Biosorption of Pb(II) and Cd(II) ions from aqueous solution using chia (<i>Salvia hispanica</i>) seed

The current study was designed to investigate the potentials of using chia (<i>Salvia hispanica</i>) seed as an efficient biosorbent for the biosorption of Pb(II) and Cd(II) from aqueous solution. The batch biosorption process was employed to study the factors involved in the biosorption process, including biosorbent dosage, initial metal concentrations, pH, and contact time. Additionally, the Langmuir and Freundlich isotherm (L &amp; F) models were evaluated. Besides, Scanning Electron Microscopy (SEM), x-ray diffractometer (XRD), and Fourier Transform Infrared Spectroscopy (FTIR) analyses were used to characterize the biosorbent before and after biosorption. The optimal pH was determined to be 5.0 as this would reduce electrostatic repulsion, while extreme pH levels would hinder the process. It was found that increasing the biosorbent concentration reduced biosorption efficiency due to the constant biosorbent concentration and possible self-aggregation. Moreover, higher initial metal concentrations were found to enhance the biosorption capacity, which would stabilize after 70 min. Furthermore, Freundlich isotherm model demonstrating the best fit for the data. Also, L&amp;F parameters illustrated favorable biosorption of Pb(II) and Cd(II) onto the chia seed. The process was identified as second-order kinetics, suggesting complexation exchange mechanisms. The Freundlich isotherm model indicated multilayer adsorption on heterogeneous surfaces. It was demonstrated that biosorption is spontaneous and endothermic, with increased randomness at the interface, thermodynamically. The mechanism involved ion exchange and surface complexation, as evidenced by the correlation between released cations and metal ion removal. The amounts of removed ions and cations released at various initial concentrations of ions.