Recovery of Nickel (Ii) Ions from Electroplating Rinse Water Using Hectorite Clay

Abstract

This paper describes the recovery of Ni (II) from electroplating rinse water using the Hectorite clay. Batch mode adsorption experiments were carried out and the effect of contact time, adsorbent dosage, pH, initial metal ion concentration and temperature were studied. Different isotherms were obtained using nickel electroplating rinse waters of various concentrations. The ion exchange process follows second order kinetics and langmuir isotherm. The paper discusses thermodynamic parameters, including changes in Gibbs free energy, entropy and enthalpy for the ion-exchange of Ni (II) from electroplating rinse water on Hectorite clay, revealed that the ion-exchange process was spontaneous and exothermic under different temperatures. The maximum adsorption capacity obtained was 62.24 mg/g at pH 7-8, the optimum adsorbent dosage and contact time was found to be 2 g/l within 5hours.

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“…where DS°(J/mol K) standard entropy change, DH°(J/mol) standard enthalpy change, R (J/K/mol) is the universal gas constant, T (K) absolute temperature and DG°(J/mol) is the free energy change of specific adsorption [30]. The plot of ln K d vs 1/T gives a linear graph.…”

“…where q e is the equilibrium adsorption capacity (mg/g) and C e is the concentration of metal ion in the liquid phase at equilibrium (mg/L) [30]. The Gibb's free energy (DG°) of adsorption can be determined using the equation,…”