Investigation of Cu(II) adsorption from aqueous solutions by NKF-6 zeolite

摘要

Adsorption of Cu(II) from aqueous solutions using NKF-6 zeolite was investigated by batch technique under ambient conditions. The adsorption was investigated as a function of pH, ionic strength, fulvic acid (FA), foreign ions and temperature. The results indicated that the adsorption of Cu(II) on NKF-6 zeolite gradually increases from 0 to 90% with increasing pH at pH < 6.5, and maintains high level at pH > 6.5. Outer-sphere complexation or ion exchange may be the main adsorption mechanism of Cu(II) to NKF-6 zeolite at low pH values, whereas the adsorption of Cu(II) at pH > 6.5 is mainly dominated by inner-sphere complexation or precipitation. A positive effect of FA on Cu(II) adsorption onto NKF-6 zeolite is observed at low pH values, while a negative effect of FA is observed at high pH values. The thermodynamic parameters (i.e., ΔH~0, ΔS~0 and ΔG~0) for the adsorption of Cu(II) were determined from the temperature dependent isotherms at 20, 40 and 60°C, respectively, and the results indicated that the adsorption reaction is favoured at low temperature. The results suggested that the adsorption process of Cu(II) on NKF-6 zeolite is spontaneous and exothermic.