Montmorillonite and modified montmorillonite as adsorbents for removal of water soluble organic dyes: A review on current status of the art

Clays are naturally occurring environment-friendly materials possessing high specific surface area and good cation exchange capacity. Montmorillonite, one of the widely available clays, is known for its accumulative capacity for water-soluble hazardous and toxic dyes on the surface. This can be further modified by introducing inorganic and/or organic species into the interlayer space of the clay with simultaneous alteration in the selectivity and the mode of montmorillonite-dye interactions. The clay surface can be activated for increased interactions by treating with acid and/or base, or by functionalization with select additives. In this work, the use of natural and modified montmorillonites as selective adsorbents for water-soluble dyes is reviewed giving an insight into the theoretical basis of the interactions and the experimental findings based on the application of the popular isotherm and kinetic models. The basic objective is to consolidate the current understanding of the clay-dye interactions from the mechanisms of the interactions.