Improving the effectiveness of clay minerals for the removal of heavy metals
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Date
2025
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Abstract
The discharge of heavy metals into the environment represents a significant threat to
ecosystems and human health. Among the available strategies, adsorption is widely considered to
be the most promising due to its clarity, affordability, and high efficiency in eliminating metal
ions, even in small amounts.
The objective of this thesis is to enhance the adsorbent capacity of kaolin-type (from
Guelma, east of Algeria) clays through chemical means, with the subsequent intention of
utilizing these materials to remove heavy metals from an aqueous phase.
The initial modification entailed the use of diphenylamine to synthesize DPA-Kaolin, with
the objective of efficiently removing lead (II) and copper (II) from aqueous solutions. The
subsequent modification involved the modification of kaolin with surfactants (SLS, SDBS, and
their mixture), with the aim of efficiently removing mercury (II) from aqueous solutions.
The characterization of the samples was conducted through a range of analytical
methodologies, encompassing X-ray diffraction (XRD) and Fourier-transform infrared
spectroscopy (FTIR) to ascertain their structural composition. In addition, scanning electron
microscopy (SEM), energy dispersive X-ray (EDX) and Brunauer-Emmett-Teller (BET) analysis
were employed to determine their morphological characteristics.
The findings showed an increase in the BET specific surface area of kaolin by nearly 25%
(from 66.69 m².g
−1
to 71.35 m².g
−1
) after DPA modification, and this increase demonstrated
significantly greater maximum adsorption capacities for Pb(II) and Cu(II) on DPA-kaolin than
on Nat-kaolin, with values of 151 µmol.g
-1
and 134 µmol.g
-1
, respectively, suggesting an
enhanced adsorption capacity, which confirmed the successful modification of kaolin using
DPA.
Conversely, the specific surface area of kaolin increased significantly with the addition of
surfactants, reaching 38.3%, 31.9%, and 17.5% for K-SLS, K-SDBS, and K-M, respectively. This
finding indicates that the mercury adsorption capacity of kaolin modified with anionic surfactant
SLS surpasses that of kaolin modified with a mixture of surfactants (SLS+SDBS) and finally
kaolin modified with anionic surfactant SDBS. The corresponding values for mercury adsorption
capacity were determined to be 17.77mg.g
-1
, 15.77mg.g
-1
, and 13.45 mg.g
1
, respectively.