Adsorption of lead(II) using bioadsorbent prepared from immobilized Gracilaria corticata algae: thermodynamics, kinetics and isotherm analysis

This work focuses on the removal of lead using immobilized Gracilaria corticata (immobilized-GC) algal based bioadsorbent. To characterize the surface morphology of the adsorbent by various analytical techniques such as scanning electron microscopy, energy-dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy; the Brunauer–Emmett–Teller and Barrett–Joyner–Halenda analysis were performed. The effect of different parameters was investigated in batch experiments. For the treatment of a Pb(II) solution at 25 mg/L, the removal efficiency of 99.1% was achieved using 1 g/L adsorbent at a mixing time of 75 min and pH of 6 during the adsorption process. Thermodynamics analyses indicate that the Pb(II) sorption on immobilized-GC is feasible, spontaneous, and endothermic with enthalpy and entropy equal to 52.01 kJ/mol and 0.185 kJ/mol K, respectively. Kinetic studies revealed that the adsorption process follows pseudo-second-order due to the higher regression coefficient and lower error coefficient. The adsorption isotherms of Pb(II) were also compared with popular models, and it was found that the Pb(II) uptake was well-described by the Langmuir model with maximum adsorption capacities of 89.1, 98.3, 108.2, and 122.1 mg/g at 20°C, 30°C, 40°C, and 50°C, respectively.