Various adsorbents for the removal of dyes from waste water may or may not be stable, resulting in the desorption of adsorbed dyes with slight changes in physical conditions. To avoid this problem, environmentally stable adsorbent such as activated aluminum oxide or alumina has been used for the removal of Diresul Black, which is a dye used in the textile processing industry. Fourier-transform infrared spectroscopy confirms the non-tetrahedral framework of alumina. The efficiency of alumina via adsorption implies that 1 g alumina having the Brunauer–Emmett–Telle surface area of 2.65 ± 0.25 m2/g is enough to achieve up to 85% removal of concentrated dye solution in just 20 minutes. Adsorption energy as well as adsorption capacity is calculated by different adsorption isotherms. The sorption energy E turns out to be 19.3 KJ/mol. The thermodynamic studies show that the value of ΔH for the adsorption process is −976.5 J/mol while that of ΔS is −4.748 J/mol/K. Desorption studies show that the dye remains in its adsorbed form over aluminum oxide up to a pH of 2. Various ions present in the matrix interfere with the adsorption process, however none can decrease the adsorption below 65%.