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 (q
e) for all of the metals than the raw clay.
A difference in q
e values for clays milled
for 2 and 19 h could be observed only for initial concentrations (C
i) of ≥100 mg dm–3.
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.
The hydrogen sorption kinetics of MgH2-VO2(B) composites synthesised by mechanical milling have been studied. The microstructural properties of composites were characterized by means of X-ray diffraction (XRD), Raman spectroscopy, Scanning electron microscopy (SEM), Particle size analysis (PSD), while sorption behaviour was followed by differential scanning calorimetry (DSC) and Sievert measurements. Results have shown that although desorption temperature reduction is moderate; there is a substantial improvement in hydrogen sorption kinetics. The complete desorption of pure MgH2 at elevated temperature takes place in more than 30 minutes while the composite fully desorbs in less than 2 minutes even at lower temperatures.It has been shown that the metastable -MgH2 phase and the point defects have a decisive role in desorption process only in the first sorption cycle, while the second and the subsequent sorption cycles are affected by microstructural and morphological characteristics of the composite.
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