120
G. Fijałkowska et al.
nitrate, and sulfate), only phosphate one had noticeable effect on heavy metal adsorption. The decrease in temperature caused an increase in As-adsorbed amount on clay
surface.
Oliveira et al. [101] compared nickel, cadmium, zinc, and copper cations’ adsorption on bentonite clay and iron clay minerals with magnetite composite from aqueous
solution. It was shown that the presence of iron oxide in adsorbent structure enhanced
the adsorption capacity of bentonite. Yuan et al. [105] investigated the removal of
Cr(VI) by montmorillonite supported by magnetite nanoparticles. The clay mineral
modified by nanoparticles of magnetite showed greater adsorption capacity per unit
mass. Moreover, the chromium adsorption process was highly pH-dependent.
Several papers related to the adsorption of heavy metals on mineral soil surface
modified by polymeric substances. Gecol et al. [102] compared tungsten removal
efficiency by natural and chitosan-coated montmorillonite. The effects of W concentration as well as pH value were studied. The W-adsorbed amount increased with
decrease in solution pH value and metal concentration. However, clay mineral coated
with biopolymer was found to be much more effective adsorbent compared to natural
montmorillonite.
Wi´ sniewska et al. [115, 116] and Fijałkowska et al. [117, 118] examined the
anionic and cationic PAM adsorption on clay minerals, i.e., montmorillonite and
kaolinite and its impact on the heavy metal ions’ accumulation. Both polyacrylamides
may strengthen the Pb(II) and Cr(VI) ions’ adsorption on the aluminosilicate surface.
Pandley and Mishra [106] used chitosan/clay nanocomposite for Cr(VI) ions’
removal from aqueous solution. The adsorption of chromium(VI) ions on montmorillonite surface modified with biopolymer was carried out in different pH values.
However, the highest metal ions’ adsorbed amount was observed at pH 3.
Another study concerned selenium adsorption on chitosan–montmorillonite
composite [108]. The adsorption process on the composite material was pHindependent. It has been shown that clay mineral modified by chitosan is a highperformance adsorbent which allows removal of the metal ions with a high concentration from solution. The Cu(II) ions’ adsorption process on bentonite surface with
polyacrylamide gel in the function of pH, ionic strength, adsorbent content, metal ion
concentration, and temperature was studied [110]. Obtained results indicated high
pH, ionic strength, and temperature dependency of copper ions’ sorption process.
With decrease in temperature and ionic strength, the adsorbed amount of Cu(II) ions
increased.
The effects of contact time, adsorbent dosage, and pH of the initial solution on
the Hg
2+ removal by polyacrylamide/attapulgite were studied [113]. The mercury
ions’ adsorption on PAM–attapulgite surface increases with increasing contact time
and pH of the initial suspension but decreases with clay mineral composite dosage.
Zhou et al. [112] studied Hg(II), Pb(II), and Co(II) ions’ adsorption on polyacrylamide/attapulgite system. The obtained results showed that the clay mineral adsorbent modified by PAM exhibits the highest sorption capacity and selectivity in relation
to mercury ions, which is manifested in their greatest adsorption compared to other
ions.
G. Fijałkowska et al.
nitrate, and sulfate), only phosphate one had noticeable effect on heavy metal adsorption. The decrease in temperature caused an increase in As-adsorbed amount on clay
surface.
Oliveira et al. [101] compared nickel, cadmium, zinc, and copper cations’ adsorption on bentonite clay and iron clay minerals with magnetite composite from aqueous
solution. It was shown that the presence of iron oxide in adsorbent structure enhanced
the adsorption capacity of bentonite. Yuan et al. [105] investigated the removal of
Cr(VI) by montmorillonite supported by magnetite nanoparticles. The clay mineral
modified by nanoparticles of magnetite showed greater adsorption capacity per unit
mass. Moreover, the chromium adsorption process was highly pH-dependent.
Several papers related to the adsorption of heavy metals on mineral soil surface
modified by polymeric substances. Gecol et al. [102] compared tungsten removal
efficiency by natural and chitosan-coated montmorillonite. The effects of W concentration as well as pH value were studied. The W-adsorbed amount increased with
decrease in solution pH value and metal concentration. However, clay mineral coated
with biopolymer was found to be much more effective adsorbent compared to natural
montmorillonite.
Wi´ sniewska et al. [115, 116] and Fijałkowska et al. [117, 118] examined the
anionic and cationic PAM adsorption on clay minerals, i.e., montmorillonite and
kaolinite and its impact on the heavy metal ions’ accumulation. Both polyacrylamides
may strengthen the Pb(II) and Cr(VI) ions’ adsorption on the aluminosilicate surface.
Pandley and Mishra [106] used chitosan/clay nanocomposite for Cr(VI) ions’
removal from aqueous solution. The adsorption of chromium(VI) ions on montmorillonite surface modified with biopolymer was carried out in different pH values.
However, the highest metal ions’ adsorbed amount was observed at pH 3.
Another study concerned selenium adsorption on chitosan–montmorillonite
composite [108]. The adsorption process on the composite material was pHindependent. It has been shown that clay mineral modified by chitosan is a highperformance adsorbent which allows removal of the metal ions with a high concentration from solution. The Cu(II) ions’ adsorption process on bentonite surface with
polyacrylamide gel in the function of pH, ionic strength, adsorbent content, metal ion
concentration, and temperature was studied [110]. Obtained results indicated high
pH, ionic strength, and temperature dependency of copper ions’ sorption process.
With decrease in temperature and ionic strength, the adsorbed amount of Cu(II) ions
increased.
The effects of contact time, adsorbent dosage, and pH of the initial solution on
the Hg
2+ removal by polyacrylamide/attapulgite were studied [113]. The mercury
ions’ adsorption on PAM–attapulgite surface increases with increasing contact time
and pH of the initial suspension but decreases with clay mineral composite dosage.
Zhou et al. [112] studied Hg(II), Pb(II), and Co(II) ions’ adsorption on polyacrylamide/attapulgite system. The obtained results showed that the clay mineral adsorbent modified by PAM exhibits the highest sorption capacity and selectivity in relation
to mercury ions, which is manifested in their greatest adsorption compared to other
ions.