ADSORPTIVE REMOVAL OF NICKEL (II) USING LUFFA CYLINDRICA: EFFECT OF NaCl CONCENTRATION ON EQUILIBRIUM AND KINETIC PARAMETERS

In this study, biosorption of Nickel (II) from saline solutions by Luffa Cylindrica, was studied as a function of pH, initial Nickel (II) and NaCl concentrations in a batch system. The sorbent exhibited the maximal Nickel (II) uptake at pH 6 in the absence and in the presence of increasing concentration of NaCl. Equilibrium uptake increased with the Nickel (II) concentration up to 100 mg·L-1 and diminished considerably in the presence of increasing concentrations of salt up to 50 g·L-1. At 100 mg·L-1, initial Nickel (II) concentration, Luffa Cylindrica 23.35 mg·g-1 of Nickel (II) without salt medium. When NaCl concentration was raised to 50 g·L-1, this value dropped to 13.55 mg·g-1 of Nickel (II) at the same conditions resulting in 41.98 % decrease in biosorption capacity. The equilibrium sorption data were analyzed by using Freundlich and Langmuir models. Freundlich was the most suitable adsorption model for describing the biosorption equilibrium data of Nickel (II) both individually and in salt-containing medium. Pseudo-second-order kinetic model also fitted well to both systems, viz. Nickel (II) and Nickel (II) + NaCl. Isotherm constants varied due to the level of salt were expressed as a function of initial NaCl concentration.