1. M. Karnib, A. Kabbani, H. Holail, Z. Olama, Heavy metals removal using activated carbon, silica and silica activated carbon composite, Enrgy. Proced., 50 (2014) 113–120.
  2. M. Barakat, New trends in removing heavy metals from industrial wastewater, Arab. J. Chem., 4 (2011) 361–377.
  3. J. Shou, M. Qiu, Adsorption of copper ions onto activated carbon from capsicum straw, Desal. Water Treat., 57 (2016) 353– 359.
  4. S. Veli, B. Alyüz, Adsorption of copper and zinc from aqueous solutions by using natural clay, J. Hazard. Mater., 149 (2007) 226–233.
  5. O.E.A. Salam, N.A. Reiad, M.M. ElShafei, A study of the removal characteristics of heavy metals from wastewater by low-cost adsorbents, J. Adv. Res., 2 (2011) 297–303.
  6. M.M. Shahata, Adsorption of some heavy metal ions by used different immobilized substances on silica gel, Arab. J. Chem., 9 (2016) 755–763.
  7. G. Crini, Non-conventional low-cost adsorbents for dye removal: a review, Biores. Technol., 97 (2006) 1061–1085.
  8. M. Yari, M. Norouzi, A.H. Mahvi, M. Rajabi, A. Yari, O. Moradi, I. Tyagi, V.K. Gupta, Removal of Pb (II) ion from aqueous solution by graphene oxide and functionalized graphene oxidethiol: effect of cysteamine concentration on the bonding constant, Desal. Water Treat., 57 (2016) 11195–11210.
  9. S. Peng, H. Meng, Y. Ouyang, J. Chang, Nanoporous magnetic cellulose–chitosan composite microspheres: preparation, characterization, and application for Cu (II) adsorption, Ind. Eng. Chem. Res., 53 (2014) 2106–2113.
  10. L. Li, C. Luo, X. Li, H. Duan, X. Wang, Preparation of magnetic ionic liquid/chitosan/graphene oxide composite and application for water treatment, Int. J. Biol. Macromol., 66 (2014) 172– 178.
  11. I. Sheet, A. Kabbani, H. Holail, Removal of heavy metals using nanostructured graphite oxide, silica nanoparticles and silica/ graphite oxide composite, Enrgy. Proced., 50 (2014) 130–138.
  12. L. Xu, J. Li, M. Zhang, Adsorption characteristics of a novel carbon-nanotube-based composite adsorbent toward organic pollutants, Ind. Eng. Chem. Res., 54 (2015) 2379–2384.
  13. N. Saeidi, M. Parvini, Z. Niavarani, High surface area and mesoporous graphene/activated carbon composite for adsorption of Pb (II) from wastewater, JECE., 3 (2015) 2697–2706.
  14. A.A. Rahim, Z.N. Garba, Optimization of preparation conditions for activated carbon from Prosopis africana seed hulls using response surface methodology, Desal. Water Treat., 57 (2016) 17985–17994.
  15. L. Wang, M. Zhang, Z. Huang, C. Zhao, X. Pei, Adsorption mechanism of activated carbon fibre/carbon nanotube composites for rhodamine b from aqueous solution, Asian J. Chem., 25 (2013) 10509.
  16. E.P. Randviir, D.A. Brownson, C.E. Banks, A decade of graphene research: production, applications and outlook, Mater. Today., 17 (2014) 426–432.
  17. W.S. Hummers Jr, R.E. Offeman, Preparation of graphitic oxide, J. Am. Chem. Soc., 80 (1958) 1339–1339.
  18. X. Li, S. Wang, Y. Liu, L. Jiang, B. Song, M. Li, G. Zeng, X. Tan, X. Cai, Y. Ding, Adsorption of Cu (II), Pb (II), and Cd (II) ions from acidic aqueous solutions by diethylenetriaminepentaacetic acid-modified magnetic graphene oxide, J. Chem. Eng. Data., 62 (2016) 407–416.
  19. M. Yun, M.S. Ahmed, S. Jeon, Thiolated graphene oxide-supported palladium cobalt alloyed nanoparticles as high performance electrocatalyst for oxygen reduction reaction, J. Power. Sources., 293 (2015) 380–387.
  20. E. Köseoğlu, C. Akmil-Başar, Preparation, structural evaluation and adsorptive properties of activated carbon from agricultural waste biomass, Adv. Powder Technol., 26 (2015) 811–818.
  21. Y. Gao, Q. Yue, B. Gao, Y. Sun, W. Wang, Q. Li, Y. Wang, Comparisons of porous, surface chemistry and adsorption properties of carbon derived from Enteromorpha prolifera activated by H4P2O7 and KOH, Chem. Eng. J., 232 (2013) 582–590.
  22. N.K. Mondal, R. Bhaumik, J.K. Datta, Removal of fluoride by aluminum impregnated coconut fiber from synthetic fluoride solution and natural water, AEJ., 54 (2015) 1273–1284.
  23. Y. Huang, E. Ma, G. Zhao, Thermal and structure analysis on reaction mechanisms during the preparation of activated carbon fibers by KOH activation from liquefied wood-based fibers, Ind. Crop. Prod., 69 (2015) 447–455.
  24. Y. Ji, T. Li, L. Zhu, X. Wang, Q. Lin, Preparation of activated carbons by microwave heating KOH activation, Appl. Surf. Sci., 254 (2007) 506–512.
  25. H. Sayğılı, F. Güzel, High surface area mesoporous activated carbon from tomato processing solid waste by zinc chloride activation: process optimization, characterization and dyes adsorption, J. Clean Prod., 113 (2016) 995–1004.
  26. Z. Melichová, L. Hromada, Adsorption of Pb2+ and Cu2+ ions from aqueous solutions on natural bentonite, Pol. J. Environ. Stud., 22 (2013) 457–464.
  27. Z. Liu, S. Zhou, Adsorption of copper and nickel on Na-bentonite, Process Saf. Environ., 88 (2010) 62–66.
  28. R. Sitko, E. Turek, B. Zawisza, E. Malicka, E. Talik, J. Heimann, A. Gagor, B. Feist, R. Wrzalik, Adsorption of divalent metal ions from aqueous solutions using graphene oxide, Dalton T., 42 (2013) 5682–5689.
  29. S. Rahimi, R.M. Moattari, L. Rajabi, A.A. Derakhshan, M. Keyhani, Iron oxide/hydroxide (α, γ-FeOOH) nanoparticles as high potential adsorbents for lead removal from polluted aquatic media, J. Ind. Eng. Chem., 23 (2015) 33–43.
  30. B. Shi, W. Zuo, J. Zhang, H. Tong, J. Zhao, Removal of lead(II) ions from aqueous solution using L. seed husk ash as a biosorbent, J. Environ. Qual., 45 (2016) 984–992.
  31. A. Bhatnagar, E. Kumar, M. Sillanpää, Fluoride removal from water by adsorption—a review, Chem. Eng. J., 171 (2011) 811– 840.
  32. C.K. Ko, W.G. Lee, Effects of pH variation in aqueous solutions on dissolution of copper oxide, Surf. Interface Anal., 42 (2010) 1128–1130.
  33. E. Sočo, J. Kalembkiewicz, Comparison of adsorption of Cd(II) and Pb(II) ions on pure and chemically modified fly ashes, Chem. Process. Eng., 37 (2016) 215–234
  34. H. Freundlich, Über die adsorption in lösungen, Z. Phys. Chem., 57 (1907) 385–470.
  35. I. Langmuir, The adsorption of gases on plane surfaces of glass, mica and platinum, J. Am. Chem. Soc., 40 (1918) 1361–1403.
  36. P.R. Choudhury, P. Mondal, S. Majumdar, Synthesis of bentonite clay based hydroxyapatite nanocomposites cross-linked by glutaraldehyde and optimization by response surface methodology for lead removal from aqueous solution, RSC Adv., 5 (2015) 100838–100848.
  37. A. Shahzad, W. Miran, K. Rasool, M. Nawaz, J. Jang, S.-R. Lim, D.S. Lee, Heavy metals removal by EDTA-functionalized chitosan graphene oxide nanocomposites, RSC Adv., 7 (2017) 9764–9771.
  38. R. Sudha, K. Srinivasan, P. Premkumar, Batch studies for the adsorption of lead (II) from aqueous phase by waste generated from Citrus Limettioides, Int. J. Chem. Sci., 13 (2015) 167–177.
  39. Z. Sui, Q. Meng, X. Zhang, R. Ma, B. Cao, Green synthesis of carbon nanotube–graphene hybrid aerogels and their use as versatile agents for water purification, J. Mater. Chem., 22 (2012) 8767–8771.
  40. S. Chakravarty, A. Mohanty, T.N. Sudha, A. Upadhyay, J. Konar, J. Sircar, A. Madhukar, K. Gupta, Removal of Pb(II) ions from aqueous solution by adsorption using bael leaves (Aegle marmelos), J. Hazard. Mater., 173 (2010) 502–509.
  41. M.H.M.A. Kamal, W.M.K.W.K. Azira, M. Kasmawati, Z. Haslizaidi, W.N.W. Saime, Sequestration of toxic Pb(II) ions by chemically treated rubber (Hevea brasiliensis) leaf powder, J. Environ. Sci., 22 (2010) 248–256.
  42. D. Kong, N. Wang, N. Qiao, Q. Wang, Z. Wang, Z. Zhou, Z. Ren, Facile preparation of ion-imprinted chitosan microspheres enwrapping Fe3O4 and graphene oxide by inverse suspension cross-linking for highly selective removal of copper(II), ACS Sustain. Chem. Eng., 5 (2017) 7401–7409.
  43. T. Anirudhan, M. Ramachandran, Synthesis and characterization of amidoximated polyacrylonitrile/organobentonite composite for Cu(II), Zn(II), and Cd(II) adsorption from aqueous solutions and industry wastewaters, Ind. Eng. Chem. Res., 47 (2008) 6175–6184.
  44. S. Lagergren, About the theory of so-called adsorption of soluble substances. K. Sven. vetensk.akad. handl., 24 (1898) 1–39.
  45. X. Gao, Y. Hu, T. Guo, X. Ye, Q. Li, M. Guo, H. Liu, Z. Wu. Comparative study of the competitive adsorption of Mg, Ca and Sr ions onto resins, Adsorpt. Sci. Technol., 31 (2013) 45–58.