Cadmium removal efficiency from synthetic wastewater using sawdust as a sustainable adsorbent

Adsorption is one of the method that can be used to remove heavy metals from polluted water. Many adsorbents are naturally available and showed high performance in removing various pollutants. This study aimed to evaluate the performance of sawdust as a natural adsorbent agent to remove Cd ions from simulated wastewater and, also, to assess the improvement of sawdust adsorption capacity after activation by sulfuric acid (H2SO4). Many factors such as pH, contact time, temperature, and weight of the adsorbent were investigated in this study to evaluate their effect on the adsorption process. The results indicated a significant improvement of sawdust after modification (95.51% removal) compared to raw sawdust (82.22% removal). Equilibrium adsorption isotherms and kinetic study have been also carried out. Compared to the Langmuir adsorption isotherm model, the Freundlich isotherm model was best represented the experimental data of the sawdust. The experimental results of this sorbent were suitable for a pseudo-second order kinetic model. Moreover, the result pointed out that the process of adsorption was an endothermic and increasing the temperature resulted in a higher removal rate. Additionally, FTIR results revealed that the groups of carboxyl and hydroxyl contributed to the metal ions' ability to bind to surfaces. Finally, images of the surface structure of the sawdust before and after modification were obtained by using scanning electron microscopy (SEM) to analyze the surface morphology of both raw and treated sawdust.