References
  -  W.Q. Zhu, W.H. Du, X.Y. Shen, H.J. Zhang, Y. Ding,
	  Comparative adsorption of Pb2+ and Cd2+ by cow manure and
  its vermicompost, Environ. Pollut., 227 (2017) 89–97. 
-  M.M.U.R. Khattak, M. Zahoor, B. Muhammad, F.A. Khan,
    R. Ullah, N.M. Abd EI-Salam, Removal of heavy
    metals from drinking water by magnetic carbon nanostructures
    prepared from biomass, J. Nanomater., 2017 (2017)
    5670371. 
-  E. Kokkinos, K. Simeonidis, A. Zouboulis, M. Mitrakas,
    Mercury removal from drinking water by single iron and
    binary iron-manganese oxyhydroxides, Desal. Wat. Treat., 54
    (2015) 2082–2090. 
-  A. Petrovič, M. Simonič, Removal of heavy metal ions from
    drinking water by alginate-immobilised Chlorella sorokiniana,
    Int. J. Environ. Sci. Technol., 13 (2016) 1761–1780. 
-  G. Iervolino, V. Vaiano, L. Rizzo, G. Sarno, A. Farinaa, D. Sannino,
    Removal of arsenic from drinking water by photocatalytic
	  oxidation on MoOx/TiO2 and adsorption on γ-Al2O3, J. Chem.
  Technol. Biotechnol., 91 (2016) 88–95. 
-  A. Jones, W.R. Knocke, Evaluating the role of soluble aluminum
	  in manganese removal via MnOx(s)-coated filtration media in
  drinking water treatment, Water Res., 111 (2017) 59–65. 
-  M.F. Zhu, L. Zhu, J.L. Wang, T.L. Yue, R.H. Li, Z.H. Li,
    Adsorption of Cd(II) and Pb(II) by in situ oxidized Fe3O4
    membrane grafted on 316L porous stainless steel filter tube
    and its potential application for drinking water treatment,
  J. Environ. Manage., 196 (2017) 127–136. 
-  B.B. Li, F. Zhou, K. Huang, Y.P. Wang, S.R. Mei, Y.K. Zhou,
    T. Jing, Environmentally friendly chitosan/PEI-grafted magnetic
    gelatin for the highly effective removal of heavy metals from
    drinking water, Sci. Rep. UK, 7 (2017) 43082. 
-  S. Lung, H.H. Li, S.C. Bondy, A. Campbell, Low concentrations
    of copper in drinking water increase AP-1 binding in the
    brain, Toxicol. Ind. Health, 31 (2015) 1178–1184. 
-  S.A. Moreira, D.Q. Melo, A.C.A.D. Lima, F.W. Sousa, A.G.
	  Oliveira, A.H.B. Oliveira, R.F. Nascimento, Removal of Ni2+,
    Cu2+, Zn2+, Cd2+ and Pb2+ ions from aqueous solutions using
    cashew peduncle bagasse as an eco-friendly biosorbent, Desal.
  Wat. Treat., 57 (2016) 10462–10475. 
-  M. Nemati, S.M. Hosseini, M. Shabanian, Novel electrodialysis
    cation exchange membrane prepared by 2-acrylamido-2-methylpropane sulfonic acid; heavy metal ions removal, J.
  Hazard. Mater., 337 (2017) 90–104. 
-  R. Ahmad, I. Hasan, L-cystein modified bentonite-cellulose
    nanocomposite (cellu/cys-bent) for adsorption of Cu2+, Pb2+,
    and Cd2+ ions from aqueous solution, Sep. Sci. Technol., 51
  (2016) 381–394. 
-  L.G. Yan, S. Li, H.Q. Yu, R.R. Shan, B. Du, T.T. Liu, Facile
	  solvothermal synthesis of Fe3O4/bentonite for efficient removal
    of heavy metals from aqueous solution, Powder Technol., 301
  (2016) 632–640. 
-  X.H. Liu, C. Cheng, C.J. Xiao, D.D. Shao, Z.M. Xu, J.Q. Wang,
    S.H. Hu, X.L. Li, W.J. Wang, Polyaniline (PANI) modified
    bentonite by plasma technique for U(VI) removal from aqueous
    solution, Appl. Surf. Sci., 411 (2017) 331–337. 
-  X.Y. Jin, M. Zheng, B. Sarkar, R. Naidu, Z.L. Chen,
    Characterization of bentonite modified with humic acid for
    the removal of Cu (II) and 2,4-dichlorophenol from aqueous
    solution, Appl. Clay Sci., 134 (2016) 89–94. 
-  K. Al-Essa, Activation of Jordanian Bentonite by hydrochloric
    acid and its potential for olive mill wastewater enhanced
    treatment, J. Chem., 2018 (2018) 8385692. 
-  T. Şahan, F. Erol, Ş. Yılmaz, Mercury(II) adsorption by a novel
    adsorbent mercapto-modified bentonite using ICP-OES and use
    of response surface methodology for optimization, Microchem.
    J., 138 (2018) 360–368. 
-  T. Schütz, S. Dolinská, P. Hudec, A. Mockovčiaková,
    I. Znamenáčková, Cadmium adsorption on manganese modified
    bentonite and bentonite-quartz sand blend, Int. J. Miner.
    Process., 150 (2016) 32–38. 
-  B. Sadeghalvad, H.S. Karimi, H. Hosseinzadegan, A.R.
    Azadmehr, A comparative study on the removal of lead from
    industrial wastewater by adsorption onto raw and modified
    Iranian bentonite (from Isfahan area), Desal. Wat. Treat., 52
    (2014) 6440–6452. 
-  Ö. Şahin, M. Kaya, C. Saka, Plasma-surface modification on
    bentonite clay to improve the performance of adsorption of
    methylene blue, Appl. Clay Sci., S116/117 (2015) 46–53. 
-  B. Benli, Effect of borax addition on the structural modification
    of bentonite in biodegradable alginate-based biocomposites, J.
    Appl. Polym. Sci., 128 (2013) 4172–4180. 
-  A. Fehervari, W.P. Gates, T.W. Turney, A.F. Patti, A. Bouazza,
    Cyclic organic carbonate modification of sodium bentonite for
    enhanced containment of hyper saline leachates, Appl. Clay
    Sci., 134 (2016) 2–12. 
-  C.F. Shi, X.C. Guo, M.J. Jiang, Y. He, Study on the effect of
    surface modification on the properties of bentonite greases,
    Chin. Petrol. Process. Petrochem. Technol., 18 (2016) 99–109. 
-  L.H. Liu, Y. Lin, Y.Y. Liu, H. Zhu, Q. He, Removal of methylene
    blue from aqueous solutions by sewage sludge based granular
    activated carbon: adsorption equilibrium, kinetics, and
    thermodynamics, J. Chem. Eng. Data, 58 (2013) 2248–2253. 
-  A. Javaid, R. Bajwa, U. Shafique, J. Anwar, Removal of
    heavy metals by adsorption on Pleurotus ostreatus, Biomass
    Bioenergy, 35 (2011) 1675–1682. 
-  B. Anna, M. Kleopas, S. Constantine, F. Anestis, B. Maria,
    Adsorption of Cd(II), Cu(II), Ni(II) and Pb(II) onto natural
    bentonite: study in mono- and multi-metal systems, Environ.
    Earth Sci., 73 (2015) 5435–5444. 
-  J.H. Yan, G.H. Lan, H.Y. Qiu, C. Chen, Y.Q. Liu, G.Y. Du,
    J.H. Zhang, Adsorption of heavy metals and methylene blue
    from aqueous solution with citric acid modified peach stone,
    Sep. Sci. Technol., 53 (2018) 1678–1688. 
-  M.E. Bouraie, A.A. Masoud, Adsorption of phosphate ions
    from aqueous solution by modified bentonite with magnesium
  hydroxide Mg(OH)2, Appl. Clay Sci., 140 (2017) 157–164. 
-  L.H. Liu, H. Lin, F. Pan, G. Wang, D.Q. Wang, Modification of
    activated carbons by HNO3 and H2O2 for removal of methylene
    blue dye from aqueous solutions, Desal. Wat. Treat., 114 (2018)
  297–306. 
-  M. Nainamalai, M. Palani, B. Soundarajan, E.J.S.S. Allwin,
    Decolorization of synthetic dye wastewater using packed bed
    electro-adsorption column, Chem. Eng. Process., 130 (2018)
    160–168. 
-  L.H. Xu, S.D. Wang, J.W. Zhou, H.H. Deng, R.L. Frost, Column
    adsorption of 2-naphthol from aqueous solution using carbon
    nanotube-based composite adsorbent, Chem. Eng. J., 335 (2018)
    450–457.