. 3, pp. 469\u2013476, 2003.\n[30] Y.-H. Li, S. Wang, Z. Luan, J. Ding, C. Xu, and D. Wu, \"Adsorption of\ncadmium (II) from aqueous solution by surface oxidized carbon\nnanotubes,\" Carbon N. Y., vol. 41, no. 5, pp. 1057\u20131062, 2003.\n[31] C. Lu and H. Chiu, \"Adsorption of zinc(II) from water with purified\ncarbon nanotubes,\" Chem. Eng. Sci., vol. 61, no. 4, pp. 1138\u20131145, Feb.\n2006.\n[32] D. Shao, Z. Jiang, X. Wang, J. Li, and Y. Meng, \"Plasma induced\ngrafting carboxymethyl cellulose on multiwalled carbon nanotubes for\nthe removal of UO2\n2+ from aqueous solution,\" J. Phys. Chem. B, vol.\n113, no. 4, pp. 860\u2013864, 2009.\n[33] H. Chen, J. Li, D. Shao, X. Ren, and X. Wang, \"Poly (acrylic acid)\ngrafted multiwall carbon nanotubes by plasma techniques for Co (II)\nremoval from aqueous solution,\" Chem. Eng. J., vol. 210, pp. 475\u2013481,\n2012.\n[34] C. L. Chen, X. K. Wang, and M. Nagatsu, \"Europium Adsorption on\nMultiwall Carbon Nanotube/Iron Oxide Magnetic Composite in the\nPresence of Polyacrylic Acid,\" Environ. Sci. Technol., vol. 43, no. 7, pp.\n2362\u20132367, Feb. 2009.\n[35] M. I. Kandah and J.-L. Meunier, \"Removal of nickel ions from water by\nmulti-walled carbon nanotubes.,\" J. Hazard. Mater., vol. 146, no. 1\u20132,\npp. 283\u20138, Jul. 2007.\n[36] M. J. Shadbad, A. Mohebbi, and A. Soltani, \"Mercury(II) removal from\naqueous solutions by adsorption on multi-walled carbon nanotubes,\"\nKorean J. Chem. Eng., vol. 28, no. 4, pp. 1029\u20131034, Mar. 2011.\n[37] W. Li, C. Liang, W. Zhou, J. Qiu, Z. Zhou, G. Sun, and Q. Xin,\n\"Preparation and characterization of multiwalled carbon nanotube-supported platinum for cathode catalysts of direct methanol fuel cells,\"\nJ. Phys. Chem. B, vol. 107, no. 26, pp. 6292\u20136299, 2003.\n[38] I. Stamatin, A. Morozan, A. Dumitru, V. Ciupina, G. Prodan, J.\nNiewolski, and H. Figiel, \"The synthesis of multi-walled carbon\nnanotubes (MWNTs) by catalytic pyrolysis of the phenol-formaldehyde\nresins,\" Phys. E Low-dimensional Syst. Nanostructures, vol. 37, no. 1,\npp. 44\u201348, 2007.\n[39] L. Bokobza and J. Zhang, \"Raman spectroscopic characterization of\nmultiwall carbon nanotubes and of composites.\" Express Polym. Lett.,\nvol. 6, no. 7, 2012.\n[40] R. Leyva Ramos, L. A. Bernal Jacome, J. Mendoza Barron, L. Fuentes\nRubio, and R. M. Guerrero Coronado, \"Adsorption of zinc (II) from an\naqueous solution onto activated carbon,\" J. Hazard. Mater., vol. 90, no.\n1, pp. 27\u201338, 2002.\n[41] D. Mohan, V. K. Gupta, S. K. Srivastava, and S. Chander, \"Kinetics of\nmercury adsorption from wastewater using activated carbon derived\nfrom fertilizer waste,\" Colloids Surfaces A Physicochem. Eng. Asp., vol.\n177, no. 2, pp. 169\u2013181, 2000.\n[42] M. Zabihi, A. Ahmadpour, and A. H. Asl, \"Removal of mercury from\nwater by carbonaceous sorbents derived from walnut shell,\" J. Hazard.\nMater., vol. 167, no. 1, pp. 230\u2013236, 2009.\n[43] C. Jeon and K. Ha Park, \"Adsorption and desorption characteristics of\nmercury (II) ions using aminated chitosan bead,\" Water Res., vol. 39, no.\n16, pp. 3938\u20133944, 2005.\n[44] D. Tiwari, \"Biomass-derived materials in the remediation of heavymetal\ncontaminated water: Removal of cadmium (II) and copper (II)\nfrom aqueous solutions,\" Water Environ. Res., vol. 83, no. 9, pp. 874\u2013\n881, 2011.\n[45] F. J. Cerino-C\u00f3rdova, A. M. Garc\u00eda-Le\u00f3n, E. Soto-Regalado, M. N.\nS\u00e1nchez-Gonz\u00e1lez, T. Lozano-Ram\u00edrez, B. C. Garc\u00eda-Avalos, and J. A.\nLoredo-Medrano, \"Experimental design for the optimization of copper\nbiosorption from aqueous solution by Aspergillus-terreus,\" J. Environ.\nManage.,vol. 95, pp. S77\u2013S82, 2012.\n[46] N. Li and R. Bai, \"Copper adsorption on chitosan\u2013cellulose hydrogel\nbeads: behaviors and mechanisms,\" Sep. Purif. Technol., vol. 42, no. 3,\npp. 237\u2013247, 2005.\n[47] I. Langmuir, \"The adsorption of gases on plane surfaces of glass, mica\nand platinum.,\" J. Am. Chem. Soc., vol. 40, no. 9, pp. 1361\u20131403, 1918.\n[48] F. H. Uber, \"Die adsorption in losungen,\" Z. Phys. Chem, vol. 57, pp.\n387\u2013470, 1985.\n[49] M. I. Temkin and V. Pyzhev, \"Kinetics of ammonia synthesis on\npromoted iron catalysts,\" Actaphysiochim. URSS, vol. 12, no. 3, pp.\n217\u2013222, 1940.\n[50] M. M. Dubinin, E. D. Zaverina, and L. V Radushkevich, \"Sorption and\nstructure of active carbons. I. Adsorption of organic vapors,\"\nZhurnalFiz. Khimii, vol. 21, pp. 1351\u20131362, 1947."]}

Multiwall carbon nanotubes, prepared by chemical vapor deposition, have an average diameter of 60-100 nm as shown by High Resolution Transmittance Electron Microscope, HR-TEM. The Multiwall carbon nanotubes (MWCNTs) were further characterized using X-ray Diffraction and Raman Spectroscopy. Mercury uptake capacity of MWCNTs was studied using batch adsorption method at different concentration ranges up to 150 ppm. Mercury concentration (before and after the treatment) was measured using cold vapor atomic absorption spectroscopy. The effect of time, concentration, pH and adsorbent dose were studied. MWCNT were found to perform complete absorption in the sub-ppm concentrations (parts per billion levels) while for high concentrations, the adsorption efficiency was 92% at the optimum conditions; 0.1 g of the adsorbent at 150 ppm mercury (II) solution. The adsorption of mercury on MWCNTs was found to follow the Freundlich adsorption isotherm and the pseudo-second order kinetic model.