Response surface modelling of the biosorption of Zn(II) and Pb(II) onto Micropogonias undulatus scales: Box–Behnken experimental approach

In this study, the scales of Micropogonias undulatus fish were investigated as precursors for the development of low-cost biosorbent for the removal of Pb(II) and Zn(II) from aqueous media. The biosorbent was characterised using Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM) and X-ray diffractometry (XRD). Adsorption parameters (temperature, biosorbent dosage and contact time) were optimised using response surface methodology Box–Behnken experimental design. The optimal factors for Zn(II) removal by croaker fish scale were 145.5 min, 7.01 g/L biosorbent dosage, 30 °C and pH 5.4. The optimal factors for the removal of Pb(II) were 179.3 min, 6.61 g/L biosorbent dosage, 20 °C and pH 3.4. The numerical optimisation revealed that the optimal removal efficiency for Zn(II) and Pb(II) sorption is 96.45% and 98.76%, respectively. The biosorption of both heavy metals was best fit to Freundlich isotherm and pseudo-second-order kinetic models. Thermodynamics studies revealed that the biosorption process was exothermic and spontaneous.