256
raw one showing remarkable selectivity and removal efficiency toward Cu
+2
ions
(Abou-El-Sherbini and Hassanien 2010). Most of the studies on adsorption revealed
that main operating parameter which influenced the surface complexation mechanism is pH. At a high pH, adsorption of copper and arsenic reduces, while it was
found to be optimum at pH 6 (Uddin 2017).
Bentonite clay consists of volcanic ash named as “montmorillonite” with high
silica, iron, magnesium, sodium, and potassium concentration. It has a very unique
quality to produce electrical charge upon hydration. Chemical treatment with acids
such as HCl, HNO 3 , and H 3 PO 4 followed by washing with NaOH made it negatively
charged material which can easily bind to cations (Shawabkeh et al. 2007).
Kaolinite clay has poor ion-exchange capacity. Varying concentrations of electrolyte from 0.01 to 0.1 molar and adsorption of various metal ions like Ni
+2
, Cu
+2
,
Pb
+2
, and Cd
+2
were significantly reduced (Jiang et al. 2010). The maximum adsorption by kaolinite observed for nickel of amount 140.84 mg g
−1
(Jiang et al. 2010). It
has been well predicted that adsorption of metal ions decreased with increasing
concentration of electrolyte because of screening effect of negative charges on surface (Coles and Yong 2002). The parameter also influences the adsorption behavior
of different adsorbents. With the increase in temperature, adsorption of metal ions
decreased. A comparative study on adsorptive nature of As
+5
ions with montmorillonite, kaolinite, and illite concludes with similar result as aforesaid (Mohapatra
et al. 2007). Though natural untreated form of kaolinite provides good results, modified form of kaolinite gives enhancement of adsorption properties. The adsorption
capacities of natural raw siderite and kaolin materials have been increased with the
surface-coated MnO 2 particles via chemical precipitation due to increase in specific
surface area (Dankova et al. 2015). Nanomagnetic Fe 3 O 4 composite with kaolinite
increases its adsorption capacity for heavy metals such as cadmium, copper, chromium, lead, and nickel with increase in pH over time.
The natural raw form of vermiculite showed excellent potential for removal of
metal ions via adsorption. Pb adsorption by vermiculite was strongly affected by pH
(Liu et al. 2007). It is important to know during studying about adsorption of positively charged metals onto clay mineral that ionic strength of inbuilt salts impart a
great role on formation complex metals and thereby competing for the adsorption
site. It was reported that competitive adsorption behavior by pure vermiculite was
investigated for different heavy metal ions like Cr
+3
, Cu
+2
, Ni
+2
, and Co
+2
(El-Bayaa
et al. 2009). Another experiment showed that lead always adsorbs on vermiculite in
comparison to other metal ions such as Ni
+2
, Ag
+1
, and Cd
+2
because lead sorption
involves more than one mechanisms (Liu et al. 2010). A comparative study of Cu
+2
adsorption on different adsorbent like vermiculite and clinoptilolite leads to the
conclusion that adsorption of copper on vermiculite is possible via two mechanisms: ion exchange and surface complexation (Dizadji et al. 2013).
Heavy metal removal using goethite requires appropriate assessment of environmental hazards. The first successful prediction comes with extended triple layer
model, which was experimented with As
+3
and As
+5
(Kanematsu et al. 2013). The
metal adsorption of Cd, Cu, Pb, and Zn on raw goethite significantly increased in
presence of sulfate in liquid phase (Swedlund et al. 2009). Various studies are
M. Maharana et al.
raw one showing remarkable selectivity and removal efficiency toward Cu
+2
ions
(Abou-El-Sherbini and Hassanien 2010). Most of the studies on adsorption revealed
that main operating parameter which influenced the surface complexation mechanism is pH. At a high pH, adsorption of copper and arsenic reduces, while it was
found to be optimum at pH 6 (Uddin 2017).
Bentonite clay consists of volcanic ash named as “montmorillonite” with high
silica, iron, magnesium, sodium, and potassium concentration. It has a very unique
quality to produce electrical charge upon hydration. Chemical treatment with acids
such as HCl, HNO 3 , and H 3 PO 4 followed by washing with NaOH made it negatively
charged material which can easily bind to cations (Shawabkeh et al. 2007).
Kaolinite clay has poor ion-exchange capacity. Varying concentrations of electrolyte from 0.01 to 0.1 molar and adsorption of various metal ions like Ni
+2
, Cu
+2
,
Pb
+2
, and Cd
+2
were significantly reduced (Jiang et al. 2010). The maximum adsorption by kaolinite observed for nickel of amount 140.84 mg g
−1
(Jiang et al. 2010). It
has been well predicted that adsorption of metal ions decreased with increasing
concentration of electrolyte because of screening effect of negative charges on surface (Coles and Yong 2002). The parameter also influences the adsorption behavior
of different adsorbents. With the increase in temperature, adsorption of metal ions
decreased. A comparative study on adsorptive nature of As
+5
ions with montmorillonite, kaolinite, and illite concludes with similar result as aforesaid (Mohapatra
et al. 2007). Though natural untreated form of kaolinite provides good results, modified form of kaolinite gives enhancement of adsorption properties. The adsorption
capacities of natural raw siderite and kaolin materials have been increased with the
surface-coated MnO 2 particles via chemical precipitation due to increase in specific
surface area (Dankova et al. 2015). Nanomagnetic Fe 3 O 4 composite with kaolinite
increases its adsorption capacity for heavy metals such as cadmium, copper, chromium, lead, and nickel with increase in pH over time.
The natural raw form of vermiculite showed excellent potential for removal of
metal ions via adsorption. Pb adsorption by vermiculite was strongly affected by pH
(Liu et al. 2007). It is important to know during studying about adsorption of positively charged metals onto clay mineral that ionic strength of inbuilt salts impart a
great role on formation complex metals and thereby competing for the adsorption
site. It was reported that competitive adsorption behavior by pure vermiculite was
investigated for different heavy metal ions like Cr
+3
, Cu
+2
, Ni
+2
, and Co
+2
(El-Bayaa
et al. 2009). Another experiment showed that lead always adsorbs on vermiculite in
comparison to other metal ions such as Ni
+2
, Ag
+1
, and Cd
+2
because lead sorption
involves more than one mechanisms (Liu et al. 2010). A comparative study of Cu
+2
adsorption on different adsorbent like vermiculite and clinoptilolite leads to the
conclusion that adsorption of copper on vermiculite is possible via two mechanisms: ion exchange and surface complexation (Dizadji et al. 2013).
Heavy metal removal using goethite requires appropriate assessment of environmental hazards. The first successful prediction comes with extended triple layer
model, which was experimented with As
+3
and As
+5
(Kanematsu et al. 2013). The
metal adsorption of Cd, Cu, Pb, and Zn on raw goethite significantly increased in
presence of sulfate in liquid phase (Swedlund et al. 2009). Various studies are
M. Maharana et al.