Determination of Cu(II) in water and food samples by Na+-cloisite nanoclay as a new adsorbent: Equilibrium, kinetic and thermodynamic studies

Abstract

Na+-MMT (sodium montmorillonite) or Na+-cloisite nanoclay as a new adsorbent was employed for the sorption of Cu(II) ions from water and food samples in batch system. Copper ion determination was carried out by applying the solid phase extraction (SPE) method followed by atomic absorption spectroscopy (AAS) and inductively coupled plasma atomic emission spectroscopy (ICP-AES). The effects of varying parameters such as initial concentration of metal ions, volume of the standard solutions, eluent and buffer solutions characteristics, amount of adsorbent, contact time, and temperature on the adsorption process, also, the role of desorption and centrifugation time on the desorption step were explored. The effect of the interfering ions on the recovery of copper ions was also examined. This optimized method was applied to a variety of real water and food samples. The adsorption data was correlated with Freundlich, Langmuir, Dubinin–Radushkevich (D–R), and Temkin isotherms. The kinetic data were described with pseudo-first-order, pseudo-second-order and double-exponential models. The adsorption process follows a pseudo-second-order reaction scheme. Calculation of ΔG0, ΔH0 and ΔS0 showed that the nature of Cu(II) ion sorption onto Na+-cloisite nanoclay was exothermic and was favored at lower temperature.