Study on a new adsorbent for biosorption of cadmium ion from aqueous solution by activated carbon prepared from Ricinus communis

Adsorption of heavy metal ions from the aqueous solutions is an important environmental challenge. In this research, as a low-cost adsorbent, the activated carbon which was prepared from Ricinus communis leaves was applied to adsorb cadmium(II) ions from aqueous solution. The prepared activated carbon was characterized using Brunauer-Emmett-Teller, scanning electron microscope, energy-dispersive X-ray spectroscopy/Map, Fourier transform infrared spectroscopy, X-ray diffraction, and thermogravimetric analysis. Batch experiments were designed to investigate the significance of adsorption important parameters including solution pH, the dosage of adsorbent, adsorption time, temperature, and cadmium initial concentration on the Cd(II) ions removal efficiency. The highest adsorption efficiency was 97.71% which was achieved in the following conditions: pH = 8, the dosage of adsorbent = 0.6 g/L, adsorption time = 70 min, 25 degrees C, and initial ion concentration = 70 ppm. Equilibrium studies showed that Langmuir isotherm performed better than the Freundlich model for fitting the data. Additionally, the kinetic behavior of the process was described by the pseudo-second-order model better than the pseudo-first-order model. Furthermore, based on thermodynamic calculations, the current process was exothermic, spontaneous with the decreased irregularities.