References
  -  Y.A. Aggour, M. Diab, T. Hegazy, S.E. Halawia, Removal of
    cadmium, lead, zinc, copper and iron from their aqueous
    solution by kaolinite clay, Int. J. Adv. Res., 3 (2015) 1922–1934. 
 
  -  S.A.M.A.S. Eqani, R. Khalid, N. Bostan, Z. Saqib, J. Mohmand,
    M. Rehan, N. Ali, I.A. Katsoyiannis, H. Shen, Human lead (Pb)
    exposure via dust from different land use settings of Pakistan: a
    case study from two urban mountainous cities, Chemosphere,
    155 (2016) 259–265. 
 
  -  N. Rahmanian, S.H.B. Ali, M. Homayoonfard, N.J. Ali,
    M. Rehan, Y. Sadef, A.S. Nizami, Analysis of Physiochemical
    Parameters to Evaluate the Drinking Water Quality in the State
    of Perak, Malaysia, J. Chem., 2015 (2015) 1–10. 
 
  -  S.A. Aljlil, F.D. Alsewailem, Adsorption of Cu and Ni on
    bentonite clay from waste water, Athens J. Sci., 1 (2014) 21–30. 
 
  -  FAO: Food and Agriculture Organization of the United Nations,
    Water Quality for Irrigation and Drainage, Paper No. 10. FAO,
    Rome, 1985. 
 
  -  M. Arshadi, M.J. Amiri, S. Mousavi, Kinetic, equilibrium and
    thermodynamic investigations of Ni(II), Cd(II), Cu(II) and
    Co(II) adsorption on barley straw ash, Water Resour. Ind.,
    6 (2014) 1–17. 
 
  -  Z. Abbasi, M. Alikarami, E.R. Nezhad, F. Moradi, V. Moradi,
    Adsorptive removal of Co2+ and Ni2+ by peels of banana from
  aqueous solution, Universal J. Chem., 1 (2013) 90–95. 
 
  -  G. Sharma, A. Kumar, M. Naushad, A. Kumar, A.H. Al-Muhtaseb,
    P. Dhiman, A.A. Ghfar, F.J. Stadler, M.R. Khan, Photoremediation
    of toxic dye from aqueous environment using
    monometallic and bimetallic quantum dots based nanocomposites.
    J. Cleaner Prod., 172 (2018) 2919–2930. 
 
  -  A. Kumar, M. Naushad, A. Rana, G. Sharma, A.A. Ghfar,
    F.J. Stadler, M.R. Khan, ZnSe-WO3 nano-hetero-assembly
    stacked on Gum ghatti for photo-degradative removal of
    Bisphenol A: symbiose of adsorption and photocatalysis,
  Int. J. Biol. Macromol., 104 (2017) 1172–1184. 
 
  -  G. Sharma, D. Pathania, M. Naushad, Preparation, characterization
    and antimicrobial activity of biopolymer based
    nanocomposite
    ion exchanger pectin zirconium (IV) selenotungstophosphate:
    application for removal of toxic metals,
    J. Ind. Eng. Chem., 20 (2014) 4482–4490. 
 
  -  M. M. Barbooti, Simultaneous removal of chromium and lead
    from water by sorption on Iraqi montmorillonite, J. Environ.
    Prot., 6 (2015) 237–249. 
 
  -  Y. Bulut, T. Zek, Adsorption studies on ground shells of
    hazelnut and almond, J. Hazard. Mater., 149 (2007) 35–41. 
 
  -  Y. Bulut, T. Zek, Removal of heavy metals from aqueous
    solution
    by sawdust adsorption, J. Environ. Sci., 19 (2007)
    160–166. 
 
  -  M.R. Awual, M.M. Hasan, G.E. Eldesoky, M.A. Khaleque,
    M.M. Rahman, M. Naushad, Facile mercury detection and
    removal from aqueous media involving ligand impregnated
    conjugate nanomaterials, Chem. Eng. J., 290 (2016) 243–251. 
 
  -  M. Naushad, Z.A. Al-Othman, M. Islam, Adsorption of
    cadmium ion using a new composite cation-exchanger polyaniline
    Sn (IV) silicate: kinetics, thermodynamic and isotherm
    studies, Int. J. Environ. Sci. Technol., 10 (2013) 567–578. 
 
  -  A.A. Alqadami, M. Naushad, Z.A. Alothman, A.A. Ghfar,
    Novel metal–organic framework (MOF) based composite
    material for the sequestration of U (VI) and Th (IV) metal
    ions from aqueous environment, ACS Appl. Mate. Interfaces,
    9 (2017) 36026–36037. 
 
  -  M. Naushad, T. Ahamad, B.M. Al-Maswari, A.A. Alqadami,
    S.M. Alshehri, Nickel ferrite bearing nitrogen-doped mesoporous
    carbon as efficient adsorbent for the removal of highly
    toxic metal ion from aqueous medium, Chem. Eng. J., 330 (2017)
    1351–1360. 
 
  -  R. Bushra, M. Naushad, R. Adnan, Z.A. ALOthman,
    M. Rafatullah, Polyaniline supported nanocomposite cation
    exchanger: synthesis, characterization and applications for the
    efficient removal of Pb2+ ion from aqueous medium, J. Ind. Eng.
  Chem., 21 (2015) 1112–1118. 
 
  -  A.A. Alqadami, M. Naushad, M.A. Abdalla, T. Ahamad,
    Z.A. ALOthman, S.M. Alshehri, A.A. Ghfar, Efficient removal
    of toxic metal ions from wastewater using a recyclable nanocomposite:
    a study of adsorption parameters and interaction
    mechanism, J. Cleaner Prod., 156 (2017) 426–436. 
 
  -  Y. Gutha, V.S. Munagapati, M. Naushad, K. Abburi, Removal
    of Ni (II) from aqueous solution by Lycopersicum esculentum (Tomato) leaf powder as a low-cost biosorbent, Desal. Wat.
    Treat., 54 (2015) 200–208. 
 
  -  M. El-Sadaawy, O. Abdelwahab, Adsorptive removal of nickel
    from aqueous solutions by activated carbons from doum
    seed (Hyphaenethebaica) coat, Alexandria Eng. J., 53 (2014)
    399–408. 
 
  -  A. Omri, M. Benzina, Removal of manganese (II) ions from
    aqueous solutions by adsorption on activated carbon derived
    a new precursor: Ziziphus spina-christi seeds, Alexandria Eng. J.,
    51 (2012) 343–350. 
 
  -  M.A.O. Badmus, T.O.K. Audu, B.U. Anayata, Removal of lead
    ion from industrial wastewaters by activated carbon prepared
    from periwinkle shells (Typanotonus fuscatus), Turkish J. Eng.
    Env. Sci., 31 (2007) 251–263. 
 
  -  P.S. Kumar, Adsorption of lead (II) ions from simulated
    wastewater using natural waste: a kinetic, thermodynamic and
    equilibrium study, Environ. Prog. Sustain. Energy, 33 (2014)
    55–64. 
 
  -  G. Moussavi, R. Khosravi, Removal of cyanide from wastewater
    by adsorption onto pistachio hull wastes: parametric experiments,
    kinetics and equilibrium analysis, J. Hazard. Mater.,
    183 (2010) 724–730. 
 
  -  N. Rajamohan, M. Rajasimman, R. Rajeshkannan, V. Saravanan,
    Equilibrium, kinetic and thermodynamic studies on the removal
    of aluminum by modified Eucalyptus camaldulensis barks,
    Alexandria Eng. J., 53 (2014) 409–415. 
 
  -  G. Sharma, M. Naushad, A. Kumar, S. Rana, S. Sharma,
    A. Bhatnagar, F.J. Stadler, A.A. Ghfar, M.R. Khan, Efficient
    removal of coomassie brilliant blue R-250 dye using starch/poly (alginic acid-cl-acrylamide) nanohydrogel, Process Saf.
    Environ. Prot., 109 (2017) 301–310. 
 
  -  R. Bushra, M. Naushad, G. Sharma, A. Azam, Z.A. ALOthman,
    Synthesis of polyaniline based composite material and its
    analytical applications for the removal of highly toxic Hg2+
    metal ion: Antibacterial activity against E. coli, Korean J. Chem.
    Eng., 34 (2017) 1970–1979. 
 
  -  G. Sharma, M. Naushad, D. Pathania, A. Kumar, A multifunctional
    nanocomposite pectin thorium (IV) tungstomolybdate
    for heavy metal separation and photoremediation of malachite
    green, Desal. Wat. Treat., 57 (2016) 19443–19455. 
 
  -  S.A. Aljlil, F.D. Alsewailem, Saudi Arabian clays for lead
    removal in wastewater, Appl. Clay Sci., 42 (2009) 671–674. 
 
  -  S.S. Al-Shahrani, Treatment of wastewater contaminated with
    nickel using khulays activated bentonite, Int. J. Eng. Technol.
    IJET-IJENS, 12 (2012). 
 
  -  S.S. Al-Shahrani, Removal of cadmium from waste water using
    Saudi activated bentonite, WIT Trans. Ecol. Environ., 163 (2012)
    391–402. 
 
  -  S.S. Al-Shahrani, Treatment of wastewater contaminated with
    cobalt using Saudi activated bentonite. Alexandria Eng. J.,
    53 (2014) 205–211. 
 
  -  N. Zahra, Adsorption of Lead from wastewater on Pakistani
    bentonites, Am. J. Sci. Ind. Res., 3 (2012) 387–389. 
 
  -  Ö. Yavuz, Y. Altunkaynak, F. Guzel, Removal of copper, nickel,
    cobalt and manganese from aqueous solution by kaolinite,
    Water Res., 37 (2003) 948–952. 
 
  -  Ö. Yavuz, R. Guzel, F. Aydin, I. Tegin, R. Ziyadanogullari,
    Removal of cadmium and lead from aqueous solution by
    calcite, Polish J. Environ. Stud., 16 (2007) 467–471. 
 
  -  J.S. Essomba, J. Ndi Nsami, P.D. Bilibi Bilibi, G.M. Tange,
    J. Ketcha Mbadcam, Adsorption of Cd (II) ions from aqueous
    solution onto kaolinite and metakaolinite, Pure Appl. Chem.
    Sci., 2 (2014) 11–30. 
 
  -  J.M. Zachara, C.E. Cowan, C.T. Resch, Sorption of divalent
    metals on calcite, Geochimica et Cosmochimica Acta, 55 (1991)
    1549–1562. 
 
  -  A.T. Sdiri, T. Higashi, F. Jamoussi, Adsorption of copper and
    zinc onto natural clay in single and binary systems, Int. J.
    Environ. Sci. Technol., 11 (2014) 1081–1092. 
 
  -  Z. Mohamed, A. Abdelkarim, K. Ziat, S. Mohamed, Adsorption
    of Cu(II) onto natural clay: Equilibrium and thermodynamic
    studies, J. Mater. Environ. Sci., 7 (2016) 566–570. 
 
  -  C.A. Christophi, L. Axe, Competition of Cd, Cu and Pb
    adsorption on goethite, J. Environ. Eng., 126 (2000) 66–74. 
 
  -  W.A. Carvalho, C. Vigando, J. Fontana, Ni(II) removal from
    aqueous effluents by silylated clays, J. Hazard. Mater., 153 (2008)
    1240–1247. 
 
  -  Z. Hongxia, W. Xiaoyun, L. Honghong, T. Tianshe, W. Wangsuo,
    Adsorption behaviour of Th(IV) onto illite: effect of contact
    time, pH value, ionic strength, humic acid and temperature,
    Appl. Clay Sci., 127 (2016) 35–43. 
 
  -  M. Torab-Mostaedi, H. Ghassabzadeh, M. Ghannadi-Maragheh,
    S.J. Ahmadi, H. Taheri, Removal of cadmium and nickel from
    aqueous solution using expanded perlite, Brazilian J. Chem.
    Eng., 27 (2010) 299–308. 
 
  -  M. Eloussaief, I. Jarraya, M. Benzina, Adsorption of copper
    ions on two clays from Tunisia: pH and temperature effects,
    Appl. Clay Sci., 46 (2009) 409–413. 
 
  -  P.N.M. Vasconcelos, W.S. Lima, M.L.P. Silva, A.L.F. Brito,
    H.M. Laborde, M.G.F. Rodrigues, Adsorption of zinc from
    aqueous solutions using modified Brazilian grey clay, Am. J.
    Anal. Chem., 4 (2013) 510–519. 
 
  -  I. Ghorbel-Abid, M. Trabelsi-Ayadi, Competitive adsorption
    of heavy metals on local landfill clay, Arabian J. Chem.,
    8 (2015) 25–31. 
 
  -  I. Langmuir, The adsorption of gases on plane surfaces of glass,
    mica and platinum, J. Am. Chem. Soc., 40 (1918) 1361–1403. 
 
  -  P. Klobes, K. Meyer, R.G. Munro, Porosity and Specific Surface
    Area Measurements for Solid Materials, U.S. Government
    Printing Office, Washington, 2006. 
 
  -  H.M.F. Freundlich, Over the adsorption in solution, J. Phys.
    Chem., 57 (1906) 1100–1107. 
 
  -  A.V. Kostin, L.V. Mostalygina, O.I. Bukhtoyarov, The mechanism
    of adsorption of zinc and cadmium ions onto bentonite clay,
    Prot. Met. Phys. Chem. Surfaces, 51 (2015) 477–482. 
 
  -  P.S. Nayak, B.K. Singh, Instrumental characterization of clay
    by XRF, XRD and FTIR, Bull. Mater. Sci., 30 (2007) 235–238. 
 
  -  M.M. Islam, M.N. Khan, S. Biswas, T.R. Choudhury, P. Haque,
    T.U. Rashid, M.M. Rahman, Preparation and characterization
    of bijoypur clay-crystalline cellulose composite for application
    as an adsorbent, Adv. Mater. Sci., 2 (2017) 1–7. 
 
  -  K. Bedoui, I. Bekri-Abbes, E. Srasra, Removal of cadmium
    (II) from aqueous solution using pure smectite and Lewatite
    S 100: the effect of time and metal concentration, Desalination,
    223 (2008) 269–273. 
 
  -  S.S. Gupta, K.G. Bhattacharyya, Immobilization of Pb (II),
    Cd (II) and Ni (II) ions on kaolinite and montmorillonite
    surfaces from aqueous medium, J. Environ. Manage., 87 (2008)
    46–58. 
 
  -  S. Ansanay-Alex, C. Lomenech, C. Hurel, N. Marmier,
    Adsorption of nickel and arsenic from aqueous solution on
  natural sepiolite, Int. J. Nanotechnol., 9 (2012) 204–215.