Adsorption kinetics and equilibrium of copper from aqueous solutions using hazelnut shell activated carbon

The adsorption of Cu(II) ions from aqueous solutions by hazelnut shell activated carbon (HSAC) was studied in a batch adsorption system. Factors influencing copper adsorption such as initial copper ion concentration (25–200 mg L−1), pH (2–6), adsorbent dosage (0.5–3.0 g L−1) and temperature (293–323 K) were investigated. The adsorption process was relatively fast and equilibrium was established about 90 min. Maximum adsorption of Cu(II) ions occurred at around pH 6. A comparison of the kinetic models on the overall adsorption rate showed that the adsorption system was best described by the pseudo second-order kinetics. Desorption experiments were carried out to test the performance of the carbon and desorption efficiencies in four cycles were found to be in the range 74–79%. The adsorption equilibrium data fitted best with the Langmuir isotherm and the monolayer adsorption capacity of Cu(II) ions was determined as 58.27 mg g−1 at 323 K. Thermodynamic parameters were calculated for the Cu(II) ion–HSAC system and the positive value of ΔH (18.77 kJ mol−1) showed that the adsorption was endothermic and physical in nature.