This paper describes the hydrothermal synthesis of a pore-expanded hydroxyapatite (PE-HAp) from fine–grained calcareous sludge using a cetyltrimethylammonium bromide (CTAB) as a template and 1,3,5-trimethylbenzene (TMB) as a pore expander for the removal of Cu2+ ions from aqueous solutions. The PE-HAp was characterized using XRD, SEM, DTA/TGA and BET surface analysis. Adsorption behavior was assessed using Langmuir, Freundlich, Dubinin–Radushkevich, Temkin and Sips isotherms. In a solution with an initial Cu2+ concentration of 200 mg L-1 and a pH of 5.0, the highest Cu2+ removal efficiency was achieved using PE-HAp synthesized at a hydrothermal temperature of 180 °C at a concentration of 15 g/L over a period of 60 min. Using Langmuir isotherms, the highest single-layer adsorption capacity value was 9.90 mg g-1. Gibbs free energy (ΔG°), changes in enthalpy (ΔH°), and changes entropy change (ΔS°) revealed that the adsorption of Cu2+ on PE-HAp was spontaneous and exothermic. The PE-HAp synthesized in this study is a promising material for the removal of Cu2+ from aqueous solutions.