Simultaneous
Removal of Divalent Heavy Metals from
Aqueous Solutions Using Raw and Mechanochemically Treated Interstratified
Montmorillonite/Kaolinite Clay
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Abstract
The removal of Pb(II),
Cd(II), Cu(II), and Zn(II) from aqueous
solutions using (un)modified Serbian interstratified montmorillonite/kaolinite
clay as an adsorbent was investigated. The clay was modified by mechanochemical
activation for different time periods. X-ray diffraction patterns
and particle size distributions were used to characterize the samples.
Batch adsorption studies were conducted to optimize various conditions.
The adsorption equilibrium was established within 60 min, and the
maximum adsorption occurred in the pH range of 4.5–6.5. The
milled clays exhibited greater equilibrium adsorption capacities (<i>q</i><sub>e</sub>) for all of the metals than the raw clay.
A difference in <i>q</i><sub>e</sub> values for clays milled
for 2 and 19 h could be observed only for initial concentrations (<i>C</i><sub>i</sub>) of ≥100 mg dm<sup>–3</sup>.
This was related to the amorphization (i.e., exfoliation) of 19-h-milled
clay particles. The adsorption equilibrium data of heavy metals on
both raw and modified clays fit the Langmuir equation, although there
were changes in the microstructure of the clay. The mechanochemical
treatment of the clay reduced the amount of adsorbent necessary to
achieve a highly efficient removal of heavy metals by a factor of
5. Thus, the mechanochemically treated interstratified clay can be
considered as an efficient adsorbent for the simultaneous removal
of divalent heavy metals
