Simultaneous removal of Pb super(2 +), Cu super(2 +), Zn super(2 +) and Cd super(2 +) from highly acidic solutions using mechanochemically synthesized montmorillonite-kaolinite/TiO sub(2) composite

The aim of the present study was to synthesize a composite of raw interstratified montmorillonite-kaolinite clay (Mt-K) with TiO sub(2) as an additive by mechanochemical activation and investigate its usability as low-cost adsorbent for simultaneous removal of heavy metals from acidic aqueous solutions. The composite synthesized with amorphous TiO sub(2) (TiO sub(2,)a) showed a significantly better removal ability of heavy metals from highly acidic solutions (pH = 2.0-4.0) compared with the Mt-K milled for an optimum period of time of 19 h (Mt-K,m) and composite synthesized with crystalline TiO sub(2) (TiO sub(2,)c). As both of the composites showed the same morphologies, the same distribution of TiO sub(2) particles on the clay matrix, the same particle size distribution (PSD) dependencies and point of zero charge (pH sub(PZC)) values, it has to be noticed that the difference in the adsorption behavior lies only in the different crystalline forms of the additive, i.e. TiO sub(2) that was used for the composite preparation. It has been shown that 20% of TiO sub(2,)a was the optimal amount of an additive in the composite to achieve improved adsorption ability.