*4.1. Acid Treatment*

In acid treatment the reaction with carbonate in the sepiolite dissolves these impurities and clears any surface obstruction. The H+ from the acid will replace the Ca2+, Mg2+, Na+, and K+ in the sepiolite interlayer, and improves the access to the surface and cavities in the sepiolite and increases the surface area and microporosity to provide improved adsorption performance [48,50,51].
