Simultaneous Removal of Divalent Heavy Metals from Aqueous Solutions Using Raw and Mechanochemically Treated Interstratified Montmorillonite/Kaolinite Clay

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 (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.

Simultaneous removal of Pb2+, Cu2+, Zn2+ and Cd2+ from highly acidic solutions using mechanochemically synthesized montmorillonite–kaolinite/TiO2 composite

“…Samples were milled for 19 h at the ball to powder ratio (BPR) 4:1. These parameters of milling were previously determined as optimal milling parameters for modification by Kumrić et al (2013). Two different forms of TiO 2 were used for the preparation of the composites, namely: TiO 2, c was procured from Sigma-Aldrich, USA and TiO 2, a was synthesized by hydrothermal process similar to that described by Kasuga et al (1998).…”

“…Numerous studies describe the influence of mechanochemical activation on the morphological and microstructural changes of the clay (Lee et al, 2007;Ramadan et al, 2010;Vdović et al, 2010), but only a limited number of studies investigated the use of mechanical milling on their adsorption properties (Nenadović et al, 2009;Vdović et al, 2010;Kumrić et al, 2013). Fragmentation, distortion, breakage of crystalline network and particle size reduction followed by an increase of the surface area, exfoliation of particles and amorphization, can lead to the increase of the removal efficiencies of the pollutants (Makó et al, 2001;Hrachová et al, 2007;Vdović et al, 2010).…”

“…On the other hand, longer milling times lead to the agglomeration of finer particles that result in the decrease of the cation exchange capacity (CEC) (Nenadović et al, 2009;Vdović et al, 2010). However, it is necessary to emphasize that the adsorption of heavy metal-ions on clay minerals is highly pHdependent, which limits their application for the removal of pollutants from highly acidic aqueous environments (pH b 4) (Nenadović et al, 2009;Vdović et al, 2010;Kumrić et al, 2013).…”

Highly selective and efficient removal and extraction of heavy metals by layered double hydroxides intercalated with the diphenylamine-4-sulfonate: A comparative study

“…In particular, with resent developments in nanotechnology, the use of different sorbents such as activated carbon, bio materials, zeolites and clay minerals, thanks to their numerous advantages such as high separation efficiency, easy operation and low cost is considered as an efficient technique for removing toxic metal ions from the aqueous medium [9][10][11][12][13]. Among these sorbents, the use of clays as sorbents to remove contaminants has increasingly received attention because they are cheaper than other materials such as activated carbon and zeolites [14][15][16][17]. However, they suffer from low selectivity and weak affinity for heavy metals [10].…”

A designed magnetic CoFe2O4–hydroxyapatite core–shell nanocomposite for Zn(II) removal with high efficiency

“…Among them, adsorption is found to be cheap, effective and easy to adapt and has been confirmed as one of the most promising technologies for removing heavy metals from wastewaters. To date, many adsorbents have been used for metal ions removal, such as zeolites [14], chitosan [15], organic resins [16], clay minerals [17], and even some industrial waste, like fly ash [18].…”