This study discusses the characteristics phase of the alumina mixture, namely the γ, α-alumina as well as its ability to adsorb the nickel (II) and magnesium (II) from nickel sulfate due to solvent differences. The γ, α-alumina was synthesized under acidic conditions (pH = 5) from poly aluminum chloride that was calcined at 800 °C by the sol-gel method. The particle size of γ, α-alumina is 15.65 μm; BET specific surface area of 104.12 m2 g−1; mesopores volume of 0.284 mL g−1; and a shape type of IV isotherm curve. Such the characteristic belongs to an adsorbent. The solution of nickel sulfate as Solution (b) has a bigger total adsorption capacity than that of the Solution (a), namely 16.46 mg L−1 and 2.49 mg L−1 respectively. The alkaline buffer formation as the ammonium hydroxide and ammonium chloride in Solution (a) may result in reducing the adsorption capability of the γ,α-alumina. The magnesium concentration of nickel sulfate in Solution (a) is smaller than that of the nickel one, namely 118.36 mg L−1 for the Mg and 486.64 mg L−1 for the Ni. However, the Mg is still more adsorbed around 29.96 mg L−1 compared to the Ni (19.80 mg L−1).

Based on variations in calcination temperature, gamma alumina has successfully been made using a simple sol-gel method for Pomalaa magnesium-laterite adsorption from the South East of Sulawesi. The laterite leached by sulfuric acid was then precipitated by ammonia, to make the magnesium was separated from its main impurities (Si, Fe and Al). Temperature variations at 500, 650, 800 and 950 °C in gamma alumina making formed the gamma alumina phase while the alpha alumina phase was formed at 1100 °C. The higher calcination temperature the lower the specific surface area respectively from 196.385, 156.239, 105.725, 96.134 and 15.396 (m 2 /g). This results in decreasing the magnesium of the laterite 9.04, 8.70, 8.09, 6.39 and 0.29 (mg/L) respectively. The 800 °C-calcination gamma alumina has the highest volume of the pore, namely 0.3265 mL/g and the radius of 61.76 Å. The gamma alumina isotherm curve is type IV. The SEM-EDS test shows an aggregation spherical shape. Gamma alumina was detected to adsorb Mg laterite. The X-ray mapping of SEM-EDS test shows even distribution between gamma alumina, magnesium, and nickel. The highest adsorption is retained by GA-800/3 sample, namely 81.31 %.