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

Abstract The aim of the present study was to synthesize a composite of raw interstratified montmorillonite–kaolinite clay (Mt–K) with TiO 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 2 (TiO 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 2 (TiO 2, c). As both of the composites showed the same morphologies, the same distribution of TiO 2 particles on the clay matrix, the same particle size distribution (PSD) dependencies and point of zero charge (pH 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 2 that was used for the composite preparation. It has been shown that 20% of TiO 2, a was the optimal amount of an additive in the composite to achieve improved adsorption ability.