S. Tong, Y. E. von Schirnding and T. Prapamontol, “Environmental Lead Exposure: A Public Health Problem of Global Dimensions,” Bulletin of the World Health Organization, Vol. 78, No. 9, 2000, pp. 1068-1077.
 L. J. Fewtrell, A. Pruss-Ustun, P. Landrigan and J. L. Ayuso-Mateos, “Estimating the Global Burden of Disease of Mild Mental Retardation and Cardiovascular Diseases from Environmental Lead Exposure,” Environmental Research, Vol. 94, No. 2, 2004, pp. 120-133.
 T. A. Kumiawan, G. Y. S. Chan, W. H. Lo and S. Ba-bel, “Physico-Chemical Treatment Technique for Waste Water Laden with Heavy Metal,” Chemical Engineering Journal, Vol. 118, No. 1-2, 2006, pp. 83-98.
 S. P. Singh, L. Q. Ma and W. G. Harris, “Heavy Metal Interactions with Phosphate Clay: Sorption and Desorption Behavior,” Journal of Environmental Quality, Vol. 30, No. 6, 2001, pp. 1961-1968.
 D. Mohan and C. U. Pittman, “Activated Carbons and Low Cost Sorbents for Remediation of Tri- and Hexa-Valent Chromium from Water,” Journal of Hazardous Materials, Vol. B137, No. 2, 2006, pp. 762-811.
 T. R. Harper and N. W. Kinham, “Removal of Arsenic from Wastewater Using Chemical Precipitation Methods,” Water Environment Research, Vol. 64, No. 3, 1992, pp. 200-203. http://dx.doi.org/10.2175/WER.64.3.2
 C. W. Gray, S. J. Dunham, P. G. Dennis, F. J. Zhao and S. P. McGrath, “Field Evaluation of in-Situ Remediation of a Heavy Metal Contaminated Soil Using Lime and Red-Mud,” Environmental Pollution, Vol. 142, No. 3, 2006, pp. 530-539.
 M. B. Mahmood, A. A. Nagham and A. T. Manal, “Removal of Chromium from Electroplating Waste-Water by Simple Chemical Treatment and Ion Exchange,” Engineering & Technology, Vol. 26, No. 11, 2008, pp. 1-9.
 R. S. Juang and L. D. Shiau, “Ion Exchange Equilibria of Metal Chelates of Ethylenediaminetetra-Acetic Acid with Amberlitet IRA-68,” Industrial & Engineering Chemistry Research, Vol. 37, No. 2, 1998, pp. 555-571.
 R. R. Krishna, C. Y. Xu and C. Supraja, “Assessment of Electrokinetic Removal of Heavy Metals from Soils by Sequential Extraction Analysis,” Journal of Hazardous Materials, Vol. 84, No. 2, 2001, pp. 279-296.
 C. M. Zvinowanda, J. O. Okonkwo, P. N. Shabalala and N. M. Agyei, “A Novel Adsorbent for Heavy Metal Remediation in Aqueous Environment,” International Journal of Environmental Science and Technology, Vol. 6, No. 3, 2009, pp. 425-434.
 M. Minamisawa, H. Minamisawa, S. Yoshida and N. Taka, “Adsorption Behavior of Heavy Metals on Biomaterials,” Journal of Agricultural and Food Chemistry, Vol. 52, No. 18, 2004, pp. 5606-5611.
 S. E. Bailey, T. J. Olin, R. M. Bricka and D. D. Adrian, “A Review of Potentially Low-Cost Sorbents for Heavy Metals,” Water Resources, Vol. 33, No. 11, 1999, pp 2469-2479. http://dx.doi.org/10.1016/S0043-1354(98)00475-8
 J. Acharya, J. N. Sahu, B. K. Sahoo, C. R. Mohanty and B. C. Meikap, “Removal of Chromium (VI) from Wastewater by Activated Carbon Developed from Tamarind Wood Activated with Zinc Chloride,” Chemical Engineering Journal, Vol. 150, No. 1, 2009, pp. 25-39.
 L. Khezami and R. Capart, “Removal of Chromium (VI) from Aqueous Solution by Activated Carbons: Kinetic and Equilibrium Studies,” Journal of Hazardous Materials, Vol. 123, No. 1-3, 2005, pp. 223-231.
 J. C. Igwe, A. A. Abia and C. A. Ibeh, “Adsorption Kinetics and Intraparticulate Diffusivities of Hg, As, and Pb Ions on Ummodified and Thiolated Coconut Fiber,” International Journal of Environmental Science and Technology, Vol. 5, No. 1, 2008, pp. 83-92.
 L. Agwaramgbo, E. Agwaramgbo, C. Mercadel, S. Edwards and E. Buckles, “Lead Remediation of Contaminated Water by Charcoal, LA Red Clay, Spinach, and Ustard Green,” Journal of Environmental Protection, Vol. 2, No. 9, 2011, pp. 1240-1244.
 L. Agwaramgbo, N. Lathan, S. Edwards and S. Nunez, “Assessing Lead Removal from Contaminated Water Using Solid Biomaterials,” Journal of Environmental Protection, Vol. 4, No. 7, 2013, pp. 741-745.
 N. Lathan, S. Edwards, C. Thomas and L. Agwaramgbo, “Comparative Study of Lead Removal by Extracts of Spinach, Coffee, and Tea,” Journal of Environmental Protection, Vol. 4, No. 3, 2013, pp. 250-257.
 L. Agwaramgbo, C. Thomas, C. Grays, J. Small and T. Young, “An Evaluation of Edible Plant Extracts for the Phytoremediarion of Lead Contaminated Water,” Journal of Environmental Protection, Vol. 3, No. 8, 2012, pp. 722-730. http://dx.doi.org/10.4236/jep.2012.38086
 L. M. Mataka, E. M. T. Henry, W. R. L. Masamba and S. M. Sajidu, “Lead Remediation of Contaminated Water Using Moringa Stenopetala and Moringa Oleifera Seed Powder,” International Journal of Environmental Science and Technology, Vol. 3, No. 2, 2006, pp. 131-139.
 G. Vankatesan and U. Senthilnathan, “Adsorption Batch Studies on the Removal of Cadmium Using Wood of Derris Indica Based Activated Carbon,” Research Journal of Chemistry and Environment, Vol. 17, No. 5, 2013, pp. 19-24.
 R. Menhage-Bena, H. Kazemian, M. Ghazi-Khansari, M. Hosseini and S. J. Shahtaheri, “Evaluation of of Some Natural Zeolites and Their Relevant Synthetic Types of Sorbents for Removal of Arsenic from Drinking Water,” Iranian Journal of Public Health, Vol. 33, No. 1, 2004, pp. 36-44.
 P. Stathi, K. Litina, D. Gournis, T. S. Giannopoulos and Y. Deligiannakis, “Physicochemical Study of Novel Organoclay as Heavy Metal Ion Adsorbents for Environmental Remediation,” Journal of Colloid and Interface Science, Vol. 316, No. 2, 2007, pp. 298-309.
 W.-Y. Shi, H.-B. Shao, H. Li, M.-A. Shao and S. Du, “Progress in the Remediation of Hazardous Heavy-Metal Polluted Soils by Natural Zeolite,” Journal of Hazardous Materials, Vol. 170, No. 1, 2009, pp. 1-6.
 E. Erden, N. Karapinar and R. Donat, “The Removal of Heavy Metal Cations by Natural Zeolites,” Journal of Colloid and Interface Science, Vol. 280, No. 2, 2004, pp. 309-314. http://dx.doi.org/10.1016/j.jcis.2004.08.028
 M. Aliabadi, K. Morshedzadeh and H. Soheyli, “Removal of Hexavalent Chromium from Aqueous Solution by Lignocellulosic Solid Wastes,” International Journal of Environmental Science and Technology, Vol. 3, No. 3, 2006, pp. 321-325. http://dx.doi.org/10.1007/BF03325940