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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.

The palm fibers powder (PFP) was evaluated for the selective removal of nickel (Ni) and cadmium (Cd) from wastewater. The adsorbent was characterized by means of Fourier transform infrared spectrophotometer (FT-IR), X-ray diffraction (XRD) and polarized light microscopy (POM) measurements. The adsorption process was found to be highly pH dependent, facilitating selective adsorption of metals tested. The best Ni (II) and Cd (II) adsorption occurred at an initial concentration of 100 mg‧L-1, 1 g doses of PFP, a temperature of 20 °C, and pH = 5, 6.5 respectively. The maximum sorption capacities obtained with PFP for the studied metal ions were 6.81 mg‧g-1 for Cd (II) at 60 min and 4.42 mg‧g-1 for Ni (II) at 45 min. The adsorption is best fitted in Freundlich isotherm. A comparison of kinetic models (pseudo first-order and the pseudo second-order) at different conditions showed that the pseudo second-order kinetic model correlate the experimental data well. Van’t Hoff equation was used to evaluate the thermodynamic parameters (ΔH°, ΔS°, and ΔG°), which indicate that adsorption process is exothermic in nature, with the absolute values of ΔH° in range of 20-50 kJ‧mol-1 for the two metal ions and the values of ΔS° are found to be -0.142 and -0.062 kJ‧mol-1 for Cd (II) and Ni (II) ions respectively.