Biosorption of nickel(II) and copper(II) ions from synthetic and real effluents by alginate-based biosorbent produced from seaweed Sargassum sp.

In this study, the alginate-based biosorbent produced from seaweed Sargassum sp. was used in biosorption of Ni and Cu ions from synthetic solutions and real electroplating effluents. Biosorption kinetics, isotherms, pH effect, thermodynamic parameters, and sorption/desorption cycles were also evaluated. Kinetic studies show the sorption equilibrium can be obtained within 180 min for Ni ions and 360 min for Cu ions, and the adsorption kinetics data are well described by the pseudo-second order and diffusion in spherical adsorbents. Langmuir model can be well used to describe the biosorption isotherm data. The maximum sorption capacity (q) and Langmuir constant (b) were up to 1.147 mmol g and 1.139 L mmol for Ni ions and 1.640 mmol g and 4.645 L mmol for Cu ions. The calculated thermodynamic parameters (ΔG°, ΔH°, and ΔS°) showed that the biosorption of Ni and Cu ions are predominantly a chemical phenomenon of endothermic nature, favorable, and spontaneous at the temperature ranges of 293-313 K. Partial desorption of the Ni and Cu ions on the biosorbent was achieved using acidic and saline eluents, allowing the biosorbent to be used in new sorption/desorption cycles. EDX analysis suggests an ion exchange mechanism between calcium ions on the biosorbent and target metals. Biosorption of Ni and Cu from real electroplating effluents with high concentrations of light metals becomes highly competitive, decreasing the amount of Ni and Cu ions biosorbed due to the ionic strength effect.