Arsenic is one of the most toxic elements that can be found. Arsenic is mainly emitted by the copper, lead and zinc production, in agriculture as pesticides and herbicides. Two forms of arsenic are common in natural waters: arsenite (AsO3
3−) and arseniate (AsO4
3−), referred to as As(III) and As(V). The nano-Mg/Al-hydrotalcites present ionic exchange and adsorbent capacities. In this work, the physic-chemical characterization of nano-Mg/Al-hydrotalcites and his arsenic removal capacityis described. The solids were synthesized by the sol-gel method with Mg/Al=2 and 3 ratio. The solids and their thermal treated products were characterized by XRD, FTIR, DTA, TGA and N2 adsorption. The solids were used as adsorbents As(III) in aqueous solutions. Adsorption isotherm studies of As(III) from aqueous solution are described. The adsorbent capacity was determined using the Langmuir, Freundlich and Dubinin–Radushkevich adsorption isotherm models. The As(III) adsorption isotherm data fit best to the isotherm Freundlich model. The maximum As(III) uptake capacity by nano-Mg/Al-hydrotalcites and the heated solids were determined using the Freundlich equation and were found to 547.46, 660.15, 799.88 and 739.12 mg As(III)/g HT-Mg/Al=2, HT-Mg/Al=3, HT-Mg/Al=2 at 350°C and HT-Mg/Al=3 at 350°C respectively. In the kinetic studies using 40 mg/L concentration of As(III) solutions was obtained an excellent removal capacity in contact times less at one minute.