This study describes the synthesis of hydrotalcite-like materials by the co-precipitation method using aluminum extracted from saline slags wastes. Saline slags were chemically treated with 2 mol/dm(3) aqueous solutions of NaOH for 2 h using a reflux system. The aluminum aqueous solutions were used as precursors with cobalt, magnesium and nickel nitrates, and Na2CO3, to obtain hydrotalcite-like materials with two mole M2+/Al3+ ratios, 2: 1 and 4:1. The resulting solids were characterized by X-ray diffraction, termogravimetric analyses, nitrogen adsorption at -196 degrees C and scanning electron microscopy. After thermal treatment at 200 degrees C, the CO2 adsorption at 50, 100 and 200 degrees C was evaluated under dry conditions. The results showed a remarkable sorption capacity of 5.26 mmol/g at a pressure of 80 kPa and at a temperature of 50 degrees C for the MgAl-2: 1 sample, with sorption capacities considerably higher than those reported in the literature for hydrotalcites under similar conditions. The Henry's law constants were obtained directly from the adsorption isotherms at low pressures and the values found are between 0.01 and 4.20 mmol/kPa.g. The isosteric heats of CO2 adsorption found, using the Clausius-Clapeyron equation, were in the range of 5.2 to 16.8 kJ/mol.